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Date:      Sat, 02 Feb 2008 21:48:00 +0100
From:      Oskar Eyb <oskar-freebsd@eyb.de>
To:        freebsd-current@freebsd.org
Subject:   Re: syncache_timer: Response timeout and other msgs, whats up?
Message-ID:  <47A4D700.90807@eyb.de>
In-Reply-To: <47985B01.6000003@eyb.de>
References:  <47985B01.6000003@eyb.de>

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no help for this issue?
Same problem with cvs RELENG_7 from Jan, 29th.


Oskar Eyb schrieb am 24.01.2008 10:31:
> Hello!
> I#m not sure if this is a issue belonging to -current, but maybe..
> 
> 
> A remote MTA cannot deliver me any email. the admin gets the following 
> errors:
> 
> "retry time not reached for any host after a long failure period"
> and "retry timeout exceeded".
> 
> After I cant find anything related to this server in my postfix log, I 
> grep'ed for <ip> in /var/log/* and got the following hits:
> 
> [...]
> dmesg.yesterday:TCP: [85.214.42.62]:43127 to [172.16.0.2]:25 tcpflags
> 0x2<SYN>; syncache_add: Received duplicate SYN, resetting timer and
> retransmitting SYN|ACK
> dmesg.yesterday:TCP: [85.214.42.62]:43127 to [172.16.0.2]:25;
> syncache_timer: Response timeout, retransmitting (1) SYN|ACK
> dmesg.yesterday:TCP: [85.214.42.62]:43127 to [172.16.0.2]:25;
> syncache_timer: Response timeout, retransmitting (2) SYN|ACK
> dmesg.yesterday:TCP: [85.214.42.62]:43127 to [172.16.0.2]:25;
> syncache_timer: Response timeout, retransmitting (3) SYN|ACK
> dmesg.yesterday:TCP: [85.214.42.62]:43127 to [172.16.0.2]:25;
> syncache_timer: Retransmits exhausted, giving up and removing syncache 
> entry
> 
> 85.214.42.62 is the other MTA, 172.16.0.2 is my jail.
> I use PF with rdr/nat on FreeBSD 7 RC4.
> 
> 
> in the daily security email I get dozens of messages like this, also to 
> other tcp ports.
> 
> 
> default-values for:
> net.inet.tcp.syncache.rst_on_sock_fail: 1
> net.inet.tcp.syncache.rexmtlimit: 3
> net.inet.tcp.syncache.hashsize: 512
> net.inet.tcp.syncache.count: 0
> net.inet.tcp.syncache.cachelimit: 15360
> net.inet.tcp.syncache.bucketlimit: 30
> 
> 
> Can anybody help me out of this?
> 
> 
> Greets,
> Oskar
> 
> 
> 
> 
> 
> +TCP: [58.182.131.11]:4216 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4216 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4216 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4217 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4217 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4217 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4218 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4218 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4219 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4219 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4220 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4220 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4220 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4221 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4221 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4222 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4222 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4222 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4223 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4223 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4224 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4224 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4224 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4225 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4225 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4226 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4226 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4226 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4227 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4227 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4227 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4228 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4228 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4229 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4230 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4231 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4232 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4230 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4231 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4234 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4234 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4234 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4235 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4235 to [172.16.0.2]:25 tcpflags 0x10<ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4235 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4236 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4236 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [58.182.131.11]:4233 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [58.182.131.11]:4233 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 6 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [58.182.131.11]:4233 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +Connection attempt to UDP 172.16.0.2:57897 from 85.214.103.56:53
> +Connection attempt to UDP 172.16.0.2:60521 from 85.214.103.56:53
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (2) SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (3) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [59.189.18.5]:1332 to [172.16.0.2]:25; syncache_timer: Retransmits 
> exhausted, giving up and removing syncache entry
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (2) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (3) SYN|ACK
> +Connection attempt to UDP 85.214.103.56:57111 from 88.191.254.7:53
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [83.40.210.36]:27836 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:1700 to [172.16.0.2]:25; syncache_timer: Retransmits 
> exhausted, giving up and removing syncache entry
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (2) SYN|ACK
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (3) SYN|ACK
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [59.189.18.5]:2189 to [172.16.0.2]:25; syncache_timer: Retransmits 
> exhausted, giving up and removing syncache entry
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (2) SYN|ACK
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (3) SYN|ACK
> +TCP: [193.43.150.242]:60772 to [85.214.103.56]:22 tcpflags 0x2<SYN>; 
> tcp_input: Connection attempt to closed port
> +Connection attempt to UDP 172.16.0.2:59259 from 85.214.103.56:53
> +Connection attempt to UDP 172.16.0.2:52025 from 85.214.103.56:53
> +TCP: [213.5.169.184]:62636 to [172.16.0.2]:25; syncache_timer: 
> Retransmits exhausted, giving up and removing syncache entry
> +TCP: [64.237.204.59]:64347 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +Connection attempt to UDP 172.16.0.2:49575 from 85.214.103.56:53
> +Connection attempt to UDP 172.16.0.2:49201 from 85.214.103.56:53
> +Connection attempt to UDP 172.16.0.2:53140 from 85.214.103.56:53
> +Connection attempt to UDP 172.16.0.2:60597 from 85.214.103.56:53
> +TCP: [209.223.48.146]:36342 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [189.132.247.46]:3006 to [172.16.0.2]:25 tcpflags 0x14<RST,ACK>; 
> syncache_chkrst: Spurious RST with ACK, SYN or FIN flag set, segment 
> ignored
> +TCP: [190.142.56.104]:1990 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [190.142.56.104]:1990 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [190.142.56.104]:2350 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [72.52.143.18]:38333 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [65.19.179.9]:1973 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [88.67.29.27]:62531 to [172.16.0.2]:25 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_2: Received 37 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [88.67.29.27]:62531 to [172.16.0.2]:25 tcpflags 0x11<FIN,ACK>; 
> syncache_expand: Segment failed SYNCOOKIE authentication, segment 
> rejected (probably spoofed)
> +TCP: [195.4.92.9]:25 to [172.16.0.2]:57654 tcpflags 0x18<PUSH,ACK>; 
> tcp_do_segment: FIN_WAIT_1: Received 69 bytes of data after socket was 
> closed, sending RST and removing tcpcb
> +TCP: [213.133.109.71]:47054 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [202.164.234.72]:3775 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [207.217.120.84]:54387 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [207.217.120.84]:54387 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [220.226.52.141]:3655 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [220.226.52.141]:3655 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [220.226.52.141]:3655 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK
> +TCP: [220.226.52.141]:3655 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [217.255.195.182]:61347 to [172.16.0.2]:25 tcpflags 0x4<RST>; 
> syncache_chkrst: Spurious RST without matching syncache entry (possibly 
> syncookie only), segment ignored
> +TCP: [220.226.52.141]:4446 to [172.16.0.2]:25; syncache_timer: Response 
> timeout, retransmitting (1) SYN|ACK
> +TCP: [220.226.52.141]:4446 to [172.16.0.2]:25 tcpflags 0x2<SYN>; 
> syncache_add: Received duplicate SYN, resetting timer and retransmitting 
> SYN|ACK



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