net: ipv4: update fnhe_pmtu when first hop's MTU changes

[mirror_ubuntu-bionic-kernel.git] / net / ipv4 / fib_semantics.c

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 1eca75a41d225670fb069d777fd3196bdb883d5e..02e17bc29f216e391305d052febb4a7e7638a5a6 100644 (file)
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1511,6 +1511,56 @@ static int call_fib_nh_notifiers(struct fib_nh *fib_nh,
        return NOTIFY_DONE;
 }
 
+/* Update the PMTU of exceptions when:
+ * - the new MTU of the first hop becomes smaller than the PMTU
+ * - the old MTU was the same as the PMTU, and it limited discovery of
+ *   larger MTUs on the path. With that limit raised, we can now
+ *   discover larger MTUs
+ * A special case is locked exceptions, for which the PMTU is smaller
+ * than the minimal accepted PMTU:
+ * - if the new MTU is greater than the PMTU, don't make any change
+ * - otherwise, unlock and set PMTU
+ */
+static void nh_update_mtu(struct fib_nh *nh, u32 new, u32 orig)
+{
+       struct fnhe_hash_bucket *bucket;
+       int i;
+
+       bucket = rcu_dereference_protected(nh->nh_exceptions, 1);
+       if (!bucket)
+               return;
+
+       for (i = 0; i < FNHE_HASH_SIZE; i++) {
+               struct fib_nh_exception *fnhe;
+
+               for (fnhe = rcu_dereference_protected(bucket[i].chain, 1);
+                    fnhe;
+                    fnhe = rcu_dereference_protected(fnhe->fnhe_next, 1)) {
+                       if (fnhe->fnhe_mtu_locked) {
+                               if (new <= fnhe->fnhe_pmtu) {
+                                       fnhe->fnhe_pmtu = new;
+                                       fnhe->fnhe_mtu_locked = false;
+                               }
+                       } else if (new < fnhe->fnhe_pmtu ||
+                                  orig == fnhe->fnhe_pmtu) {
+                               fnhe->fnhe_pmtu = new;
+                       }
+               }
+       }
+}
+
+void fib_sync_mtu(struct net_device *dev, u32 orig_mtu)
+{
+       unsigned int hash = fib_devindex_hashfn(dev->ifindex);
+       struct hlist_head *head = &fib_info_devhash[hash];
+       struct fib_nh *nh;
+
+       hlist_for_each_entry(nh, head, nh_hash) {
+               if (nh->nh_dev == dev)
+                       nh_update_mtu(nh, dev->mtu, orig_mtu);
+       }
+}
+
 /* Event              force Flags           Description
  * NETDEV_CHANGE      0     LINKDOWN        Carrier OFF, not for scope host
  * NETDEV_DOWN        0     LINKDOWN|DEAD   Link down, not for scope host