From: Wei Wang weiwan@google.com
[ Upstream commit 510e2ceda031eed97a7a0f9aad65d271a58b460d ]
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 mikael.kernel@lists.m7n.se Bisected-by: David Ahern dsahern@gmail.com Signed-off-by: Wei Wang weiwan@google.com Cc: Martin Lau kafai@fb.com Cc: Eric Dumazet edumazet@google.com Acked-by: Martin KaFai Lau kafai@fb.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/route.c | 51 +++++++++++++++++++++++++++------------------------ 1 file changed, 27 insertions(+), 24 deletions(-)
--- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -110,8 +110,8 @@ static int rt6_fill_node(struct net *net int iif, int type, u32 portid, u32 seq, unsigned int flags); static struct rt6_info *rt6_find_cached_rt(struct fib6_info *rt, - struct in6_addr *daddr, - struct in6_addr *saddr); + const struct in6_addr *daddr, + const struct in6_addr *saddr);
#ifdef CONFIG_IPV6_ROUTE_INFO static struct fib6_info *rt6_add_route_info(struct net *net, @@ -1542,31 +1542,44 @@ out: * Caller has to hold rcu_read_lock() */ static struct rt6_info *rt6_find_cached_rt(struct fib6_info *rt, - struct in6_addr *daddr, - struct in6_addr *saddr) + const struct in6_addr *daddr, + const struct in6_addr *saddr) { + const struct in6_addr *src_key = NULL; struct rt6_exception_bucket *bucket; - struct in6_addr *src_key = NULL; struct rt6_exception *rt6_ex; struct rt6_info *res = NULL;
- bucket = rcu_dereference(rt->rt6i_exception_bucket); - #ifdef CONFIG_IPV6_SUBTREES /* rt6i_src.plen != 0 indicates rt is in subtree * and exception table is indexed by a hash of * both rt6i_dst and rt6i_src. - * Otherwise, the exception table is indexed by - * a hash of only rt6i_dst. + * However, the src addr used to create the hash + * might not be exactly the passed in saddr which + * is a /128 addr from the flow. + * So we need to use f6i->fib6_src to redo lookup + * if the passed in saddr does not find anything. + * (See the logic in ip6_rt_cache_alloc() on how + * rt->rt6i_src is updated.) */ if (rt->fib6_src.plen) src_key = saddr; +find_ex: #endif + bucket = rcu_dereference(rt->rt6i_exception_bucket); rt6_ex = __rt6_find_exception_rcu(&bucket, daddr, src_key);
if (rt6_ex && !rt6_check_expired(rt6_ex->rt6i)) res = rt6_ex->rt6i;
+#ifdef CONFIG_IPV6_SUBTREES + /* Use fib6_src as src_key and redo lookup */ + if (!res && src_key && src_key != &rt->fib6_src.addr) { + src_key = &rt->fib6_src.addr; + goto find_ex; + } +#endif + return res; }
@@ -2650,10 +2663,8 @@ out: u32 ip6_mtu_from_fib6(struct fib6_info *f6i, struct in6_addr *daddr, struct in6_addr *saddr) { - struct rt6_exception_bucket *bucket; - struct rt6_exception *rt6_ex; - struct in6_addr *src_key; struct inet6_dev *idev; + struct rt6_info *rt; u32 mtu = 0;
if (unlikely(fib6_metric_locked(f6i, RTAX_MTU))) { @@ -2662,18 +2673,10 @@ u32 ip6_mtu_from_fib6(struct fib6_info * goto out; }
- src_key = NULL; -#ifdef CONFIG_IPV6_SUBTREES - if (f6i->fib6_src.plen) - src_key = saddr; -#endif - - bucket = rcu_dereference(f6i->rt6i_exception_bucket); - rt6_ex = __rt6_find_exception_rcu(&bucket, daddr, src_key); - if (rt6_ex && !rt6_check_expired(rt6_ex->rt6i)) - mtu = dst_metric_raw(&rt6_ex->rt6i->dst, RTAX_MTU); - - if (likely(!mtu)) { + rt = rt6_find_cached_rt(f6i, daddr, saddr); + if (unlikely(rt)) { + mtu = dst_metric_raw(&rt->dst, RTAX_MTU); + } else { struct net_device *dev = fib6_info_nh_dev(f6i);
mtu = IPV6_MIN_MTU;