[Bug 1173483] Re: dhclient segfaults on interfaces it can not handle

[AVAUX Fabrice]

The problem exists in version ISC 4.3 but it does not generate segfault but a message :  Unsupported device type 512 for "ppp0" in syslog.
The problem has been solved by a patch in fedora (https://bugzilla.redhat.com/show_bug.cgi?id=626514).
It is a problem of implementation by ISC because it is the normal way using DHCP with ipv6 on ppp (https://datatracker.ietf.org/doc/rfc6204/).

Workaround : use the wide DHCP package, it is old but it is working !

** Bug watch added: Red Hat Bugzilla #626514
   https://bugzilla.redhat.com/show_bug.cgi?id=626514

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https://bugs.launchpad.net/bugs/1173483

Title:
  dhclient segfaults on interfaces it can not handle

Status in “isc-dhcp” package in Ubuntu:
  Confirmed

Bug description:
  
  Hi,

  This is with version: 4.2.4-5ubuntu2wf1, which is a backport to
  precise of the current raring dhcp verion (4.2.4-5ubuntu2).

  The only modification is changing the targeted release.

  I was under the impression that ISC DHCP (now) supported prefix
  delegation.

  # dhclient -d -v -6 -P --no-pid ppp0
  Internet Systems Consortium DHCP Client 4.2.4
  Copyright 2004-2012 Internet Systems Consortium.
  All rights reserved.
  For info, please visit https://www.isc.org/software/dhcp/

  Bound to *:546
  Segmentation fault (core dumped)

  Installing the isc-client-dbg is a bit more revealing:

  # gdb --args dhclient -d -v -6 -P --no-pid ppp0
  GNU gdb (Ubuntu/Linaro 7.4-2012.02-0ubuntu2) 7.4-2012.02
  Copyright (C) 2012 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "x86_64-linux-gnu".
  For bug reporting instructions, please see:
  <http://bugs.launchpad.net/gdb-linaro/>...
  Reading symbols from /sbin/dhclient...Reading symbols from /usr/lib/debug/sbin/dhclient...done.
  done.
  (gdb) run
  Starting program: /sbin/dhclient -d -v -6 -P --no-pid ppp0
  Internet Systems Consortium DHCP Client 4.2.4
  Copyright 2004-2012 Internet Systems Consortium.
  All rights reserved.
  For info, please visit https://www.isc.org/software/dhcp/

  Bound to *:546

  Program received signal SIGSEGV, Segmentation fault.
  0x00007f94311a2161 in vfprintf () from /lib/x86_64-linux-gnu/libc.so.6
  (gdb) bt
  #0  0x00007f94311a2161 in vfprintf () from /lib/x86_64-linux-gnu/libc.so.6
  #1  0x00007f943125ed80 in __vsnprintf_chk () from /lib/x86_64-linux-gnu/libc.so.6
  #2  0x00007f94317979a8 in vsnprintf (__ap=0x7ffff261ab08, __fmt=0x7f9431adcba0 "Unsupported device type %h for \"%s\"", __n=1024, 
      __s=0x7f9431adcfa0 "Unsupported device type % for \"www.isc.org/software/dhcp/") at /usr/include/x86_64-linux-gnu/bits/stdio2.h:78
  #3  log_fatal (fmt=<optimised out>) at errwarn.c:64
  #4  0x00007f9431773ffd in get_hw_addr (info=0x7f9432b26a50) at lpf.c:712
  #5  0x00007f9431789318 in if_register6 (info=0x7f9432b26a50, do_multicast=<optimised out>) at socket.c:501
  #6  0x00007f943176d72d in discover_interfaces (state=4) at discover.c:1264
  #7  0x00007f9431750d95 in main (argc=<optimised out>, argv=<optimised out>) at dhclient.c:569
  (gdb) 

  
  It is a shame that ISC DHCP still does not support DHCPv6 PD over PPP interfaces but it certainly should not segfault when attempting to report an error.

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