The reporter is running a SMTP server behind pasta, and the client
waits for the server's banner before sending any data. In turn, the
server waits for our ACK after sending SYN,ACK, which never comes.
If we use the ACK_IF_NEEDED indication to tcp_send_flag(), given that
there's no pending data, we delay sending the ACK segment at the end
of the three-way handshake until we have some data to send to the
server.
This was actually intended, as I thought we would lower the latency
for new connections, but we can't assume that the client will start
sending data first (SMTP is the typical example where this doesn't
happen).
And, trying out this patch with SSH (where the client starts sending
data first), the reporter actually noticed we have a lower latency
by forcing an ACK right away. Comparing a capture before the patch:
13:07:14.007704 IP 10.1.2.1.42056 > 10.1.2.140.1234: Flags [S], seq 1797034836, win 65535, options [mss 4096,nop,wscale 7], length 0
13:07:14.007769 IP 10.1.2.140.1234 > 10.1.2.1.42056: Flags [S.], seq 2297052481, ack 1797034837, win 65480, options [mss 65480,nop,wscale 7], length 0
13:07:14.008462 IP 10.1.2.1.42056 > 10.1.2.140.1234: Flags [.], seq 1:22, ack 1, win 65535, length 21
13:07:14.008496 IP 10.1.2.140.1234 > 10.1.2.1.42056: Flags [.], ack 22, win 512, length 0
13:07:14.011799 IP 10.1.2.140.1234 > 10.1.2.1.42056: Flags [P.], seq 1:515, ack 22, win 512, length 514
and after:
13:10:26.165364 IP 10.1.2.1.59508 > 10.1.2.140.1234: Flags [S], seq 4165939595, win 65535, options [mss 4096,nop,wscale 7], length 0
13:10:26.165391 IP 10.1.2.140.1234 > 10.1.2.1.59508: Flags [S.], seq 985607380, ack 4165939596, win 65480, options [mss 65480,nop,wscale 7], length 0
13:10:26.165418 IP 10.1.2.1.59508 > 10.1.2.140.1234: Flags [.], ack 1, win 512, length 0
13:10:26.165683 IP 10.1.2.1.59508 > 10.1.2.140.1234: Flags [.], seq 1:22, ack 1, win 512, length 21
13:10:26.165698 IP 10.1.2.140.1234 > 10.1.2.1.59508: Flags [.], ack 22, win 512, length 0
13:10:26.167107 IP 10.1.2.140.1234 > 10.1.2.1.59508: Flags [P.], seq 1:515, ack 22, win 512, length 514
the latency between the initial SYN segment and the first data
transmission actually decreases from 792µs to 334µs. This is not
statistically relevant as we have a single measurement, but it can't
be that bad, either.
Reported-by: cr3bs (from IRC)
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
When the guest tries to establish a connection, it could give up on it by
sending a FIN,ACK instead of a plain ACK to our SYN,ACK. It could then
make a new attempt to establish a connection with the same addresses and
ports with a new SYN.
Although it's unlikely, it could send the 2nd SYN very shortly after the
FIN,ACK resulting in both being received in the same batch of packets from
the tap interface.
Currently, we don't handle that correctly, when we receive a FIN,ACK on a
not fully established connection we discard the remaining packets in the
batch, and so will never process the 2nd SYN. Correct this by returning
1 from tcp_tap_handler() in this case, so we'll just consume the FIN,ACK
and continue to process the rest of the batch.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There are a number of conditions where we will issue a TCP RST in response
to something unexpected we received from the tap interface. These occur in
both tcp_data_from_tap() and tcp_tap_handler(). In tcp_tap_handler() use
a 'goto out of line' technique to consolidate all these paths into one
place. For the tcp_data_from_tap() cases use a negative return code and
direct that to the same path in tcp_tap_handler(), its caller.
In this case we want to discard all remaining packets in the batch we have
received: even if they're otherwise good, they'll be invalidated when the
guest receives the RST we're sending. This is subtly different from the
case where we *receive* an RST, where we could in theory get a new SYN
immediately afterwards. Clarify that with a common on the now common
reset path.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Although it's unlikely in practice, the guest could theoretically
reset one TCP connection then immediately start a new one with the
same addressses and ports, such that we get an RST then a SYN in the
same batch of received packets in tcp_tap_handler().
We don't correctly handle that unlikely case, because when we receive
the RST, we discard any remaining packets in the batch so we'd never
see the SYN. This could happen in either tcp_tap_handler() or
tcp_data_from_tap(). Correct that by returning 1, so that the caller
will continue calling tcp_tap_handler() on subsequent packets allowing
us to process any subsequent SYN.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently tcp_data_from_tap() is assumed to consume all packets remaining
in the packet pool it is given. However there are some edge cases where
that's not correct. In preparation for fixing those, change it to return
a count of packets consumed and use that in its caller.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
>From a practical point of view, when a TCP connection ends, whether by
FIN or by RST, we set the CLOSED event, then some time later we remove the
connection from the hash table and clean it up. However, from a protocol
point of view, once it's closed, it's gone, and any new packets with
matching addresses and ports are either forming a new connection, or are
invalid packets to discard.
Enforce these semantics in the TCP hash logic by never hash matching closed
connections.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Both tcp_data_from_tap() and tcp_tap_handler() call packet_get() to get
the entire L4 packet length, then immediately call it again to check that
the packet is long enough to include a TCP header. The features of
packet_get() let us easily combine these together, we just need to adjust
the length slightly, because we want the value to include the TCP header
length.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In both tap4_handler() and tap6_handler(), once we've sorted incoming l3
packets into "sequences", we then step through all the packets in each TCP
sequence calling tcp_tap_handler(). Or so it appears.
In fact, tcp_tap_handler() doesn't take an index and always looks at packet
0 of the sequence, except when it calls tcp_data_from_tap() to process
data packets. It appears to be written with the idea that the struct pool
is a queue, from which it consumes packets as it processes them, but that's
not how the pool data structure works - they are more like an array of
packets.
We only get away with this, because setup packets for TCP tend to come in
separate batches (because we need to reply in between) and so we only get
a bunch of packets for the same connection together when they're data
packets (tcp_data_from_tap() has its own loop through packets).
Correct this by adding an index parameter to tcp_tap_handler() and altering
the loops in tap.c to step through the pool properly.
Link: https://bugs.passt.top/show_bug.cgi?id=68
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_defer_handler() performs a potentially expensive linear scan of the
connection table. So, to mitigate the cost of that we skip if if we're not
under at least moderate pressure: either 30% of available connections or
30% (estimated) of available fds used.
But, the calculation for this has been broken since it was introduced: we
calculate "max_conns" based on c->tcp.conn_count, not TCP_MAX_CONNS,
meaning we only exit early if conn_count is less than 30% of itself, i.e.
never.
If that calculation is "corrected" to be based on TCP_MAX_CONNS, it
completely tanks the TCP CRR times for passt - from ~60ms to >1000ms on my
laptop. My guess is that this is because in the case of many short lived
connections, we're letting the table become much fuller before compacting
it. That means that other places which perform a table scan now have to
do much, much more.
For the time being, simply remove the tests, since they're not doing
anything useful. We can reintroduce them more carefully if we see a need
for them.
This also removes the only user of c->tcp.splice_conn_count, so that can
be removed as well.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The in_epoll boolean is one of only two fields (currently) in the common
structure shared between tap and spliced connections. It seems like it
belongs there, because both tap and spliced connections use it, and it has
roughly the same meaning.
Roughly, however, isn't exactly: which fds this flag says are in the epoll
varies between the two connection types, and are in type specific fields.
So, it's only possible to meaningfully use this value locally in type
specific code anyway.
This common field is going to get in the way of more widespread
generalisation of connection / flow tracking, so move it to separate fields
in the tap and splice specific structures.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Because packets sent on the tap interface will always be going to the
guest/namespace, we more-or-less know what address they'll be going to. So
we pre-fill this destination address in our header buffers for IPv4. We
can't do the same for IPv6 because we could need either the global or
link-local address for the guest. In future we're going to want more
flexibility for the destination address, so this pre-filling will get in
the way.
Change the flow so we always fill in the IPv4 destination address for each
packet, rather than prefilling it from proto_update_l2_buf(). In fact for
TCP we already redundantly filled the destination for each packet anyway.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We partially prepopulate IP and TCP header structures including, amongst
other things the destination address, which for IPv4 is always the known
address of the guest/namespace. We partially precompute both the IPv4
header checksum and the TCP checksum based on this.
In future we're going to want more flexibility with controlling the
destination for IPv4 (as we already do for IPv6), so this precomputed value
gets in the way. Therefore remove the IPv4 destination from the
precomputed checksum and fold it into the checksum update when we actually
send a packet.
Doing this means we no longer need to recompute those partial sums when
the destination address changes ({tcp,udp}_update_l2_buf()) and instead
the computation can be moved to compile time. This means while we perform
slightly more computations on each packet, we slightly reduce the amount of
memory we need to access.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In tcp_seq_init() the meaning of "src" and "dst" isn't really clear since
it's used for connections in both directions. However, these values are
just feeding a hash, so as long as we're consistent and include all the
information we want, it doesn't really matter.
