tcp: record pkts sent and retransmistted

Add two stats in SCM_TIMESTAMPING_OPT_STATS:

TCP_NLA_DATA_SEGS_OUT: total data packets sent including retransmission
TCP_NLA_TOTAL_RETRANS: total data packets retransmitted

The names are picked to be consistent with corresponding fields in
TCP_INFO. This allows applications that are using the timestamping
API to measure latency stats to also retrive retransmission rate
of application write.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@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>

include/uapi/linux/tcp.h

@@ -227,6 +227,8 @@ enum {
 	TCP_NLA_BUSY,		/* Time (usec) busy sending data */
 	TCP_NLA_RWND_LIMITED,	/* Time (usec) limited by receive window */
 	TCP_NLA_SNDBUF_LIMITED,	/* Time (usec) limited by send buffer */
+	TCP_NLA_DATA_SEGS_OUT,	/* Data pkts sent including retransmission */
+	TCP_NLA_TOTAL_RETRANS,	/* Data pkts retransmitted */
 };
 
 /* for TCP_MD5SIG socket option */

net/ipv4/tcp.c

@@ -2870,7 +2870,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
 	struct sk_buff *stats;
 	struct tcp_info info;
 
-	stats = alloc_skb(3 * nla_total_size_64bit(sizeof(u64)), GFP_ATOMIC);
+	stats = alloc_skb(5 * nla_total_size_64bit(sizeof(u64)), GFP_ATOMIC);
 	if (!stats)
 		return NULL;
 
@@ -2881,6 +2881,10 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
 			  info.tcpi_rwnd_limited, TCP_NLA_PAD);
 	nla_put_u64_64bit(stats, TCP_NLA_SNDBUF_LIMITED,
 			  info.tcpi_sndbuf_limited, TCP_NLA_PAD);
+	nla_put_u64_64bit(stats, TCP_NLA_DATA_SEGS_OUT,
+			  tp->data_segs_out, TCP_NLA_PAD);
+	nla_put_u64_64bit(stats, TCP_NLA_TOTAL_RETRANS,
+			  tp->total_retrans, TCP_NLA_PAD);
 	return stats;
 }