Coredns is not forwarding the domains to external dns-CodePudding

I tried to customize the coredns of kubernetes by adding a domain and forwarded it to another server using forward plugin in coredns as below.

Corefile: |
    console.chn1s1.pub:53 {
      log
      errors
      cache 30
      whoami
      forward . 10.94.66.8
      reload
    }
    .:53 {
      log
      errors
      health {
        lameduck 5s
      }
      ready
      whoami
      kubernetes cluster.local in-addr.arpa ip6.arpa {
        pods insecure
        fallthrough in-addr.arpa ip6.arpa
      }
      prometheus :9153
      forward . "/etc/resolv.conf"
      cache 30
      loop
      reload
      loadbalance
    }

I tried using dig command to resolve as below:

dnstools# dig console.chn1s1.pub

; <<>> DiG 9.11.3 <<>> console.chn1s1.pub
;; global options:  cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 17671
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: fffd92ca8a1f341b (echoed)
;; QUESTION SECTION:
;console.chn1s1.pub.       IN      A

;; Query time: 2 msec
;; SERVER: 10.43.0.10#53(10.43.0.10)
;; WHEN: Fri Apr 01 14:05:04 UTC 2022
;; MSG SIZE  rcvd: 64

I see in coredns logs it is trying for search options in resolv.conf which means this dns query forwarded to .:53 server block (default one). I have seen the reload completed logs after changing the coredns Corefile.

[INFO] Reloading
[INFO] plugin/health: Going into lameduck mode for 5s
[INFO] 127.0.0.1:39697 - 30224 "HINFO IN 8546588560289937675.1040920946066232789. udp 57 false 512" NXDOMAIN qr,rd,ra 132 0.033646039s
[INFO] plugin/reload: Running configuration MD5 = 704f45a88b35bcfc3d65ab9a4bf70fe8
[INFO] Reloading complete

[INFO] 10.42.1.19:40365 - 28204 "A IN console.chn1s1.pub.default.svc.cluster.local. udp 67 false 512" NXDOMAIN qr,aa,rd 160 0.000288693s
[INFO] 10.42.1.19:56662 - 62228 "A IN console.chn1s1.pub.svc.cluster.local. udp 59 false 512" NXDOMAIN qr,aa,rd 152 0.00016752s
[INFO] 10.42.1.19:44234 - 41058 "A IN console.chn1s1.pub.cluster.local. udp 55 false 512" NXDOMAIN qr,aa,rd 148 0.000163651s
[INFO] 10.42.1.19:53530 - 44256 "A IN console.chn1s1.pub.openstacklocal. udp 56 false 512" NXDOMAIN qr,rd,ra 131 2.024311363s
[INFO] 10.42.1.19:37942 - 4348 "A IN console.chn1s1.pub. udp 41 false 512" FORMERR qr,rd 41 0.001628102s

/etc/resolv.conf

dnstools# cat /etc/resolv.conf
nameserver 10.43.0.10
search default.svc.cluster.local svc.cluster.local cluster.local openstacklocal
options ndots:5

As I am quite new to coredns and kubernetes, it would be really helpful if someone explains why this is trying .:53 server block always and how to make it work. How to debug it further to find the root cause of this issue. Thanks in advance!!!

CodePudding user response：

The request from kubernetes nameserver to my internal nameserver (I used to forward to ) is not reachable. This issue got solved after making my internal nameserver to allow requests from kubernetes nameserver IP.