netdev - [PATCH bpf] bpf: correctly set initial window on active Fast Open sender

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Message-Id: <20190109021224.6244-1-ycheng@google.com>
Date:   Tue,  8 Jan 2019 18:12:24 -0800
From:   Yuchung Cheng <ycheng@...gle.com>
To:     ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, brakmo@...com, ncardwell@...gle.com,
        edumazet@...gle.com, Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH bpf] bpf: correctly set initial window on active Fast Open sender

The existing BPF TCP initial congestion window (TCP_BPF_IW) does not
to work on (active) Fast Open sender. This is because it changes the
(initial) window only if data_segs_out is zero -- but data_segs_out
is also incremented on SYN-data.  This patch fixes the issue by
proerly accounting for SYN-data additionally.

Fixes: fc7478103c84 ("bpf: Adds support for setting initial cwnd")
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Reviewed-by: Neal Cardwell <ncardwell@...gle.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 447dd1bad31f..2b3b436ef545 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4203,7 +4203,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 			/* Only some options are supported */
 			switch (optname) {
 			case TCP_BPF_IW:
-				if (val <= 0 || tp->data_segs_out > 0)
+				if (val <= 0 || tp->data_segs_out > tp->syn_data)
 					ret = -EINVAL;
 				else
 					tp->snd_cwnd = val;
-- 
2.20.1.97.g81188d93c3-goog