Oddly, for the "src" side we supply the (tap side) forwarding address but
the (tap side) endpoint port. This again doesn't really matter, but it's
confusing. So swap this with dstport, so "src" is always forwarding
and "dst" is always endpoint.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In a number of places the comments and variable names we use to describe
addresses and ports are ambiguous. It's not sufficient to describe a port
as "tap-facing" or "socket-facing", because on both the tap side and the
socket side there are two ports for the two ends of the connection.
Similarly, "local" and "remote" aren't particularly helpful, because it's
not necessarily clear whether we're talking from the point of view of the
guest/namespace, the host, or passt itself.
This patch makes a number of changes to be more precise about this. It
introduces two new terms in aid of this:
A "forwarding" address (or port) refers to an address which is local
from the point of view of passt itself. That is a source address for
traffic sent by passt, whether it's to the guest via the tap interface
or to a host on the internet via a socket.
The "endpoint" address (or port) is the reverse: a remote address
from passt's point of view, the destination address for traffic sent
by passt.
Between them the "side" (either tap/guest-facing or sock/host-facing)
and forwarding vs. endpoint unambiguously describes which address or
port we're talking about.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The tap code passes the IPv4 or IPv6 destination address of packets it
receives to the protocol specific code. Currently that protocol code
doesn't use the source address, but we want it to in future. So, in
preparation, pass the IPv4/IPv6 source address of tap packets to those
functions as well.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_sock_handler() handles both listening TCP sockets, and connected TCP
sockets, but what it needs to do in those cases has essentially nothing in
common. Therefore, give listening sockets their own epoll_type value and
dispatch directly to their own handler from the top level. Furthermore,
the two handlers need essentially entirely different information from the
reference: we re-(ab)used the index field in the tcp_epoll_ref to indicate
the port for the listening socket, but that's not the same meaning. So,
switch listening sockets to their own reference type which we can lay out
as we please. That lets us remove the listen and outbound fields from the
normal (connected) tcp_epoll_ref, reducing it to just the connection table
index.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_sock_handler() actually handles several different types of fd events.
This includes timerfds that aren't sockets at all. The handling of these
has essentially nothing in common with the other cases. So, give the
TCP timers there own epoll_type value and dispatch directly to their
handler. This also means we can remove the timer field from tcp_epoll_ref,
the information it encoded is now implicit in the epoll_type value.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The epoll_ref type includes fields for the IP protocol of a socket, and the
socket fd. However, we already have a few things in the epoll which aren't
protocol sockets, and we may have more in future. Rename these fields to
an abstract "fd type" and file descriptor for more generality.
Similarly, rather than using existing IP protocol numbers for the type,
introduce our own number space. For now these just correspond to the
supported protocols, but we'll expand on that in future.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
union epoll_ref has a deeply nested set of structs and unions to let us
subdivide it into the various different fields we want. This means that
referencing elements can involve an awkward long string of intermediate
fields.
Using C11 anonymous structs and unions lets us do this less clumsily.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In practical terms, passt doesn't benefit from the additional
protection offered by the AGPL over the GPL, because it's not
suitable to be executed over a computer network.
Further, restricting the distribution under the version 3 of the GPL
wouldn't provide any practical advantage either, as long as the passt
codebase is concerned, and might cause unnecessary compatibility
dilemmas.
Change licensing terms to the GNU General Public License Version 2,
or any later version, with written permission from all current and
past contributors, namely: myself, David Gibson, Laine Stump, Andrea
Bolognani, Paul Holzinger, Richard W.M. Jones, Chris Kuhn, Florian
Weimer, Giuseppe Scrivano, Stefan Hajnoczi, and Vasiliy Ulyanov.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Since commit cc6d8286d1 ("tcp: Reset ACK_FROM_TAP_DUE flag only as
needed, update timer"), we don't clear ACK_FROM_TAP_DUE whenever we
process an ACK segment, but, more correctly, only if we're really not
waiting for a further ACK segment, that is, only if the acknowledged
sequence matches what we sent.
In the new function implementing this, tcp_update_seqack_from_tap(),
we also reset the retransmission counter and store the updated ACK
sequence. Both should be done iff forward progress is acknowledged,
implied by the fact that the new ACK sequence is greater than the
one we previously stored.
At that point, it looked natural to also include the statements that
clear and set the ACK_FROM_TAP_DUE flag inside the same conditional
block: if we're not making forward progress, the need for an ACK, or
lack thereof, should remain unchanged.
There might be cases where this isn't true, though: without the
previous commit 4e73e9bd65 ("tcp: Don't special case the handling
of the ack of a syn"), this would happen if a tap-side client
initiated a connection, and the server didn't send any data.
At that point we would never, in the established state of the
connection, call tcp_update_seqack_from_tap() with reported forward
progress.
That issue itself is fixed by the previous commit, now, but clearing
ACK_FROM_TAP_DUE only on ACK sequence progress doesn't really follow
any logic.
Clear the ACK_FROM_TAP_DUE flag regardless of reported forward
progress. If we clear it when it's already unset, conn_flag() will do
nothing with it.
This doesn't fix any known functional issue, rather a conceptual one.
Fixes: cc6d8286d1 ("tcp: Reset ACK_FROM_TAP_DUE flag only as needed, update timer")
Reported-by: David Gibson <david@gibson.dropbear.id.au>
Analysed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
TCP treats the SYN packets as though they occupied 1 byte in the logical
data stream described by the sequence numbers. That is, the very first ACK
(or SYN-ACK) each side sends should acknowledge a sequence number one
greater than the initial sequence number given in the SYN or SYN-ACK it's
responding to.
In passt we were tracking that by advancing conn->seq_to_tap by one when
we send a SYN or SYN-ACK (in tcp_send_flag()). However, we also
initialized conn->seq_ack_from_tap, representing the acks we've already
seen from the tap side, to ISN+1, meaning we treated it has having
acknowledged the SYN before it actually did.
There were apparently reasons for this in earlier versions, but it causes
problems now. Because of this when we actually did receive the initial ACK
or SYN-ACK, we wouldn't see the acknoweldged serial number as advancing,
and so wouldn't clear the ACK_FROM_TAP_DUE flag.
In most cases we'd get away because subsequent packets would clear the
flag. However if one (or both) sides didn't send any data, the other side
would (correctly) keep sending ISN+1 as the acknowledged sequence number,
meaning we would never clear the ACK_FROM_TAP_DUE flag. That would mean
we'd treat the connection as if we needed to retransmit (although we had
0 bytes to retransmit), and eventaully (after around 30s) reset the
connection due to too many retransmits. Specifically this could cause the
iperf3 throughput tests in the testsuite to fail if set for a long enough
test period.
Correct this by initializing conn->seq_ack_from_tap to the ISN and only
advancing it when we actually get the first ACK (or SYN-ACK).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Comments suggest that this should only be called for an ESTABLISHED
connection. However, it's non-trivial to ascertain that from the actual
control flow in the caller. Add an ASSERT() to make it very clear that
this is only called in ESTABLISHED state.
In fact, there were some circumstances where it could be called on a CLOSED
connection. In a sense that is "established", but with that assert this
does require specific (trivial) handling to avoid a spurious abort().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is mostly symmetric with commit cc6d8286d1 ("tcp: Reset
ACK_FROM_TAP_DUE flag only as needed, update timer"): we shouldn't
reset the ACK_TO_TAP_DUE flag on any inbound ACK segment, but only
once we acknowledge everything we received from the guest or the
container.
If we don't, a client might unnecessarily hold off further data,
especially during slow start, and in general we won't converge to the
usable bandwidth.
This is very visible especially with traffic tests on links with
non-negligible latency, such as in the reported issue. There, a
public iperf3 server sometimes aborts the test due do what appears to
be a low iperf3's --rcv-timeout (probably less than a second). Even
if this doesn't happen, the throughput will converge to a fraction of
the usable bandwidth.
Clear ACK_TO_TAP_DUE if we acknowledged everything, set it if we
didn't, and reschedule the timer in case the flag is still set as the
timer expires.
While at it, decrease the ACK timer interval to 10ms.
A 50ms interval is short enough for any bandwidth-delay product I had
in mind (local connections, or non-local connections with limited
bandwidth), but here I am, testing 1gbps transfers to a peer with
100ms RTT.
Indeed, we could eventually make the timer interval dependent on the
current window and estimated bandwidth-delay product, but at least
for the moment being, 10ms should be long enough to avoid any
measurable syscall overhead, yet usable for any real-world
application.
Reported-by: Lukas Mrtvy <lukas.mrtvy@gmail.com>
Link: https://bugs.passt.top/show_bug.cgi?id=44
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Fix a copy and paste typo I added in commit 5474bc5485 ("tcp,
tcp_splice: Get rid of false positive CWE-394 Coverity warning from
fls()") and --debug altogether.
Fixes: 5474bc5485 ("tcp, tcp_splice: Get rid of false positive CWE-394 Coverity warning from fls()")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
da46fdac "tcp: Suppress knownConditionTrueFalse cppcheck false positive"
introduced a suppression to work around a cppcheck bug causing a false
positive warning. However, the suppression will itself cause a spurious
unmatchedSuppression warning if used with a version of cppcheck from before
the bug was introduced. That includes the packaged version of cppcheck in
Fedora.
Suppress the unmatchedSuppression as well.
