git.openwrt.org Git - openwrt/openwrt.git/blob

   1 From 5189446ba995556eaa3755a6e875bc06675b88bd Mon Sep 17 00:00:00 2001
   2 From: Oscar Maes <oscmaes92@gmail.com>
   3 Date: Wed, 27 Aug 2025 08:23:21 +0200
   4 Subject: [PATCH] net: ipv4: fix regression in local-broadcast routes
   5
   6 Commit 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
   7 introduced a regression where local-broadcast packets would have their
   8 gateway set in __mkroute_output, which was caused by fi = NULL being
   9 removed.
  10
  11 Fix this by resetting the fib_info for local-broadcast packets. This
  12 preserves the intended changes for directed-broadcast packets.
  13
  14 Cc: stable@vger.kernel.org
  15 Fixes: 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
  16 Reported-by: Brett A C Sheffield <bacs@librecast.net>
  17 Closes: https://lore.kernel.org/regressions/20250822165231.4353-4-bacs@librecast.net
  18 Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
  19 Reviewed-by: David Ahern <dsahern@kernel.org>
  20 Link: https://patch.msgid.link/20250827062322.4807-1-oscmaes92@gmail.com
  21 Signed-off-by: Paolo Abeni <pabeni@redhat.com>
  22 ---
  23  net/ipv4/route.c | 10 +++++++---
  24  1 file changed, 7 insertions(+), 3 deletions(-)
  25
  26 --- a/net/ipv4/route.c
  27 +++ b/net/ipv4/route.c
  28 @@ -2532,12 +2532,16 @@ static struct rtable *__mkroute_output(c
  29                     !netif_is_l3_master(dev_out))
  30                         return ERR_PTR(-EINVAL);
  31
  32 -       if (ipv4_is_lbcast(fl4->daddr))
  33 +       if (ipv4_is_lbcast(fl4->daddr)) {
  34                 type = RTN_BROADCAST;
  35 -       else if (ipv4_is_multicast(fl4->daddr))
  36 +
  37 +               /* reset fi to prevent gateway resolution */
  38 +               fi = NULL;
  39 +       } else if (ipv4_is_multicast(fl4->daddr)) {
  40                 type = RTN_MULTICAST;
  41 -       else if (ipv4_is_zeronet(fl4->daddr))
  42 +       } else if (ipv4_is_zeronet(fl4->daddr)) {
  43                 return ERR_PTR(-EINVAL);
  44 +       }
  45
  46         if (dev_out->flags & IFF_LOOPBACK)
  47                 flags |= RTCF_LOCAL;