Avoid a bunch of syscalls on forwarding paths by:
- storing minimum and maximum file descriptor numbers for each
protocol, fall back to SO_PROTOCOL query only on overlaps
- allocating a larger receive buffer -- this can result in more
coalesced packets than sendmmsg() can take (UIO_MAXIOV, i.e. 1024),
so make sure we don't exceed that within a single call to protocol
tap handlers
- nesting the handling loop in tap_handler() in the receive loop,
so that we have better chances of filling our receive buffer in
fewer calls
- skipping the recvfrom() in the UDP handler on EPOLLERR -- there's
nothing to be done in that case
and while at it:
- restore the 20ms timer interval for periodic (TCP) events, I
accidentally changed that to 100ms in an earlier commit
- attempt using SO_ZEROCOPY for UDP -- if it's not available,
sendmmsg() will succeed anyway
- fix the handling of the status code from sendmmsg(), if it fails,
we'll try to discard the first message, hence return 1 from the
UDP handler
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Otherwise, buffers for UNIX domain sockets are limited to about
200KB. This makes performance testing a bit more consistent.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It looks like some versions of ISC's IPv6 dhclient not only discard
the DNS Recursive Name Server option if other options (Domain Search
List? FQDN?) are absent, but they also drop existing entries
configured via SLAAC from /etc/resolv.conf.
Don't pass option 23 until I figure this out, it's anyway redundant
as we pass DNS information via SLAAC (RFC 8106).
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is symmetric with tap operation and addressing model, and
allows again to reach the guest behind the tap interface by
contacting the local address.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Receive packets in batches from AF_UNIX, check if they can be sent
with a single syscall, and batch them up with sendmmsg() in case.
A bit rudimentary, currently only implemented for UDP, but it seems
to work.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
dhcpv6_opt() needs to subtract option length _before_ returning,
so that callers can conveniently pass the remaining length on
subsequent calls.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The NotOnLink status code needs to be appended to the existing IA
content, because if we omit the requested addresses in the reply,
ISC's dhclient handles it as a NoAddrsAvail response.
Also fix length accounting (we would send a bunch of zeroes after
the IA otherwise), and print an informational message with the
requested address, if it's not appropriate for the link.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This implementation, similarly to the IPv4 DHCP one, hands out a
single address, which is the same as the upstream address for the
host.
This avoids the need for address translation as long as the client
runs a DHCPv6 client. The NDP "Managed" flag is now set in Router
Advertisements.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
For simplicity, we just send all available options, so there's no
distinction between forced and requested option anymore.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...and mention it in the README.
While at it, remove useless escaping in the README, and fix
indentation in the syslog message with the qemu command line
example.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...otherwise, both IPv4 and IPv6 are considered disabled, and nothing
works anymore.
While at it, don't fork to background on debug builds, and log to
stderr too in that case.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Default value for /proc/sys/fs/nr_open is 2^20, which is more than
enough: set this hard limit as current (soft) limit on start, and
drop the 'ulimit -n' from the demo script.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...and, while at it, a second patch to fail when connect() fails in turn
with EINVAL. These two patches haven't been sent upstream yet.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It's nice to be able to confirm connectivity using ICMP or ICMPv6
echo requests, and "ping" sockets on Linux (IPPROTO_ICMP datagram)
allow us to do that without any special capability.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We don't need to keep small data as static variables, move the only
small variable we have so far to the new struct.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Replace the dummy, full array scan implementation, by a hash table
based on SipHash, with chained hashing for collisions.
This table is also statically allocated, and it's simply an array
of socket numbers. Connection entries are chained by pointers in
the connection entry itself, which now also contains socket number
and hash bucket index to keep removal reasonably fast.
New entries are inserted at the head of the chain, that is, the most
recently inserted entry is directly mapped from the bucket.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We might receive out-of-order ACK packets from the tap device, just
like any other packet.