Fixes: da46fdac36 ("tcp: Suppress knownConditionTrueFalse cppcheck false positive")
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Commit 89e38f55 "treewide: Fix header includes to build with musl" added
extra #includes to work with musl. Unfortunately with the cppcheck version
I'm using (cppcheck-2.9-1.fc37.x86_64 in Fedora 37) this causes weird false
positives: specifically cppcheck seems to hit a #error in <bits/unistd.h>
complaining about including it directly instead of via <unistd.h> (which is
not something we're doing).
I have no idea why that would be happening; but I'm guessing it has to be
a bug in the cpp implementation in that cppcheck version. In any case,
it's possible to work around this by moving the include of <unistd.h>
before the include of <signal.h>. So, do that.
Fixes: 89e38f5540 ("treewide: Fix header includes to build with musl")
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The logic in tcp_timer() was inverted. fwd_out should expose the host
ports in the ns. Therfore it must read the ports on the host and then
bind them in the netns. The same for fwd_in which checks ports in the
ns and then exposes them on the host.
Note that this only fixes tcp ports, udp does not seems to work at all
right now with the auto mode.
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Fixes: 1128fa03fe ("Improve types and names for port forwarding configuration")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Tom reports that a pattern of repated ~1 MiB chunks downloads over
NNTP over TLS, on Podman 4.4 using pasta as network back-end, results
in pasta taking one full CPU thread after a while, and the download
never succeeds.
On that setup, we end up re-sending the same frame over and over,
with a consistent 65 534 bytes size, and never get an
acknowledgement from the tap-side client. This only happens for the
default MTU value (65 520 bytes) or for values that are slightly
smaller than that (down to 64 499 bytes).
We hit this condition because the MSS value we use in
tcp_data_from_sock(), only in pasta mode, is simply clamped to
USHRT_MAX, and not to the actual size of the buffers we pre-cooked
for sending, which is a bit less than that.
It looks like we got away with it until commit 0fb7b2b908 ("tap:
Use different io vector bases depending on tap type") fixed the
setting of iov_len.
Luckily, since it's pasta, we're queueing up to two frames at a time,
so the worst that can happen is a badly segmented TCP stream: we
always have some space at the tail of the buffer.
Clamp the MSS value to the appropriate maximum given by struct
tcp{4,6}_buf_data_t, no matter if we're running in pasta or passt
mode.
While at it, fix the comments to those structs to reflect the current
struct size. This is not really relevant for any further calculation
or consideration, but it's convenient to know while debugging this
kind of issues.
Thanks to Tom for reporting the issue in a very detailed way and for
providing a test setup.
Reported-by: Tom Mombourquette <tom@devnode.com>
Link: https://github.com/containers/podman/issues/17703
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
The comments say we should return 0 on partial success, and an error
code on complete failure. Rationale: if the user configures a port
forwarding, and we succeed to bind that port for IPv4 or IPv6 only,
that might actually be what the user intended.
Adjust the two functions to reflect the comments.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
...starting from sock_l4(), pass negative error (errno) codes instead
of -1. They will only be used in two commits from now, no functional
changes intended here.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Roughly inspired from a patch by Chris Kuhn: fix up includes so that
we can build against musl: glibc is more lenient as headers generally
include a larger amount of other headers.
Compared to the original patch, I only included what was needed
directly in C files, instead of adding blanket includes in local
header files. It's a bit more involved, but more consistent with the
current (not ideal) situation.
Reported-by: Chris Kuhn <kuhnchris+github@kuhnchris.eu>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
I didn't notice earlier: libslirp (and slirp4netns) supports binding
outbound sockets to specific IPv4 and IPv6 addresses, to force the
source addresse selection. If we want to claim feature parity, we
should implement that as well.
Further, Podman supports specifying outbound interfaces as well, but
this is simply done by resolving the primary address for an interface
when the network back-end is started. However, since kernel version
5.7, commit c427bfec18f2 ("net: core: enable SO_BINDTODEVICE for
non-root users"), we can actually bind to a specific interface name,
which doesn't need to be validated in advance.
Implement -o / --outbound ADDR to bind to IPv4 and IPv6 addresses,
and --outbound-if4 and --outbound-if6 to bind IPv4 and IPv6 sockets
to given interfaces.
Given that it probably makes little sense to select addresses and
routes from interfaces different than the ones given for outbound
sockets, also assign those as "template" interfaces, by default,
unless explicitly overridden by '-i'.
For ICMP and UDP, we call sock_l4() to open outbound sockets, as we
already needed to bind to given ports or echo identifiers, and we
can bind() a socket only once: there, pass address (if any) and
interface (if any) for the existing bind() and setsockopt() calls.
For TCP, in general, we wouldn't otherwise bind sockets. Add a
specific helper to do that.
For UDP outbound sockets, we need to know if the final destination
of the socket is a loopback address, before we decide whether it
makes sense to bind the socket at all: move the block mangling the
address destination before the creation of the socket in the IPv4
path. This was already the case for the IPv6 path.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
If tcp_timer_ctl() gets a socket number greater than SOCKET_MAX
(2 ^ 24), we return error but we don't close the socket. This is a
rather formal issue given that, at least on Linux, socket numbers are
monotonic and we're in general not allowed to open so many sockets.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
If there are no TCP options in the header, tcp_tap_handler() will
pass the corresponding pointer, fetched via packet_get(), as NULL to
tcp_conn_from_sock_finish(), which in turn indirectly calls
tcp_opt_get().
If there are no options, tcp_opt_get() will stop right away because
the option length is indicated as zero. However, if the logic is
complicated enough to follow for static checkers, adding an explicit
check against NULL in tcp_opt_get() is probably a good idea.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
We use the return value of fls() as array index for debug strings.
While fls() can return -1 (if no bit is set), Coverity Scan doesn't
see that we're first checking the return value of another fls() call
with the same bitmask, before using it.
Call fls() once, store its return value, check it, and use the stored
value as array index.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Recently, commit 4ddbcb9c0c ("tcp: Disable optimisations
for tcp_hash()") worked around yet another issue we hit with gcc 12
and '-flto -O2': some stores affecting the input data to siphash_20b()
were omitted altogether, and tcp_hash() wouldn't get the correct hash
for incoming connections.
Digging further into this revealed that, at least according to gcc's
interpretation of C99 aliasing rules, passing pointers to functions
with different types compared to the effective type of the object
(for example, a uint8_t pointer to an anonymous struct, as it happens
in tcp_hash()), doesn't guarantee that stores are not reordered
across the function call.
This means that, in general, our checksum and hash functions might
not see parts of input data that was intended to be provided by
callers.
Not even switching from uint8_t to character types, which should be
appropriate here, according to C99 (ISO/IEC 9899, TC3, draft N1256),
section 6.5, "Expressions", paragraph 7:
An object shall have its stored value accessed only by an lvalue
expression that has one of the following types:
[...]
— a character type.
does the trick. I guess this is also subject to interpretation:
casting passed pointers to character types, and then using those as
different types, might still violate (dubious) aliasing rules.
Disable gcc strict aliasing rules for potentially affected functions,
which, in turn, disables gcc's Type-Based Alias Analysis (TBAA)
optimisations based on those function arguments.
Drop the existing workarounds. Also the (seemingly?) bogus
'maybe-uninitialized' warning on the tcp_tap_handler() > tcp_hash() >
siphash_20b() path goes away with -fno-strict-aliasing on
siphash_20b().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
cppcheck 2.10 reports:
tcp.c:1815:12: style: Condition 'wnd>prev_scaled' is always false [knownConditionTrueFalse]
if ((wnd > prev_scaled && wnd * 99 / 100 < prev_scaled) ||
^
tcp.c:1808:8: note: Assignment 'wnd=((1<<(16+8))<(wnd))?(1<<(16+8)):(wnd)', assigned value is less than 1
wnd = MIN(MAX_WINDOW, wnd);
^
tcp.c:1811:19: note: Assuming condition is false
if (prev_scaled == wnd)
^
tcp.c:1815:12: note: Condition 'wnd>prev_scaled' is always false
if ((wnd > prev_scaled && wnd * 99 / 100 < prev_scaled) ||
^
but this is not actually the case: wnd is typically greater than 1,
and might very well be greater than prev_scaled as well.
I bisected this down to cppcheck commit b4d455df487c ("Fix 11349: FP
negativeIndex for clamped array index (#4627)") and reported findings
at https://github.com/danmar/cppcheck/pull/4627.
Suppress the warning for the moment being.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
I'm not sure if we're breaking some aliasing rule here, but with gcc
12.2.1 on x86_64 and -flto, the siphash_20b() call in tcp_hash()
doesn't see the connection address -- it gets all zeroes instead.
Fix this temporarily by disabling optimisations for this tcp_hash().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This goto exists purely to move this exception case out of line. Although
that does make the "normal" path a little clearer, it comes at the cost of
not knowing how where control will flow after jumping to the zero_len
label. The exceptional case isn't that long, so just put it inline.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This goto can be handled just as simply and more clearly with a do while.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
passt supports ranges of forwarded ports as well as 'all' for TCP and
UDP, so it might be convenient to proceed if we fail to bind only
some of the desired ports.
But if we fail to bind even a single port for a given specification,
we're clearly, unexpectedly, conflicting with another network
service. In that case, report failure and exit.
