[pkg-dhcp-devel] Bug#648401: Harmfull with debconf

Geert Stappers stappers at stappers.nl
Fri Mar 16 14:40:39 UTC 2012

Hello ISC DHCP maintainers,

Bug 648401, isc-dhcp-relay: dhcrelay(8) doesn't mention need for -i on server facing interface,
is harmfull in combination with current debconf text.

The text in

   +--------------------------| DHCP Relay |-----------------------------+
   |                                                                     |
   | Please specify which network interface(s) the DHCP relay should     |
   | attempt to configure. Multiple interface names should be entered    |
   | as a space-separated list.                                          |
   |                                                                     |
   | Leave this field blank to allow for automatic detection and         |
   | configuration of network interfaces by the DHCP relay, in which     |
   | case only broadcast interfaces will be used (if possible).          |
   |                                                                     |
   | Interfaces the DHCP relay should listen on:                         |
   |                                                                     |
   |   __________________________________________________________        |
   |                                                                     |
   |                                   <Ok>                              |
   |                                                                     |

did trick me to enter only the interface I thought it should listen on.

It took me several hours to find that it is actual asking:

  Enumerate all involved interfaces,
  so that remaining interfaces can be excluded.

Leaving the interface list empty,
did get my (two interface) DHCP relay working in the end.

Having the patch

--- dhcrelay.8.orig	2011-11-11 16:41:22.000000000 +1100
+++ dhcrelay.8	2011-11-11 16:43:01.000000000 +1100
@@ -178,7 +178,10 @@
 interfaces may be specified by using more than one \fB-i\fR option.  If
 no interfaces are specified on the command line, dhcrelay will identify
 all network interfaces, eliminating non-broadcast interfaces if possible,
-and attempt to listen on all of them.
+and attempt to listen on all of them. If you use -i, you should ensure you
+include an -i option for the interface that is used to communicate with the
+DHCP server. Otherwise reply packets from the DHCP server are likely to be
 -m \fIappend\fR|\fIreplace\fR|\fIforward\fR|\fIdiscard\fR
 Control the handling of incoming DHCPv4 packets which already contain

in the manual page would have me saved some time
and will surely save time for others.

Thanks & Cheers
Geert Stappers

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