[RFC 02/14] tcp: Pass sock and skb to tcp_options_write

[Christoph Paasch <cpaasch@apple.com>]

An upcoming patch adds a configurable, per-socket list of TCP options to
populate in the TCP header. This requires tcp_options_write() to know the
socket (to use the options list) and the skb (to provide visibility to the
packet data for options like TCP_MD5SIG).

Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/ipv4/tcp_output.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0f66d101d0ca..efe599a41e36 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -444,10 +444,14 @@ struct tcp_out_options {
  * At least SACK_PERM as the first option is known to lead to a disaster
  * (but it may well be that other scenarios fail similarly).
  */
-static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
+static void tcp_options_write(__be32 *ptr, struct sk_buff *skb, struct sock *sk,
 			      struct tcp_out_options *opts)
 {
 	u16 options = opts->options;	/* mungable copy */
+	struct tcp_sock *tp = NULL;
+
+	if (sk_fullsock(sk))
+		tp = tcp_sk(sk);
 
 	if (unlikely(OPTION_MD5 & options)) {
 		*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
@@ -1136,7 +1140,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 		 */
 		th->window	= htons(min(tp->rcv_wnd, 65535U));
 	}
-	tcp_options_write((__be32 *)(th + 1), tp, &opts);
+	tcp_options_write((__be32 *)(th + 1), skb, sk, &opts);
 #ifdef CONFIG_TCP_MD5SIG
 	/* Calculate the MD5 hash, as we have all we need now */
 	if (md5) {
@@ -3243,7 +3247,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
 	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
 	th->doff = (tcp_header_size >> 2);
-	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
+	tcp_options_write((__be32 *)(th + 1), skb, req_to_sk(req), &opts);
 	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
 
 #ifdef CONFIG_TCP_MD5SIG
-- 
2.15.0