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,
  32         "Upgrade":           true,
  33 }
  34
  35 type ResponseFilter func(*http.Response, error) (*http.Response, error)
  36
  37 func (p *proxy) Do(w http.ResponseWriter,
  38         reqIn *http.Request,
  39         urlOut *url.URL,
  40         client *http.Client,
  41         filter ResponseFilter) {
  42
  43         // Copy headers from incoming request, then add/replace proxy
  44         // headers like Via and X-Forwarded-For.
  45         hdrOut := http.Header{}
  46         for k, v := range reqIn.Header {
  47                 if !dropHeaders[k] {
  48                         hdrOut[k] = v
  49                 }
  50         }
  51         xff := reqIn.RemoteAddr
  52         if xffIn := reqIn.Header.Get("X-Forwarded-For"); xffIn != "" {
  53                 xff = xffIn + "," + xff
  54         }
  55         hdrOut.Set("X-Forwarded-For", xff)
  56         if hdrOut.Get("X-Forwarded-Proto") == "" {
  57                 hdrOut.Set("X-Forwarded-Proto", reqIn.URL.Scheme)
  58         }
  59         hdrOut.Add("Via", reqIn.Proto+" arvados-controller")
  60
  61         ctx := reqIn.Context()
  62         if p.RequestTimeout > 0 {
  63                 var cancel context.CancelFunc
  64                 ctx, cancel = context.WithDeadline(ctx, time.Now().Add(time.Duration(p.RequestTimeout)))
  65                 defer cancel()
  66         }
  67
  68         reqOut := (&http.Request{
  69                 Method: reqIn.Method,
  70                 URL:    urlOut,
  71                 Host:   reqIn.Host,
  72                 Header: hdrOut,
  73                 Body:   reqIn.Body,
  74         }).WithContext(ctx)
  75
  76         resp, err := client.Do(reqOut)
  77         if filter == nil && err != nil {
  78                 httpserver.Error(w, err.Error(), http.StatusBadGateway)
  79                 return
  80         }
  81
  82         // make sure original response body gets closed
  83         originalBody := resp.Body
  84         if originalBody != nil {
  85                 defer originalBody.Close()
  86         }
  87
  88         if filter != nil {
  89                 resp, err = filter(resp, err)
  90
  91                 if err != nil {
  92                         httpserver.Error(w, err.Error(), http.StatusBadGateway)
  93                         return
  94                 }
  95                 if resp == nil {
  96                         // filter() returned a nil response, this means suppress
  97                         // writing a response, for the case where there might
  98                         // be multiple response writers.
  99                         return
 100                 }
 101
 102                 // the filter gave us a new response body, make sure that gets closed too.
 103                 if resp.Body != originalBody {
 104                         defer resp.Body.Close()
 105                 }
 106         }
 107
 108         for k, v := range resp.Header {
 109                 for _, v := range v {
 110                         w.Header().Add(k, v)
 111                 }
 112         }
 113         w.WriteHeader(resp.StatusCode)
 114         n, err := io.Copy(w, resp.Body)
 115         if err != nil {
 116                 httpserver.Logger(reqIn).WithError(err).WithField("bytesCopied", n).Error("error copying response body")
 117         }
 118 }