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Client automount occasionally fails due to DNS query failure

  1. Last updated
    Dec 18, 2024
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Category:
fas-systems
Specialty:
nas
Last Updated:
12/18/2024, 4:41:33 PM

Applies to

On-box DNS load balancing
 

Issue

  • In a mount storm environment, it is possible that the external linux DNS server with Bind version equo or greater than bind-9.9.4-69.el7 which start to support 0 ttl forwards DNS query request to non-listener On-box DNS server LIFs
  • If external DNS server forwards DNS query request to non-listener On-box DNS server LIFs, ONTAP refuses initial connection request
  • It finally results in client DNS query failure
 
Example:
 
/// IP info
 
NFS client:
192.168.0.61
External DNS server IP:
192.168.0.188
Storage IPs:
192.168.0.134
192.168.0.135 (only this IP is allowed to process DNS query request. listen-for-dns-query:true)
192.168.0.136
192.168.0.137
192.168.0.139
 
/// OTNAP config
 
cluster1::*> net int show -vserver svm2_cluster1 -fields listen-for-dns-query,dns-zone,address
(network interface show)
vserver   lif    address   dns-zone   listen-for-dns-query
------------- --------------------- ------------- ----------------------- --------------------
svm2_cluster1 lif_svm2_cluster1_433 192.168.0.135 storage_hostname.test.com true
svm2_cluster1 lif_svm2_cluster1_453 192.168.0.137 storage_hostname.test.com false
svm2_cluster1 lif_svm2_cluster1_583 192.168.0.134 storage_hostname.test.com false
svm2_cluster1 lif_svm2_cluster1_858 192.168.0.136 storage_hostname.test.com false
svm2_cluster1 lif_svm2_cluster1_996 192.168.0.139 storage_hostname.test.com false
 
/// Zone file config
 
/var/named/test.zone
------------------------------------------
;TR guide setting
$ORIGIN storage_hostname.com.
@    IN    NS    storage_hostname.com.
IN    NS    ansible.seccae.com.
storage_hostname.test.com.   IN    A   192.168.0.135
 

/// Log analysis

NFS client returns SERVFAIL error and automount fail message 

Sun Jun 26 15:14:06 UTC 2022
storage_hostname.test.com has address 192.168.0.134
Host storage_hostname.test.com not found: 2(SERVFAIL)
Host storage_hostname.test.com not found: 2(SERVFAIL)
Sun Jun 26 15:14:07 UTC 2022
Host storage_hostname.test.com not found: 2(SERVFAIL)

May 9 07:55:12 client_hostname automount[1364] : add_host_addrs: hostname lookup for storage_hostname failed: Name or service not known

External DNS server returns connection refused info level message from named.run log

6-Jun-2022 15:10:02.301 resolver: debug 1: fetch: storage_hostname.test.com/AAAA
26-Jun-2022 15:10:02.335 resolver: debug 1: fetch: storage_hostname.test.com/MX
26-Jun-2022 15:14:06.990 resolver: debug 1: fetch: storage_hostname.test.com/A
26-Jun-2022 15:14:07.004 resolver: debug 1: fetch: storage_hostname.test.com/AAAA
26-Jun-2022 15:14:07.005 lame-servers: info: connection refused resolving 'storage_hostname.test.com/AAAA/IN': 192.168.0.134#5326-Jun-2022 15:14:07.005 resolver: debug 1: fetch: storage_hostname.test.com/AAAA
26-Jun-2022 15:14:07.005 query-errors: debug 1: client @0x7f5362edac20 192.168.0.61#60563 (storage_hostname.test.com): query failed (SERVFAIL) for storage_hostname.test.com/IN/AAAA at ../../../bin/named/query.c:8580
26-Jun-2022 15:14:07.005 lame-servers: debug 1: lame server resolving 'storage_hostname.test.com' (in 'storage_hostname.test.com'?): 192.168.0.188#53
26-Jun-2022 15:14:07.005 resolver: debug 1: fetch: storage_hostname.test.com/MX
26-Jun-2022 15:14:07.006 lame-servers: info: connection refused resolving 'storage_hostname.test.com/AAAA/IN': 192.168.0.134#53
26-Jun-2022 15:14:07.006 lame-servers: info: connection refused resolving 'storage_hostname.test.com/MX/IN': 192.168.0.134#53
26-Jun-2022 15:14:07.006 query-errors: debug 1: client @0x7f53600aa070 192.168.0.61#57471 (storage_hostname.test.com): query failed (SERVFAIL) for storage_hostname.test.com/IN/MX at ../../../bin/named/query.c:8580
26-Jun-2022 15:14:07.017 resolver: debug 1: fetch: storage_hostname.test.com/A
26-Jun-2022 15:14:07.017 lame-servers: info: connection refused resolving 'storage_hostname.test.com/A/IN': 192.168.0.134#53
26-Jun-2022 15:14:07.017 query-errors: debug 1: client @0x7f5362edac20 192.168.0.61#48698 (storage_hostname.test.com): query failed (SERVFAIL) for storage_hostname.test.com/IN/A at ../../../bin/named/query.c:8580

Storage side pakcet trace clearly recorded this behavior
Here, only 192.168.0.135 is On-box DNS listner IP

72   2022-06-26 23:14:19.572835   6.154698   192.168.0.188   38078    192.168.0.135   53   DNS   Standard query 0x1d9c A storage_hostname.test.com OPT
73   2022-06-26 23:14:19.585266   0.012431   192.168.0.135   53   192.168.0.188   38078   DNS   Standard query response 0x1d9c A storage_hostname.test.com A 192.168.0.134 NS storage_hostname.test.com OPT
74   2022-06-26 23:14:19.586980   0.001714   192.168.0.188   33860    192.168.0.134   53   DNS   Standard query 0x88a9 AAAA storage_hostname.test.com OPT
75   2022-06-26 23:14:19.587027   0.000047   192.168.0.134   33860    192.168.0.188   53   ICMP   Destination unreachable (Port unreachable)

