Commit 510e2ced authored by Wei Wang's avatar Wei Wang Committed by David S. Miller
Browse files

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: 2b760fcf ("ipv6: hook up exception table to store dst cache")
Reported-by: default avatarMikael Magnusson <mikael.kernel@lists.m7n.se>
Bisected-by: default avatarDavid Ahern <dsahern@gmail.com>
Signed-off-by: default avatarWei Wang <weiwan@google.com>
Cc: Martin Lau <kafai@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9a6c8bf9

net/ipv6/route.c

+27 −24
Original line number Diff line number Diff line
@@ -111,8 +111,8 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb, 
			 int iif, int type, u32 portid, u32 seq,

			 unsigned int flags);

static struct rt6_info *rt6_find_cached_rt(const struct fib6_result *res,

					   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,
@@ -1573,31 +1573,44 @@ out: 
 * Caller has to hold rcu_read_lock()

 */

static struct rt6_info *rt6_find_cached_rt(const struct fib6_result *res,

					   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 *ret = NULL;



	bucket = rcu_dereference(res->f6i->rt6i_exception_bucket);



#ifdef CONFIG_IPV6_SUBTREES

	/* fib6i_src.plen != 0 indicates f6i is in subtree

	 * and exception table is indexed by a hash of

	 * both fib6_dst and fib6_src.

	 * Otherwise, the exception table is indexed by

	 * a hash of only fib6_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 (res->f6i->fib6_src.plen)

		src_key = saddr;

find_ex:

#endif

	bucket = rcu_dereference(res->f6i->rt6i_exception_bucket);

	rt6_ex = __rt6_find_exception_rcu(&bucket, daddr, src_key);



	if (rt6_ex && !rt6_check_expired(rt6_ex->rt6i))

		ret = rt6_ex->rt6i;



#ifdef CONFIG_IPV6_SUBTREES

	/* Use fib6_src as src_key and redo lookup */

	if (!ret && src_key && src_key != &res->f6i->fib6_src.addr) {

		src_key = &res->f6i->fib6_src.addr;

		goto find_ex;

	}

#endif



	return ret;

}
@@ -2672,12 +2685,10 @@ u32 ip6_mtu_from_fib6(const struct fib6_result *res, 
		      const struct in6_addr *daddr,

		      const struct in6_addr *saddr)

{

	struct rt6_exception_bucket *bucket;

	const struct fib6_nh *nh = res->nh;

	struct fib6_info *f6i = res->f6i;

	const struct in6_addr *src_key;

	struct rt6_exception *rt6_ex;

	struct inet6_dev *idev;

	struct rt6_info *rt;

	u32 mtu = 0;



	if (unlikely(fib6_metric_locked(f6i, RTAX_MTU))) {
@@ -2686,18 +2697,10 @@ u32 ip6_mtu_from_fib6(const struct fib6_result *res, 
			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(res, daddr, saddr);

	if (unlikely(rt)) {

		mtu = dst_metric_raw(&rt->dst, RTAX_MTU);

	} else {

		struct net_device *dev = nh->fib_nh_dev;



		mtu = IPV6_MIN_MTU;

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