tcp: properly scale window in tcp_v[46]_reqsk_send_ack() (20a2b49f) · Commits · 戴 / test

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:

Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Acked-by:

Yuchung Cheng <ycheng@google.com> Acked-by:

Neal Cardwell <ncardwell@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

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);

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