[lwip-devel] [bug #41700] Call to tcp_listen_dual() should not accept IPv4 listen PCB args

[Drew Stebbins]

URL:
  <http://savannah.nongnu.org/bugs/?41700>

                 Summary: Call to tcp_listen_dual() should not accept IPv4
listen PCB args
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: astebbin
            Submitted on: Tue 25 Feb 2014 10:38:52 PM GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: 1.3.1

    _______________________________________________________

Details:

tcp_listen_dual() should fail and return NULL when its pcb arg is IPv4-only.
Currently, tcp_listen_dual() will incorrectly make lwip listen for IPv4 OR
IPv6 connections to a given IPv4-only PCB, disregarding this PCB's 'isipv6'
value of 0.

Allowing IPv4 listen PCBs to accept IPv6 connections also has the side-effect
of decrementing pending_accepts on the wrong PCB in tcp_pcb_purge(), in the
case where an IPv6 listen PCB is bound to the same port. This is because
tcp_pcb_purge() matches its active PCB arg to its listen PCB parent with a
by-value comparison. The active PCB which was created to handle the IPv4
listen PCB's accepted connection has isipv6 == 1, whereas its listen PCB
parent has isipv6 == 0. This causes tcp_pcb_purge() to decrement
pending_accepts for the wrong listen PCB, in some cases wrapping this field
around to its maximum value.




    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?41700>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/