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net: pure Go resolver(netdns) can not resolve hostname.local #35067

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atlas-comstock opened this issue Oct 22, 2019 · 10 comments
Open

net: pure Go resolver(netdns) can not resolve hostname.local #35067

atlas-comstock opened this issue Oct 22, 2019 · 10 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Unplanned

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@atlas-comstock
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atlas-comstock commented Oct 22, 2019 •
edited

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

go version go1.13.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/atlas/Library/Caches/go-build"
GOENV="/Users/atlas/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/yonghao.hu/mycode/go_dir_path"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.13.3/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.13.3/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/yonghao.hu/mycode/go_dir_path/src/test/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/wf/nw471wh91nj2j_dsrfrk4htnjtqhhw/T/go-build666420423=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

package main

import (
	"fmt"
	"net"
)

func main() {
	dialer := &net.Dialer{
		LocalAddr: nil,
	}

	_, err := dialer.Dial("tcp", "atalas-mac.local:4150")
	if err != nil {
		fmt.Println("resolve atalas-mac.local failed: ", err)
	} else {
		fmt.Println("resolve myaliashost success")
	}
	_, err = dialer.Dial("tcp", "myaliashost:4150")
	if err != nil {
		fmt.Println("resolve myaliashost failed: ", err)
	}
	fmt.Println("resolve myaliashost success")
}

Just run GODEBUG=netdns=go+4 go run test.go

What did you expect to see?

Resolve to 127.0.0.1

What did you see instead?

resolve mac.local failed: dial tcp: lookup mac.local on 10.22.12.45:53: no such host
@bradfitz bradfitz changed the title pure Go resolver(netdns) can not resolve hostname.local net: pure Go resolver(netdns) can not resolve hostname.local Oct 22, 2019
@bradfitz
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Yes, that's known, as the docs at https://golang.org/pkg/net/#hdr-Name_Resolution imply, and we're unlikely to implement it.

If you need to resolve those names, use a different resolver.

@bradfitz bradfitz added this to the Unplanned milestone Oct 22, 2019
@atlas-comstock
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atlas-comstock commented Oct 22, 2019 •
edited

@bradfitz Hi, thanks for your reply . I know sth about this before writing the issue. Could u plz tell me why not to implement it ? What is the consideration?

@bradfitz
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It's a lot of code for very few users and the system DNS resolver is usually fine. The advantage of using the pure Go resolver is usually to avoid cgo and expensive threads being tied up during resolution, but that only matters when you have, say, tens of thousands of outstanding lookups. (e.g. you're a web crawler binary) But if you have tens of thousands of mDNS lookups outstanding, you probably have bigger problems on your LAN.

@dmitshur dmitshur added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 22, 2019
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@pmahoney pmahoney mentioned this issue Nov 22, 2019
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@inoc603 inoc603 mentioned this issue Feb 10, 2020
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h44z added a commit to h44z/wg-portal that referenced this issue Apr 8, 2021
@h44z
fix .local DNS lookup (golang/go#35067)
2ca1226
@zaggash zaggash mentioned this issue Apr 15, 2021
Closed
@yiannistri yiannistri mentioned this issue Oct 21, 2021
Merged
@GeorgeMac GeorgeMac mentioned this issue Aug 30, 2022
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@eaglesemanation eaglesemanation mentioned this issue Mar 7, 2023
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@bradfitz @davecheney @jdmarshall @dmitshur @ianlancetaylor @alex-leonhardt @atlas-comstock