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ipv6: clear RA flags when adding a static route 

When an IPv6 Router Advertisement (RA) is received for a prefix, the
kernel creates the corresponding on-link route with flags RTF_ADDRCONF
and RTF_PREFIX_RT configured and RTF_EXPIRES if lifetime is set.

If later a user configures a static IPv6 address on the same prefix the
kernel clears the RTF_EXPIRES flag but it doesn't clear the RTF_ADDRCONF
and RTF_PREFIX_RT. When the next RA for that prefix is received, the
kernel sees the route as RA-learned and wrongly configures back the
lifetime. This is problematic because if the route expires, the static
address won't have the corresponding on-link route.

This fix clears the RTF_ADDRCONF and RTF_PREFIX_RT flags preventing that
the lifetime is configured when the next RA arrives. If the static
address is deleted, the route becomes RA-learned again.

Fixes: 14ef37b6d0 ("ipv6: fix route lookup in addrconf_prefix_rcv()")
Reported-by: Garri Djavadyan <g.djavadyan@gmail.com>
Closes: https://lore.kernel.org/netdev/ba807d39aca5b4dcf395cc11dca61a130a52cfd3.camel@gmail.com/
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20251115095939.6967-1-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
pull/1354/merge
Fernando Fernandez Mancera 2025-11-15 10:59:38 +01:00 committed by Jakub Kicinski
parent cbf4d314ac
commit f72514b3c5
1 changed files with 4 additions and 0 deletions
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4
net/ipv6/ip6_fib.c
View File

@ -1138,6 +1138,10 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
fib6_set_expires(iter, rt->expires);
fib6_add_gc_list(iter);
}
if (!(rt->fib6_flags & (RTF_ADDRCONF | RTF_PREFIX_RT))) {
iter->fib6_flags &= ~RTF_ADDRCONF;
iter->fib6_flags &= ~RTF_PREFIX_RT;
}
if (rt->fib6_pmtu)
fib6_metric_set(iter, RTAX_MTU,