ipv4: consistent reporting of pmtu data in case of corking

We report different pmtu values back on the first write and on further
writes on an corked socket.

Also don't include the dst.header_len (respectively exthdrlen) as this
should already be dealt with by the interface mtu of the outgoing
(virtual) interface and policy of that interface should dictate if
fragmentation should happen.

Instead reduce the pmtu data by IP options as we do for IPv6. Make the
same changes for ip_append_data, where we did not care about options or
dst.header_len at all.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 912402752f2ffce701d697de1bb7a32b05c3b482..df184616493f707ea8a0ea353a33d3a5aa981fc7 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -828,7 +828,7 @@ static int __ip_append_data(struct sock *sk,
 
        if (cork->length + length > maxnonfragsize - fragheaderlen) {
                ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
-                              mtu-exthdrlen);
+                              mtu - (opt ? opt->optlen : 0));
                return -EMSGSIZE;
        }
 
@@ -1151,7 +1151,8 @@ ssize_t   ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
                         mtu : 0xFFFF;
 
        if (cork->length + size > maxnonfragsize - fragheaderlen) {
-               ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport, mtu);
+               ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
+                              mtu - (opt ? opt->optlen : 0));
                return -EMSGSIZE;
        }