tcp: add pacing_rate information into tcp_info

Add two new fields to struct tcp_info, to report sk_pacing_rate
and sk_max_pacing_rate to monitoring applications, as ss from iproute2.

User exported fields are 64bit, even if kernel is currently using 32bit
fields.

lpaa5:~# ss -i
..
	 skmem:(r0,rb357120,t0,tb2097152,f1584,w1980880,o0,bl0) ts sack cubic
wscale:6,6 rto:400 rtt:0.875/0.75 mss:1448 cwnd:1 ssthresh:12 send
13.2Mbps pacing_rate 3336.2Mbps unacked:15 retrans:1/5448 lost:15
rcv_space:29200

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/tcp.h

@@ -186,6 +186,9 @@ struct tcp_info {
 	__u32	tcpi_rcv_space;
 
 	__u32	tcpi_total_retrans;
+
+	__u64	tcpi_pacing_rate;
+	__u64	tcpi_max_pacing_rate;
 };
 
 /* for TCP_MD5SIG socket option */

net/ipv4/tcp.c

@@ -2794,6 +2794,11 @@ void tcp_get_info(const struct sock *sk, struct tcp_info *info)
 	info->tcpi_rcv_space = tp->rcvq_space.space;
 
 	info->tcpi_total_retrans = tp->total_retrans;
+
+	info->tcpi_pacing_rate = sk->sk_pacing_rate != ~0U ?
+					sk->sk_pacing_rate : ~0ULL;
+	info->tcpi_max_pacing_rate = sk->sk_max_pacing_rate != ~0U ?
+					sk->sk_max_pacing_rate : ~0ULL;
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);