Reported-by: Yalan Zhang <yalzhang@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
When creating a new spliced connection, we need to get a socket in the
other ns from the originating one. To avoid excessive ns switches we
usually get these from a pool refilled on a timer. However, if the pool
runs out we need a fallback. Currently that's done by passing -1 as the
socket to tcp_splice_connnect() and running it in the target ns.
This means that tcp_splice_connect() itself needs to have different cases
depending on whether it's given an existing socket or not, which is
a separate concern from what it's mostly doing. We change it to require
a suitable open socket to be passed in, and ensuring in the caller that we
have one.
This requires adding the fallback paths to the caller, tcp_splice_new().
We use slightly different approaches for a socket in the init ns versus the
guest ns.
This also means that we no longer need to run tcp_splice_connect() itself
in the guest ns, which allows us to remove a bunch of boilerplate code.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_conn_new_sock() first looks for a socket in a pre-opened pool, then if
that's empty creates a new socket in the init namespace. Both parts of
this are duplicated in other places: the pool lookup logic is duplicated in
tcp_splice_new(), and the socket opening logic is duplicated in
tcp_sock_refill_pool().
Split the function into separate parts so we can remove both these
duplications.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_splice.c has some explicit extern declarations to access the
socket pools. This is pretty dangerous - if we changed the type of
these variables in tcp.c, we'd have tcp.c and tcp_splice.c using the
same memory in different ways with no compiler error. So, move the
extern declarations to tcp_conn.h so they're visible to both tcp.c and
tcp_splice.c, but not the rest of pasta.
In fact the pools for the guest namespace are necessarily only used by
tcp_splice.c - we have no sockets on the guest side if we're not
splicing. So move those declarations and the functions that deal
exclusively with them to tcp_splice.c
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
With the creation of the tcp_sock_refill_pool() helper, the ns==true and
ns==false paths for tcp_sock_refill() now have almost nothing in common.
Split the two versions into tcp_sock_refill_init() and tcp_sock_refill_ns()
functions.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_sock_refill() contains two near-identical loops to refill the IPv4
and IPv6 socket pools. In addition, if we get an error on the IPv4
pool we exit early and won't attempt to refill the IPv6 pool. At
least theoretically, these are independent from each other and there's
value to filling up either pool without the other. So, there's no
strong reason to give up on one because the other failed.
Address both of these with a helper function 'tcp_sock_refill_pool()' to
refill a single given pool.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There are some places in passt/pasta which #include <assert.h> and make
various assertions. If we hit these something has already gone wrong, but
they're there so that we a useful message instead of cryptic misbehaviour
if assumptions we thought were correct turn out not to be.
Except.. the glibc implementation of assert() uses syscalls that aren't in
our seccomp filter, so we'll get a SIGSYS before it actually prints the
message. Work around this by adding our own ASSERT() implementation using
our existing err() function to log the message, and an abort(). The
abort() probably also won't work exactly right with seccomp, but once we've
printed the message, dying with a SIGSYS works just as well as dying with
a SIGABRT.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
David reports that TCP transfers might stall, especially with smaller
socket buffer sizes, because we reset the ACK_FROM_TAP_DUE flag, in
tcp_tap_handler(), whenever we receive an ACK segment, regardless of
its sequence number and the fact that we might still be waiting for
one. This way, we might fail to re-transmit frames on ACK timeouts.
We need, instead, to:
- indicate with the @retrans field only re-transmissions for the same
data sequences. If we make progress, it should be reset, given that
it's used to abort a connection when we exceed a given number of
re-transmissions for the same data
- unset the ACK_FROM_TAP_DUE flag if and only if the acknowledged
sequence is the same as the last one we sent, as suggested by David
- keep it set otherwise, if progress was done but not all the data we
sent was acknowledged, and update the expiration of the ACK timeout
Add a new helper for these purposes, tcp_update_seqack_from_tap().
To extend the ACK timeout, the new helper sets the ACK_FROM_TAP_DUE
flag, even if it was already set, and conn_flag_do() triggers a timer
update. This part should be revisited at a later time, because,
strictly speaking, ACK_FROM_TAP_DUE isn't a flag anymore. One
possibility might be to introduce another connection attribute for
events affecting timer deadlines.
Reported-by: David Gibson <david@gibson.dropbear.id.au>
Link: https://bugs.passt.top/show_bug.cgi?id=41
Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Fixes: be5bbb9b06 ("tcp: Rework timers to use timerfd instead of periodic bitmap scan")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Update the TCP code to use the tap layer abstractions for initializing and
updating the L2 and lower headers. This will make adding other tap
backends in future easier.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_l2_buf_fill_headers() returns the size of the generated frame including
the ethernet header. The caller then adds on the size of the vnet_len
field to get the total frame size to be passed to the tap device.
Outside the tap code, though, we never care about the ethernet header size
only the final total size we need to put into an iovec. So, consolidate
the total frame size calculation within tcp_l2_buf_fill_headers().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_sock[46]_iov_init() initialize the length of each iovec buffer to
MSS_DEFAULT. That will always be overwritten before use in
tcp_data_to_tap, so it's redundant. It also wasn't correct, because it
didn't correctly account for the header lengths in all cases.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We have separate IPv4 and IPv6 versions of a macro to construct an
initializer for ethernet headers. However, now that we have htons_constant
it's easy to simply paramterize this with the ethernet protocol number.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Both the TCP and UDP iov_init functions have some large structure literals
defined in "field order" style. These are pretty hard to read since it's
not obvious what value corresponds to what field. Use named field style
initializers instead to make this clearer.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The functions which do the final steps of sending TCP packets on through
the tap interface - tcp_l2_buf_flush*() - no longer have anything that's
actually specific to TCP in them, other than comments and names. Move them
all to tap.c.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_l2_buf_flush() open codes the loop across each frame in a group, but
but calls tcp_l2_buf_write_one() to send each frame to the pasta tuntap
device. Combine these two pasta-specific operations into
tcp_l2_buf_flush_pasta() which is a little cleaner and will enable further
cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently this takes a msghdr, but the only thing we actually care
about in there is the io vector. Make it take an io vector directly.
We also have a weird side effect of zeroing @buf_used. Just pass this
by value and zero it in the caller instead.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp[46]_l2_buf_bytes keep track of the total number of bytes we have
queued to send to the tap interface. tcp_l2_buf_flush_passt() uses this
to determine if sendmsg() has sent all the data we requested, or whether
we need to resend a trailing portion.
However, the logic for finding where we're up to in the case of a short
sendmsg() can equally well tell whether we've had one at all, without
knowing the total number in advance. This does require an extra loop after
each sendmsg(), but it's doing simple arithmetic on values we've already
been accessing, and it leads to overall simpler code.
tcp[46]_l2_flags_buf_bytes were being calculated, but never used for
anything, so simply remove them.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_l2_buf_flush() open codes the "primary" send of message to the passt
tap interface, but calls tcp_l2_buf_flush_part() to handle the case of a
short send. Combine these two passt-specific operations into
tcp_l2_buf_flush_passt() which is a little cleaner and will enable furrther
cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
pcapm() captures multiple frames from a msghdr, however the only thing it
cares about in the msghdr is the list of buffers, where it assumes there is
one frame to capture per buffer. That's what we want for its single caller
but it's not the only obvious choice here (one frame per msghdr would
arguably make more sense in isolation). In addition pcapm() has logic
that only makes sense in the context of the passt specific path its called
from: it skips the first 4 bytes of each buffer, because those have the
qemu vnet_len rather than the frame proper.
Make this clearer by replacing pcapm() with pcap_multiple() which more
explicitly takes one struct iovec per frame, and parameterizes how much of
each buffer to skip (i.e. the offset of the frame within the buffer).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reported by Coverity (CWE-606, Untrusted loop bound), and actually
harmless because we'll exit the option-scanning loop if the remaining
length is not enough for a new option, instead of reading past the
header.
In any case, it looks like a good idea to explicitly check for
reasonable values of option lengths.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
The pointers are actually the same, but we later pass the container
union to tcp_table_compact(), which might zero the size of the whole
union, and this confuses Coverity Scan.
Given that we have pointers to the container union to start with,
just pass those instead, all the way down to tcp_table_compact().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Platforms like Linux allow IPv6 sockets to listen for IPv4 connections as
well as native IPv6 connections. By doing this we halve the number of
listening sockets we need for TCP (assuming passt/pasta is listening on the
same ports for IPv4 and IPv6). When forwarding many ports (e.g. -t all)
this can significantly reduce the amount of kernel memory that passt
consumes.
When forwarding all TCP and UDP ports for both IPv4 and IPv6 (-t all
-u all), this reduces kernel memory usage from ~677MiB to ~487MiB
(kernel version 6.0.8 on Fedora 37, x86_64).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Previous cleanups mean that tcp_sock_init4() and tcp_sock_init6() are
almost identical, and the remaining differences can be easily
parameterized. Combine both into a single tcp_sock_init_af() function.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
passt usually doesn't NAT, but it does do so for the remapping of the
gateway address to refer to the host. Currently we perform this NAT with
slightly different rules on both IPv4 addresses and IPv6 addresses, but not
on IPv4-mapped IPv6 addresses. This means we won't correctly handle the
case of an IPv4 connection over an IPv6 socket, which is possible on Linux
(and probably other platforms).
Refactor tcp_conn_from_sock() to perform the NAT after converting either
address family into an inany_addr, so IPv4 and and IPv4-mapped addresses
have the same representation.
