diff mbox series

[v4,net-next,14/15] tcp: accecn: try to fit AccECN option with SACK

Message ID 20250417230029.21905-15-chia-yu.chang@nokia-bell-labs.com (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series AccECN protocol patch series | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 9 of 9 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 22 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 1 this patch: 1
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2025-04-18--09-00 (tests: 916)

Commit Message

Chia-Yu Chang (Nokia) April 17, 2025, 11 p.m. UTC 
From: Ilpo Järvinen <ij@kernel.org>

As SACK blocks tend to eat all option space when there are
many holes, it is useful to compromise on sending many SACK
blocks in every ACK and try to fit AccECN option there
by reduction the number of SACK blocks. But never go below
two SACK blocks because of AccECN option.

As AccECN option is often not put to every ACK, the space
hijack is usually only temporary.

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 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8e1535635aab..936ec8788c8e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -981,8 +981,21 @@  static int tcp_options_fit_accecn(struct tcp_out_options *opts, int required,
 		opts->num_accecn_fields--;
 		size -= TCPOLEN_ACCECN_PERFIELD;
 	}
-	if (opts->num_accecn_fields < required)
+	if (opts->num_accecn_fields < required) {
+		if (opts->num_sack_blocks > 2) {
+			/* Try to fit the option by removing one SACK block */
+			opts->num_sack_blocks--;
+			size = tcp_options_fit_accecn(opts, required,
+						      remaining +
+						      TCPOLEN_SACK_PERBLOCK,
+						      max_combine_saving);
+			if (opts->options & OPTION_ACCECN)
+				return size - TCPOLEN_SACK_PERBLOCK;
+
+			opts->num_sack_blocks++;
+		}
 		return 0;
+	}
 
 	opts->options |= OPTION_ACCECN;
 	return size;