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@@ -0,0 +1,394 @@
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+package dpcore
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+
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+import (
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+ "errors"
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+ "fmt"
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+ "io"
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+ "log"
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+ "net"
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+ "net/http"
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+ "net/url"
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+ "path/filepath"
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+ "strings"
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+ "sync"
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+ "time"
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+)
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+
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+var onExitFlushLoop func()
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+
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+const (
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+ defaultTimeout = time.Minute * 5
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+)
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+
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+// ReverseProxy is an HTTP Handler that takes an incoming request and
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+// sends it to another server, proxying the response back to the
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+// client, support http, also support https tunnel using http.hijacker
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+type ReverseProxy struct {
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+ // Set the timeout of the proxy server, default is 5 minutes
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+ Timeout time.Duration
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+
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+ // Director must be a function which modifies
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+ // the request into a new request to be sent
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+ // using Transport. Its response is then copied
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+ // back to the original client unmodified.
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+ // Director must not access the provided Request
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+ // after returning.
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+ Director func(*http.Request)
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+
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+ // The transport used to perform proxy requests.
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+ // default is http.DefaultTransport.
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+ Transport http.RoundTripper
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+
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+ // FlushInterval specifies the flush interval
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+ // to flush to the client while copying the
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+ // response body. If zero, no periodic flushing is done.
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+ FlushInterval time.Duration
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+
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+ // ErrorLog specifies an optional logger for errors
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+ // that occur when attempting to proxy the request.
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+ // If nil, logging goes to os.Stderr via the log package's
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+ // standard logger.
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+ ErrorLog *log.Logger
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+
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+ // ModifyResponse is an optional function that
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+ // modifies the Response from the backend.
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+ // If it returns an error, the proxy returns a StatusBadGateway error.
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+ ModifyResponse func(*http.Response) error
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+
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+ //Prepender is an optional prepend text for URL rewrite
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+ //
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+ Prepender string
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+}
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+
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+type requestCanceler interface {
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+ CancelRequest(req *http.Request)
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+}
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+
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+func NewDynamicProxyCore(target *url.URL, prepender string) *ReverseProxy {
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+ targetQuery := target.RawQuery
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+ director := func(req *http.Request) {
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+ req.URL.Scheme = target.Scheme
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+ req.URL.Host = target.Host
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+ req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
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+
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+ // If Host is empty, the Request.Write method uses
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+ // the value of URL.Host.
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+ // force use URL.Host
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+ req.Host = req.URL.Host
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+ if targetQuery == "" || req.URL.RawQuery == "" {
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+ req.URL.RawQuery = targetQuery + req.URL.RawQuery
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+ } else {
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+ req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
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+ }
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+
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+ if _, ok := req.Header["User-Agent"]; !ok {
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+ req.Header.Set("User-Agent", "")
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+ }
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+ }
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+
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+ return &ReverseProxy{
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+ Director: director,
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+ Prepender: prepender,
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+ }
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+}
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+
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+func singleJoiningSlash(a, b string) string {
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+ aslash := strings.HasSuffix(a, "/")
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+ bslash := strings.HasPrefix(b, "/")
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+ switch {
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+ case aslash && bslash:
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+ return a + b[1:]
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+ case !aslash && !bslash:
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+ return a + "/" + b
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+ }
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+ return a + b
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+}
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+
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+func copyHeader(dst, src http.Header) {
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+ for k, vv := range src {
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+ for _, v := range vv {
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+ dst.Add(k, v)
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+ }
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+ }
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+}
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+
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+// Hop-by-hop headers. These are removed when sent to the backend.
