net: DNS default resolver vs custom resolver behaviors.

[andymacau853]

What version of Go are you using (go version)?

$ go version
go version go1.11.4 windows/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
$ go env
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Administrator\AppData\Local\go-build
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=C:\Project\Go\maas
set GOPROXY=
set GORACE=
set GOROOT=C:\Go
set GOTMPDIR=
set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
set GCCGO=gccgo
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=
0 -fdebug-prefix-map=C:\Users\Administrator\AppData\Local\Temp\go-build757481154=/tmp/go-
build -gno-record-gcc-switches

What did you do?

My current PC is not set any DNS server, because I need to test Go's custom resolver, now the code seems not work, the DNS server: 8.8.4.4 is not to use, why?

r := &net.Resolver{
	PreferGo: true,
	Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
		d := net.Dialer{
			Timeout: time.Millisecond * time.Duration(10000),
		}
		return d.DialContext(ctx, "udp", "8.8.4.4:53")
	},
}
ip, err := r.LookupIPAddr(context.Background(), host)

What did you expect to see?

The DNS query should use my custom resolver to get IP address, but it seems not work above code.

What did you see instead?

the error message is "lookup www.xxxxxx.com: no such host"

[julieqiu]

/cc @mikioh @bradfitz

[mikioh]

The docs on the net packages say:

On Windows, the resolver always uses C library functions, such as GetAddrInfo and DnsQuery.

See https://godoc.org/net. I think it's fine to change this issue to a proposal for enabling the built-in DNS stub resolver even on Windows, although, I'm not a Windows user and have no Windows stuff.

[andymacau853]

The docs on the net packages says:

On Windows, the resolver always uses C library functions, such as GetAddrInfo and DnsQuery.

See https://godoc.org/net. I think it's fine to change this issue to a proposal for enabling the built-in DNS stub resolver even on Windows, although, I'm not a Windows user and have no Windows stuff.

So do u mean, when i deploy to Linux platform, Is above code work?

[mikioh]

above code work?

I don't say "yup" instantly because I don't know any detail on your circumstances; please be informed that DNS is a system requiring three role nodes, a stub resolver, a recursive server (aka full resolver) and an authoritative server on IP-based transport networks. If you can ensure that your circumstances are pretty clear (nowadays, it's pretty hard to find out such "clear/ideal circumstances", though), your approach may succeed.

[mikioh]

@andymacau853,

Please re-title this issue like "proposal: net: enable built-in DNS stub resolver on Windows" if you really want the functionality.

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)