diff mbox series

[v5,net-next,08/15] tcp: sack option handling improvements

Message ID 20250422153602.54787-9-chia-yu.chang@nokia-bell-labs.com
State New
Headers show
Series AccECN protocol patch series | expand

Commit Message

Chia-Yu Chang (Nokia) April 22, 2025, 3:35 p.m. UTC 
From: Ilpo Järvinen <ij@kernel.org>

1) Don't early return when sack doesn't fit. AccECN code will be
   placed after this fragment so no early returns please.

2) Make sure opts->num_sack_blocks is not left undefined. E.g.,
   tcp_current_mss() does not memset its opts struct to zero.
   AccECN code checks if SACK option is present and may even
   alter it to make room for AccECN option when many SACK blocks
   are present. Thus, num_sack_blocks needs to be always valid.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 net/ipv4/tcp_output.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d63f505a30e2..ad97bb9951fd 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1103,17 +1103,18 @@  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;
+		}
+	} else {
+		opts->num_sack_blocks = 0;
 	}
 
 	if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,