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+// http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
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+var hopHeaders = []string{
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+ //"Connection",
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+ "Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
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+ "Keep-Alive",
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+ "Proxy-Authenticate",
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+ "Proxy-Authorization",
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+ "Te", // canonicalized version of "TE"
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+ "Trailer", // not Trailers per URL above; http://www.rfc-editor.org/errata_search.php?eid=4522
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+ "Transfer-Encoding",
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+ //"Upgrade",
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+}
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+
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+func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader) {
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+ if p.FlushInterval != 0 {
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+ if wf, ok := dst.(writeFlusher); ok {
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+ mlw := &maxLatencyWriter{
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+ dst: wf,
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+ latency: p.FlushInterval,
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+ done: make(chan bool),
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+ }
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+
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+ go mlw.flushLoop()
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+ defer mlw.stop()
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+ dst = mlw
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+ }
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+ }
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+
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+ io.Copy(dst, src)
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+}
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+
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+type writeFlusher interface {
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+ io.Writer
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+ http.Flusher
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+}
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+
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+type maxLatencyWriter struct {
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+ dst writeFlusher
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+ latency time.Duration
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+ mu sync.Mutex
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+ done chan bool
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+}
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+
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+func (m *maxLatencyWriter) Write(b []byte) (int, error) {
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+ m.mu.Lock()
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+ defer m.mu.Unlock()
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+ return m.dst.Write(b)
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+}
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+
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+func (m *maxLatencyWriter) flushLoop() {
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+ t := time.NewTicker(m.latency)
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+ defer t.Stop()
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+ for {
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+ select {
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+ case <-m.done:
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+ if onExitFlushLoop != nil {
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+ onExitFlushLoop()
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+ }
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+ return
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+ case <-t.C:
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+ m.mu.Lock()
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+ m.dst.Flush()
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+ m.mu.Unlock()
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+ }
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+ }
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+}
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+
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+func (m *maxLatencyWriter) stop() {
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+ m.done <- true
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+}
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+
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+func (p *ReverseProxy) logf(format string, args ...interface{}) {
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+ if p.ErrorLog != nil {
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+ p.ErrorLog.Printf(format, args...)
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+ } else {
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+ log.Printf(format, args...)
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+ }
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+}
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+
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+func removeHeaders(header http.Header) {
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+ // Remove hop-by-hop headers listed in the "Connection" header.
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+ if c := header.Get("Connection"); c != "" {
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+ for _, f := range strings.Split(c, ",") {
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+ if f = strings.TrimSpace(f); f != "" {
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+ header.Del(f)
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+ }
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+ }
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+ }
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+
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+ // Remove hop-by-hop headers
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+ for _, h := range hopHeaders {
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+ if header.Get(h) != "" {
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+ header.Del(h)
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+ }
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+ }
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+
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+ if header.Get("A-Upgrade") != "" {
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+ header.Set("Upgrade", header.Get("A-Upgrade"))
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+ header.Del("A-Upgrade")
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+ }
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+}
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+
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+func addXForwardedForHeader(req *http.Request) {
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+ if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
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+ // If we aren't the first proxy retain prior
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+ // X-Forwarded-For information as a comma+space
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+ // separated list and fold multiple headers into one.
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+ if prior, ok := req.Header["X-Forwarded-For"]; ok {
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+ clientIP = strings.Join(prior, ", ") + ", " + clientIP
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+ }
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+ req.Header.Set("X-Forwarded-For", clientIP)
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+ }
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+}
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+
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+func (p *ReverseProxy) ProxyHTTP(rw http.ResponseWriter, req *http.Request) error {
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+ transport := p.Transport
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+ if transport == nil {
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+ transport = http.DefaultTransport
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+ }
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+
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+ outreq := new(http.Request)
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+ // Shallow copies of maps, like header
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+ *outreq = *req
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+
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+ if cn, ok := rw.(http.CloseNotifier); ok {
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+ if requestCanceler, ok := transport.(requestCanceler); ok {
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+ // After the Handler has returned, there is no guarantee
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+ // that the channel receives a value, so to make sure
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+ reqDone := make(chan struct{})
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+ defer close(reqDone)
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+ clientGone := cn.CloseNotify()
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+
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+ go func() {
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+ select {
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+ case <-clientGone:
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+ requestCanceler.CancelRequest(outreq)
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+ case <-reqDone:
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+ }
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+ }()
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+ }
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+ }
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+
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+ p.Director(outreq)
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+ outreq.Close = false
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+
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+ // We may modify the header (shallow copied above), so we only copy it.
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+ outreq.Header = make(http.Header)
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+ copyHeader(outreq.Header, req.Header)
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+
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+ // Remove hop-by-hop headers listed in the "Connection" header, Remove hop-by-hop headers.
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+ removeHeaders(outreq.Header)
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+
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+ // Add X-Forwarded-For Header.
