[PATCH iproute2-next] man: ip-route: document tcp_usec_ts route feature

[Prijesh Patel <prijeshpatel.dev@gmail.com>]

ip route supports a "tcp_usec_ts" per-route feature
(RTAX_FEATURE_TCP_USEC_TS) to request microsecond-resolution TCP
timestamps for connections to/from a given destination, but this was
never added to the ip-route(8) man page or its FEATURES synopsis.

Document tcp_usec_ts alongside the existing ecn feature.

Signed-off-by: Prijesh Patel <prijeshpatel.dev@gmail.com>
---
 man/man8/ip-route.8.in | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/man/man8/ip-route.8.in b/man/man8/ip-route.8.in
index fd04432f..ed901fb9 100644
--- a/man/man8/ip-route.8.in
+++ b/man/man8/ip-route.8.in
@@ -186,7 +186,7 @@ throw " | " unreachable " | " prohibit " | " blackhole " | " nat " ]"
 
 .ti -8
 .IR FEATURES " := [ "
-.BR ecn " | ]"
+.BR ecn " | " tcp_usec_ts " ]"
 
 .ti -8
 .IR PREF " := [ "
@@ -569,16 +569,26 @@ Actual window size is this value multiplied by the MSS of the connection.
 The default value is zero, meaning to use Slow Start value.
 
 .TP
-.BI features " FEATURES " (Linux 3.18+ only)
-Enable or disable per-route features. Only available feature at this
-time is
+.BI features " FEATURES "
+Enable or disable per-route features. Available features are
 .B ecn
-to enable explicit congestion notification when initiating connections to the
+and
+.B tcp_usec_ts.
+.in +8
+.B ecn
+.RI ( "Linux 3.18+ only" )
+Enables explicit congestion notification when initiating connections to the
 given destination network.
 When responding to a connection request from the given network, ecn will
 also be used even if the
 .B net.ipv4.tcp_ecn
 sysctl is set to 0.
+.sp
+.B tcp_usec_ts
+.RI ( "Linux 6.7+ only" )
+Enables microsecond-resolution TCP timestamps for connections to/from the
+given destination network, instead of the default millisecond resolution.
+.in -8
 
 .TP
 .BI quickack " BOOL " "(Linux 3.11+ only)"
-- 
2.52.0