This implements flow preparation on the source, transfer of data with
a format roughly inspired by struct tcp_tap_conn, plus a specific
structure for parameters that don't fit in the flow table, and flow
insertion on the target, with all the appropriate window options,
window scaling, MSS, etc.
Contents of pending queues are transferred as well.
The target side is rather convoluted because we first need to create
sockets and switch them to repair mode, before we can apply options
that are *not* stored in the flow table. This also means that, if
we're testing this on the same machine, in the same namespace, we need
to close the listening socket on the source before we can start moving
data.
Further, we need to connect() the socket on the target before we can
restore data queues, but we can't do that (again, on the same machine)
as long as the matching source socket is open, which implies an
arbitrary limit on queue sizes we can transfer, because we can only
dump pending queues on the source as long as the socket is open, of
course.
Co-authored-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In vhost-user mode, by default, create a second UNIX domain socket
accepting connections from passt-repair, with the usual listener
socket.
When we need to set or clear TCP_REPAIR on sockets, we'll send them
via SCM_RIGHTS to passt-repair, who sets the socket option values we
ask for.
To that end, introduce batched functions to request TCP_REPAIR
settings on sockets, so that we don't have to send a single message
for each socket, on migration. When needed, repair_flush() will
send the message and check for the reply.
Co-authored-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Most of the information in struct ctx doesn't need to be migrated.
Either it's strictly back end information which is allowed to differ
between the two ends, or it must already be configured identically on
the two ends.
There are a few exceptions though. In particular passt learns several
addresses of the guest by observing what it sends out. If we lose
this information across migration we might get away with it, but if
there are active flows we might misdirect some packets before
re-learning the guest address.
Avoid this by migrating the guest's observed addresses.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Coding style stuff, comments, etc.]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Introduce facilities for guest migration on top of vhost-user
infrastructure. Add migration facilities based on top of the current
vhost-user infrastructure, moving vu_migrate() and related functions
to migrate.c.
Versioned migration stages define function pointers to be called on
source or target, or data sections that need to be transferred.
The migration header consists of a magic number, a version number for the
encoding, and a "compat_version" which represents the oldest version which
is compatible with the current one. We don't use it yet, but that allows
for the future possibility of backwards compatible protocol extensions.
Co-authored-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
