tcp: fix initial tp->rcvq_space.space value for passive TS enabled flows

[ Upstream commit cd171461b90a2d2cf230943df60d580174633718 ]

tcp_rcv_state_process() must tweak tp->advmss for TS enabled flows
before the call to tcp_init_transfer() / tcp_init_buffer_space().

Otherwise tp->rcvq_space.space is off by 120 bytes
(TCP_INIT_CWND * TCPOLEN_TSTAMP_ALIGNED).

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Wei Wang <weiwan@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 000557f5c54bc3987ab97ef994e68299662d6a69..a52d5b718e6e1dacbe3d4cb6f16268abcb2cc08b 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6573,6 +6573,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
                if (!tp->srtt_us)
                        tcp_synack_rtt_meas(sk, req);
 
+               if (tp->rx_opt.tstamp_ok)
+                       tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
+
                if (req) {
                        tcp_rcv_synrecv_state_fastopen(sk);
                } else {
@@ -6597,9 +6600,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
                tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
                tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
 
-               if (tp->rx_opt.tstamp_ok)
-                       tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
-
                if (!inet_csk(sk)->icsk_ca_ops->cong_control)
                        tcp_update_pacing_rate(sk);