From 4e914ef063de40397e25a025c70d9737a9e45a8c Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Wed, 9 Jul 2025 16:30:10 +0200 Subject: [PATCH] gre: Fix IPv6 multicast route creation. Use addrconf_add_dev() instead of ipv6_find_idev() in addrconf_gre_config() so that we don't just get the inet6_dev, but also install the default ff00::/8 multicast route. Before commit 3e6a0243ff00 ("gre: Fix again IPv6 link-local address generation."), the multicast route was created at the end of the function by addrconf_add_mroute(). But this code path is now only taken in one particular case (gre devices not bound to a local IP address and in EUI64 mode). For all other cases, the function exits early and addrconf_add_mroute() is not called anymore. Using addrconf_add_dev() instead of ipv6_find_idev() in addrconf_gre_config(), fixes the problem as it will create the default multicast route for all gre devices. This also brings addrconf_gre_config() a bit closer to the normal netdevice IPv6 configuration code (addrconf_dev_config()). Cc: stable@vger.kernel.org Fixes: 3e6a0243ff00 ("gre: Fix again IPv6 link-local address generation.") Reported-by: Aiden Yang Closes: https://lore.kernel.org/netdev/CANR=AhRM7YHHXVxJ4DmrTNMeuEOY87K2mLmo9KMed1JMr20p6g@mail.gmail.com/ Reviewed-by: Gary Guo Tested-by: Gary Guo Signed-off-by: Guillaume Nault Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/027a923dcb550ad115e6d93ee8bb7d310378bd01.1752070620.git.gnault@redhat.com Signed-off-by: Jakub Kicinski --- net/ipv6/addrconf.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index ba2ec7c870cc..870a0bd6c2ba 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3525,11 +3525,9 @@ static void addrconf_gre_config(struct net_device *dev) ASSERT_RTNL(); - idev = ipv6_find_idev(dev); - if (IS_ERR(idev)) { - pr_debug("%s: add_dev failed\n", __func__); + idev = addrconf_add_dev(dev); + if (IS_ERR(idev)) return; - } /* Generate the IPv6 link-local address using addrconf_addr_gen(), * unless we have an IPv4 GRE device not bound to an IP address and @@ -3543,9 +3541,6 @@ static void addrconf_gre_config(struct net_device *dev) } add_v4_addrs(idev); - - if (dev->flags & IFF_POINTOPOINT) - addrconf_add_mroute(dev); } #endif -- 2.25.1