Possible DHCP Issues

AsgardianFW

OK. I started a packet capture when pfSense was showing hostnames for all my devices (except the ones I know don't provide hostnames). Just 15 minutes into the packet capture and pfSense "lost" the hostnames for 2 devices. Only 18 DHCP packets were captured and I was able to study each one carefully (in Wireshark). For the 2 devices that lost their hostname, there were no DHCP packets that referenced the devices MAC address or IP address.

Note this was in the DHCP log a few minutes into the packet capture:

Feb 28 20:18:37	dhcpd		Wrote 22 leases to leases file.
Feb 28 20:18:37	dhcpd		Wrote 0 new dynamic host decls to leases file.
Feb 28 20:18:37	dhcpd		Wrote 0 deleted host decls to leases file.
.
.
Feb 28 20:22:20	dhclient	Creating resolv.conf
Feb 28 20:22:20	dhclient	RENEW

AsgardianFW

Perhaps more info in addition to previous post. I was going to start another packet capture test for overnight. The starting state is no hostname for my phone. I was going to start packet capture, switch phone from WiFi to cell and the back to WiFi (which usually gets the hostname back into pfSense) and then wait until the hostname is dropped again. While doing this procedure, I noticed that the dhcp.leases file has 2 entries for my phone (1 with hostname and 1 without). I'm not sure if this is expected behavior or not.

lease 10.11.12.224 {
  starts 0 2016/02/28 21:23:22;
  ends 1 2016/02/29 21:23:22;
  cltt 1 2016/02/29 00:33:55;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 24:da:3b:a9:5f:1b;
  uid "\001$\332\073\251\137\033";
  set vendor-class-identifier = "dhcpcd-5.5.6";
}
.
.
.
lease 10.11.12.224 {
  starts 1 2016/02/29 04:51:32;
  ends 2 2016/03/01 04:51:32;
  cltt 1 2016/02/29 04:51:32;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 24:da:3b:a9:5f:1b;
  uid "\001$\332\073\251\137\033";
  set vendor-class-identifier = "dhcpcd-5.5.6";
  client-hostname "android-dc49b48ab4ff452";
}

AsgardianFW

I completed my overnight test and replicated the problem again.

Start in no hostname state
Start packet capture
Switch cell phone from WiFi to Cell to WiFi to force a DHCP request and to make pfSense pick up hostname (verified)
Sleep 7.5 hours
Verify pfSense lost the hostname for cell phone in gui and dhcp.leases file
Stop packet capture (40 total packets)

When looking through all 40 packets, everything looks normal. I see the initial packets from step 3 above which do indeed include the hostname. The remaining packets also look normal but are for other devices. Besides the initial request, there are no other packets for the phone's MAC or IP yet it still lost the hostname. Same as the first (shorter) test.

I'd be open to other ideas to help figure out why pfSense is dropping the hostname for some devices.

MikeV7896

Just thought I'd mention that I'm seeing this issue as well. I have two Apple devices that usually show hostnames (and always did under 2.2.6), but now after running 2.3 for a few days, neither is showing a hostname in the DHCP Leases table.

cmb

Anything that's happening here is something to do with dhcpd itself, nothing in our code has any relation. The change from dhcpd 4.2 to 4.3 is probably at fault I'd guess, since that's the only thing that's changed. After a bit of searching I don't see any mention of issues along those lines in dhcpd or any relevant changes in behavior.

MikeV7896

Now that you've mentioned that, I checked the dhcpd.leases file and it doesn't have hostnames for the (now) three devices that don't have hostnames in the pfSense list… so I guess it must be something in dhcpd...

AsgardianFW

Is dhcpd capable of doing any kind of debug logging so that we can ascertain under what conditions it feels obligated to remove the hostname? If so, how can I enable it?
In a previous post, I mentioned that the same IP lease will be listed twice in dhcp.leases (one with a hostname and one without and each entry has different lease/expire times). Is this expected behavior?

(Please forgive my ignorant questions. I'm a Windows developer and FreeBSD isn't in my core skill set.)

AsgardianFW

As an added FYI…I checked a couple of my 2.2.5 installations and while the dhcp.leases file seems correct all the time on those, the /var/unbound/dhcpleases_entries.conf file seems to lose the occasional entry similar to the way 2.3 does in both files.

AsgardianFW

I'm still interested in trying to diagnose this problem. Is it possible for me to go back to dhcpd 4.2 in pfSense 2.3 to see if the problem still happens? This could help narrow down if there were changes in 4.3 that caused this.

gsiemon

I've just upgraded from 2.2.6 to 2.3 over the weekend and I'm seeing the same problem. Some of my devices are no longer showing hostnames in dhcpd.leases. This seems to affect all of our iOS and OS X devices

I have managed to get them to show up for a short time by editing their hostnames and then forcing a lease renewal on the client but a short time later (I suspect its when the device sleeps or goes out of range) it disappears again. I never saw this behaviour on 2.2.6.

dhcpd is configured with default settings for lease times etc. I do register the leases in a DNS server (not pfsense) and the leases file correctly lists the hostname in the FQDN registered in DNS for every device (affected or otherwise).

The only common thing I can see at the moment (and this may be a red herring) is that all of the devices that seem to have missing hostnames have 24 hour leases. The ones that seem to have sticky hostnames only have 2 hour leases.

cmb

I found one situation where it'll put in a lease entry with no hostname. If you 'ipconfig/release' on Windows, you end up with a "binding state free" lease entry like:

lease 192.168.1.100 {
  starts 2 2016/03/08 00:45:14;
  ends 2 2016/03/08 01:10:17;
  tstp 2 2016/03/08 01:10:17;
  cltt 2 2016/03/08 00:45:14;
  binding state free;
  hardware ethernet 00:0c:29:49:35:f4;
  uid "\001\000\014)I5\364";
}

but dhcpleases still finds the earlier leases and registers the hostname from the leases prior to the release.

Asgardian: if you still have the pcap files from earlier, could you send me those?

The full contents of your dhcpd.leases file from anyone that's affected would be helpful as well.

AsgardianFW

cmb,
I was just checking in to see if you figured out anything from the info I sent? I can still do more debugging for you if needed. Just let me know. Thanks.

cmb

Added a bug ticket for this issue, as there definitely is something to it.
https://redmine.pfsense.org/issues/6589