[INET]: Add IP(V6)_PMTUDISC_RPOBE
Add IP(V6)_PMTUDISC_PROBE value for IP(V6)_MTU_DISCOVER. This option forces
us not to fragment, but does not make use of the kernel path MTU discovery.
That is, it allows for user-mode MTU probing (or, packetization-layer path
MTU discovery). This is particularly useful for diagnostic utilities, like
traceroute/tracepath.
Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 5a5b7d4..f508171 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -137,9 +137,17 @@
return NF_HOOK(PF_INET6, NF_IP6_POST_ROUTING, skb,NULL, skb->dev,ip6_output_finish);
}
+static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
+{
+ struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+
+ return (np && np->pmtudisc == IPV6_PMTUDISC_PROBE) ?
+ skb->dst->dev->mtu : dst_mtu(skb->dst);
+}
+
int ip6_output(struct sk_buff *skb)
{
- if ((skb->len > dst_mtu(skb->dst) && !skb_is_gso(skb)) ||
+ if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
dst_allfrag(skb->dst))
return ip6_fragment(skb, ip6_output2);
else
@@ -566,7 +574,7 @@
hlen = ip6_find_1stfragopt(skb, &prevhdr);
nexthdr = *prevhdr;
- mtu = dst_mtu(&rt->u.dst);
+ 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
@@ -1063,7 +1071,8 @@
inet->cork.fl = *fl;
np->cork.hop_limit = hlimit;
np->cork.tclass = tclass;
- mtu = dst_mtu(rt->u.dst.path);
+ mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
+ rt->u.dst.dev->mtu : dst_mtu(rt->u.dst.path);
if (np->frag_size < mtu) {
if (np->frag_size)
mtu = np->frag_size;