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net: ipv4: fix regression in local-broadcast routes

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Commit 9e30ecf23b ("net: ipv4: fix incorrect MTU in broadcast routes")
introduced a regression where local-broadcast packets would have their
gateway set in __mkroute_output, which was caused by fi = NULL being
removed.

Fix this by resetting the fib_info for local-broadcast packets. This
preserves the intended changes for directed-broadcast packets.

Cc: stable@vger.kernel.org
Fixes: 9e30ecf23b ("net: ipv4: fix incorrect MTU in broadcast routes")
Reported-by: Brett A C Sheffield <bacs@librecast.net>
Closes: https://lore.kernel.org/regressions/20250822165231.4353-4-bacs@librecast.net
Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250827062322.4807-1-oscmaes92@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Oscar Maes 2025-08-27 08:23:21 +02:00 committed by Paolo Abeni
parent dac978e51c
commit 5189446ba9
1 changed files with 7 additions and 3 deletions
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10
net/ipv4/route.c
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@ -2575,12 +2575,16 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
!netif_is_l3_master(dev_out)) !netif_is_l3_master(dev_out))
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
if (ipv4_is_lbcast(fl4->daddr)) if (ipv4_is_lbcast(fl4->daddr)) {
type = RTN_BROADCAST; type = RTN_BROADCAST;
else if (ipv4_is_multicast(fl4->daddr))
/* reset fi to prevent gateway resolution */
fi = NULL;
} else if (ipv4_is_multicast(fl4->daddr)) {
type = RTN_MULTICAST; type = RTN_MULTICAST;
else if (ipv4_is_zeronet(fl4->daddr)) } else if (ipv4_is_zeronet(fl4->daddr)) {
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
}
if (dev_out->flags & IFF_LOOPBACK) if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL; flags |= RTCF_LOCAL;