[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>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 0ccb7cb22b15..624e2b2c7f53 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/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.