lib/controller/proxy.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package controller
   6
   7 import (
   8         "context"
   9         "io"
  10         "net/http"
  11         "net/url"
  12         "time"
  13
  14         "git.curoverse.com/arvados.git/sdk/go/httpserver"
  15 )
  16
  17 type proxy struct {
  18         Name           string // to use in Via header
  19         RequestTimeout time.Duration
  20 }
  21
  22 // headers that shouldn't be forwarded when proxying. See
  23 // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers
  24 var dropHeaders = map[string]bool{
  25         "Connection":          true,
  26         "Keep-Alive":          true,
  27         "Proxy-Authenticate":  true,
  28         "Proxy-Authorization": true,
  29         "TE":                true,
  30         "Trailer":           true,
  31         "Transfer-Encoding": true, // *-Encoding headers interfer with Go's automatic compression/decompression
  32         "Content-Encoding":  true,
  33         "Accept-Encoding":   true,
  34         "Upgrade":           true,
  35 }
  36
  37 type ResponseFilter func(*http.Response, error) (*http.Response, error)
  38
  39 func (p *proxy) Do(w http.ResponseWriter,
  40         reqIn *http.Request,
  41         urlOut *url.URL,
  42         client *http.Client,
  43         filter ResponseFilter) {
  44
  45         // Copy headers from incoming request, then add/replace proxy
  46         // headers like Via and X-Forwarded-For.
  47         hdrOut := http.Header{}
  48         for k, v := range reqIn.Header {
  49                 if !dropHeaders[k] {
  50                         hdrOut[k] = v
  51                 }
  52         }
  53         xff := reqIn.RemoteAddr
  54         if xffIn := reqIn.Header.Get("X-Forwarded-For"); xffIn != "" {
  55                 xff = xffIn + "," + xff
  56         }
  57         hdrOut.Set("X-Forwarded-For", xff)
  58         if hdrOut.Get("X-Forwarded-Proto") == "" {
  59                 hdrOut.Set("X-Forwarded-Proto", reqIn.URL.Scheme)
  60         }
  61         hdrOut.Add("Via", reqIn.Proto+" arvados-controller")
  62
  63         ctx := reqIn.Context()
  64         if p.RequestTimeout > 0 {
  65                 var cancel context.CancelFunc
  66                 ctx, cancel = context.WithDeadline(ctx, time.Now().Add(time.Duration(p.RequestTimeout)))
  67                 defer cancel()
  68         }
  69
  70         reqOut := (&http.Request{
  71                 Method: reqIn.Method,
  72                 URL:    urlOut,
  73                 Host:   reqIn.Host,
  74                 Header: hdrOut,
  75                 Body:   reqIn.Body,
  76         }).WithContext(ctx)
  77
  78         resp, err := client.Do(reqOut)
  79         if filter == nil && err != nil {
  80                 httpserver.Error(w, err.Error(), http.StatusBadGateway)
  81                 return
  82         }
  83
  84         // make sure original response body gets closed
  85         var originalBody io.ReadCloser
  86         if resp != nil {
  87                 originalBody = resp.Body
  88                 if originalBody != nil {
  89                         defer originalBody.Close()
  90                 }
  91         }
  92
  93         if filter != nil {
  94                 resp, err = filter(resp, err)
  95
  96                 if err != nil {
  97                         httpserver.Error(w, err.Error(), http.StatusBadGateway)
  98                         return
  99                 }
 100                 if resp == nil {
 101                         // filter() returned a nil response, this means suppress
 102                         // writing a response, for the case where there might
 103                         // be multiple response writers.
 104                         return
 105                 }
 106
 107                 // the filter gave us a new response body, make sure that gets closed too.
 108                 if resp.Body != originalBody {
 109                         defer resp.Body.Close()
 110                 }
 111         }
 112
 113         for k, v := range resp.Header {
 114                 for _, v := range v {
 115                         w.Header().Add(k, v)
 116                 }
 117         }
 118         w.WriteHeader(resp.StatusCode)
 119         n, err := io.Copy(w, resp.Body)
 120         if err != nil {
 121                 httpserver.Logger(reqIn).WithError(err).WithField("bytesCopied", n).Error("error copying response body")
 122         }
 123 }