mptcp: add mib for token creation fallback

If the MPTCP protocol is unable to create a new token,
the socket fallback to plain TCP, let's keep track
of such events via a specific MIB.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/mib.c

@@ -13,6 +13,7 @@ static const struct snmp_mib mptcp_snmp_list[] = {
 	SNMP_MIB_ITEM("MPCapableACKRX", MPTCP_MIB_MPCAPABLEPASSIVEACK),
 	SNMP_MIB_ITEM("MPCapableFallbackACK", MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK),
 	SNMP_MIB_ITEM("MPCapableFallbackSYNACK", MPTCP_MIB_MPCAPABLEACTIVEFALLBACK),
+	SNMP_MIB_ITEM("MPFallbackTokenInit", MPTCP_MIB_TOKENFALLBACKINIT),
 	SNMP_MIB_ITEM("MPTCPRetrans", MPTCP_MIB_RETRANSSEGS),
 	SNMP_MIB_ITEM("MPJoinNoTokenFound", MPTCP_MIB_JOINNOTOKEN),
 	SNMP_MIB_ITEM("MPJoinSynRx", MPTCP_MIB_JOINSYNRX),

net/mptcp/mib.h

@@ -6,6 +6,7 @@ enum linux_mptcp_mib_field {
 	MPTCP_MIB_MPCAPABLEPASSIVEACK,	/* Received third ACK with MP_CAPABLE */
 	MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK,/* Server-side fallback during 3-way handshake */
 	MPTCP_MIB_MPCAPABLEACTIVEFALLBACK, /* Client-side fallback during 3-way handshake */
+	MPTCP_MIB_TOKENFALLBACKINIT,	/* Could not init/allocate token */
 	MPTCP_MIB_RETRANSSEGS,		/* Segments retransmitted at the MPTCP-level */
 	MPTCP_MIB_JOINNOTOKEN,		/* Received MP_JOIN but the token was not found */
 	MPTCP_MIB_JOINSYNRX,		/* Received a SYN + MP_JOIN */

net/mptcp/protocol.c

@@ -3224,8 +3224,10 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
 		mptcp_subflow_early_fallback(msk, subflow);
 #endif
-	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk))
+	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk)) {
+		MPTCP_INC_STATS(sock_net(ssock->sk), MPTCP_MIB_TOKENFALLBACKINIT);
 		mptcp_subflow_early_fallback(msk, subflow);
+	}
 
 do_connect:
 	err = ssock->ops->connect(ssock, uaddr, addr_len, flags);

net/mptcp/subflow.c

@@ -165,6 +165,7 @@ static int subflow_check_req(struct request_sock *req,
 			if (mptcp_token_exists(subflow_req->token)) {
 				if (retries-- > 0)
 					goto again;
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
 			} else {
 				subflow_req->mp_capable = 1;
 			}
@@ -176,6 +177,8 @@ static int subflow_check_req(struct request_sock *req,
 			subflow_req->mp_capable = 1;
 		else if (retries-- > 0)
 			goto again;
+		else
+			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
 
 	} else if (mp_opt.mp_join && listener->request_mptcp) {
 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;