[NET]: Add software TSOv4

This patch adds the GSO implementation for IPv4 TCP.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index b197a9e..ca3d38d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1086,6 +1086,8 @@
 
 extern int tcp_v4_destroy_sock(struct sock *sk);
 
+extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg);
+
 #ifdef CONFIG_PROC_FS
 extern int  tcp4_proc_init(void);
 extern void tcp4_proc_exit(void);