[PATCH 3/3] fwd: Preserve non-standard loopback address when splice forwarding

When forwarding "spliced" connections outwards (-T or -U) we listen on the guest's loopback and always forward to 127.0.0.1 (or ::1) on the host. However, it's also possible for clients on the guest to attempt connecting to other addresses in 127.0.0.0/8 (systemd-resolved uses 127.0.0.53 in practice). If the host side server is only listening on that specific non-standard loopback address, the forward won't work. Fix this by preserving the specific (loopback) address when forwarding such connections. Link: https://bugs.passt.top/show_bug.cgi?id=113 Signed-off-by: David Gibson --- fwd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fwd.c b/fwd.c index c417e0f5..44a0e109 100644 --- a/fwd.c +++ b/fwd.c @@ -660,7 +660,9 @@ uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto, return PIF_NONE; } - if (inany_v4(&ini->eaddr)) + if (!inany_is_unspecified(&ini->oaddr)) + tgt->eaddr = ini->oaddr; + else if (inany_v4(&ini->oaddr)) tgt->eaddr = inany_loopback4; else tgt->eaddr = inany_loopback6; -- 2.51.1