GODEBUG=netdns=1 prints a one-time strategy decision. (cgo or go DNS lookups)
GODEBUG=netdns=2 prints the per-lookup strategy as a function of the hostname.
The new "netcgo" build tag forces cgo DNS lookups.
GODEBUG=netdns=go (or existing build tag "netgo") forces Go DNS resolution.
GODEBUG=netdns=cgo (or new build tag "netcgo") forces libc DNS resolution.
Options can be combined with e.g. GODEBUG=netdns=go+1 or GODEBUG=netdns=2+cgo.
Fixes#11322Fixes#11450
Change-Id: I7a67e9f759fd0a02320e7803f9ded1638b19e861
Reviewed-on: https://go-review.googlesource.com/11584
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Android has (had?) its own local DNS resolver daemon, also my fault:
007e987fee
And you access that via libc, not DNS.
Fixes#10714
Change-Id: Iaff752872ce19bb5c7771ab048fd50e3f72cb73c
Reviewed-on: https://go-review.googlesource.com/9793
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Per resolv.conf man page, "If this file does not exist, only the name
server on the local machine will be queried."
This behavior also occurs if file is present but unreadable,
or if no nameservers are listed.
Fixes#10566
Change-Id: Id5716da0eae534d5ebfafea111bbc657f302e307
Reviewed-on: https://go-review.googlesource.com/9380
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
If the machine's network configuration files (resolv.conf,
nsswitch.conf) don't have any unsupported options, prefer Go's DNS
resolver, which doesn't have the cgo & thread over.
It means users can have more than 500 DNS requests outstanding (our
current limit for cgo lookups) and not have one blocked thread per
outstanding request.
Discussed in thread https://groups.google.com/d/msg/golang-dev/2ZUi792oztM/Q0rg_DkF5HMJ
Change-Id: I3f685d70aff6b47bec30b63e9fba674b20507f95
Reviewed-on: https://go-review.googlesource.com/8945
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
