4.18-stable review patch. If anyone has any objections, please let me know.
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From: David Ahern dsahern@gmail.com
[ Upstream commit 15a81b418e22a9aa4a0504471fdcb0f4ebf69b96 ]
Jan reported a regression after an update to 4.18.5. In this case ipv6 default route is setup by systemd-networkd based on data from an RA. The RA contains an MTU of 1492 which is used when the route is first inserted but then systemd-networkd pushes down updates to the default route without the mtu set.
Prior to the change to fib6_info, metrics such as MTU were held in the dst_entry and rt6i_pmtu in rt6_info contained an update to the mtu if any. ip6_mtu would look at rt6i_pmtu first and use it if set. If not, the value from the metrics is used if it is set and finally falling back to the idev value.
After the fib6_info change metrics are contained in the fib6_info struct and there is no equivalent to rt6i_pmtu. To maintain consistency with the old behavior the new code should only reset the MTU in the metrics if the route update has it set.
Fixes: d4ead6b34b67 ("net/ipv6: move metrics from dst to rt6_info") Reported-by: Jan Janssen medhefgo@web.de Signed-off-by: David Ahern dsahern@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/ip6_fib.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -987,7 +987,10 @@ static int fib6_add_rt2node(struct fib6_ fib6_clean_expires(iter); else fib6_set_expires(iter, rt->expires); - fib6_metric_set(iter, RTAX_MTU, rt->fib6_pmtu); + + if (rt->fib6_pmtu) + fib6_metric_set(iter, RTAX_MTU, + rt->fib6_pmtu); return -EEXIST; } /* If we have the same destination and the same metric,