tcp: Stop non-TSO packets morphing into TSO

If a socket starts out on a non-TSO route, and then switches to
a TSO route, then the tail on the tx queue can morph into a TSO
packet, causing mischief because the rest of the stack does not
expect a partially linear TSO packet.

This patch fixes this by ensuring that skb->ip_summed is set to
CHECKSUM_PARTIAL before declaring a packet as TSO.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 416fc4c2e7eb..5bdf08d312d9 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -725,7 +725,8 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb,
                                  unsigned int mss_now)
 {
-        if (skb->len <= mss_now || !sk_can_gso(sk)) {
+        if (skb->len <= mss_now || !sk_can_gso(sk) ||
+            skb->ip_summed == CHECKSUM_NONE) {
                 /* Avoid the costly divide in the normal
                  * non-TSO case.
                  */