netdev - [RFC PATCH v2 25/45] tcp: Check for filled TCP option space before SACK

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Message-Id: <20191002233655.24323-26-mathew.j.martineau@linux.intel.com>
Date:   Wed,  2 Oct 2019 16:36:35 -0700
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org, edumazet@...gle.com
Cc:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        cpaasch@...le.com, fw@...len.de, pabeni@...hat.com,
        peter.krystad@...ux.intel.com, dcaratti@...hat.com,
        matthieu.baerts@...sares.net
Subject: [RFC PATCH v2 25/45] tcp: Check for filled TCP option space before SACK

The SACK code would potentially add four bytes to the expected
TCP option size even if all option space was already used.

Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/ipv4/tcp_output.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3de804531231..dd9be5169aa3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -805,6 +805,9 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 		}
 	}
 
+	if (size + TCPOLEN_SACK_BASE_ALIGNED >= MAX_TCP_OPTION_SPACE)
+		return size;
+
 	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
 	if (unlikely(eff_sacks)) {
 		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
-- 
2.23.0