1 files changed, 45 insertions, 31 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 939d122e71b4..a2ed9fdd58d4 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -128,7 +128,7 @@ struct uncached_list {
 
 static DEFINE_PER_CPU_ALIGNED(struct uncached_list, rt6_uncached_list);
 
-static void rt6_uncached_list_add(struct rt6_info *rt)
+void rt6_uncached_list_add(struct rt6_info *rt)
 {
         struct uncached_list *ul = raw_cpu_ptr(&rt6_uncached_list);
 
@@ -139,7 +139,7 @@ static void rt6_uncached_list_add(struct rt6_info *rt)
         spin_unlock_bh(&ul->lock);
 }
 
-static void rt6_uncached_list_del(struct rt6_info *rt)
+void rt6_uncached_list_del(struct rt6_info *rt)
 {
         if (!list_empty(&rt->rt6i_uncached)) {
                 struct uncached_list *ul = rt->rt6i_uncached_list;
@@ -1514,7 +1514,30 @@ static void rt6_exceptions_remove_prefsrc(struct rt6_info *rt)
         }
 }
 
-static void rt6_exceptions_update_pmtu(struct rt6_info *rt, int mtu)
+static bool rt6_mtu_change_route_allowed(struct inet6_dev *idev,
+                                         struct rt6_info *rt, int mtu)
+{
+        /* If the new MTU is lower than the route PMTU, this new MTU will be the
+         * lowest MTU in the path: always allow updating the route PMTU to
+         * reflect PMTU decreases.
+         *
+         * If the new MTU is higher, and the route PMTU is equal to the local
+         * MTU, this means the old MTU is the lowest in the path, so allow
+         * updating it: if other nodes now have lower MTUs, PMTU discovery will
+         * handle this.
+         */
+
+        if (dst_mtu(&rt->dst) >= mtu)
+                return true;
+
+        if (dst_mtu(&rt->dst) == idev->cnf.mtu6)
+                return true;
+
+        return false;
+}
+
+static void rt6_exceptions_update_pmtu(struct inet6_dev *idev,
+                                       struct rt6_info *rt, int mtu)
 {
         struct rt6_exception_bucket *bucket;
         struct rt6_exception *rt6_ex;
@@ -1523,20 +1546,22 @@ static void rt6_exceptions_update_pmtu(struct rt6_info *rt, int mtu)
         bucket = rcu_dereference_protected(rt->rt6i_exception_bucket,
                                         lockdep_is_held(&rt6_exception_lock));
 
-        if (bucket) {
-                for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
-                        hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) {
-                                struct rt6_info *entry = rt6_ex->rt6i;
-                                /* For RTF_CACHE with rt6i_pmtu == 0
-                                 * (i.e. a redirected route),
-                                 * the metrics of its rt->dst.from has already
-                                 * been updated.
-                                 */
-                                if (entry->rt6i_pmtu && entry->rt6i_pmtu > mtu)
-                                        entry->rt6i_pmtu = mtu;
-                        }
-                        bucket++;
+        if (!bucket)
+                return;
+
+        for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
+                hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) {
+                        struct rt6_info *entry = rt6_ex->rt6i;
+
+                        /* For RTF_CACHE with rt6i_pmtu == 0 (i.e. a redirected
+                         * route), the metrics of its rt->dst.from have already
+                         * been updated.
+                         */
+                        if (entry->rt6i_pmtu &&
+                            rt6_mtu_change_route_allowed(idev, entry, mtu))
+                                entry->rt6i_pmtu = mtu;
                 }
+                bucket++;
         }
 }
 
@@ -3899,25 +3924,13 @@ static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
            Since RFC 1981 doesn't include administrative MTU increase
            update PMTU increase is a MUST. (i.e. jumbo frame)
          */
-        /*
-           If new MTU is less than route PMTU, this new MTU will be the
-           lowest MTU in the path, update the route PMTU to reflect PMTU
-           decreases; if new MTU is greater than route PMTU, and the
-           old MTU is the lowest MTU in the path, update the route PMTU
-           to reflect the increase. In this case if the other nodes' MTU
-           also have the lowest MTU, TOO BIG MESSAGE will be lead to
-           PMTU discovery.
-         */
         if (rt->dst.dev == arg->dev &&
-            dst_metric_raw(&rt->dst, RTAX_MTU) &&
             !dst_metric_locked(&rt->dst, RTAX_MTU)) {
                 spin_lock_bh(&rt6_exception_lock);
-                if (dst_mtu(&rt->dst) >= arg->mtu ||
-                    (dst_mtu(&rt->dst) < arg->mtu &&
-                     dst_mtu(&rt->dst) == idev->cnf.mtu6)) {
+                if (dst_metric_raw(&rt->dst, RTAX_MTU) &&
+                    rt6_mtu_change_route_allowed(idev, rt, arg->mtu))
                         dst_metric_set(&rt->dst, RTAX_MTU, arg->mtu);
-                }
-                rt6_exceptions_update_pmtu(rt, arg->mtu);
+                rt6_exceptions_update_pmtu(idev, rt, arg->mtu);
                 spin_unlock_bh(&rt6_exception_lock);
         }
         return 0;
@@ -4189,6 +4202,7 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
                                 r_cfg.fc_encap_type = nla_get_u16(nla);
                 }
 
+                r_cfg.fc_flags |= (rtnh->rtnh_flags & RTNH_F_ONLINK);
                 rt = ip6_route_info_create(&r_cfg, extack);
                 if (IS_ERR(rt)) {
                         err = PTR_ERR(rt);