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>

include/uapi/linux/snmp.h

@@ -252,6 +252,7 @@ enum
 	LINUX_MIB_TCPCHALLENGEACK,		/* TCPChallengeACK */
 	LINUX_MIB_TCPSYNCHALLENGE,		/* TCPSYNChallenge */
 	LINUX_MIB_TCPFASTOPENACTIVE,		/* TCPFastOpenActive */
+	LINUX_MIB_TCPFASTOPENACTIVEFAIL,	/* TCPFastOpenActiveFail */
 	LINUX_MIB_TCPFASTOPENPASSIVE,		/* TCPFastOpenPassive*/
 	LINUX_MIB_TCPFASTOPENPASSIVEFAIL,	/* TCPFastOpenPassiveFail */
 	LINUX_MIB_TCPFASTOPENLISTENOVERFLOW,	/* TCPFastOpenListenOverflow */
@@ -262,6 +263,8 @@ enum
 	LINUX_MIB_TCPFROMZEROWINDOWADV,		/* TCPFromZeroWindowAdv */
 	LINUX_MIB_TCPTOZEROWINDOWADV,		/* TCPToZeroWindowAdv */
 	LINUX_MIB_TCPWANTZEROWINDOWADV,		/* TCPWantZeroWindowAdv */
+	LINUX_MIB_TCPSYNRETRANS,		/* TCPSynRetrans */
+	LINUX_MIB_TCPORIGDATASENT,		/* TCPOrigDataSent */
 	__LINUX_MIB_MAX
 };
 

net/ipv4/proc.c

@@ -273,6 +273,7 @@ static const struct snmp_mib snmp4_net_list[] = {
 	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 @@ static const struct snmp_mib snmp4_net_list[] = {
 	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
 };
 

net/ipv4/tcp_input.c

@@ -5393,9 +5393,12 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 				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;
 }
 

net/ipv4/tcp_ipv4.c

@@ -854,8 +854,10 @@ static int tcp_v4_rtx_synack(struct sock *sk, struct request_sock *req)
 {
 	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;
 }
 

net/ipv4/tcp_output.c

@@ -86,6 +86,9 @@ static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
 	    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 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 	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 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 
 	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;

net/ipv4/tcp_timer.c

@@ -165,6 +165,9 @@ static int tcp_write_timeout(struct sock *sk)
 			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;

net/ipv6/tcp_ipv6.c

@@ -501,8 +501,10 @@ static int tcp_v6_rtx_synack(struct sock *sk, struct request_sock *req)
 	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;
 }