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From: Oscar Maes <oscmaes92@gmail.com>
Date: Tue, 26 Aug 2025 14:17:49 +0200
Subject: net: ipv4: fix regression in local-broadcast routes
Origin: https://lore.kernel.org/regressions/20250826121750.8451-1-oscmaes92@gmail.com/
Commit 9e30ecf23b1b ("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: 9e30ecf23b1b ("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>
---
net/ipv4/route.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f639a2ae881a..baa43e5966b1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2575,12 +2575,16 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
!netif_is_l3_master(dev_out))
return ERR_PTR(-EINVAL);
- if (ipv4_is_lbcast(fl4->daddr))
+ if (ipv4_is_lbcast(fl4->daddr)) {
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;
- else if (ipv4_is_zeronet(fl4->daddr))
+ } else if (ipv4_is_zeronet(fl4->daddr)) {
return ERR_PTR(-EINVAL);
+ }
if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL;
--
2.50.1
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