From 2e8e18ef52e7dd1af0a3bd1f7d990a1d0b249586 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@davemloft.net>
Date: Thu, 8 Apr 2010 11:32:30 -0700
Subject: [PATCH] tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb
Back in commit 04a0551c87363f100b04d28d7a15a632b70e18e7
("loopback: Drop obsolete ip_summed setting") we stopped
setting CHECKSUM_UNNECESSARY in the loopback xmit.
This is because such a setting was a lie since it implies that the
checksum field of the packet is properly filled in.
Instead what happens normally is that CHECKSUM_PARTIAL is set and
skb->csum is calculated as needed.
But this was only happening for TCP data packets (via the
skb->ip_summed assignment done in tcp_sendmsg()). It doesn't
happen for non-data packets like ACKs etc.
Fix this by setting skb->ip_summed in the common non-data packet
constructor. It already is setting skb->csum to zero.
But this reminds us that we still have things like ip_output.c's
ip_dev_loopback_xmit() which sets skb->ip_summed to the value
CHECKSUM_UNNECESSARY, which Herbert's patch teaches us is not
valid. So we'll have to address that at some point too.
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/tcp_output.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0ae7ce7a71a6..e46849989a53 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -350,6 +350,7 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
*/
static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
{
+ skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum = 0;
TCP_SKB_CB(skb)->flags = flags;
--
GitLab