ipv6: Use 1280 as min MTU for ipv6 forwarding
Clients will set their MTU to 1280 if they receive a
ICMPV6_PKT_TOOBIG message with an MTU less than 1280.
To allow encapsulating of packets over a 1280 link
we should always accept packets with a size of 1280
for forwarding even if the path has a lower MTU and
fragment the encapsulated packets afterwards.
In case a forwarded packet is not going to be encapsulated
a ICMPV6_PKT_TOOBIG msg will still be send by ip6_fragment()
with the correct MTU.
Signed-off-by: Ulrich Weber <uweber@astaro.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 1a5fe9a..dabf108a 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -402,6 +402,7 @@
struct ipv6hdr *hdr = ipv6_hdr(skb);
struct inet6_skb_parm *opt = IP6CB(skb);
struct net *net = dev_net(dst->dev);
+ u32 mtu;
if (net->ipv6.devconf_all->forwarding == 0)
goto error;
@@ -508,10 +509,14 @@
}
}
- if (skb->len > dst_mtu(dst)) {
+ mtu = dst_mtu(dst);
+ if (mtu < IPV6_MIN_MTU)
+ mtu = IPV6_MIN_MTU;
+
+ if (skb->len > mtu) {
/* Again, force OUTPUT device used as source address */
skb->dev = dst->dev;
- icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, dst_mtu(dst));
+ icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
IP6_INC_STATS_BH(net,
ip6_dst_idev(dst), IPSTATS_MIB_INTOOBIGERRORS);
IP6_INC_STATS_BH(net,
@@ -621,8 +626,7 @@
mtu = ip6_skb_dst_mtu(skb);
/* We must not fragment if the socket is set to force MTU discovery
- * or if the skb it not generated by a local socket. (This last
- * check should be redundant, but it's free.)
+ * or if the skb it not generated by a local socket.
*/
if (!skb->local_df) {
skb->dev = skb_dst(skb)->dev;