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ipv6: fix src addr routing with the exception table

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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: 2b760fcf5c ("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>
This commit is contained in:
Wei Wang 2019-05-16 13:30:54 -07:00 committed by David S. Miller
parent 9a6c8bf91b
commit 510e2ceda0
1 changed files with 27 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
net/ipv6/route.c
View File

@ -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;