[lwip-devel] [bug #50498] tcp: do not keep sending SYNs when getting ACKs

[David van Moolenbroek]

URL:
  <http://savannah.nongnu.org/bugs/?50498>

                 Summary: tcp: do not keep sending SYNs when getting ACKs
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: dcvmoole
            Submitted on: Wed 08 Mar 2017 07:56:14 PM UTC
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

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Details:

An amendment to git-2e26fc9 ("tcp: Avoid 3-second delay for a half-open
connection")

===

If a locally generated TCP SYN packet is replied to with an ACK packet, lwIP
immediately sends a RST packet followed by resending the SYN packet.  This is
expected, but on loopback interfaces the resent SYN packet may immediately get
another ACK reply, typically when the other endpoint is in TIME_WAIT state
(which ignores the RSTs).  The result is an endless loop of SYN, ACK, RST
packets.

This patch applies the normal SYN retransmission limit in this scenario, such
that the endless loop is limited to a brief storm.



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File Attachments:


-------------------------------------------------------
Date: Wed 08 Mar 2017 07:56:14 PM UTC  Name:
0001-tcp-do-not-keep-sending-SYNs-when-getting-ACKs.patch  Size: 2kB   By:
dcvmoole

<http://savannah.nongnu.org/bugs/download.php?file_id=39950>

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