net: TestLookupGmailTXT failing on Plan 9

[0intro]

Since CL 157638, TestLookupGmailTXT is failing on Plan 9.

--- FAIL: TestLookupGmailTXT (0.01s)
    lookup_test.go:248: got [globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=]; want a record containing spf, google.com
    lookup_test.go:248: got [globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=]; want a record containing spf, google.com
FAIL
FAIL	net	28.014s

See https://build.golang.org/log/10777f5ddff9d26836ac135c8c451166efa529ca

[0intro]

This is related to issue #22857.

[0intro]

The Plan 9 DNS resolver (ndb/dns) only returns a single TXT record, so the TXT request on gmail.com returns either the SPF or the S/MIME record depending on the machine on which ndb/dns is run.

cpu% ndb/dnsquery
> gmail.com txt
gmail.com txt	v=spf1 redirect=_spf.google.com

cpu% ndb/dnsquery
> gmail.com txt
gmail.com txt globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=

[gopherbot]

Change https://golang.org/cl/157737 mentions this issue: net: skip TestLookupGmailTXT on Plan 9

[fhs]

Update: 9front can return multiple txt records, but there is a bug with caching. You lose the SPF record after it expires.

cpu% ndb/dnsdebug
> gmail.com txt
....
----------------------------
answer gmail.com                        5 min           txt   v=spf1 redirect=_spf.google.com
answer gmail.com                        1 hr            txt   globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=
----------------------------

cpu% ndb/dnsquery
> gmail.com txt
gmail.com txt v=spf1 redirect=_spf.google.com
gmail.com txt globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=
> [wait 5 minutes here]
> gmail.com txt
gmail.com txt globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8=
> 

@gopherbot please add label OS-Plan9