netdev - [RFC PATCH 18/28] tcp: don't early return when sack doesn't fit

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Date:   Wed, 18 Mar 2020 11:37:59 +0200
From:   Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
To:     netdev@...r.kernel.org
Cc:     Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Olivier Tilmans <olivier.tilmans@...ia-bell-labs.com>
Subject: [RFC PATCH 18/28] tcp: don't early return when sack doesn't fit

From: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>

AccECN code will be placed after this fragment so no early
returns please.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>
---
 net/ipv4/tcp_output.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9ff6d14363df..084ebd2e725f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -875,17 +875,16 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
 	if (unlikely(eff_sacks)) {
 		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
-		if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
-					 TCPOLEN_SACK_PERBLOCK))
-			return size;
-
-		opts->num_sack_blocks =
-			min_t(unsigned int, eff_sacks,
-			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
-			      TCPOLEN_SACK_PERBLOCK);
-
-		size += TCPOLEN_SACK_BASE_ALIGNED +
-			opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+		if (likely(remaining >= TCPOLEN_SACK_BASE_ALIGNED +
+					 TCPOLEN_SACK_PERBLOCK)) {
+			opts->num_sack_blocks =
+				min_t(unsigned int, eff_sacks,
+				      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
+				      TCPOLEN_SACK_PERBLOCK);
+
+			size += TCPOLEN_SACK_BASE_ALIGNED +
+				opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+		}
 	}
 
 	return size;
-- 
2.20.1