tcp: Do not tack on TSO data to non-TSO packet

If a socket starts out on a non-TSO route, and then switches to
a TSO route, then we will tack on data to the tail of the tx queue
even if it started out life as non-TSO.  This is suboptimal because
all of it will then be copied and checksummed unnecessarily.

This patch fixes this by ensuring that skb->ip_summed is set to
CHECKSUM_PARTIAL before appending extra data beyond the MSS.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 5 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 17b89c523f9..7870a535dac 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -903,13 +903,17 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
                 iov++;
 
                 while (seglen > 0) {
-                        int copy;
+                        int copy = 0;
+                        int max = size_goal;
 
                         skb = tcp_write_queue_tail(sk);
+                        if (tcp_send_head(sk)) {
+                                if (skb->ip_summed == CHECKSUM_NONE)
+                                        max = mss_now;
+                                copy = max - skb->len;
+                        }
 
-                        if (!tcp_send_head(sk) ||
-                            (copy = size_goal - skb->len) <= 0) {
-
+                        if (copy <= 0) {
 new_segment:
                                 /* Allocate new segment. If the interface is SG,
                                  * allocate skb fitting to single page.
@@ -930,6 +934,7 @@ new_segment:
 
                                 skb_entail(sk, skb);
                                 copy = size_goal;
+                                max = size_goal;
                         }
 
                         /* Try to append data to the end of skb. */
@@ -1028,7 +1033,7 @@ new_segment:
                         if ((seglen -= copy) == 0 && iovlen == 0)
                                 goto out;
 
-                        if (skb->len < size_goal || (flags & MSG_OOB))
+                        if (skb->len < max || (flags & MSG_OOB))
                                 continue;
 
                         if (forced_push(tp)) {