go proxy 源码
golang proxy 代码
文件路径：/src/cmd/go/internal/modfetch/proxy.go
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package modfetch
import (
"encoding/json"
"errors"
"fmt"
"io"
"io/fs"
"net/url"
"path"
pathpkg "path"
"path/filepath"
"strings"
"sync"
"time"
"cmd/go/internal/base"
"cmd/go/internal/cfg"
"cmd/go/internal/modfetch/codehost"
"cmd/go/internal/web"
"golang.org/x/mod/module"
"golang.org/x/mod/semver"
)
var HelpGoproxy = &base.Command{
UsageLine: "goproxy",
Short: "module proxy protocol",
Long: `
A Go module proxy is any web server that can respond to GET requests for
URLs of a specified form. The requests have no query parameters, so even
a site serving from a fixed file system (including a file:/// URL)
can be a module proxy.
For details on the GOPROXY protocol, see
https://golang.org/ref/mod#goproxy-protocol.
`,
}
var proxyOnce struct {
sync.Once
list []proxySpec
err error
}
type proxySpec struct {
// url is the proxy URL or one of "off", "direct", "noproxy".
url string
// fallBackOnError is true if a request should be attempted on the next proxy
// in the list after any error from this proxy. If fallBackOnError is false,
// the request will only be attempted on the next proxy if the error is
// equivalent to os.ErrNotFound, which is true for 404 and 410 responses.
fallBackOnError bool
}
func proxyList() ([]proxySpec, error) {
proxyOnce.Do(func() {
if cfg.GONOPROXY != "" && cfg.GOPROXY != "direct" {
proxyOnce.list = append(proxyOnce.list, proxySpec{url: "noproxy"})
}
goproxy := cfg.GOPROXY
for goproxy != "" {
var url string
fallBackOnError := false
if i := strings.IndexAny(goproxy, ",|"); i >= 0 {
url = goproxy[:i]
fallBackOnError = goproxy[i] == '|'
goproxy = goproxy[i+1:]
} else {
url = goproxy
goproxy = ""
}
url = strings.TrimSpace(url)
if url == "" {
continue
}
if url == "off" {
// "off" always fails hard, so can stop walking list.
proxyOnce.list = append(proxyOnce.list, proxySpec{url: "off"})
break
}
if url == "direct" {
proxyOnce.list = append(proxyOnce.list, proxySpec{url: "direct"})
// For now, "direct" is the end of the line. We may decide to add some
// sort of fallback behavior for them in the future, so ignore
// subsequent entries for forward-compatibility.
break
}
// Single-word tokens are reserved for built-in behaviors, and anything
// containing the string ":/" or matching an absolute file path must be a
// complete URL. For all other paths, implicitly add "https://".
if strings.ContainsAny(url, ".:/") && !strings.Contains(url, ":/") && !filepath.IsAbs(url) && !path.IsAbs(url) {
url = "https://" + url
}
// Check that newProxyRepo accepts the URL.
// It won't do anything with the path.
if _, err := newProxyRepo(url, "golang.org/x/text"); err != nil {
proxyOnce.err = err
return
}
proxyOnce.list = append(proxyOnce.list, proxySpec{
url: url,
fallBackOnError: fallBackOnError,
})
}
if len(proxyOnce.list) == 0 ||
len(proxyOnce.list) == 1 && proxyOnce.list[0].url == "noproxy" {
// There were no proxies, other than the implicit "noproxy" added when
// GONOPROXY is set. This can happen if GOPROXY is a non-empty string
// like "," or " ".
proxyOnce.err = fmt.Errorf("GOPROXY list is not the empty string, but contains no entries")
}
})
return proxyOnce.list, proxyOnce.err
}
// TryProxies iterates f over each configured proxy (including "noproxy" and
// "direct" if applicable) until f returns no error or until f returns an
// error that is not equivalent to fs.ErrNotExist on a proxy configured
// not to fall back on errors.
//
// TryProxies then returns that final error.
//
// If GOPROXY is set to "off", TryProxies invokes f once with the argument
// "off".
func TryProxies(f func(proxy string) error) error {
proxies, err := proxyList()
if err != nil {
return err
}
if len(proxies) == 0 {
panic("GOPROXY list is empty")
}
// We try to report the most helpful error to the user. "direct" and "noproxy"
// errors are best, followed by proxy errors other than ErrNotExist, followed
// by ErrNotExist.
