migrate, tcp: bind() migrated sockets in repair mode

Currently on a migration target, we create then immediately bind() new
sockets for the TCP connections we're reconstructing.  Mostly, this works,
since a socket() that is bound but hasn't had listen() or connect() called
is essentially passive.  However, this bind() is subject to the usual
address conflict checking.  In particular that means if we already have
a listening socket on that port, we'll get an EADDRINUSE.  This will happen
for every connection we try to migrate that was initiated from outside to
the guest, since we necessarily created a listening socket for that case.

We set SO_REUSEADDR on the socket in an attempt to avoid this, but that's
not sufficient; even with SO_REUSEADDR address conflicts are still
prohibited for listening sockets.  Of course once these incoming sockets
are fully repaired and connect()ed they'll no longer conflict, but that
doesn't help us if we fail at the bind().

We can avoid this by not calling bind() until we're already in repair mode
which suppresses this transient conflict.  Because of the batching of
setting repair mode, to do that we need to move the bind to a step in
tcp_flow_migrate_target_ext().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions