[PATCH net-next v2 4/5] tcp: add u32 counter in tcp_sock and an SNMP counter for PLB

[Mubashir Adnan Qureshi <mubashirmaq@gmail.com>]

From: Mubashir Adnan Qureshi <mubashirq@google.com>

A u32 counter is added to tcp_sock for counting the number of PLB
triggered rehashes for a TCP connection. An SNMP counter is also
added to count overall PLB triggered rehash events for a host. These
counters are hooked up to PLB implementation for DCTCP.

TCP_NLA_REHASH is added to SCM_TIMESTAMPING_OPT_STATS that reports
the rehash attempts triggered due to PLB or timeouts. This gives
a historical view of sustained congestion or timeouts experienced
by the TCP connection.

Signed-off-by: Mubashir Adnan Qureshi <mubashirq@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/tcp.h       | 1 +
 include/uapi/linux/snmp.h | 1 +
 include/uapi/linux/tcp.h  | 1 +
 net/ipv4/proc.c           | 1 +
 net/ipv4/tcp.c            | 3 +++
 net/ipv4/tcp_plb.c        | 2 ++
 6 files changed, 9 insertions(+)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a9fbe22732c3..332870bb09fc 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -417,6 +417,7 @@ struct tcp_sock {
 		u32		  probe_seq_start;
 		u32		  probe_seq_end;
 	} mtu_probe;
+	u32     plb_rehash;     /* PLB-triggered rehash attempts */
 	u32	mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 			   * while socket was owned by user.
 			   */
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 4d7470036a8b..6600cb0164c2 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -292,6 +292,7 @@ enum
 	LINUX_MIB_TCPDSACKIGNOREDDUBIOUS,	/* TCPDSACKIgnoredDubious */
 	LINUX_MIB_TCPMIGRATEREQSUCCESS,		/* TCPMigrateReqSuccess */
 	LINUX_MIB_TCPMIGRATEREQFAILURE,		/* TCPMigrateReqFailure */
+	LINUX_MIB_TCPPLBREHASH,			/* TCPPLBRehash */
 	__LINUX_MIB_MAX
 };
 
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 8fc09e8638b3..c9abe86eda5f 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -315,6 +315,7 @@ enum {
 	TCP_NLA_BYTES_NOTSENT,	/* Bytes in write queue not yet sent */
 	TCP_NLA_EDT,		/* Earliest departure time (CLOCK_MONOTONIC) */
 	TCP_NLA_TTL,		/* TTL or hop limit of a packet received */
+	TCP_NLA_REHASH,         /* PLB and timeout triggered rehash attempts */
 };
 
 /* for TCP_MD5SIG socket option */
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 5386f460bd20..f88daace9de3 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -297,6 +297,7 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("TCPDSACKIgnoredDubious", LINUX_MIB_TCPDSACKIGNOREDDUBIOUS),
 	SNMP_MIB_ITEM("TCPMigrateReqSuccess", LINUX_MIB_TCPMIGRATEREQSUCCESS),
 	SNMP_MIB_ITEM("TCPMigrateReqFailure", LINUX_MIB_TCPMIGRATEREQFAILURE),
+	SNMP_MIB_ITEM("TCPPLBRehash", LINUX_MIB_TCPPLBREHASH),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 648b5c54bb32..685c06c6d33f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3173,6 +3173,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	tp->sacked_out = 0;
 	tp->tlp_high_seq = 0;
 	tp->last_oow_ack_time = 0;
+	tp->plb_rehash = 0;
 	/* There's a bubble in the pipe until at least the first ACK. */
 	tp->app_limited = ~0U;
 	tp->rack.mstamp = 0;
@@ -3969,6 +3970,7 @@ static size_t tcp_opt_stats_get_size(void)
 		nla_total_size(sizeof(u32)) + /* TCP_NLA_BYTES_NOTSENT */
 		nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_EDT */
 		nla_total_size(sizeof(u8)) + /* TCP_NLA_TTL */
+		nla_total_size(sizeof(u32)) + /* TCP_NLA_REHASH */
 		0;
 }
 
@@ -4045,6 +4047,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 		nla_put_u8(stats, TCP_NLA_TTL,
 			   tcp_skb_ttl_or_hop_limit(ack_skb));
 
+	nla_put_u32(stats, TCP_NLA_REHASH, tp->plb_rehash + tp->timeout_rehash);
 	return stats;
 }
 
diff --git a/net/ipv4/tcp_plb.c b/net/ipv4/tcp_plb.c
index 26ffc5a45f53..04f4cac8645b 100644
--- a/net/ipv4/tcp_plb.c
+++ b/net/ipv4/tcp_plb.c
@@ -73,6 +73,8 @@ void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb)
 	if (!plb->pause_until && (can_idle_rehash || can_force_rehash)) {
 		sk_rethink_txhash(sk);
 		plb->consec_cong_rounds = 0;
+		tcp_sk(sk)->plb_rehash++;
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPLBREHASH);
 	}
 }
 EXPORT_SYMBOL_GPL(tcp_plb_check_rehash);
-- 
2.38.0.rc1.362.ged0d419d3c-goog