ipv4: Fix packet size calculation in __ip_append_data

Git commit 59104f06 (ip: take care of last fragment in ip_append_data)
added a check to see if we exceed the mtu when we add trailer_len.
However, the mtu is already subtracted by the trailer length when the
xfrm transfomation bundles are set up. So IPsec packets with mtu
size get fragmented, or if the DF bit is set the packets will not
be send even though they match the mtu perfectly fine. This patch
actually reverts commit 59104f06.

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

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index a8024eaa0e87b15ebdc86058a87c24f0813a610a..6b894d430e616fca9eb192853f81bbd75ea49cde 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -888,12 +888,9 @@ alloc_new_skb:
                         * because we have no idea what fragment will be
                         * the last.
                         */
-                       if (datalen == length + fraggap) {
+                       if (datalen == length + fraggap)
                                alloclen += rt->dst.trailer_len;
-                               /* make sure mtu is not reached */
-                               if (datalen > mtu - fragheaderlen - rt->dst.trailer_len)
-                                       datalen -= ALIGN(rt->dst.trailer_len, 8);
-                       }
+
                        if (transhdrlen) {
                                skb = sock_alloc_send_skb(sk,
                                                alloclen + hh_len + 15,