With two new helpers this lets us remove the IPv4 and IPv6 specific paths
from tcp_conn_from_sock().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This bit in the TCP specific epoll reference indicates whether the
connection is IPv6 or IPv4. However the sites which refer to it are
already calling accept() which (optionally) returns an address for the
remote end of the connection. We can use the sa_family field in that
address to determine the connection type independent of the epoll
reference.
This does have a cost: for the spliced case, it means we now need to get
that address from accept() which introduces an extran copy_to_user().
However, in future we want to allow handling IPv4 connectons through IPv6
sockets, which means we won't be able to determine the IP version at the
time we create the listening socket and epoll reference. So, at some point
we'll have to pay this cost anyway.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It looks like tcp_seq_init() is supposed to advance the sequence number
by one every 32ns. However we only right shift the ns part of the timespec
not the seconds part, meaning that we'll advance by an extra 32 steps on
each second.
I don't know if that's exploitable in any way, but it doesn't appear to be
the intent, nor what RFC 6528 suggests.
In addition, we convert from seconds to nanoseconds with a multiplication
by '1E9'. In C '1E9' is a floating point constant, forcing a conversion
to floating point and back for what should be an integer calculation
(confirmed with objdump and Makefile default compiler flags). Spell out
1000000000 in full to avoid that.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_seq_init() takes a number of parameters for the connection, but at
every call site, these are already populated in the tcp_conn structure.
Likewise we always store the result into the @seq_to_tap field.
Use this to simplify tcp_seq_init().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_seq_init() has separate paths for IPv4 and IPv6 addresses, which means
we will calculate different sequence numbers for IPv4 and equivalent
IPv4-mapped IPv6 addresses.
Change it to treat these the same by always converting the input address
into an inany_addr representation and use that to calculate the sequence
number.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_hash_match() can take either an IPv4 (struct in_addr) or IPv6 (struct
in6_addr) address. It has two different paths for each of those cases.
However, its only caller has already constructed an equivalent inany
representation of the address, so we can have tcp_hash_match take that
directly and use a simpler comparison with the inany_equals() helper.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_hash_insert() takes an address to control which hash bucket the
connection will go into. However, an inany_addr representation of that
address is already stored in struct tcp_conn.
Now that we've made the hashing of IPv4 and IPv4-mapped IPv6 addresses
equivalent, we can simplify tcp_hash_insert() to use the address in
struct tcp_conn, rather than taking it as an extra parameter.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In the tcp_conn structure, we represent the address with an inany_addr
which could be an IPv4 or IPv6 address. However, we have different paths
which will calculate different hashes for IPv4 and equivalent IPv4-mapped
IPv6 addresses. This will cause problems for some future changes.
Make the hash function work the same for these two cases, by taking an
inany_addr directly. Since this represents IPv4 and IPv4-mapped IPv6
addresses the same way, it will trivially hash the same for both cases.
Callers are changed to construct an inany_addr from whatever they have.
Some of that will be elided in later changes.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
struct tcp_conn stores an address which could be IPv6 or IPv4 using a
union. We can do this without an additional tag by encoding IPv4 addresses
as IPv4-mapped IPv6 addresses.
This approach is useful wider than the specific place in tcp_conn, so
expose a new 'union inany_addr' like this from a new inany.h. Along with
that create a number of helper functions to make working with these "inany"
addresses easier.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently when we insert a connection into the hash table, we store its
bucket number so we can find it when removing entries. However, we can
recompute the hash value from other contents of the structure so we don't
need to store it. This brings the size of tcp_tap_conn down to 64 bytes
again, which means it will fit in a single cacheline on common machines.
This change also removes a non-obvious constraint that the hash table have
less than twice TCP_MAX_CONNS buckets, because of the way
TCP_HASH_BUCKET_BITS was constructed.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently the epoll reference for tcp sockets includes a bit indicating
whether the socket maps to a spliced connection. However, the reference
also has the index of the connection structure which also indicates whether
it is spliced. We can therefore avoid the splice bit in the epoll_ref by
unifying the first part of the non-spliced and spliced handlers where we
look up the connection state.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In pasta mode, tcp_sock_init[46]() create separate sockets to listen for
spliced connections (these are bound to localhost) and non-spliced
connections (these are bound to the host address). This introduces a
subtle behavioural difference between pasta and passt: by default, pasta
will listen only on a single host address, whereas passt will listen on
all addresses (0.0.0.0 or ::). This also prevents us using some additional
optimizations that only work with the unspecified (0.0.0.0 or ::) address.
However, it turns out we don't need to do this. We can splice a connection
if and only if it originates from the loopback address. Currently we
ensure this by having the "spliced" listening sockets listening only on
loopback. Instead, defer the decision about whether to splice a connection
until after accept(), by checking if the connection was made from the
loopback address.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In tcp_sock_handler() we split off to handle spliced sockets before
checking anything else. However the first steps of the "new connection"
path for each case are the same: allocate a connection entry and accept()
the connection.
Remove this duplication by making tcp_conn_from_sock() handle both spliced
and non-spliced cases, with help from more specific tcp_tap_conn_from_sock
and tcp_splice_conn_from_sock functions for the later stages which differ.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcp_sock_init*() can create either sockets listening on the host, or in
the pasta network namespace (with @ns==1). There are, however, a number
of differences in how these two cases work in practice though. "ns"
sockets are only used in pasta mode, and they always lead to spliced
connections only. The functions are also only ever called in "ns" mode
with a NULL address and interface name, and it doesn't really make sense
for them to be called any other way.
Later changes will introduce further differences in behaviour between these
two cases, so it makes more sense to use separate functions for creating
the ns listening sockets than the regular external/host listening sockets.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There is very little common between the tcp_tap_conn and tcp_splice_conn
structures. However, both do have an IN_EPOLL flag which has the same
meaning in each case, though it's stored in a different location.
Simplify things slightly by moving this bit into the common header of the
two structures.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
These two functions scan all the non-splced and spliced connections
respectively and perform timed updates on them. Avoid scanning the now
unified table twice, by having tcp_timer scan it once calling the
relevant per-connection function for each one.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
These two functions each step through non-spliced and spliced connections
respectively and clean up entries for closed connections. To avoid
scanning the connection table twice, we merge these into a single function
which scans the unified table and performs the appropriate sort of cleanup
action on each one.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently spliced and non-spliced connections are stored in completely
separate tables, so there are completely independent limits on the number
of spliced and non-spliced connections. This is a bit counter-intuitive.
More importantly, the fact that the tables are separate prevents us from
unifying some other logic between the two cases. So, merge these two
tables into one, using the 'c.spliced' common field to distinguish between
them when necessary.
For now we keep a common limit of 128k connections, whether they're spliced
or non-spliced, which means we save memory overall. If necessary we could
increase this to a 256k or higher total, which would cost memory but give
some more flexibility.
For now, the code paths which need to step through all extant connections
are still separate for the two cases, just skipping over entries which
aren't for them. We'll improve that in later patches.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When we compact the connection tables (both spliced and non-spliced) we
need to move entries from one slot to another. That requires some updates
in the entries themselves. Add helpers to make all the necessary updates
for the spliced and non-spliced cases. This will simplify later cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently, the tables for spliced and non-spliced connections are entirely
separate, with different types in different arrays. We want to unify them.
As a first step, create a union type which can represent either a spliced
or non-spliced connection. For them to be distinguishable, the individual
types need to have a common header added, with a bit indicating which type
this structure is.
This comes at the cost of increasing the size of tcp_tap_conn to over one
(64 byte) cacheline. This isn't ideal, but it makes things simpler for now
and we'll re-optimize this later.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently spliced and non-spliced connections use completely independent
tracking structures. We want to unify these, so as a preliminary step move
the definitions for both variants into a new tcp_conn.h header, shared by
tcp.c and tcp_splice.c.
This requires renaming some #defines with the same name but different
meanings between the two cases. In the process we correct some places that
are slightly out of sync between the comments and the code for various
event bit names.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The macro CONN_OR_NULL() is used to look up connections by index with
bounds checking. Replace it with an inline function, which means:
- Better type checking
- No danger of multiple evaluation of an @index with side effects
Also add a helper to perform the reverse translation: from connection
pointer to index. Introduce a macro for this which will make later
cleanups easier and safer.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we disable a given IP version automatically (no corresponding
default route on host) or administratively (--ipv4-only or
--ipv6-only options), we don't initialise related buffers and
services (DHCP for IPv4, NDP and DHCPv6 for IPv6). The "tap"
handlers will also ignore packets with a disabled IP version.
However, in commit 3c6ae62510 ("conf, tcp, udp: Allow address
specification for forwarded ports") I happily changed socket
initialisation functions to take AF_UNSPEC meaning "any enabled
IP version", but I forgot to add checks back for the "enabled"
part.
Reported by Paul: on a host without default IPv6 route, but IPv6
enabled, connect, using IPv6, to a port handled by pasta, which
tries to send data to a tap device without initialised buffers
for that IP version and exits because the resulting write() fails.
Simpler way to reproduce: pasta -6 and inbound IPv4 connection, or
pasta -4 and inbound IPv6 connection.
