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conf: Add command line switch to enable IP_FREEBIND socket option

In a couple of recent reports, we've seen that it can be useful for pasta
to forward ports from addresses which are not currently configured on the
host, but might be in future.  That can be done with the sysctl
net.ipv4.ip_nonlocal_bind, but that does require CAP_NET_ADMIN to set in
the first place.  We can allow the same thing on a per-socket basis with
the IP_FREEBIND (or IPV6_FREEBIND) socket option.

Add a --freebind command line argument to enable this socket option on
all listening sockets.

Link: https://bugs.passt.top/show_bug.cgi?id=101
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-10-03 14:48:32 +10:00 committed by Stefano Brivio
parent 151dbe0d3d
commit 9d66df9a9a
4 changed files with 30 additions and 0 deletions

10
passt.1
View file

@ -327,6 +327,16 @@ namespace will be silently dropped.
Disable Router Advertisements. Router Solicitations coming from guest or target
namespace will be ignored.
.TP
.BR \-\-freebind
Allow any binding address to be specified for \fB-t\fR and \fB-u\fR
options. Usually binding addresses must be addresses currently
configured on the host. With \fB\-\-freebind\fR, the
\fBIP_FREEBIND\fR or \fBIPV6_FREEBIND\fR socket option is enabled
allowing any address to be used. This is typically used to bind
addresses which might be configured on the host in future, at which
point the forwarding will immediately start operating.
.TP
.BR \-\-map-host-loopback " " \fIaddr
Translate \fIaddr\fR to refer to the host. Packets from the guest to