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net: tryOneName logs the wrong server on error when the Dial function is overridden #54242

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th0m opened this issue Aug 3, 2022 · 1 comment
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net: tryOneName logs the wrong server on error when the Dial function is overridden #54242

th0m opened this issue Aug 3, 2022 · 1 comment
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@th0m
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th0m commented Aug 3, 2022

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

$ go version
go version go1.18.2 linux/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
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/vagrant/.cache/go-build"
GOENV="/home/vagrant/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/vagrant/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/vagrant/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1847147377=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Create a Resolver, override its Dial function to set a fixed resolver ip to be used: 1.2.3.4:53.
Use it to resolve cloudflare.com.
Notice that the error message has the wrong resolver ip after lookup cloudflare.com on

Minimal reproducer: https://go.dev/play/p/4Se0BI1xwJx

What did you expect to see?

lookup cloudflare.com on 1.2.3.4:53: dial udp 1.2.3.4:53: connect: no route to host

What did you see instead?

lookup cloudflare.com on 169.254.169.254:53: dial udp 1.2.3.4:53: connect: no route to host

I have tracked the issue down to tryOneName not being aware Dial has been overridden.
Therefore, in its error message it is using the server it got from the lookup function that gets a list of servers from resolv.conf .

			p, h, err := r.exchange(ctx, server, q, cfg.timeout, cfg.useTCP)
			if err != nil {
				dnsErr := &DNSError{
					Err:    err.Error(),
					Name:   name,
					Server: server,
				}
@seankhliao
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Duplicate of #43703

@seankhliao seankhliao marked this as a duplicate of #43703 Aug 3, 2022
@seankhliao seankhliao closed this as not planned Won't fix, can't repro, duplicate, stale Aug 3, 2022
@golang golang locked and limited conversation to collaborators Aug 3, 2023
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@th0m @gopherbot @seankhliao