[TCP]: SNMPv2 tcpAttemptFails counter error

Refer to RFC2012, tcpAttemptFails is defined as following:
  tcpAttemptFails OBJECT-TYPE
      SYNTAX      Counter32
      MAX-ACCESS  read-only
      STATUS      current
      DESCRIPTION
              "The number of times TCP connections have made a direct
              transition to the CLOSED state from either the SYN-SENT
              state or the SYN-RCVD state, plus the number of times TCP
              connections have made a direct transition to the LISTEN
              state from the SYN-RCVD state."
      ::= { tcp 7 }

When I lookup into RFC793, I found that the state change should occured
under following condition:
  1. SYN-SENT -> CLOSED
     a) Received ACK,RST segment when SYN-SENT state.

  2. SYN-RCVD -> CLOSED
     b) Received SYN segment when SYN-RCVD state(came from LISTEN).
     c) Received RST segment when SYN-RCVD state(came from SYN-SENT).
     d) Received SYN segment when SYN-RCVD state(came from SYN-SENT).

  3. SYN-RCVD -> LISTEN
     e) Received RST segment when SYN-RCVD state(came from LISTEN).

In my test, those direct state transition can not be counted to
tcpAttemptFails.

Signed-off-by: Wei Yongjun <yjwei@nanjing-fnst.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -914,6 +914,9 @@ static inline void tcp_set_state(struct sock *sk, int state)
 
 static inline void tcp_done(struct sock *sk)
 {
+	if(sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
+		TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
+
 	tcp_set_state(sk, TCP_CLOSE);
 	tcp_clear_xmit_timers(sk);
 

net/ipv4/tcp_ipv4.c

@@ -438,7 +438,6 @@ void tcp_v4_err(struct sk_buff *skb, u32 info)
 			       It can f.e. if SYNs crossed.
 			     */
 		if (!sock_owned_by_user(sk)) {
-			TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 			sk->sk_err = err;
 
 			sk->sk_error_report(sk);
@@ -874,7 +873,6 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 drop_and_free:
 	reqsk_free(req);
 drop:
-	TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 	return 0;
 }
 

net/ipv4/tcp_minisocks.c

@@ -589,8 +589,10 @@ struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
 		/* RFC793: "second check the RST bit" and
 		 *	   "fourth, check the SYN bit"
 		 */
-		if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN))
+		if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) {
+			TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 			goto embryonic_reset;
+		}
 
 		/* ACK sequence verified above, just make sure ACK is
 		 * set.  If ACK not set, just silently drop the packet.

net/ipv6/tcp_ipv6.c

@@ -427,7 +427,6 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	case TCP_SYN_RECV:  /* Cannot happen.
 			       It can, it SYNs are crossed. --ANK */ 
 		if (!sock_owned_by_user(sk)) {
-			TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 			sk->sk_err = err;
 			sk->sk_error_report(sk);		/* Wake people up to see the error (see connect in sock.c) */
 
@@ -831,7 +830,6 @@ drop:
 	if (req)
 		reqsk_free(req);
 
-	TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 	return 0; /* don't send reset */
 }