tcp: refactor setting the initial congestion window

Relocate the congestion window initialization from tcp_init_metrics()
to tcp_init_transfer() to improve code readability.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 706a99ec73f6..077d9abdfcf5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5647,6 +5647,32 @@ discard:
 }
 EXPORT_SYMBOL(tcp_rcv_established);
 
+void tcp_init_transfer(struct sock *sk, int bpf_op)
+{
+        struct inet_connection_sock *icsk = inet_csk(sk);
+        struct tcp_sock *tp = tcp_sk(sk);
+
+        tcp_mtup_init(sk);
+        icsk->icsk_af_ops->rebuild_header(sk);
+        tcp_init_metrics(sk);
+
+        /* Initialize the congestion window to start the transfer.
+         * Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
+         * retransmitted. In light of RFC6298 more aggressive 1sec
+         * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
+         * retransmission has occurred.
+         */
+        if (tp->total_retrans > 1 && tp->undo_marker)
+                tp->snd_cwnd = 1;
+        else
+                tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
+        tp->snd_cwnd_stamp = tcp_jiffies32;
+
+        tcp_call_bpf(sk, bpf_op, 0, NULL);
+        tcp_init_congestion_control(sk);
+        tcp_init_buffer_space(sk);
+}
+
 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 {
         struct tcp_sock *tp = tcp_sk(sk);