data-source/dns_txt_record_set: Large (>512 byte) Records Return Errors

[bflad]

Terraform Version

Terraform v1.0.3
on darwin_amd64

Affected Data Source

• dns_txt_record_set

Terraform Configuration Files

data "dns_txt_record_set" "test" {
  host = "terraform.io"
}

Expected Behavior

Successful data source results, with 7 records.

Actual Behavior

=== RUN   TestAccDataDnsTxtRecordSet_Basic
    data_dns_txt_record_set_test.go:13: Step 1/1 error: Error running pre-apply refresh: exit status 1
        2021/06/24 15:53:58 [DEBUG] Using modified User-Agent: Terraform/0.12.30 HashiCorp-terraform-exec/0.13.3
        
        Error: error looking up TXT records for "terraform.io": lookup terraform.io on 127.0.0.53:53: no such host
        
          on terraform_plugin_test.tf line 2, in data "dns_txt_record_set" "test":
           2: data "dns_txt_record_set" "test" {

--- FAIL: TestAccDataDnsTxtRecordSet_Basic (0.59s)
    data_dns_txt_record_set_test.go:13: Step 1/1 error: Error running pre-apply refresh: exit status 1
        Error: error looking up TXT records for "terraform.io": lookup terraform.io on 192.168.69.1:53: cannot unmarshal DNS message
          on terraform_plugin_test.tf line 2, in data "dns_txt_record_set" "test":
           2: data "dns_txt_record_set" "test" {

Same occurs across other large TXT records, such as:

• google.com (625 bytes locally)
• hashicorp.com (950 bytes locally)

Steps to Reproduce

1. go test -count=1 -run=TestAccDataDnsTxtRecordSet_Basic -v ./internal/provider on main (soon to be its own test)

Important Factoids

# Note: MSG SIZE and EDNS being enabled

$ dig TXT terraform.io

; <<>> DiG 9.10.6 <<>> TXT terraform.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13897
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;terraform.io.			IN	TXT

;; ANSWER SECTION:
terraform.io.		300	IN	TXT	"google-site-verification=LQZvxDzrGE-ZLudDpkpj-gcXN-5yF7Z6C-4Rljs3I_Q"
terraform.io.		300	IN	TXT	"_globalsign-domain-verification=O81xyb7YxpdGeHWkniit_VBT4vTXz9__NFrNMoTwFg"
terraform.io.		300	IN	TXT	"google-site-verification=y974ACvos30pN7_OBgEZb_byZV8qYtK0G6WZfE7OX8s"
terraform.io.		300	IN	TXT	"google-site-verification=8d7FpfB8aOEYAIkoaVKxg7Ibj438CEypjZTH424Pews"
terraform.io.		300	IN	TXT	"google-site-verification=9D7erI6Bfd9EOHKSIXRe0XQaqAFAjToBtZmyYRzMm34"
terraform.io.		300	IN	TXT	"v=spf1 -all"
terraform.io.		300	IN	TXT	"keybase-site-verification=5HKqMvJnTWpe8W-Aa8r0y3wuy1bhQ6LwcjaxKE9BOQU"

;; Query time: 22 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Mon Jul 26 09:53:53 EDT 2021
;; MSG SIZE  rcvd: 558

# dig will automatically failover to TCP, which Go's stub resolver may not

$ dig +noedns TXT terraform.io
;; Truncated, retrying in TCP mode.

; <<>> DiG 9.10.6 <<>> +noedns TXT terraform.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 60177
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;terraform.io.			IN	TXT

;; ANSWER SECTION:
terraform.io.		203	IN	TXT	"_globalsign-domain-verification=O81xyb7YxpdGeHWkniit_VBT4vTXz9__NFrNMoTwFg"
terraform.io.		203	IN	TXT	"keybase-site-verification=5HKqMvJnTWpe8W-Aa8r0y3wuy1bhQ6LwcjaxKE9BOQU"
terraform.io.		203	IN	TXT	"google-site-verification=9D7erI6Bfd9EOHKSIXRe0XQaqAFAjToBtZmyYRzMm34"
terraform.io.		203	IN	TXT	"v=spf1 -all"
terraform.io.		203	IN	TXT	"google-site-verification=LQZvxDzrGE-ZLudDpkpj-gcXN-5yF7Z6C-4Rljs3I_Q"
terraform.io.		203	IN	TXT	"google-site-verification=8d7FpfB8aOEYAIkoaVKxg7Ibj438CEypjZTH424Pews"
terraform.io.		203	IN	TXT	"google-site-verification=y974ACvos30pN7_OBgEZb_byZV8qYtK0G6WZfE7OX8s"

;; Query time: 12 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Mon Jul 26 09:55:30 EDT 2021
;; MSG SIZE  rcvd: 547

Failures can be influenced by intermediate DNS resolvers changing the response message size.

References

• TestAccDataDnsTxtRecordSet_Basic fails in GitHub Actions #154
• net: issue with DNS response > 512 bytes (cannot unmarshal DNS message) golang/go#21160
• net: re-enable or delete TestLookupLongTXT golang/go#22857
• net: don't keep reading from UDP resolver after truncated packet golang/go#23873

[bflad]

This should be partially resolved with golang/go#51127 with Go 1.18 and more fully if EDNS support is added in Go 1.19.

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