Commit 3687b1dc authored by Wei Yongjun's avatar Wei Yongjun Committed by David S. Miller
Browse files

[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: default avatarWei Yongjun <yjwei@nanjing-fnst.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 118075b3

include/net/tcp.h

+3 −0
Original line number Diff line number Diff line
@@ -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

+0 −2
Original line number Diff line number Diff line
@@ -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

+3 −1
Original line number Diff line number Diff line
@@ -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

+0 −2
Original line number Diff line number Diff line
@@ -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 */

}

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