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+ addXForwardedForHeader(outreq)
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+
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+ res, err := transport.RoundTrip(outreq)
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ rw.WriteHeader(http.StatusBadGateway)
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+ return err
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+ }
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+
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+ // Remove hop-by-hop headers listed in the "Connection" header of the response, Remove hop-by-hop headers.
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+ removeHeaders(res.Header)
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+
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+ if p.ModifyResponse != nil {
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+ if err := p.ModifyResponse(res); err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ rw.WriteHeader(http.StatusBadGateway)
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+ return err
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+ }
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+ }
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+
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+ //Custom header rewriter functions
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+ if res.Header.Get("Location") != "" {
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+ //Custom redirection fto this rproxy relative path
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+ fmt.Println(res.Header.Get("Location"))
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+ res.Header.Set("Location", filepath.ToSlash(filepath.Join(p.Prepender, res.Header.Get("Location"))))
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+ }
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+ // Copy header from response to client.
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+ copyHeader(rw.Header(), res.Header)
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+
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+ // The "Trailer" header isn't included in the Transport's response, Build it up from Trailer.
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+ if len(res.Trailer) > 0 {
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+ trailerKeys := make([]string, 0, len(res.Trailer))
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+ for k := range res.Trailer {
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+ trailerKeys = append(trailerKeys, k)
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+ }
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+ rw.Header().Add("Trailer", strings.Join(trailerKeys, ", "))
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+ }
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+
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+ rw.WriteHeader(res.StatusCode)
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+ if len(res.Trailer) > 0 {
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+ // Force chunking if we saw a response trailer.
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+ // This prevents net/http from calculating the length for short
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+ // bodies and adding a Content-Length.
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+ if fl, ok := rw.(http.Flusher); ok {
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+ fl.Flush()
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+ }
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+ }
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+
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+ p.copyResponse(rw, res.Body)
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+ // close now, instead of defer, to populate res.Trailer
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+ res.Body.Close()
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+ copyHeader(rw.Header(), res.Trailer)
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+
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+ return nil
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+}
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+
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+func (p *ReverseProxy) ProxyHTTPS(rw http.ResponseWriter, req *http.Request) error {
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+ hij, ok := rw.(http.Hijacker)
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+ if !ok {
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+ p.logf("http server does not support hijacker")
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+ return errors.New("http server does not support hijacker")
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+ }
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+
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+ clientConn, _, err := hij.Hijack()
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ return err
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+ }
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+
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+ proxyConn, err := net.Dial("tcp", req.URL.Host)
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ return err
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+ }
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+
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+ // The returned net.Conn may have read or write deadlines
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+ // already set, depending on the configuration of the
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+ // Server, to set or clear those deadlines as needed
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+ // we set timeout to 5 minutes
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+ deadline := time.Now()
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+ if p.Timeout == 0 {
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+ deadline = deadline.Add(time.Minute * 5)
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+ } else {
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+ deadline = deadline.Add(p.Timeout)
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+ }
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+
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+ err = clientConn.SetDeadline(deadline)
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ return err
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+ }
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+
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+ err = proxyConn.SetDeadline(deadline)
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ return err
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+ }
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+
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+ _, err = clientConn.Write([]byte("HTTP/1.0 200 OK\r\n\r\n"))
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+ if err != nil {
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+ p.logf("http: proxy error: %v", err)
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+ return err
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+ }
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+
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+ go func() {
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+ io.Copy(clientConn, proxyConn)
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|
|
|
+ clientConn.Close()
|
|
|
|
+ proxyConn.Close()
|
|
|
|
+ }()
|
|
|
|
+
|
|
|
|
+ io.Copy(proxyConn, clientConn)
|
|
|
|
+ proxyConn.Close()
|
|
|
|
+ clientConn.Close()
|
|
|
|
+
|
|
|
|
+ return nil
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) error {
|
|
|
|
+ if req.Method == "CONNECT" {
|
|
|
|
+ err := p.ProxyHTTPS(rw, req)
|
|
|
|
+ return err
|
|
|
|
+ } else {
|
|
|
|
+ err := p.ProxyHTTP(rw, req)
|
|
|
|
+ return err
|
|
|
|
+ }
|
|
|
|
+}
|