tcp: snmp stats for Fast Open, SYN rtx, and data pkts

Add the following snmp stats:

TCPFastOpenActiveFail: Fast Open attempts (SYN/data) failed beacuse
the remote does not accept it or the attempts timed out.

TCPSynRetrans: number of SYN and SYN/ACK retransmits to break down
retransmissions into SYN, fast-retransmits, timeout retransmits, etc.

TCPOrigDataSent: number of outgoing packets with original data (excluding
retransmission but including data-in-SYN). This counter is different from
TcpOutSegs because TcpOutSegs also tracks pure ACKs. TCPOrigDataSent is
more useful to track the TCP retransmission rate.

Change TCPFastOpenActive to track only successful Fast Opens to be symmetric to
TCPFastOpenPassive.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: Lawrence Brakmo <brakmo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 99d2e9b..ad737fa 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -273,6 +273,7 @@
 	SNMP_MIB_ITEM("TCPChallengeACK", LINUX_MIB_TCPCHALLENGEACK),
 	SNMP_MIB_ITEM("TCPSYNChallenge", LINUX_MIB_TCPSYNCHALLENGE),
 	SNMP_MIB_ITEM("TCPFastOpenActive", LINUX_MIB_TCPFASTOPENACTIVE),
+	SNMP_MIB_ITEM("TCPFastOpenActiveFail", LINUX_MIB_TCPFASTOPENACTIVEFAIL),
 	SNMP_MIB_ITEM("TCPFastOpenPassive", LINUX_MIB_TCPFASTOPENPASSIVE),
 	SNMP_MIB_ITEM("TCPFastOpenPassiveFail", LINUX_MIB_TCPFASTOPENPASSIVEFAIL),
 	SNMP_MIB_ITEM("TCPFastOpenListenOverflow", LINUX_MIB_TCPFASTOPENLISTENOVERFLOW),
@@ -283,6 +284,8 @@
 	SNMP_MIB_ITEM("TCPFromZeroWindowAdv", LINUX_MIB_TCPFROMZEROWINDOWADV),
 	SNMP_MIB_ITEM("TCPToZeroWindowAdv", LINUX_MIB_TCPTOZEROWINDOWADV),
 	SNMP_MIB_ITEM("TCPWantZeroWindowAdv", LINUX_MIB_TCPWANTZEROWINDOWADV),
+	SNMP_MIB_ITEM("TCPSynRetrans", LINUX_MIB_TCPSYNRETRANS),
+	SNMP_MIB_ITEM("TCPOrigDataSent", LINUX_MIB_TCPORIGDATASENT),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 23a41d9..6e48093 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5393,9 +5393,12 @@
 				break;
 		}
 		tcp_rearm_rto(sk);
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
 		return true;
 	}
 	tp->syn_data_acked = tp->syn_data;
+	if (tp->syn_data_acked)
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
 	return false;
 }
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 17c0fb1..c4f1d9a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -854,8 +854,10 @@
 {
 	int res = tcp_v4_send_synack(sk, NULL, req, 0);
 
-	if (!res)
+	if (!res) {
 		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
+	}
 	return res;
 }
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index bf38b1f..aaa68f5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -86,6 +86,9 @@
 	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		tcp_rearm_rto(sk);
 	}
+
+	NET_ADD_STATS_BH(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
+			 tcp_skb_pcount(skb));
 }
 
 /* SND.NXT, if window was not shrunk.
@@ -2433,7 +2436,8 @@
 	if (err == 0) {
 		/* Update global TCP statistics. */
 		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
-
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
 		tp->total_retrans++;
 
 #if FASTRETRANS_DEBUG > 0
@@ -2958,7 +2962,7 @@
 
 	if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
 		tp->syn_data = (fo->copied > 0);
-		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
 		goto done;
 	}
 	syn_data = NULL;
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 64f0354..286227a 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -165,6 +165,9 @@
 			dst_negative_advice(sk);
 			if (tp->syn_fastopen || tp->syn_data)
 				tcp_fastopen_cache_set(sk, 0, NULL, true);
+			if (tp->syn_data)
+				NET_INC_STATS_BH(sock_net(sk),
+						 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
 		}
 		retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
 		syn_set = true;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 889079b..3277680 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -501,8 +501,10 @@
 	int res;
 
 	res = tcp_v6_send_synack(sk, NULL, &fl6, req, 0);
-	if (!res)
+	if (!res) {
 		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
+	}
 	return res;
 }