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Message-Id: <20190516203054.13066-1-tracywwnj@gmail.com>
Date: Thu, 16 May 2019 13:30:54 -0700
From: Wei Wang <tracywwnj@...il.com>
To: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc: Martin KaFai Lau <kafai@...com>, Wei Wang <weiwan@...gle.com>,
Mikael Magnusson <mikael.kernel@...ts.m7n.se>,
David Ahern <dsahern@...il.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3 net] ipv6: fix src addr routing with the exception table
From: Wei Wang <weiwan@...gle.com>
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@...ts.m7n.se>
Bisected-by: David Ahern <dsahern@...il.com>
Signed-off-by: Wei Wang <weiwan@...gle.com>
Cc: Martin Lau <kafai@...com>
Cc: Eric Dumazet <edumazet@...gle.com>
---
Changes from v2:
- modified the check in rt6_find_cached_rt() to prevent infinite loop
- add const to src_key to prevent kernel compile warning
Changes from v1:
- restructure the code to only include the new logic in
rt6_find_cached_rt()
---
net/ipv6/route.c | 51 +++++++++++++++++++++++++-----------------------
1 file changed, 27 insertions(+), 24 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 23a20d62daac..0f52d18cb83b 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -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,
@@ -1566,31 +1566,44 @@ void rt6_flush_exceptions(struct fib6_info *rt)
* 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;
}
@@ -2665,12 +2678,10 @@ 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))) {
@@ -2679,18 +2690,10 @@ 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;
--
2.21.0.1020.gf2820cf01a-goog
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