//
// Note that errProxyOff, errNoproxy, and errUseProxy are equivalent to
// ErrNotExist. errUseProxy should only be returned if "noproxy" is the only
// proxy. errNoproxy should never be returned, since there should always be a
// more useful error from "noproxy" first.
const (
notExistRank = iota
proxyRank
directRank
)
var bestErr error
bestErrRank := notExistRank
for _, proxy := range proxies {
err := f(proxy.url)
if err == nil {
return nil
}
isNotExistErr := errors.Is(err, fs.ErrNotExist)
if proxy.url == "direct" || (proxy.url == "noproxy" && err != errUseProxy) {
bestErr = err
bestErrRank = directRank
} else if bestErrRank <= proxyRank && !isNotExistErr {
bestErr = err
bestErrRank = proxyRank
} else if bestErrRank == notExistRank {
bestErr = err
}
if !proxy.fallBackOnError && !isNotExistErr {
break
}
}
return bestErr
}
type proxyRepo struct {
url *url.URL
path string
redactedURL string
listLatestOnce sync.Once
listLatest *RevInfo
listLatestErr error
}
func newProxyRepo(baseURL, path string) (Repo, error) {
base, err := url.Parse(baseURL)
if err != nil {
return nil, err
}
switch base.Scheme {
case "http", "https":
// ok
case "file":
if *base != (url.URL{Scheme: base.Scheme, Path: base.Path, RawPath: base.RawPath}) {
return nil, fmt.Errorf("invalid file:// proxy URL with non-path elements: %s", base.Redacted())
}
case "":
return nil, fmt.Errorf("invalid proxy URL missing scheme: %s", base.Redacted())
default:
return nil, fmt.Errorf("invalid proxy URL scheme (must be https, http, file): %s", base.Redacted())
}
enc, err := module.EscapePath(path)
if err != nil {
return nil, err
}
redactedURL := base.Redacted()
base.Path = strings.TrimSuffix(base.Path, "/") + "/" + enc
base.RawPath = strings.TrimSuffix(base.RawPath, "/") + "/" + pathEscape(enc)
return &proxyRepo{base, path, redactedURL, sync.Once{}, nil, nil}, nil
}
func (p *proxyRepo) ModulePath() string {
return p.path
}
var errProxyReuse = fmt.Errorf("proxy does not support CheckReuse")
func (p *proxyRepo) CheckReuse(old *codehost.Origin) error {
return errProxyReuse
}
// versionError returns err wrapped in a ModuleError for p.path.
func (p *proxyRepo) versionError(version string, err error) error {
if version != "" && version != module.CanonicalVersion(version) {
return &module.ModuleError{
Path: p.path,
Err: &module.InvalidVersionError{
Version: version,
Pseudo: module.IsPseudoVersion(version),
Err: err,
},
}
}
return &module.ModuleError{
Path: p.path,
Version: version,
Err: err,
}
}
func (p *proxyRepo) getBytes(path string) ([]byte, error) {
body, err := p.getBody(path)
if err != nil {
return nil, err
}
defer body.Close()
b, err := io.ReadAll(body)
if err != nil {
// net/http doesn't add context to Body errors, so add it here.
// (See https://go.dev/issue/52727.)
return b, &url.Error{Op: "read", URL: pathpkg.Join(p.redactedURL, path), Err: err}
}
return b, nil
}
func (p *proxyRepo) getBody(path string) (r io.ReadCloser, err error) {
fullPath := pathpkg.Join(p.url.Path, path)
target := *p.url
target.Path = fullPath
target.RawPath = pathpkg.Join(target.RawPath, pathEscape(path))
resp, err := web.Get(web.DefaultSecurity, &target)
if err != nil {
return nil, err
}
if err := resp.Err(); err != nil {
resp.Body.Close()
return nil, err
}
return resp.Body, nil
}
func (p *proxyRepo) Versions(prefix string) (*Versions, error) {
data, err := p.getBytes("@v/list")
if err != nil {
p.listLatestOnce.Do(func() {
p.listLatest, p.listLatestErr = nil, p.versionError("", err)
})
return nil, p.versionError("", err)
}
var list []string
allLine := strings.Split(string(data), "\n")
for _, line := range allLine {
f := strings.Fields(line)
if len(f) >= 1 && semver.IsValid(f[0]) && strings.HasPrefix(f[0], prefix) && !module.IsPseudoVersion(f[0]) {
list = append(list, f[0])
}
}
p.listLatestOnce.Do(func() {
p.listLatest, p.listLatestErr = p.latestFromList(allLine)
})
semver.Sort(list)
return &Versions{List: list}, nil
}
func (p *proxyRepo) latest() (*RevInfo, error) {
p.listLatestOnce.Do(func() {
data, err := p.getBytes("@v/list")
if err != nil {
p.listLatestErr = p.versionError("", err)
return
}
list := strings.Split(string(data), "\n")
p.listLatest, p.listLatestErr = p.latestFromList(list)
})
return p.listLatest, p.listLatestErr
}
func (p *proxyRepo) latestFromList(allLine []string) (*RevInfo, error) {
var (
bestTime time.Time
bestVersion string
)
for _, line := range allLine {
f := strings.Fields(line)
if len(f) >= 1 && semver.IsValid(f[0]) {
// If the proxy includes timestamps, prefer the timestamp it reports.
