tcp: add SYN/data info to TCP_INFO

Add a bit TCPI_OPT_SYN_DATA (32) to the socket option TCP_INFO:tcpi_options.
It's set if the data in SYN (sent or received) is acked by SYN-ACK. Server or
client application can use this information to check Fast Open success rate.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 8a7fc4be2d7..60b7aac15e0 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -191,7 +191,8 @@ struct tcp_sock {
         u8      do_early_retrans:1,/* Enable RFC5827 early-retransmit  */
                 early_retrans_delayed:1, /* Delayed ER timer installed */
                 syn_data:1,     /* SYN includes data */
-                syn_fastopen:1; /* SYN includes Fast Open option */
+                syn_fastopen:1, /* SYN includes Fast Open option */
+                syn_data_acked:1;/* data in SYN is acked by SYN-ACK */
 
 /* RTT measurement */
         u32     srtt;           /* smoothed round trip time << 3        */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index c4b89a5cb7d..e962faa5ab0 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -130,6 +130,7 @@ enum {
 #define TCPI_OPT_WSCALE         4
 #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 */
 
 enum tcp_ca_state {
         TCP_CA_Open = 0,