On Sun, Jan 18, 2026 at 05:16:07PM -0500, Jon Maloy wrote:
As a preparation for handling multiple addresses, we update fwd_guest_accessible4() and fwd_guest_accessible6() to check against all addresses in the addrs[] array.
This ensures that when multiple addresses are configured via -a options, inbound traffic for any of them is correctly detected as having no valid forwarding path, and subsequently dropped. This occurs when a peer address collides with an address the guest is using, and we have no translation for it.
Signed-off-by: Jon Maloy
--- v2: Updated commit log to make it clearer --- fwd.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/fwd.c b/fwd.c index 8d8151b..f1db34c 100644 --- a/fwd.c +++ b/fwd.c @@ -502,6 +502,8 @@ static bool is_dns_flow(uint8_t proto, const struct flowside *ini) static bool fwd_guest_accessible4(const struct ctx *c, const struct in_addr *addr)
fwd_guest_accesible[46]() are only ever called via fwd_guest_accessible() which takes an inny_addr. Again, you can simplify this a bunch by actually exploiting the fact that the arrays are now also inany_addr, rather than having an inany_addr but still having separate v4 and v6 paths everywhere.
{ + int i; + if (IN4_IS_ADDR_LOOPBACK(addr)) return false;
@@ -513,11 +515,15 @@ static bool fwd_guest_accessible4(const struct ctx *c, if (IN4_IS_ADDR_UNSPECIFIED(addr)) return false;
- /* For IPv4, addr_seen is initialised to addr, so is always a valid - * address + /* Check against all configured guest addresses */ + for (i = 0; i < c->ip4.addr_count; i++) + if (IN4_ARE_ADDR_EQUAL(addr, inany_v4(&c->ip4.addrs[i].addr))) + return false; + + /* Also check addr_seen: it tracks the address the guest is actually + * using, which may differ from configured addresses. */ - if (IN4_ARE_ADDR_EQUAL(addr, inany_v4(&c->ip4.addrs[0].addr)) || - IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr_seen)) + if (IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr_seen)) return false;
return true; @@ -534,11 +540,15 @@ static bool fwd_guest_accessible4(const struct ctx *c, static bool fwd_guest_accessible6(const struct ctx *c, const struct in6_addr *addr) { + int i; + if (IN6_IS_ADDR_LOOPBACK(addr)) return false;
- if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addrs[0].addr.a6)) - return false; + /* Check against all configured guest addresses */ + for (i = 0; i < c->ip6.addr_count; i++) + if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addrs[i].addr.a6)) + return false;
/* For IPv6, addr_seen starts unspecified, because we don't know what LL * address the guest will take until we see it. Only check against it -- 2.52.0
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson