From: David S. Miller Date: Thu, 8 Apr 2010 18:32:30 +0000 (-0700) Subject: tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb X-Git-Tag: v2.6.35-rc1~473^2~523 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=2e8e18ef52e7dd1af0a3bd1f7d990a1d0b249586 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 --- diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0ae7ce7..e468499 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;