ipv6: fix src addr routing with the exception table

When inserting route cache into the exception table, the key is
generated with both src_addr and dest_addr with src addr routing.
However, current logic always assumes the src_addr used to generate the
key is a /128 host address. This is not true in the following scenarios:
1. When the route is a gateway route or does not have next hop.
   (rt6_is_gw_or_nonexthop() == false)
2. When calling ip6_rt_cache_alloc(), saddr is passed in as NULL.
This means, when looking for a route cache in the exception table, we
have to do the lookup twice: first time with the passed in /128 host
address, second time with the src_addr stored in fib6_info.

This solves the pmtu discovery issue reported by Mikael Magnusson where
a route cache with a lower mtu info is created for a gateway route with
src addr. However, the lookup code is not able to find this route cache.

Fixes: 2b760fcf5cfb ("ipv6: hook up exception table to store dst cache")
Reported-by: Mikael Magnusson <[email protected]>
Bisected-by: David Ahern <[email protected]>
Signed-off-by: Wei Wang <[email protected]>
Cc: Martin Lau <[email protected]>
Cc: Eric Dumazet <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

0 files changed, 0 insertions, 0 deletions