Reported-by: Paul Holzinger <pholzing@redhat.com>
Fixes: 3c6ae62510 ("conf, tcp, udp: Allow address specification for forwarded ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
A number of functions describe themselves as taking a pointer to 'sin_addr
or sin6_addr'. Those are field names, not type names. Replace them with
the correct type names, in_addr or in6_addr.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We recently corrected some errors handling the endianness of IPv4
addresses. These are very easy errors to make since although we mostly
store them in network endianness, we sometimes need to manipulate them in
host endianness.
To reduce the chances of making such mistakes again, change to always using
a (struct in_addr) instead of a bare in_addr_t or uint32_t to store network
endian addresses. This makes it harder to accidentally do arithmetic or
comparisons on such addresses as if they were host endian.
We introduce a number of IN4_IS_ADDR_*() helpers to make it easier to
directly work with struct in_addr values. This has the additional benefit
of making the IPv4 and IPv6 paths more visually similar.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If the user specifies an explicit loopback address for a port
binding, we're going to use that address for the 'tap' socket, and
the same exact address for the 'spliced' socket (because those are,
by definition, only bound to loopback addresses).
This means that the second binding will fail, and, unexpectedly, the
port is forwarded, but via tap device, which means the source address
in the namespace won't be a loopback address.
Make it explicit under which conditions we're creating which kind of
socket, by refactoring tcp_sock_init() into two separate functions
for IPv4 and IPv6 and gathering those conditions at the beginning.
Also, don't create spliced sockets if the user specifies explicitly
a non-loopback address, those are harmless but not desired either.
Fixes: 3c6ae62510 ("conf, tcp, udp: Allow address specification for forwarded ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In pasta mode, when we receive a new inbound connection, we need to
select a socket that was created in the namespace to proceed and
connect() it to its final destination.
The existing condition might pick a wrong socket, though, if the
destination port is remapped, because we'll check the bitmap of
inbound ports using the remapped port (stored in the epoll reference)
as index, and not the original port.
Instead of using the port bitmap for this purpose, store this
information in the epoll reference itself, by adding a new 'outbound'
bit, that's set if the listening socket was created the namespace,
and unset otherwise.
Then, use this bit to pick a socket on the right side.
Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Fixes: 33482d5bf2 ("passt: Add PASTA mode, major rework")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
For tcp_sock_init_ns(), "inbound" connections used to be the ones
being established toward any listening socket we create, as opposed
to sockets we connect().
Similarly, tcp_splice_new() used to handle "inbound" connections in
the sense that they originated from listening sockets, and they would
in turn cause a connect() on an "outbound" socket.
Since commit 1128fa03fe ("Improve types and names for port
forwarding configuration"), though, inbound connections are more
broadly defined as the ones directed to guest or namepsace, and
outbound the ones originating from there.
Update comments for those two functions.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Since kernel version 5.7, commit c427bfec18f2 ("net: core: enable
SO_BINDTODEVICE for non-root users"), we can bind sockets to
interfaces, if they haven't been bound yet (as in bind()).
Introduce an optional interface specification for forwarded ports,
prefixed by %, that can be passed together with an address.
Reported use case: running local services that use ports we want
to have externally forwarded:
https://github.com/containers/podman/issues/14425
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Logging to file is going to add some further complexity that we don't
want to squeeze into util.c.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Recent versions of cppcheck give a warning due to the NULL buffer passed
to recv() in tcp_sock_consume(). Since this apparently works, I assume
it's actually valid, but cppcheck doesn't know that recv() can take a NULL
buffer. So, use a suppression to get rid of the error.
Also add an unmatchedSuppression suppression since only some cppcheck
versions complain about this.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Some versions of cppcheck could errneously report a NULL pointer deference
inside a sizeof(). This is now fixed in cppcheck upstream[0]. For systems
using an affected version, add a suppression to work around the bug. Also
add an unmatchedSuppression suppression so the suppression itself doesn't
cause a warning if you *do* have a fixed cppcheck.
[0] https://github.com/danmar/cppcheck/pull/4471
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Port numbers (for both TCP and UDP) are 16-bit, and so fit exactly into a
'short'. USHRT_MAX is therefore the maximum port number and this is widely
used in the code. Unfortunately, a lot of those places don't actually
want the maximum port number (USHRT_MAX == 65535), they want the total
number of ports (65536). This leads to a number of potentially nasty
consequences:
* We have buffer overruns on the port_fwd::delta array if we try to use
port 65535
* We have similar potential overruns for the tcp_sock_* arrays
* Interestingly udp_act had the correct size, but we can calculate it in
a more direct manner
* We have a logical overrun of the ports bitmap as well, although it will
just use an unused bit in the last byte so isnt harmful
* Many loops don't consider port 65535 (which does mitigate some but not
all of the buffer overruns above)
* In udp_invert_portmap() we incorrectly compute the reverse port
translation for return packets
Correct all these by using a new NUM_PORTS defined explicitly for this
purpose.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Port numbers are unsigned values, but we're storing them in (signed) int
variables in some places. This isn't actually harmful, because int is
large enough to hold the entire range of ports. However in places we don't
want to use an in_port_t (usually to avoid overflow on the last iteration
of a loop) it makes more conceptual sense to use an unsigned int. This will
also avoid some problems with later cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Now that we've delayed initialization of the UDP specific "reverse" map
until udp_init(), the only difference between the various 'remap' functions
used in conf_ports() is which array they target. So, simplify by open
coding the logic into conf_ports() with a pointer to the correct mapping
array.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The configuration for how to forward ports in and out of the guest/ns is
divided between several different variables. For each connect direction
and protocol we have a mode in the udp/tcp context structure, a bitmap
of which ports to forward also in the context structure and an array of
deltas to apply if the outward facing and inward facing port numbers are
different. This last is a separate global variable, rather than being in
the context structure, for no particular reason. UDP also requires an
additional array which has the reverse mapping used for return packets.
Consolidate these into a re-used substructure in the context structure.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
enum conf_port_type is local to conf.c and is used to track the port
forwarding mode during configuration. We don't keep it around in the
context structure, however the 'init_detect_ports' and 'ns_detect_ports'
fields in the context are based solely on this. Rather than changing
encoding, just include the forwarding mode into the context structure.
Move the type definition to a new port_fwd.h, which is kind of trivial at
the moment but will have more stuff later.
While we're there, "conf_port_type" doesn't really convey that this enum is
describing how port forwarding is configured. Rename it to port_fwd_mode.
The variables (now fields) of this type also have mildly confusing names
since it's not immediately obvious whether 'ns' and 'init' refer to the
source or destination of the packets. Use "in" (host to guest / init to
ns) and "out" (guest to host / ns to init) instead.
This has the added bonus that we no longer have locals 'udp_init' and
'tcp_init' which shadow global functions.
In addition, add a typedef 'port_fwd_map' for a bitmap of each port number,
which is used in several places.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The context structure contains a batch of fields specific to IPv4 and to
IPv6 connectivity. Split those out into a sub-structure.
This allows the conf_ip4() and conf_ip6() functions, which take the
entire context but touch very little of it, to be given more specific
parameters, making it clearer what it affects without stepping through the
code.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
After recent changes, conf_ip() now has essentially entirely disjoint paths
for IPv4 and IPv6 configuration. So, it's cleaner to split them out into
different functions conf_ip4() and conf_ip6().
Splitting these out also lets us make the interface a bit nicer, having
them return success or failure directly, rather than manipulating c->v4
and c->v6 to indicate success/failure of the two versions.
Since these functions may also initialize the interface index for each
protocol, it turns out we can then drop c->v4 and c->v6 entirely, replacing
tests on those with tests on whether c->ifi4 or c->ifi6 is non-zero (since
a 0 interface index is never valid).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Whitespace fixes]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It's quite plausible for a host to have both IPv4 and IPv6 connectivity,
but only via different interfaces. For example, this will happen in the
case that IPv6 connectivity is via a tunnel (e.g. 6in4 or 6rd). It would
also happen in the case that IPv4 access is via a tunnel on an otherwise
IPv6 only local network, which is a setup that might become more common in
the post IPv4 address exhaustion world.
In turns out there's no real need for passt/pasta to get its IPv4 and IPv6
connectivity via the same interface, so we can handle this situation fairly
easily. Change the core to allow eparate external interfaces for IPv4 and
IPv6. We don't actually set these separately for now.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
If the first packet_get() call doesn't assign len, the second one
will also return NULL, but gcc doesn't see this.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
gcc 12.1.x (e.g. current OpenSUSE Tumbleweed, x86_64 only,
gcc-12-1.4.x86_64) reports:
tcp.c: In function ‘tcp_send_flag’:
tcp.c:1014:9: warning: writing 16 bytes into a region of size 0 [-Wstringop-overflow=]
1014 | memcpy(low_rtt_dst + hole++, &conn->a.a6, sizeof(conn->a.a6));
| ^
tcp.c:559:24: note: at offset -16 into destination object ‘low_rtt_dst’ of size 128
559 | static struct in6_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
|
but 'hole' can't be -1, because the low_rtt_dst table is guaranteed
to have a hole: if we happened to write to the last entry, we'll go
back to index 0 and clear that one.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This feature is available in slirp4netns but was missing in passt and
pasta.
