Add interfaces and configuration bits for passt-repair

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>

1 files changed, 11 insertions, 0 deletions

diff --git a/passt.1 b/passt.1
index 9d347d8..60066c2 100644
--- a/passt.1
+++ b/passt.1
@@ -429,6 +429,17 @@ Enable vhost-user. The vhost-user command socket is provided by \fB--socket\fR.
 Print back-end capabilities in JSON format, only meaningful for vhost-user mode.
 
 .TP
+.BR \-\-repair-path " " \fIpath
+Path for UNIX domain socket used by the \fBpasst-repair\fR(1) helper to connect
+to \fBpasst\fR in order to set or clear the TCP_REPAIR option on sockets, during
+migration. \fB--repair-path none\fR disables this interface (if you need to
+specify a socket path called "none" you can prefix the path by \fI./\fR).
+
+Default, for \-\-vhost-user mode only, is to append \fI.repair\fR to the path
+chosen for the hypervisor UNIX domain socket. No socket is created if not in
+\-\-vhost-user mode.
+
+.TP
 .BR \-F ", " \-\-fd " " \fIFD
 Pass a pre-opened, connected socket to \fBpasst\fR. Usually the socket is opened
 in the parent process and \fBpasst\fR inherits it when run as a child. This