0003-ss-display-ecn_low-if-tcp_info-tcpi_options-TCPI_OPT.patch

From 107339d7f48c95ae8a7461150e143fc53b08fea9 Mon Sep 17 00:00:00 2001
From: Neal Cardwell <ncardwell@google.com>
Date: Sun, 23 Jul 2023 23:33:21 -0400
Subject: [PATCH] ss: display "ecn_low" if tcp_info tcpi_options
 TCPI_OPT_ECN_LOW bit is set

Display "ecn_low" if the TCPI_OPT_ECN_LOW bit is set in the
tcpi_options field in tcp_info.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
---
 include/uapi/linux/tcp.h | 1 +
 misc/ss.c                | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 4ee5d7721c6f..238e95d7693c 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -170,6 +170,7 @@ enum tcp_fastopen_client_fail {
 #define TCPI_OPT_ECN		8 /* ECN was negociated at TCP session init */
 #define TCPI_OPT_ECN_SEEN	16 /* we received at least one packet with ECT */
 #define TCPI_OPT_SYN_DATA	32 /* SYN-ACK acked data in SYN sent or rcvd */
+#define TCPI_OPT_ECN_LOW	64 /* Low-latency ECN configured at init */
 
 /*
  * Sender's congestion state indicating normal or abnormal situations
diff --git a/misc/ss.c b/misc/ss.c
index 5f413118f0dd..634285adb7d3 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -907,6 +907,7 @@ struct tcpstat {
 	bool		    has_sack_opt;
 	bool		    has_ecn_opt;
 	bool		    has_ecnseen_opt;
+	bool		    has_ecn_low_opt;
 	bool		    has_fastopen_opt;
 	bool		    has_wscale_opt;
 	bool		    app_limited;
@@ -2621,6 +2622,8 @@ static void tcp_stats_print(struct tcpstat *s)
 		out(" ecn");
 	if (s->has_ecnseen_opt)
 		out(" ecnseen");
+	if (s->has_ecn_low_opt)
+		out(" ecn_low");
 	if (s->has_fastopen_opt)
 		out(" fastopen");
 	if (s->cong_alg[0])
@@ -3134,6 +3137,7 @@ static void tcp_show_info(const struct nlmsghdr *nlh, struct inet_diag_msg *r,
 			s.has_sack_opt	   = TCPI_HAS_OPT(info, TCPI_OPT_SACK);
 			s.has_ecn_opt	   = TCPI_HAS_OPT(info, TCPI_OPT_ECN);
 			s.has_ecnseen_opt  = TCPI_HAS_OPT(info, TCPI_OPT_ECN_SEEN);
+			s.has_ecn_low_opt  = TCPI_HAS_OPT(info, TCPI_OPT_ECN_LOW);
 			s.has_fastopen_opt = TCPI_HAS_OPT(info, TCPI_OPT_SYN_DATA);
 		}
 
-- 
2.41.0.487.g6d72f3e995-goog