[PATCH iproute2] ss: add fastopen support

[Eric Dumazet <eric.dumazet@gmail.com>]

From: Eric Dumazet <edumazet@google.com>

ss -i can output "fastopen" attribute if socket used Fast Open

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
---
 include/netinet/tcp.h |    5 +++--
 misc/ss.c             |    2 ++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/netinet/tcp.h b/include/netinet/tcp.h
index 3f890a1..ba79c63 100644
--- a/include/netinet/tcp.h
+++ b/include/netinet/tcp.h
@@ -171,8 +171,9 @@ enum
 # define TCPI_OPT_TIMESTAMPS	1
 # define TCPI_OPT_SACK		2
 # define TCPI_OPT_WSCALE	4
-# define TCPI_OPT_ECN		8
-# define TCPI_OPT_ECN_SEEN	16
+# 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 */
 
 /* Values for tcpi_state.  */
 enum tcp_ca_state
diff --git a/misc/ss.c b/misc/ss.c
index da9d32c..b7bcd80 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -1392,6 +1392,8 @@ static void tcp_show_info(const struct nlmsghdr *nlh, struct inet_diag_msg *r)
 				printf(" ecn");
 			if (info->tcpi_options & TCPI_OPT_ECN_SEEN)
 				printf(" ecnseen");
+			if (info->tcpi_options & TCPI_OPT_SYN_DATA)
+				printf(" fastopen");
 		}
 
 		if (tb[INET_DIAG_CONG])