On Mon, Aug 22, 2016 at 11:31 AM, Eric Dumazet <eric.duma...@gmail.com> wrote: > From: Eric Dumazet <eduma...@google.com> > > 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 <eduma...@google.com> > Cc: Yuchung Cheng <ych...@google.com> > Cc: Neal Cardwell <ncardw...@google.com> > --- Acked-by: Yuchung Cheng <ych...@google.com>
Nice fix! > net/ipv4/tcp_ipv4.c | 8 +++++++- > net/ipv6/tcp_ipv6.c | 8 +++++++- > 2 files changed, 14 insertions(+), 2 deletions(-) > > > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > index 32b048e524d6..7158d4f8dae4 100644 > --- a/net/ipv4/tcp_ipv4.c > +++ b/net/ipv4/tcp_ipv4.c > @@ -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, > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c > index 33df8b8575cc..94f4f89d73e7 100644 > --- a/net/ipv6/tcp_ipv6.c > +++ b/net/ipv6/tcp_ipv6.c > @@ -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); > >
