xfrm6: Don't call icmpv6_send on local error

Calling icmpv6_send() on a local message size error leads to
an incorrect update of the path mtu. So use xfrm6_local_rxpmtu()
to notify about the pmtu if the IPV6_DONTFRAG socket option is
set on an udp or raw socket, according RFC 3542 and use
ipv6_local_error() otherwise.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 54 insertions, 2 deletions

diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index 49a91c5f5623..faae41737fca 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -28,6 +28,43 @@ int xfrm6_find_1stfragopt(struct xfrm_state *x, struct sk_buff *skb,
 
 EXPORT_SYMBOL(xfrm6_find_1stfragopt);
 
+static int xfrm6_local_dontfrag(struct sk_buff *skb)
+{
+        int proto;
+        struct sock *sk = skb->sk;
+
+        if (sk) {
+                proto = sk->sk_protocol;
+
+                if (proto == IPPROTO_UDP || proto == IPPROTO_RAW)
+                        return inet6_sk(sk)->dontfrag;
+        }
+
+        return 0;
+}
+
+static void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu)
+{
+        struct flowi6 fl6;
+        struct sock *sk = skb->sk;
+
+        fl6.flowi6_oif = sk->sk_bound_dev_if;
+        ipv6_addr_copy(&fl6.daddr, &ipv6_hdr(skb)->daddr);
+
+        ipv6_local_rxpmtu(sk, &fl6, mtu);
+}
+
+static void xfrm6_local_error(struct sk_buff *skb, u32 mtu)
+{
+        struct flowi6 fl6;
+        struct sock *sk = skb->sk;
+
+        fl6.fl6_dport = inet_sk(sk)->inet_dport;
+        ipv6_addr_copy(&fl6.daddr, &ipv6_hdr(skb)->daddr);
+
+        ipv6_local_error(sk, EMSGSIZE, &fl6, mtu);
+}
+
 static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 {
         int mtu, ret = 0;
@@ -39,7 +76,13 @@ static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 
         if (!skb->local_df && skb->len > mtu) {
                 skb->dev = dst->dev;
-                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+
+                if (xfrm6_local_dontfrag(skb))
+                        xfrm6_local_rxpmtu(skb, mtu);
+                else if (skb->sk)
+                        xfrm6_local_error(skb, mtu);
+                else
+                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                 ret = -EMSGSIZE;
         }
 
@@ -93,9 +136,18 @@ static int __xfrm6_output(struct sk_buff *skb)
 {
         struct dst_entry *dst = skb_dst(skb);
         struct xfrm_state *x = dst->xfrm;
+        int mtu = ip6_skb_dst_mtu(skb);
+
+        if (skb->len > mtu && xfrm6_local_dontfrag(skb)) {
+                xfrm6_local_rxpmtu(skb, mtu);
+                return -EMSGSIZE;
+        } else if (!skb->local_df && skb->len > mtu && skb->sk) {
+                xfrm6_local_error(skb, mtu);
+                return -EMSGSIZE;
+        }
 
         if ((x && x->props.mode == XFRM_MODE_TUNNEL) &&
-            ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
+            ((skb->len > mtu && !skb_is_gso(skb)) ||
                 dst_allfrag(skb_dst(skb)))) {
                         return ip6_fragment(skb, x->outer_mode->afinfo->output_finish);
         }