tcp: Handle CHECKSUM_PARTIAL for SYNACK packets for IPv4

tcp: Handle CHECKSUM_PARTIAL for SYNACK packets for IPv4

This patch moves the common code between tcp_v4_send_check and
tcp_v4_gso_send_check into a new function __tcp_v4_send_check.

It then uses the new function in tcp_v4_send_synack so that it
handles CHECKSUM_PARTIAL properly.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Yinghai <yinghai.lu@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 17 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3c23e70885f4..aebfd28c5089 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -519,26 +519,31 @@ out:
         sock_put(sk);
 }
 
-/* This routine computes an IPv4 TCP checksum. */
-void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
+static void __tcp_v4_send_check(struct sk_buff *skb,
+                                __be32 saddr, __be32 daddr)
 {
-        struct inet_sock *inet = inet_sk(sk);
         struct tcphdr *th = tcp_hdr(skb);
 
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
-                th->check = ~tcp_v4_check(len, inet->inet_saddr,
-                                          inet->inet_daddr, 0);
+                th->check = ~tcp_v4_check(skb->len, saddr, daddr, 0);
                 skb->csum_start = skb_transport_header(skb) - skb->head;
                 skb->csum_offset = offsetof(struct tcphdr, check);
         } else {
-                th->check = tcp_v4_check(len, inet->inet_saddr,
-                                         inet->inet_daddr,
+                th->check = tcp_v4_check(skb->len, saddr, daddr,
                                          csum_partial(th,
                                                       th->doff << 2,
                                                       skb->csum));
         }
 }
 
+/* This routine computes an IPv4 TCP checksum. */
+void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
+{
+        struct inet_sock *inet = inet_sk(sk);
+
+        __tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
+}
+
 int tcp_v4_gso_send_check(struct sk_buff *skb)
 {
         const struct iphdr *iph;
@@ -551,10 +556,8 @@ int tcp_v4_gso_send_check(struct sk_buff *skb)
         th = tcp_hdr(skb);
 
         th->check = 0;
-        th->check = ~tcp_v4_check(skb->len, iph->saddr, iph->daddr, 0);
-        skb->csum_start = skb_transport_header(skb) - skb->head;
-        skb->csum_offset = offsetof(struct tcphdr, check);
         skb->ip_summed = CHECKSUM_PARTIAL;
+        __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
         return 0;
 }
 
@@ -763,13 +766,7 @@ static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
         skb = tcp_make_synack(sk, dst, req, rvp);
 
         if (skb) {
-                struct tcphdr *th = tcp_hdr(skb);
-
-                th->check = tcp_v4_check(skb->len,
-                                         ireq->loc_addr,
-                                         ireq->rmt_addr,
-                                         csum_partial(th, skb->len,
-                                                      skb->csum));
+                __tcp_v4_send_check(skb, ireq->loc_addr, ireq->rmt_addr);
 
                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
                                             ireq->rmt_addr,