x/net/webdav: cannot handle symbolic link that points to a non existed file

[jjm2473]

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

$ go version
go1.18

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/jjm/Library/Caches/go-build"
GOENV="/Users/jjm/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/jjm/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/jjm/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Volumes/data/src/gowebdav/go.mod"
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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/7b/lr1hrhyd3ts3v_d8m7bjngdh0000gn/T/go-build747360344=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I have build a webdav server and run it on a router, serve router's /mnt as webdav root, then mount it on macOS. When I create a symbol link in /mnt ln -s /tmp/noexist /mnt/noexist (/tmp/noexist does not existed)，then PROPFIND / with Depth=1 will get a Internal Server Error (Wireshark capture below).

===== Request =====
PROPFIND / HTTP/1.1
Host: 192.168.31.1:6086
Content-Type: text/xml
Depth: 1
Accept: */*
User-Agent: WebDAVFS/3.0.0 (03008000) Darwin/21.6.0 (x86_64)
Authorization: Basic ***
Content-Length: 179
Connection: keep-alive

<?xml version="1.0" encoding="utf-8"?>
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:getlastmodified/>
<D:getcontentlength/>
<D:creationdate/>
<D:resourcetype/>
</D:prop>
</D:propfind>

===== Response =====
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset=utf-8
Date: Thu, 22 Sep 2022 06:12:53 GMT
Content-Length: 516

<?xml version="1.0" encoding="UTF-8"?><D:multistatus xmlns:D="DAV:"><D:response><D:href>/</D:href><D:propstat><D:prop><D:getlastmodified>Thu, 22 Sep 2022 06:12:32 GMT</D:getlastmodified><D:resourcetype><D:collection xmlns:D="DAV:"/></D:resourcetype></D:prop><D:status>HTTP/1.1 200 OK</D:status></D:propstat><D:propstat><D:prop><D:getcontentlength></D:getcontentlength><D:creationdate></D:creationdate></D:prop><D:status>HTTP/1.1 404 Not Found</D:status></D:propstat></D:response></D:multistatus>Internal Server Error

What did you expect to see?

List root dir

What did you see instead?

Internal Server Error

[cherrymui]

cc @neild @ianlancetaylor