tcp: use tcp_v4_send_synack on first SYN-ACK
To avoid large code duplication in IPv6, we need to first simplify
the complicate SYN-ACK sending code in tcp_v4_conn_request().
To use tcp_v4(6)_send_synack() to send all SYN-ACKs, we need to
initialize the mini socket's receive window before trying to
create the child socket and/or building the SYN-ACK packet. So we move
that initialization from tcp_make_synack() to tcp_v4_conn_request()
as a new function tcp_openreq_init_req_rwin().
After this refactoring the SYN-ACK sending code is simpler and easier
to implement Fast Open for IPv6.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Daniel Lee <longinus00@gmail.com>
Signed-off-by: Jerry Chu <hkchu@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 05c1b15..e68e0d4 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -362,6 +362,37 @@
}
EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
+void tcp_openreq_init_rwin(struct request_sock *req,
+ struct sock *sk, struct dst_entry *dst)
+{
+ struct inet_request_sock *ireq = inet_rsk(req);
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u8 rcv_wscale;
+ int mss = dst_metric_advmss(dst);
+
+ if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
+ mss = tp->rx_opt.user_mss;
+
+ /* Set this up on the first call only */
+ req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+
+ /* limit the window selection if the user enforce a smaller rx buffer */
+ if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+ (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
+ req->window_clamp = tcp_full_space(sk);
+
+ /* tcp_full_space because it is guaranteed to be the first packet */
+ tcp_select_initial_window(tcp_full_space(sk),
+ mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+ &req->rcv_wnd,
+ &req->window_clamp,
+ ireq->wscale_ok,
+ &rcv_wscale,
+ dst_metric(dst, RTAX_INITRWND));
+ ireq->rcv_wscale = rcv_wscale;
+}
+EXPORT_SYMBOL(tcp_openreq_init_rwin);
+
static inline void TCP_ECN_openreq_child(struct tcp_sock *tp,
struct request_sock *req)
{