Complete behavior can be checked from the packet trace which is captured from external DNS server

  • A query succed
    • Client send A query request to external DNS server
    • External DNS server forward this A query request to On-box DNS IP 192.168.0.135
    • On-box DNS reply with A query response to external DNS server (at this point, it seems external DNS erver remember the IP 192.168.0.134)
    • External DNS server respond client with A query response (use 192.168.0.134 to mount storage system)
  • AAAA query failed
    • Client send AAAA query request to external DNS server
    • External DNS server forward this AAAA query request to On-box DNS IP 192.168.0.134
    • On-box DNS reply with Destination unreachable to external DNS server
    • External DNS server respond Client with query failed (SERVFAIL)
  • MX query failed
    • Client send MX query request to external DNS server
    • External DNS server forward this MX query request to On-box DNS IP 192.168.0.134
    • On-box DNS reply with Destination unreachable to external DNS server
    • External DNS server respond Client with query failed (SERVFAIL)
  • A query failed
    • Client send A query request to external DNS server
    • External DNS server forward this A query request to On-box DNS IP 192.168.0.134
    • On-box DNS reply with Destination unreachable to external DNS server
    • External DNS server respond Client with query failed (SERVFAIL)

967   2022-06-26 23:14:06.989631   0.000501   192.168.0.61   36365    192.168.0.188   53   DNS   Standard query 0x6fea A storage_hostname.test.com
969   2022-06-26 23:14:06.990708   0.000557   192.168.0.188   38078    192.168.0.135   53   DNS   Standard query 0x1d9c A storage_hostname.test.com OPT
970   2022-06-26 23:14:07.003287   0.012579   192.168.0.135   53   192.168.0.188   38078    DNS   Standard query response 0x1d9c A storage_hostname.test.com A 192.168.0.134 NS storage_hostname.test.com OPT
971   2022-06-26 23:14:07.003852   0.000565   192.168.0.188   53   192.168.0.61   36365    DNS   Standard query response 0x6fea A storage_hostname.test.com A 192.168.0.134 NS storage_hostname.test.com
972   2022-06-26 23:14:07.004491   0.000639   192.168.0.61   60563    192.168.0.188   53   DNS   Standard query 0x47bc AAAA storage_hostname.test.com
973   2022-06-26 23:14:07.004892   0.000401   192.168.0.188   33860    192.168.0.134   53   DNS   Standard query 0x88a9 AAAA storage_hostname.test.com OPT
974   2022-06-26 23:14:07.005017   0.000125   192.168.0.134   33860    192.168.0.188   53   ICMP   Destination unreachable (Port unreachable)
975   2022-06-26 23:14:07.005451   0.000434   192.168.0.188   53   192.168.0.61   60563    DNS   Standard query response 0x47bc Server failure AAAA storage_hostname.test.com
976   2022-06-26 23:14:07.005710   0.000259   192.168.0.61   57471    192.168.0.188   53   DNS   Standard query 0xe348 MX storage_hostname.test.com
977   2022-06-26 23:14:07.005742   0.000032   192.168.0.188   59080    192.168.0.134   53   DNS   Standard query 0xde2d AAAA storage_hostname.test.com OPT
978   2022-06-26 23:14:07.005809   0.000067   192.168.0.134   59080    192.168.0.188   53   ICMP   Destination unreachable (Port unreachable)
979   2022-06-26 23:14:07.005901   0.000092   192.168.0.188   51515    192.168.0.134   53   DNS   Standard query 0x0a65 MX storage_hostname.test.com OPT
980   2022-06-26 23:14:07.005999   0.000098   192.168.0.134   51515    192.168.0.188   53   ICMP   Destination unreachable (Port unreachable)
981   2022-06-26 23:14:07.006199   0.000200   192.168.0.188   53   192.168.0.61   57471    DNS   Standard query response 0xe348 Server failure MX storage_hostname.test.com
982   2022-06-26 23:14:07.016776   0.010577   192.168.0.61   48698    192.168.0.188   53   DNS   Standard query 0x573a A storage_hostname.test.com
983   2022-06-26 23:14:07.017217   0.000441   192.168.0.188   46874    192.168.0.134   53   DNS   Standard query 0xf57a A storage_hostname.test.com OPT
984   2022-06-26 23:14:07.017343   0.000126   192.168.0.134   46874    192.168.0.188   53   ICMP   Destination unreachable (Port unreachable)
985   2022-06-26 23:14:07.017536   0.000193   192.168.0.188   53   192.168.0.61   48698    DNS   Standard query response 0x573a Server failure A storage_hostname.test.com
987   2022-06-26 23:14:07.027914   0.010016   192.168.0.61   53770    192.168.0.188   53   DNS   Standard query 0x4a57 A storage_hostname.test.com
989   2022-06-26 23:14:07.028215   0.000217   192.168.0.188   53   192.168.0.61   53770    DNS   Standard query response 0x4a57 Server failure A storage_hostname.test.com
995   2022-06-26 23:14:07.038529   0.009511   192.168.0.61   41057    192.168.0.188   53   DNS   Standard query 0x498a A storage_hostname.test.com
996   2022-06-26 23:14:07.038756   0.000227   192.168.0.188   53   192.168.0.61   41057    DNS   Standard query response 0x498a Server failure A storage_hostname.test.com

 

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