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Commit 20a2b49f authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: properly scale window in tcp_v[46]_reqsk_send_ack() 



When sending an ack in SYN_RECV state, we must scale the offered
window if wscale option was negotiated and accepted.

Tested:
 Following packetdrill test demonstrates the issue :

0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0

+0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0

// Establish a connection.
+0 < S 0:0(0) win 20000 <mss 1000,sackOK,wscale 7, nop, TS val 100 ecr 0>
+0 > S. 0:0(0) ack 1 win 28960 <mss 1460,sackOK, TS val 100 ecr 100, nop, wscale 7>

+0 < . 1:11(10) ack 1 win 156 <nop,nop,TS val 99 ecr 100>
// check that window is properly scaled !
+0 > . 1:1(0) ack 1 win 226 <nop,nop,TS val 200 ecr 100>

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6c389fc9

net/ipv4/tcp_ipv4.c

+7 −1
Original line number Diff line number Diff line
@@ -814,8 +814,14 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb, 
	u32 seq = (sk->sk_state == TCP_LISTEN) ? tcp_rsk(req)->snt_isn + 1 :

					     tcp_sk(sk)->snd_nxt;



	/* RFC 7323 2.3

	 * The window field (SEG.WND) of every outgoing segment, with the

	 * exception of <SYN> segments, MUST be right-shifted by

	 * Rcv.Wind.Shift bits:

	 */

	tcp_v4_send_ack(sock_net(sk), skb, seq,

			tcp_rsk(req)->rcv_nxt, req->rsk_rcv_wnd,

			tcp_rsk(req)->rcv_nxt,

			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,

			tcp_time_stamp,

			req->ts_recent,

			0,

net/ipv6/tcp_ipv6.c

+7 −1
Original line number Diff line number Diff line
@@ -944,9 +944,15 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb, 
	/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV

	 * sk->sk_state == TCP_SYN_RECV -> for Fast Open.

	 */

	/* RFC 7323 2.3

	 * The window field (SEG.WND) of every outgoing segment, with the

	 * exception of <SYN> segments, MUST be right-shifted by

	 * Rcv.Wind.Shift bits:

	 */

	tcp_v6_send_ack(sk, skb, (sk->sk_state == TCP_LISTEN) ?

			tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,

			tcp_rsk(req)->rcv_nxt, req->rsk_rcv_wnd,

			tcp_rsk(req)->rcv_nxt,

			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,

			tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,

			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),

			0, 0);