dhcp-workers Digest, Vol 11, Issue 8

Yong Bo Hu huyongbo at cn.ibm.com
Tue Jan 5 07:35:46 UTC 2010

Anybody can help about the Interface Discovery issue?



Andy Hu(Yong Bo)
IBM China System & Technology Lab in Beijing
TEL: (8610)82454525
E-Mail:huyongbo at cn.ibm.com

  From:       dhcp-workers-request at lists.isc.org                                                                           
  To:         dhcp-workers at lists.isc.org                                                                                   
  Date:       2009-12-31 20:00                                                                                             
  Subject:    dhcp-workers Digest, Vol 11, Issue 8                                                                         
  Sent by:    dhcp-workers-bounces+huyongbo=cn.ibm.com at lists.isc.org                                                       

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Today's Topics:

   1. DHCPD port on Win32? (Autuori Gianluigi)
   2. Interface Discover issue in ISC DHCP 4.1.0 (Yong Bo Hu)


Message: 1
Date: Wed, 30 Dec 2009 23:32:37 +0100
From: "Autuori Gianluigi" <Autuori.Gianluigi.Wintime at ansaldobreda.it>
Subject: DHCPD port on Win32?
To: <dhcp-workers at lists.isc.org>

<A691B9541CD614449A7702B21C5BBD59038E2878 at abnaex01.ab.ansaldobreda.it>
Content-Type: text/plain;            charset="Windows-1252"

I have to use win32 platform and I need dhcpd. Is there any port of isc



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Message: 2
Date: Thu, 31 Dec 2009 12:05:48 +0800
From: Yong Bo Hu <huyongbo at cn.ibm.com>
Subject: Interface Discover issue in ISC DHCP 4.1.0
To: dhcp-workers at lists.isc.org

<OF3A8330EE.916E1B71-ON4825769D.00164935-4825769D.00167E1F at cn.ibm.com>
Content-Type: text/plain; charset="us-ascii"

Not sure whether it's fine to send this there.

The scenario:
Interface ETH0, has and only has IPv4: and IPv6 aaaa::cccc.  Now
the IPv4 address is down, and the IPv6 address is up.  And ranges of and aaaa::/64  are configured.  Next start the DHCP server with
IPv6(-6), the result is the ETH0 is skipped with no message in the log
about this interface.     If the IPv4 is up, the ETH0 can be listened.

After debug, I locate the code in discover.c:.

        /* Skip non broadcast interfaces (plus loopback and
           point-to-point in case an OS incorrectly marks them
           as broadcast). Also skip down interfaces unless we're:
           trying to get a list of configurable interfaces. */
        if (((!(info.flags & IFF_BROADCAST) ||
              info.flags & IFF_LOOPBACK ||)
              info.flags & IFF_POINTOPOINT) && !tmp) ||
            (!(info.flags & IFF_UP) &&
             state != DISCOVER_UNCONFIGURED))

On the surface, the interface can be listened depending on the state of
IPv4 address when starting IPv6 DHCP, but it shouldn't.  The key point here
is the IFF_BROADCAST flag, for ordinary IPv4 address, it's broadcast
address valid, but for IPv6, which has not broadcast, but has multicast
(IFF_MULTICAST), so i think it would need to differentiate the IPv4 and
IPv6 when to check which interface needs to skip.

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