On 05/06/2015 07:23 AM, Kevin Mason wrote:
I would say you are looking in the wrong direction. Your question
should be why is 10.1.0.13 taking so long to reply?
Or why is the client application so impatient :) It could be the client
application isn't willing to wait all that long for the connection to be
established. So, if that timer pops in the application before the
SYN|ACK arrives, the client application's closing of the socket would
likely mean there is no TCP endpoint when the SYN|ACK arrives and so an
RST is emitted.
rick jones
the
TSecr=3660943802 in frame 2141 says the syn/ack is to frame 2139.
Since the client already did a retransmission of the Syn with
TSval=3660944802 in frame 2140, this shows 10.1.0.13 has something
very wrong with it.
Kevin
———————
On May 6, 2015, at 09:15, Dennis Jacobfeuerborn <dennisml@xxxxxxxxxxxx> wrote:
Hi,
I have a strange case where sometimes a client responds to a SYN+ACK
packet with a RST. This only seems to happen though after a
retransmission of the SYN packet. My question is why would that matter
given that sequence numbers and other parameters all are correct? I
would expect the client to properly acknowledge the SYN+ACK packet
instead of sending a RST. Are there any other reasons besides sequence
number or TSval/TSecr issues that could cause the client side to repond
with a RST to a SYN+ACK?
Here is a wireshark summary of such a failed handshake:
2139 73.154288 10.0.0.10 10.1.0.13 TCP 74 33298→80 [SYN] Seq=0 Win=14600
Len=0 MSS=1460 SACK_PERM=1 TSval=3660943802 TSecr=0 WS=128
2140 74.153741 10.0.0.10 10.1.0.13 TCP 74 [TCP Retransmission] 33298→80
[SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=3660944802
TSecr=0 WS=128
2141 74.166255 10.1.0.13 10.0.0.10 TCP 74 80→33298 [SYN, ACK] Seq=0
Ack=1 Win=28960 Len=0 MSS=1460 SACK_PERM=1 TSval=3342367258
TSecr=3660943802 WS=128
2142 74.166266 10.0.0.10 10.1.0.13 TCP 54 33298→80 [RST] Seq=1 Win=0 Len=0
Regards,
Dennis
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