From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dennis Jacobfeuerborn Date: Wed, 06 May 2015 13:15:49 +0000 Subject: SYN+ACK responded to with RST Message-Id: <554A1405.10601@conversis.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: lartc@vger.kernel.org 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 Win600 Len=0 MSS60 SACK_PERM=1 TSval660943802 TSecr=0 WS8 2140 74.153741 10.0.0.10 10.1.0.13 TCP 74 [TCP Retransmission] 33298→80 [SYN] Seq=0 Win600 Len=0 MSS60 SACK_PERM=1 TSval660944802 TSecr=0 WS8 2141 74.166255 10.1.0.13 10.0.0.10 TCP 74 80→33298 [SYN, ACK] Seq=0 Ack=1 Win(960 Len=0 MSS60 SACK_PERM=1 TSval342367258 TSecr660943802 WS8 2142 74.166266 10.0.0.10 10.1.0.13 TCP 54 33298→80 [RST] Seq=1 Win=0 Len=0 Regards, Dennis