[PATCH net-next] tcp: add SRTT to SCM_TIMESTAMPING_OPT_STATS

[Yousuk Seung]

Add TCP_NLA_SRTT to SCM_TIMESTAMPING_OPT_STATS that reports the smoothed
round trip time in microseconds (tcp_sock.srtt_us >> 3).

Signed-off-by: Yousuk Seung <ysse...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Soheil Hassas Yeganeh <soh...@google.com>
Acked-by: Neal Cardwell <ncardw...@google.com>
Acked-by: Yuchung Cheng <ych...@google.com>
---
 include/uapi/linux/tcp.h | 1 +
 net/ipv4/tcp.c           | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index e02d31986ff91..8bb6cc5f32356 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -266,6 +266,7 @@ enum {
        TCP_NLA_BYTES_RETRANS,  /* Data bytes retransmitted */
        TCP_NLA_DSACK_DUPS,     /* DSACK blocks received */
        TCP_NLA_REORD_SEEN,     /* reordering events seen */
+       TCP_NLA_SRTT,           /* smoothed RTT in usecs */
 };
 
 /* for TCP_MD5SIG socket option */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9e6bc4d6daa75..0363a0ebee57d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3246,6 +3246,7 @@ static size_t tcp_opt_stats_get_size(void)
                nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BYTES_RETRANS */
                nla_total_size(sizeof(u32)) + /* TCP_NLA_DSACK_DUPS */
                nla_total_size(sizeof(u32)) + /* TCP_NLA_REORD_SEEN */
+               nla_total_size(sizeof(u32)) + /* TCP_NLA_SRTT */
                0;
 }
 
@@ -3299,6 +3300,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const 
struct sock *sk)
                          TCP_NLA_PAD);
        nla_put_u32(stats, TCP_NLA_DSACK_DUPS, tp->dsack_dups);
        nla_put_u32(stats, TCP_NLA_REORD_SEEN, tp->reord_seen);
+       nla_put_u32(stats, TCP_NLA_SRTT, tp->srtt_us >> 3);
 
        return stats;
 }
-- 
2.19.1.1215.g8438c0b245-goog