I guess I've been overcautious and regarded it as a condition we
can't recover from, but all that happens is that we have already seen
a higher ACK sequence number, which means that data has been already
received and discarded from the buffer. We have to ignore the lower
sequence number we receive later, though, because that would force
the buffer bookkeeping into throwing away more data than expected.
Drop the ACK sequence assignment from tcp_tap_handler(), which was
redundant, and let tcp_sock_consume() take exclusive care of that.
Now that tcp_sock_consume() can never fail, make it a void, and
drop checks from callers.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Implement siphash routines for initial TCP sequence numbers (12 bytes
input for IPv4, 36 bytes input for IPv6), and while at it, also
functions we'll use later on for hash table indices and TCP timestamp
offsets (with 8, 20, 32 bytes of input).
Use these to set the initial sequence number, according to RFC 6528,
for connections originating either from the tap device or from
sockets.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
A bunch of fixes not worth single commits at this stage, notably:
- make buffer, length parameter ordering consistent in ARP, DHCP,
NDP handlers
- strict checking of buffer, message and option length in DHCP
handler (a malicious client could have easily crashed it)
- set up forwarding for IPv4 and IPv6, and masquerading with nft for
IPv4, from demo script
- get rid of separate slow and fast timers, we don't save any
overhead that way
- stricter checking of buffer lengths as passed to tap handlers
- proper dequeuing from qemu socket back-end: I accidentally trashed
messages that were bundled up together in a single tap read
operation -- the length header tells us what's the size of the next
frame, but there's no apparent limit to the number of messages we
get with one single receive
- rework some bits of the TCP state machine, now passive and active
connection closes appear to be robust -- introduce a new
FIN_WAIT_1_SOCK_FIN state indicating a FIN_WAIT_1 with a FIN flag
from socket
- streamline TCP option parsing routine
- track TCP state changes to stderr (this is temporary, proper
debugging and syslogging support pending)
- observe that multiplying a number by four might very well change
its value, and this happens to be the case for the data offset
from the TCP header as we check if it's the same as the total
length to find out if it's a duplicated ACK segment
- recent estimates suggest that the duration of a millisecond is
closer to a million nanoseconds than a thousand of them, this
trend is now reflected into the timespec_diff_ms() convenience
routine
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is a reimplementation, partially building on the earlier draft,
that uses L4 sockets (SOCK_DGRAM, SOCK_STREAM) instead of SOCK_RAW,
providing L4-L2 translation functionality without requiring any
security capability.
Conceptually, this follows the design presented at:
https://gitlab.com/abologna/kubevirt-and-kvm/-/blob/master/Networking.md
The most significant novelty here comes from TCP and UDP translation
layers. In particular, the TCP state and translation logic follows
the intent of being minimalistic, without reimplementing a full TCP
stack in either direction, and synchronising as much as possible the
TCP dynamic and flows between guest and host kernel.
Another important introduction concerns addressing, port translation
and forwarding. The Layer 4 implementations now attempt to bind on
all unbound ports, in order to forward connections in a transparent
way.
While at it:
- the qemu 'tap' back-end can't be used as-is by qrap anymore,
because of explicit checks now introduced in qemu to ensure that
the corresponding file descriptor is actually a tap device. For
this reason, qrap now operates on a 'socket' back-end type,
accounting for and building the additional header reporting
frame length
- provide a demo script that sets up namespaces, addresses and
routes, and starts the daemon. A virtual machine started in the
network namespace, wrapped by qrap, will now directly interface
with passt and communicate using Layer 4 sockets provided by the
host kernel.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
With this, merd provides a fully functional IPv4 environment to
guests, requiring a single capability, CAP_NET_RAW.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We can bypass a full-fledged network interface between qemu and merd by
connecting the qemu tap file descriptor to a provided UNIX domain
socket: this could be implemented in qemu eventually, qrap covers this
meanwhile.
This also avoids the need for the AF_PACKET socket towards the guest.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
