[patch 53/59] TCP: rare bad TCP checksum with 2.6.19

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Jarek Poplawski <jarkao2@xxxxx>

The patch "Replace CHECKSUM_HW by CHECKSUM_PARTIAL/CHECKSUM_COMPLETE"
changed to unconditional copying of ip_summed field from collapsed
skb. This patch reverts this change.

The majority of substantial work including heavy testing
and diagnosing by: Michael Tokarev <mjt@xxxxxxxxxx>
Possible reasons pointed by: Herbert Xu and Patrick McHardy.

Signed-off-by: Jarek Poplawski <jarkao2@xxxxx>
Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 net/ipv4/tcp_output.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux-2.6.19.2.orig/net/ipv4/tcp_output.c
+++ linux-2.6.19.2/net/ipv4/tcp_output.c
@@ -1590,7 +1590,8 @@ static void tcp_retrans_try_collapse(str
 
 		memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size);
 
-		skb->ip_summed = next_skb->ip_summed;
+		if (next_skb->ip_summed == CHECKSUM_PARTIAL)
+			skb->ip_summed = CHECKSUM_PARTIAL;
 
 		if (skb->ip_summed != CHECKSUM_PARTIAL)
 			skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);

--
-
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