DHCPREQUEST of <null address>

Alan Jenkins aj504 at cs.york.ac.uk
Mon May 5 23:39:19 UTC 2008

David W. Hankins wrote:
> On Sun, May 04, 2008 at 01:31:45PM +0100, Alan Jenkins wrote:
>> May  4 11:52:36 alan-eeepc dhclient: DHCPREQUEST of <null address> on eth1 
> ISC DHCP logs of the form:
>         snprintf (msgbuf, sizeof msgbuf,
>                  "DHCPREQUEST for %s%s from %s %s%s%svia %s",
> So I know not what sources you are running that nets 'DHCPREQUEST of '
> in syslog.
> <null address> will appear whenever piaddr() is called with an
> address of zero length.  In stock sources, I believe this to be
> impossible on that log line ("DHCPREQUEST for ").
Well caught.  For completeness, I'm using 
dhcp3-client-3.0.6.dfsg-1ubuntu9 from Ubuntu Hardy.  I've downloaded the 
source package corresponding to my installation.  It sounds like you 
might be referring to the dhcp server and not the client, because in the 
original source tarball the message starts "DHCPREQUST on", and not 
"for".  But you're certainly right that the original sources don't 
include a line "DHCPREQUEST of".

The line "DHCPREQUEST of" comes from a particular Ubuntu-specific patch 
called "dhclient-more-debug".  That probably explains why I couldn't 
find any useful hits on Google.

Here's the relevant hunk of the patch.  All it's supposed to do is add 
the IP address dhclient requests to the log messages.  It's this address 
which is reported as being null.

@@ -1703,7 +1706,8 @@
                        client -> packet.secs = htons (65535);

-       log_info ("DHCPREQUEST on %s to %s port %d",
+       log_info ("DHCPREQUEST of %s on %s to %s port %d",
+               piaddr(client->requested_address),
              client -> name ? client -> name : client -> interface -> name,
              inet_ntoa (destination.sin_addr),
              ntohs (destination.sin_port));

W.r.t to trying stock sources, I've just compiled ipv6 support into my 
kernel to see if I can get dhcp-4.0.0 working.  Even when I included the 
-4 command-line option, it complained

"Error opening '/proc/net/if_inet6' to list IPv6 interfaces"

Anyway, it works now so I just need to leave it long enough and see what 


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