Filterdns has stopped resolving hostnames in firewall aliases

SteveITS

I ran across https://redmine.pfsense.org/issues/14734 which sounds like a possible cause...the IP is incorrectly removed if an FQDN resolving to it changes IPs.

Also per https://forum.netgate.com/topic/199152/unexpected-alias-behaviour-two-ranges/ aliases that contain IPs and an FQDN may fail to populate all the IPs.

SteveITS

14734 was marked as a duplicate of https://redmine.pfsense.org/issues/13792.

I am trying to think of a way around that...have a separate alias+rule for FQDNs that might ever overlap, say for each laptop...?

Patch

Agree
That bug really does make alias much less useful. Two example I currently use aliases for which will fail with this bug

White list for remote access to work server from periheral sites. The laptops will roam between sites

Peripheral site DDNS FQDN
Peripheral site relatively static IPv4 addresses
Laptop 1 DDNS FQDN
Laptop 1 DDNS FQDN

White list from a VoIP supplier with redundant servers in multiple cities. During fault conditions the supplier redirects traffic to better functioning servers in another city

city1.Voipsuppler.com
city2.Voipsuppler.com
city3.Voipsuppler.com
city4.Voipsuppler.com
city5.Voipsuppler.com
city6.Voipsuppler.com
city7.Voipsuppler.com
city8.Voipsuppler.com

Imo
The variable FQDN component of an alias should be completely recalculated from scratch then combined with the constant (explicitly specified) IPs each time. After which only changes from the current IP addressees written to filterdns to update the firewall filtering.

NWOSwamp

Having this issue and follows symptoms already mentioned.

Use DNS in aliases for access in FW rules. Access to a remote site drops. The Source IP is hitting Default Deny rule at the remote end. Remote end Tables doesn't have the IP for the DNS name, not sure if a DNS issue or filterdns stalls.

None of the reload suggestions found worked /etc/rc.update_urltables, /etc/rc.update_urltables now forceupdate and /etc/rc.update_alias_url_data. The IP never returned in Tables following those commands. Maybe because filterdns appeared stalled - process still running and was not exiting.

Also noticed:

DNS resolution was working after the issue started and no issues were noticed before
This occurred twice seemingly sporadically, both were after 1am. pfBlocker update does not run at that time.
First time noticed occurred after an ISP modem outage/reboot. Didn't figure out the Tables issue then. Rebooting the ISP modem again resolved the issue. Apparently, manually deleting an IP from the table, followed by downing the WAN interface caused pfSense to repopulate the IP in the table.
Second time there was no modem outage. Restarting unbound service did not resolve the issue. Saw filterdns in the process table still running. Did resolve with a suggestion above

killall filterdns then Status -> Filter Reload

pfSense is 2.8.1 - packages: frr, mtr, nut, pfBlockerNG, Service_Watchdog (watching OpenVPN), and System_Patches

SteveITS

@NWOSwamp Due to the above mentioned bugs, AFAIK the workarounds are:

any FQDNs that might ever overlap (same IP) need to be in their own alias (therefore, rule)
avoid mixing IP ranges and FQDNs in the same alias

NWOSwamp

@SteveITS I don't have either of these. I went and did an nslookup on all the FQDNs (including LAN IPs). Sorting and sorting for unique resulted in the same number of IPs, meaning no overlaps/none with the same IP. None of the FQDNs should have changed, but it also doesn't mean the wrong answer was returned by DNS when this happened. I don't have aliases with mixed IPs and FQDN.

I will keep these in mind specifically looking for them next time.

I do have:

aliases referenced in other aliases
the same FQDN in an alias and as the Remote Gateway for IPsec - these would end up in different rules, though.

Alias in Alias example:
Alias Name: location1_IP
FQDN: location1.foobar.com

Alias Name: allow_ping
FQDN: "location1_IP"
FQDN: anotherserver.foobar.com

Alias Name: OpenVPN_backup
FQDN: "location1_IP"
FQDN: mobiledevice.foobar.com

allow_ping and OpenVPN_backup would then be used as the source in separate WAN rules. IPs of location1.foobar.com, anotherserver.foobar.com and mobiledevice.foobar.com would never be the same under normal circumstances.

Patch

For me, pfsense removing transiently overlapping IP addresses make alias based IP filtering unreliable, so not a usable solution. The bug has been there for at least 3 years, and doesn't appears unlikely to be resolved in the near term.

I wonder if as a work around, it is possible to:

use pfBlockerNG to generate/maintain these aliases.
Store the "feed" for these work around alias locally
Set their alias update frequency to hourly

Hopefully that would result in pfBlockerNG generating the aliases from scratch each time, including the associated duplicate removal. pfsense filterdns would then only see an IP being removed when it is duplicated zero times (actually removed from the alias), and so avoid the pfsense redmine bug 13792.

tinfoilmatt

@Patch said in Filterdns has stopped resolving hostnames in firewall aliases:

I wonder if as a work around, it is possible to:

use pfBlockerNG to generate/maintain these aliases.

Indeed it's possible—and pfBlockerNG additionally contains deduplication functionality for IP lists.

SteveITS

@tinfoilmatt just be aware pfB dedupe has its own issues:
https://forum.netgate.com/topic/185901/pfblockerng-not-blocking-some-foreign-sites-using-geoip/8

tinfoilmatt

@SteveITS said in Filterdns has stopped resolving hostnames in firewall aliases:

https://forum.netgate.com/topic/185901/pfblockerng-not-blocking-some-foreign-sites-using-geoip/8

Was not aware. Thanks for the share.

Tangentially related—but as does CIDR aggregation when using a combination of IP blacklists (i.e., 'action' Deny) and whitelists (i.e., 'action' Permit).