Given that we don't do dynamic memory allocation, we need to bind
sockets while parsing port configuration. This means we need to
process all other options first, as they might affect addressing and
IP version support. It also implies a minor rework of how TCP and UDP
implementations bind sockets.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reported by Coverity: it doesn't see that tcp{4,6}_l2_buf_used are
set to zero by tcp_l2_data_buf_flush(), repeat that explicitly here.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
All instances were harmless, but it might be useful to have some
debug messages here and there. Reported by Coverity.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Field doff in struct tcp_hdr is 4 bits wide, so optlen in
tcp_tap_handler() is already bound, but make that explicit.
Reported by Coverity.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The existing sizes provide no measurable differences in throughput
and packet rates at this point. They were probably needed as batched
implementations were not complete, but they can be decreased quite a
bit now.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...we don't really need two extra bits, but it's easier to organise
things differently than to silence this.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Implement a packet abstraction providing boundary and size checks
based on packet descriptors: packets stored in a buffer can be queued
into a pool (without storage of its own), and data can be retrieved
referring to an index in the pool, specifying offset and length.
Checks ensure data is not read outside the boundaries of buffer and
descriptors, and that packets added to a pool are within the buffer
range with valid offset and indices.
This implies a wider rework: usage of the "queueing" part of the
abstraction mostly affects tap_handler_{passt,pasta}() functions and
their callees, while the "fetching" part affects all the guest or tap
facing implementations: TCP, UDP, ICMP, ARP, NDP, DHCP and DHCPv6
handlers.
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...by:
- storing the chained-hash next connection pointer as numeric
reference rather than as pointer
- storing the MSS as 14-bit value, and rounding it
- using only the effective amount of bits needed to store the hash
bucket number
- explicitly limiting window scaling factors to 4-bit values
(maximum factor is 14, from RFC 7323)
- scaling SO_SNDBUF values, and using a 8-bit representation for
the duplicate ACK sequence
- keeping window values unscaled, as received and sent
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We can't take for granted that the hard limit for open files is
big enough as to allow to delay closing sockets to a timer.
Store the value of RTLIMIT_NOFILE we set at start, and use it to
understand if we're approaching the limit with pending, spliced
TCP connections. If that's the case, close sockets right away as
soon as they're not needed, instead of deferring this task to a
timer.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
With a lot of concurrent connections, the bitmap scan approach is
not really sustainable.
Switch to per-connection timerfd timers, set based on events and on
two new flags, ACK_FROM_TAP_DUE and ACK_TO_TAP_DUE. Timers are added
to the common epoll list, and implement the existing timeouts.
While at it, drop the CONN_ prefix from flag names, otherwise they
get quite long, and fix the logic to decide if a connection has a
local, possibly unreachable endpoint: we shouldn't go through the
rest of tcp_conn_from_tap() if we reset the connection due to a
successful bind(2), and we'll get EACCES if the port number is low.
Suggested by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This should never happen, but there are no formal guarantees: ensure
socket numbers are below SOCKET_MAX.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Using events and flags instead of states makes the implementation
much more straightforward: actions are mostly centered on events
that occurred on the connection rather than states.
An example is given by the ESTABLISHED_SOCK_FIN_SENT and
FIN_WAIT_1_SOCK_FIN abominations: we don't actually care about
which side started closing the connection to handle closing of
connection halves.
Split out the spliced implementation, as it has very little in
common with the "regular" TCP path.
Refactor things here and there to improve clarity. Add helpers
to trace where resets and flag settings come from.
No functional changes intended.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In pasta mode, when we get data from sockets and write it as single
frames to the tap device, we batch receive operations considerably,
and then (conceptually) split the data in many smaller writes.
It looked like an obvious choice, but performance is actually better
if we receive data in many small frame-sized recvmsg()/recvmmsg().
The syscall overhead with the previous behaviour, observed by perf,
comes predominantly from write operations, but receiving data in
shorter chunks probably improves cache locality by a considerable
amount.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
To reach (at least) a conceptually equivalent security level as
implemented by --enable-sandbox in slirp4netns, we need to create a
new mount namespace and pivot_root() into a new (empty) mountpoint, so
that passt and pasta can't access any filesystem resource after
initialisation.
While at it, also detach IPC, PID (only for passt, to prevent
vulnerabilities based on the knowledge of a target PID), and UTS
namespaces.
With this approach, if we apply the seccomp filters right after the
configuration step, the number of allowed syscalls grows further. To
prevent this, defer the application of seccomp policies after the
initialisation phase, before the main loop, that's where we expect bad
things to happen, potentially. This way, we get back to 22 allowed
syscalls for passt and 34 for pasta, on x86_64.
While at it, move #syscalls notes to specific code paths wherever it
conceptually makes sense.
We have to open all the file handles we'll ever need before
sandboxing:
- the packet capture file can only be opened once, drop instance
numbers from the default path and use the (pre-sandbox) PID instead
- /proc/net/tcp{,v6} and /proc/net/udp{,v6}, for automatic detection
of bound ports in pasta mode, are now opened only once, before
sandboxing, and their handles are stored in the execution context
- the UNIX domain socket for passt is also bound only once, before
sandboxing: to reject clients after the first one, instead of
closing the listening socket, keep it open, accept and immediately
discard new connection if we already have a valid one
Clarify the (unchanged) behaviour for --netns-only in the man page.
To actually make passt and pasta processes run in a separate PID
namespace, we need to unshare(CLONE_NEWPID) before forking to
background (if configured to do so). Introduce a small daemon()
implementation, __daemon(), that additionally saves the PID file
before forking. While running in foreground, the process itself can't
move to a new PID namespace (a process can't change the notion of its
own PID): mention that in the man page.
For some reason, fork() in a detached PID namespace causes SIGTERM
and SIGQUIT to be ignored, even if the handler is still reported as
SIG_DFL: add a signal handler that just exits.
We can now drop most of the pasta_child_handler() implementation,
that took care of terminating all processes running in the same
namespace, if pasta started a shell: the shell itself is now the
init process in that namespace, and all children will terminate
once the init process exits.
Issuing 'echo $$' in a detached PID namespace won't return the
actual namespace PID as seen from the init namespace: adapt
demo and test setup scripts to reflect that.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
clang-tidy from LLVM 13.0.1 reports some new warnings from these
checkers:
- altera-unroll-loops, altera-id-dependent-backward-branch: ignore
for the moment being, add a TODO item
- bugprone-easily-swappable-parameters: ignore, nothing to do about
those
- readability-function-cognitive-complexity: ignore for the moment
being, add a TODO item
- altera-struct-pack-align: ignore, alignment is forced in protocol
headers
- concurrency-mt-unsafe: ignore for the moment being, add a TODO
item
Fix bugprone-implicit-widening-of-multiplication-result warnings,
though, that's doable and they seem to make sense.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The existing behaviour is not really practical: an automated agent in
charge of starting both qemu and passt would need to fork itself to
start passt, because passt won't fork to background until qemu
connects, and the agent needs to unblock to start qemu.
Instead of waiting for a connection to daemonise, do it right away as
soon as a socket is available: that can be considered an initialised
state already.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Depending on the C library, but not necessarily in all the
functions we use, statx() might be used instead of stat(),
getdents() instead of getdents64(), readlinkat() instead of
readlink(), openat() instead of open().
On aarch64, it's clone() and not fork(), and dup3() instead of
dup2() -- just allow the existing alternative instead of dealing
with per-arch selections.
Since glibc commit 9a7565403758 ("posix: Consolidate fork
implementation"), we need to allow set_robust_list() for
fork()/clone(), even in a single-threaded context.
On some architectures, epoll_pwait() is provided instead of
epoll_wait(), but never both. Same with newfstat() and
fstat(), sigreturn() and rt_sigreturn(), getdents64() and
getdents(), readlink() and readlinkat(), unlink() and
unlinkat(), whereas pipe() might not be available, but
pipe2() always is, exclusively or not.
Seen on Fedora 34: newfstatat() is used on top of fstat().
syslog() is an actual system call on some glibc/arch combinations,
instead of a connect()/send() implementation.
On ppc64 and ppc64le, _llseek(), recv(), send() and getuid()
are used. For ppc64 only: ugetrlimit() for the getrlimit()
implementation, plus sigreturn() and fcntl64().
On s390x, additionally, we need to allow socketcall() (on top
of socket()), and sigreturn() also for passt (not just for
pasta).
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Bitmap manipulating functions would otherwise refer to inconsistent
sets of bits on big-endian architectures. While at it, fix up a
couple of casts.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tcpi_bytes_acked and tcpi_min_rtt are only available on recent
kernel versions: provide fall-back paths (incurring some grade of
performance penalty).
Support for getrandom() was introduced in Linux 3.17 and glibc 2.25:
provide an alternate mechanism for that as well, reading from
/dev/random.
Also check if NETLINK_GET_STRICT_CHK is defined before using it:
it's not strictly needed, we'll filter out irrelevant results from
netlink anyway.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is the only remaining Linux-specific include -- drop it to avoid
clang-tidy warnings and to make code more portable.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This was actually fine "on the wire", but it's inconsistent with the
way we hash other addresses/protocols and also ends up with a wrong
endianness in captures in case we replace the address with our
default gateway.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...mostly false positives, but a number of very relevant ones too,
in tcp_get_sndbuf(), tcp_conn_from_tap(), and siphash PREAMBLE().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Unions and structs, you all have names now.
Take the chance to enable bugprone-reserved-identifier,
cert-dcl37-c, and cert-dcl51-cpp checkers in clang-tidy.
Provide a ffsl() weak declaration using gcc built-in.
