mptcp: add and use MIB counter infrastructure

Exported via same /proc file as the Linux TCP MIB counters, so "netstat -s"
or "nstat" will show them automatically.

The MPTCP MIB counters are allocated in a distinct pcpu area in order to
avoid bloating/wasting TCP pcpu memory.

Counters are allocated once the first MPTCP socket is created in a
network namespace and free'd on exit.

If no sockets have been allocated, all-zero mptcp counters are shown.

The MIB counter list is taken from the multipath-tcp.org kernel, but
only a few counters have been picked up so far.  The counter list can
be increased at any time later on.

v2 -> v3:
 - remove 'inline' in foo.c files (David S. Miller)

Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 8 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8d2777092390..1833bc1f4a43 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -21,6 +21,7 @@
 #endif
 #include <net/mptcp.h>
 #include "protocol.h"
+#include "mib.h"
 
 #define MPTCP_SAME_STATE TCP_MAX_STATES
 
@@ -1032,6 +1033,7 @@ static void mptcp_worker(struct work_struct *work)
 		if (ret < 0)
 			break;
 
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
 		copied += ret;
 		dfrag->data_len -= ret;
 		dfrag->offset += ret;
@@ -1081,17 +1083,22 @@ static int __mptcp_init_sock(struct sock *sk)
 
 static int mptcp_init_sock(struct sock *sk)
 {
-	int ret = __mptcp_init_sock(sk);
+	struct net *net = sock_net(sk);
+	int ret;
 
+	if (!mptcp_is_enabled(net))
+		return -ENOPROTOOPT;
+
+	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
+		return -ENOMEM;
+
+	ret = __mptcp_init_sock(sk);
 	if (ret)
 		return ret;
 
 	sk_sockets_allocated_inc(sk);
 	sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[2];
 
-	if (!mptcp_is_enabled(sock_net(sk)))
-		return -ENOPROTOOPT;
-
 	return 0;
 }
 
@@ -1327,7 +1334,12 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
 		list_add(&subflow->node, &msk->conn_list);
 
 		bh_unlock_sock(new_mptcp_sock);
+
+		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
 		local_bh_enable();
+	} else {
+		MPTCP_INC_STATS(sock_net(sk),
+				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
 	}
 
 	return newsk;
@@ -1448,13 +1460,15 @@ void mptcp_finish_connect(struct sock *ssk)
 	u64 ack_seq;
 
 	subflow = mptcp_subflow_ctx(ssk);
-
-	if (!subflow->mp_capable)
-		return;
-
 	sk = subflow->conn;
 	msk = mptcp_sk(sk);
 
+	if (!subflow->mp_capable) {
+		MPTCP_INC_STATS(sock_net(sk),
+				MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
+		return;
+	}
+
 	pr_debug("msk=%p, token=%u", sk, subflow->token);
 
 	mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);