dhcpd.conf hostnames instead of ip addresses stopped working

AchilleTalon

I have my dhcp server on the same box as the nameserver. I am using systemd as well on this box. Both dhcp server and nameserver are chrooted, they were both working fine. They nameserver is still working fine, however for an unknown reason since I didn't catch the problem when it occurs, the dhcpd.conf file no longer accepts a hostname in the fixed-address definition, it requires an ip address to work properly.

The man page for dhcpd.conf clearly state the hostname is an admissible entry instead of the ip address. It should work everywhere an ip address is required like option routers, option domain-name-servers, etc.

Anyone has an idea why this stopped working?

# emerge --info net-misc/dhcp

AchilleTalon · Posted: Tue Oct 07, 2014 5:01 pm Post subject:

For the records, my chroot directory is /chroot/dhcp and the content of /chroot/dhcp/etc/resolv.conf is:

UberLord · Posted: Tue Oct 07, 2014 8:21 pm Post subject:

The DHCP server cannot resolve the hosname to an IP adress.
This could be a variety of reasons, one being that DHCP server was started *before* DNS is actually available.
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AchilleTalon · Posted: Tue Oct 07, 2014 8:51 pm Post subject:

Nope, the DNS is up and running. I did the test after everything is up and running and restarting the dhcp server, wiping out the leases. There is something else, however the output doesn't provide with much information to discover what is going on.

I can see the DHCPDISCOVER with the hardware ethernet address given to the server which replies with a DHCPOFFER skipping the fixed-address stanza to pick an address in the dynamic address pool instead, then the offer is accepted and acknowledged.

I am trying to recompile this thing to provide more debugging information about the lease finding step which seems where the problem occurs.
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AchilleTalon · Posted: Wed Oct 08, 2014 2:39 am Post subject:

After patching the code to make the debugging messages working properly here is the kind of messages I get:

UberLord · Posted: Wed Oct 08, 2014 8:58 am Post subject:

Can you lookup the hostname from within the DHCP chroot?
ie

AchilleTalon · Posted: Wed Oct 08, 2014 3:09 pm Post subject:

Since I don't have access to the bind tools from within the chroot environment I cannot perform this test right now. The dhcpd implementation is compiling its own set of bind related libraries and functions. The best thing would be to compile a utility command to perform the binding using these libraries or to extend some piece of code called at initialization to perform a dummy test.

I am looking at it.

Addendum:
From the netdb.h file the set of errors for gethostbyname() and their meaning is as follow:

AchilleTalon · Posted: Wed Oct 08, 2014 6:07 pm Post subject:

I did write a test function which loops around a list of hostnames to query resolution from the initialization code of dhcpd. No matter what the hostname is, even for those which do not exist at all, the gethostbyname() function always returns h_errno == 0; as if there was no error while the returned pointer is NULL.

The real gethostbyname() function seems wrapped by some code in the bind version bundled with dhcpd.

It did work before, same version of dhcp. The only things I can think it depends on is /chroot/dhcp/etc/resolv.conf, /dev, /proc and /sys even if /dev and /sys were not mounted in the chrooted environment before it doesn't change anything if I mount them or not.

I tested dhcpd outside a chrooted environment and it is working fine. It is then something with the chroot environment.
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