path: root/net/ipv4/route.c
diff options
authorSabrina Dubroca <sd@queasysnail.net>2018-10-09 17:48:15 +0200
committerDavid S. Miller <davem@davemloft.net>2018-10-10 22:44:46 -0700
commit28d35bcdd3925e7293408cdb8aa5f2aac5f0d6e3 (patch)
tree57dd5ec8a63d7a9df7cde67afa189b8d02abe83b /net/ipv4/route.c
parentnet: ipv4: update fnhe_pmtu when first hop's MTU changes (diff)
net: ipv4: don't let PMTU updates increase route MTU
When an MTU update with PMTU smaller than net.ipv4.route.min_pmtu is received, we must clamp its value. However, we can receive a PMTU exception with PMTU < old_mtu < ip_rt_min_pmtu, which would lead to an increase in PMTU. To fix this, take the smallest of the old MTU and ip_rt_min_pmtu. Before this patch, in case of an update, the exception's MTU would always change. Now, an exception can have only its lock flag updated, but not the MTU, so we need to add a check on locking to the following "is this exception getting updated, or close to expiring?" test. Fixes: d52e5a7e7ca4 ("ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu") Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Reviewed-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/route.c')
1 files changed, 4 insertions, 3 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index b678466da451..8501554e96a4 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1001,21 +1001,22 @@ out: kfree_skb(skb);
static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
struct dst_entry *dst = &rt->dst;
+ u32 old_mtu = ipv4_mtu(dst);
struct fib_result res;
bool lock = false;
if (ip_mtu_locked(dst))
- if (ipv4_mtu(dst) < mtu)
+ if (old_mtu < mtu)
if (mtu < ip_rt_min_pmtu) {
lock = true;
- mtu = ip_rt_min_pmtu;
+ mtu = min(old_mtu, ip_rt_min_pmtu);
- if (rt->rt_pmtu == mtu &&
+ if (rt->rt_pmtu == mtu && !lock &&
time_before(jiffies, dst->expires - ip_rt_mtu_expires / 2))