SERVFAIL

[mirazsarker]

i am faceing this

root@vmi697131:/zdns# echo "199.59.243.200" | ./zdns alookup
{"name":"199.59.243.200","status":"SERVFAIL","timestamp":"2022-06-02T19:47:14+02:00"}
root@vmi697131:/zdns# echo "censys.io" | ./zdns mxlookup --ipv4-lookup
{"name":"censys.io","status":"SERVFAIL","timestamp":"2022-06-02T19:50:40+02:00"}

[PenelopeFudd]

I'm getting SERVFAIL too.

I figured out why:

• If not specified, zdns uses the nameserver listed in the file /etc/resolv.conf
• On Ubuntu 18.04 and 20.04, that is 127.0.0.53, the address of the systemd resolver called systemd-resolved.
• When zdns sends a request to 127.0.0.53, it should use the source ip address 127.0.0.1, but instead uses the default address for the machine
• systemd-resolved generates the following error and returns the SERVFAIL message to zdns:

# journalctl -u systemd-resolved | grep Got | tail -n1
Nov 03 12:17:26 ns3.example.com systemd-resolved[508]: Got packet on unexpected IP range, refusing.

• systemd-resolved is expecting the source ip to be in the range 127.0.0.0 to 127.255.255.255 (127.0.0.1/8).

Solutions:

• Tell zdns to use the local address 127.0.0.1: zdns -local-addr 127.0.0.1 ......
• Tell zdns to use another name server: zdns -name-servers 8.8.8.8 .....
• Tell systemd-resolved to allow that IP?
• Use some iptables rules to change the source IP?
• Update zdns to use the ip address of the interface it's using?
  • This may already be fixed in the current version of zdns, I haven't checked.

Good luck!