@@ -245,16 +245,16 @@ static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
}
-static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb)
+static void tcp_ecn_accept_cwr(struct sock *sk, const struct sk_buff *skb)
{
if (tcp_hdr(skb)->cwr) {
- tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
+ tcp_sk(sk)->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
/* If the sender is telling us it has entered CWR, then its
* cwnd may be very low (even just 1 packet), so we should ACK
* immediately.
*/
- tcp_enter_quickack_mode((struct sock *)tp, 2);
+ inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
}
}
@@ -4703,7 +4703,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
skb_dst_drop(skb);
__skb_pull(skb, tcp_hdr(skb)->doff * 4);
- tcp_ecn_accept_cwr(tp, skb);
+ tcp_ecn_accept_cwr(sk, skb);
tp->rx_opt.dsack = 0;
Previously commit 9aee40006190 ("tcp: ack immediately when a cwr packet arrives") calls tcp_enter_quickack_mode to force sending two immediate ACKs upon receiving a packet w/ CWR flag. The side effect is it'll also reset the delayed ACK timer and interactive session tracking. This patch removes that side effect by using the new ACK_NOW flag to force an immmediate ACK. Packetdrill to demonstrate: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 setsockopt(3, SOL_TCP, TCP_CONGESTION, "dctcp", 5) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +0 < [ect0] SEW 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7> +0 > SE. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8> +.1 < [ect0] . 1:1(0) ack 1 win 257 +0 accept(3, ..., ...) = 4 +0 < [ect0] . 1:1001(1000) ack 1 win 257 +0 > [ect01] . 1:1(0) ack 1001 +0 write(4, ..., 1) = 1 +0 > [ect01] P. 1:2(1) ack 1001 +0 < [ect0] . 1001:2001(1000) ack 2 win 257 +0 write(4, ..., 1) = 1 +0 > [ect01] P. 2:3(1) ack 2001 +0 < [ect0] . 2001:3001(1000) ack 3 win 257 +0 < [ect0] . 3001:4001(1000) ack 3 win 257 // Ack delayed ... +.01 < [ce] P. 4001:4501(500) ack 3 win 257 +0 > [ect01] . 3:3(0) ack 4001 +0 > [ect01] E. 3:3(0) ack 4501 +.001 read(4, ..., 4500) = 4500 +0 write(4, ..., 1) = 1 +0 > [ect01] PE. 3:4(1) ack 4501 win 100 +.01 < [ect0] W. 4501:5501(1000) ack 4 win 257 // No delayed ACK on CWR flag +0 > [ect01] . 4:4(0) ack 5501 +.31 < [ect0] . 5501:6501(1000) ack 4 win 257 +0 > [ect01] . 4:4(0) ack 6501 Fixes: 9aee40006190 ("tcp: ack immediately when a cwr packet arrives") Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> --- net/ipv4/tcp_input.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)