netdev - [RFC 01/14] tcp: Write options after the header has been fully done

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Message-id: <20171218215109.38700-2-cpaasch@apple.com>
Date:   Mon, 18 Dec 2017 13:50:56 -0800
From:   Christoph Paasch <cpaasch@...le.com>
To:     netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [RFC 01/14] tcp: Write options after the header has been fully done

The generic TCP-option framework will need to have access to the full
TCP-header (e.g., if we want to compute a checksum for TCP-MD5).

Thus, we move the call to tcp_options_write() to after all the fields in
the header have been filled out.

Signed-off-by: Christoph Paasch <cpaasch@...le.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/ipv4/tcp_output.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 04be9f833927..0f66d101d0ca 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1126,7 +1126,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 		}
 	}
 
-	tcp_options_write((__be32 *)(th + 1), tp, &opts);
 	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
 	if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
 		th->window      = htons(tcp_select_window(sk));
@@ -1137,6 +1136,7 @@ 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);
 #ifdef CONFIG_TCP_MD5SIG
 	/* Calculate the MD5 hash, as we have all we need now */
 	if (md5) {
@@ -3242,8 +3242,8 @@ 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));
-	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
 	th->doff = (tcp_header_size >> 2);
+	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
 	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
 
 #ifdef CONFIG_TCP_MD5SIG
-- 
2.15.0