Start reordering includes, but that's not enough for the
llvm-include-order checker yet.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Detect missing tcpi_snd_wnd in struct tcp_info at build time,
otherwise build fails with a pre-5.3 linux/tcp.h header.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This shouldn't happen on any sane configuration, but I just met an
example of that: the default IPv6 gateway on the host is configured
with a global unicast address, we use that as source for RA, DHCPv6
replies, and the guest ignores it. Same later on if we talk TCP or
UDP and the guest has no idea where that address comes from.
Use our link-local address in case the gateway address is global.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
A mix of unchecked return values, a missing permission mask for
open(2) with O_CREAT, and some false positives from
-Wstringop-overflow and -Wmaybe-uninitialized.
Reported-by: Martin Hauke <mardnh@gmx.de>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
For some reason, on 4.19, splice() doesn't honour SOCK_NONBLOCK from
accept4() while reading from a TCP socket. Pass SPLICE_F_NONBLOCK
explicitly in all cases.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If the window isn't updated on !c->tcp.kernel_snd_wnd, we still
have to send ACKs if the ACK sequence was updated, or if an error
occurred while querying TCP_INFO.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...and while at it, reverse the operands in the window equality
comparison to detect the need for fast re-transmit: it's easier
to read this way.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
I thought I'd get away with it, but no, after some clean-ups, I
finally got a socket with number 0. Fix up all the convenient,
yet botched assumptions.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Caching iov_len for messages from socket doesn't actually decrease
overhead by the tiniest bit, and added a lot of complexity. Drop
that.
Also drop the sendmmsg(), we don't need to send multiple messages
with TCP, as long as we make sure no messages with a length
descriptor are sent partially, qemu is fine with it.
Just like it's done for segments without data (flags), also defer
the sendmsg() for sending data segments, to improve batching.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Otherwise, tcp4_l2_flags_buf_t is not consistent with tcp4_l2_buf_t and
header fields get all mixed up in tcp_l2_buf_fill_headers().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
List of allowed syscalls comes from comments in the form:
#syscalls <list>
for syscalls needed both in passt and pasta mode, and:
#syscalls:pasta <list>
#syscalls:passt <list>
for syscalls specifically needed in pasta or passt mode only.
seccomp.sh builds a list of BPF statements from those comments,
prefixed by a binary search tree to keep lookup fast.
While at it, clean up a bit the Makefile using wildcards.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Move netlink routines to their own file, and use netlink to configure
or fetch all the information we need, except for the TUNSETIFF ioctl.
Move pasta-specific functions to their own file as well, add
parameters and calls to configure the tap interface in the namespace.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Based on a patch from Giuseppe Scrivano, this adds the ability to:
- specify paths and names of target namespaces to join, instead of
a PID, also for user namespaces, with --userns
- request to join or create a network namespace only, without
entering or creating a user namespace, with --netns-only
- specify the base directory for netns mountpoints, with --nsrun-dir
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
[sbrivio: reworked logic to actually join the given namespaces when
they're not created, implemented --netns-only and --nsrun-dir,
updated pasta demo script and man page]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
That's the first thing we have to do, before sending SYN, ACK:
if tcp_send_to_tap() fails, we'll get a lot of useless events
otherwise.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Now that we have a proper function checking when and how to send
ACKs and window updates, we don't need to duplicate this logic in
tcp_data_from_tap().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...using pre-cooked buffers, just like we do with other segments.
While at it, remove some code duplication by having separate
functions for updating ACK sequence and window, and for filling in
buffer headers.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Now that we fixed the issue with small receiving buffers, we can
safely increase this back and get slightly lower syscall overhead.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If net.core.rmem_max and net.core.wmem_max sysctls have low values,
we can get bigger buffers by not trying to set them high -- the
kernel would lock their values to what we get.
Try, instead, to get bigger buffers by queueing as much as possible,
and if maximum values in tcp_wmem and tcp_rmem are bigger than this,
that will work.
While at it, drop QUICKACK option for non-spliced sockets, I set
that earlier by mistake.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If the connection is local or the RTT was comparable to the time it
takes to queue a batch of messages, we can safely use a large MSS
regardless of the sending buffer, but otherwise not.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we start with a very small sending buffer, we can make the kernel
expand it if we cause the congestion window to get bigger, but this
won't reliably happen if we use just half (other half is accounted
as overhead).
Scale usage depending on its own size, we might eventually get some
retransmissions because we can't queue messages the sender sends us
in-window, but it's better than keeping that small buffer forever.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...and from the sending socket only if the MTU is not configured.
Otherwise, a connection to a host from a local guest, with a
non-loopback destination address, will get its MSS from the MTU of the
outbound interface with that address, which is unnecessary as we know
the guest can send us larger segments.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Detecting bound ports at start-up time isn't terribly useful: do this
periodically instead, if configured.
This is only implemented for TCP at the moment, UDP is somewhat more
complicated: leave a TODO there.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This introduces a number of fundamental changes that would be quite
messy to split. Summary:
- advertised window scaling can be as big as we want, we just need
to clamp window sizes to avoid exceeding the size of our "discard"
buffer for unacknowledged data from socket
- add macros to compare sequence numbers
- force sending ACK to guest/tap on PSH segments, always in pasta
mode, whenever we see an overlapping segment, or when we reach a
given threshold compared to our window
- we don't actually use recvmmsg() here, fix comments and label
- introduce pools for pre-opened sockets and pipes, to decrease
latency on new connections
- set receiving and sending buffer sizes to the maximum allowed,
kernel will clamp and round appropriately
- defer clean-up of spliced and non-spliced connection to timer
- in tcp_send_to_tap(), there's no need anymore to keep a large
buffer, shrink it down to what we actually need
- introduce SO_RCVLOWAT setting and activity tracking for spliced
connections, to coalesce data moved by splice() calls as much as
possible
- as we now have a compacted connection table, there's no need to
keep sparse bitmaps tracking connection activity -- simply go
through active connections with a loop in the timer handler
- always clamp the advertised window to half our sending buffer,
too, to minimise retransmissions from the guest/tap
- set TCP_QUICKACK for originating socket in spliced connections,
there's no need to delay them
- fix up timeout for unacknowledged data from socket
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Until now, messages would be passed to protocol handlers in a single
batch only if they happened to be dequeued in a row. Packets
interleaved between different connections would result in multiple
calls to the same protocol handler for a single connection.
Instead, keep track of incoming packet descriptors, arrange them in
sequences, and call protocol handlers only as we completely sorted
input messages in batches.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
That might just mean we shut down the socket -- but we still have to
go through the other states to ensure a orderly shutdown guest-side.
While at it, drop the EPOLLHUP check for unhandled states: we should
never hit that, but if we do, resetting the connection at that point
is probably the wrong thing to do.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Now that we dropped EPOLLET, we'll keep getting EPOLLRDHUP, and
possibly EPOLLIN, even if there's nothing to read anymore.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
EPOLLHUP just means we shut down one side of the connection on
*one* socket: remember, we have two sockets here.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...throughput isn't everything: this leads (of course) to horrible
latency with small, sparse messages. As a consequence, there's no
need to set TCP_NODELAY either.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we're at the first message in a batch, it's safe to get the
window value from it, and there's no need to subtract anything for
a comparison on that's not even done -- we'll override it later in
any case if we find messages with a higher ACK sequence number.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...tcp_handler_splice() doesn't guarantee we read all the available
data, the sending buffer might be full.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Checking it only when the cached value is smaller than the current
window of the receiver is not enough: it might shrink further while
the receiver window is growing.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we couldn't write the whole batch of received packets to the socket,
and we have missing segments, we still need to request their
retransmission right away, otherwise it will take ages for the guest to
figure out we're missing them.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...instead of waiting for the remote peer to do that -- it's
especially important in case we request retransmissions from the
guest, but it also helps speeding up slow start. This should
probably be a configurable behaviour in the future.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Seen with iperf3: a control connection is established, no data flows
for a while, all segments are acknowledged. The socket starts closing
it, and we immediately time out because the last ACK from tap was one
minute before that.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Seen with iperf3: the first packet from socket (data connection) is
65520 bytes and doesn't fit in the window.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This fixes a number of issues found with some heavier testing with
uperf and neper:
- in most closing states, we can still accept data, check for EPOLLIN
when appropriate
- introduce a new state, ESTABLISHED_SOCK_FIN_SENT, to track the fact
we already sent a FIN segment to the tap device, for proper sequence
number bookkeeping
- for pasta mode only: spliced connections also need tracking of
(inferred) FIN segments and clean half-pipe shutdowns
- streamline resetting epoll_wait bitmaps with a new function,
tcp_tap_epoll_mask(), instead of repeating the logic all over the
place
- set EPOLLET for tap connections too, whenever we are waiting for
EPOLLRDHUP or an event from the tap to proceed with data transfer,
to avoid useless loops with EPOLLIN set
- impose an additional limit on the sending window advertised to the
guest, given by SO_SNDBUF: it makes no sense to completely fill
the sending buffer and send a zero window: stop a bit before we
hit that
- handle *all* interrupted system calls as needed
- simplify the logic for reordering of out-of-order segments received
from tap: it's not a corner case, and the previous logic allowed
for deadloops
- fix comparison of seen IPv4 address when we get a new connection
from a socket directed to the configured guest address
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