// Otherwise, derive the timestamp from the pseudo-version.
var (
ft time.Time
)
if len(f) >= 2 {
ft, _ = time.Parse(time.RFC3339, f[1])
} else if module.IsPseudoVersion(f[0]) {
ft, _ = module.PseudoVersionTime(f[0])
} else {
// Repo.Latest promises that this method is only called where there are
// no tagged versions. Ignore any tagged versions that were added in the
// meantime.
continue
}
if bestTime.Before(ft) {
bestTime = ft
bestVersion = f[0]
}
}
}
if bestVersion == "" {
return nil, p.versionError("", codehost.ErrNoCommits)
}
// Call Stat to get all the other fields, including Origin information.
return p.Stat(bestVersion)
}
func (p *proxyRepo) Stat(rev string) (*RevInfo, error) {
encRev, err := module.EscapeVersion(rev)
if err != nil {
return nil, p.versionError(rev, err)
}
data, err := p.getBytes("@v/" + encRev + ".info")
if err != nil {
return nil, p.versionError(rev, err)
}
info := new(RevInfo)
if err := json.Unmarshal(data, info); err != nil {
return nil, p.versionError(rev, fmt.Errorf("invalid response from proxy %q: %w", p.redactedURL, err))
}
if info.Version != rev && rev == module.CanonicalVersion(rev) && module.Check(p.path, rev) == nil {
// If we request a correct, appropriate version for the module path, the
// proxy must return either exactly that version or an error — not some
// arbitrary other version.
return nil, p.versionError(rev, fmt.Errorf("proxy returned info for version %s instead of requested version", info.Version))
}
return info, nil
}
func (p *proxyRepo) Latest() (*RevInfo, error) {
data, err := p.getBytes("@latest")
if err != nil {
if !errors.Is(err, fs.ErrNotExist) {
return nil, p.versionError("", err)
}
return p.latest()
}
info := new(RevInfo)
if err := json.Unmarshal(data, info); err != nil {
return nil, p.versionError("", fmt.Errorf("invalid response from proxy %q: %w", p.redactedURL, err))
}
return info, nil
}
func (p *proxyRepo) GoMod(version string) ([]byte, error) {
if version != module.CanonicalVersion(version) {
return nil, p.versionError(version, fmt.Errorf("internal error: version passed to GoMod is not canonical"))
}
encVer, err := module.EscapeVersion(version)
if err != nil {
return nil, p.versionError(version, err)
}
data, err := p.getBytes("@v/" + encVer + ".mod")
if err != nil {
return nil, p.versionError(version, err)
}
return data, nil
}
func (p *proxyRepo) Zip(dst io.Writer, version string) error {
if version != module.CanonicalVersion(version) {
return p.versionError(version, fmt.Errorf("internal error: version passed to Zip is not canonical"))
}
encVer, err := module.EscapeVersion(version)
if err != nil {
return p.versionError(version, err)
}
path := "@v/" + encVer + ".zip"
body, err := p.getBody(path)
if err != nil {
return p.versionError(version, err)
}
defer body.Close()
lr := &io.LimitedReader{R: body, N: codehost.MaxZipFile + 1}
if _, err := io.Copy(dst, lr); err != nil {
// net/http doesn't add context to Body errors, so add it here.
// (See https://go.dev/issue/52727.)
err = &url.Error{Op: "read", URL: pathpkg.Join(p.redactedURL, path), Err: err}
return p.versionError(version, err)
}
if lr.N <= 0 {
return p.versionError(version, fmt.Errorf("downloaded zip file too large"))
}
return nil
}
// pathEscape escapes s so it can be used in a path.
// That is, it escapes things like ? and # (which really shouldn't appear anyway).
// It does not escape / to %2F: our REST API is designed so that / can be left as is.
func pathEscape(s string) string {
return strings.ReplaceAll(url.PathEscape(s), "%2F", "/")
}
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