Re: [PATCH] Add support for HTTP proxies

[Mark H Weaver]

Here's a much simpler patch that discards the keyword arguments of the
previous version, so that the only new interfaces are:

* The 'http_proxy' environment variable.
* The 'current-http-proxy' parameter.
* The 'http-proxy-port?' object property (only needed if you connect to
  a proxy yourself, without using 'open-socket-for-uri').

Given that we'll eventually want to add support for other kinds of
proxies (e.g. https_proxy and ftp_proxy), I guess the keyword argument
approach is not really practical here.

What do you think?

    Mark


>From 681daf7311d423408cdc1fd21482c3dabc6fc98c Mon Sep 17 00:00:00 2001
From: Mark H Weaver <address@hidden>
Date: Fri, 7 Jun 2013 00:47:33 -0400
Subject: [PATCH] Add support for HTTP proxies (PRELIMINARY)

* module/web/http.scm (http-proxy-port?): New exported object property.
  (write-request-line): If we're using an http proxy, write an
  absolute-URI in the request line.

* module/web/client.scm: Import (web http).
  (current-http-proxy): New exported parameter.
  (choose-http-proxy): New procedure.
  (open-socket-for-uri): If 'choose-http-proxy' returns a true value,
  connect to the proxy instead of the URI host, and set the
  'http-proxy-port?' object property on the socket.
---
 module/web/client.scm |   19 +++++++++++++++++--
 module/web/http.scm   |   21 ++++++++++++++++++++-
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/module/web/client.scm b/module/web/client.scm
index 7d5ea49..c401a80 100644
--- a/module/web/client.scm
+++ b/module/web/client.scm
@@ -39,8 +39,10 @@
   #:use-module (web request)
   #:use-module (web response)
   #:use-module (web uri)
+  #:use-module (web http)
   #:use-module (srfi srfi-1)
-  #:export (open-socket-for-uri
+  #:export (current-http-proxy
+            open-socket-for-uri
             http-get
             http-get*
             http-head
@@ -50,6 +52,16 @@
             http-trace
             http-options))
 
+(define current-http-proxy (make-parameter 'auto))
+
+(define (choose-http-proxy)
+  (let ((proxy (current-http-proxy)))
+    (if (not (eq? proxy 'auto))
+        proxy
+        (let ((proxy (getenv "http_proxy")))
+          (and (not (equal? proxy ""))
+               proxy)))))
+
 (define (ensure-uri uri-or-string)
   (cond
    ((string? uri-or-string) (string->uri uri-or-string))
@@ -58,7 +70,8 @@
 
 (define (open-socket-for-uri uri-or-string)
   "Return an open input/output port for a connection to URI."
-  (define uri (ensure-uri uri-or-string))
+  (define http-proxy (choose-http-proxy))
+  (define uri (ensure-uri (or http-proxy uri-or-string)))
   (define addresses
     (let ((port (uri-port uri)))
       (delete-duplicates
@@ -84,6 +97,8 @@
           (setvbuf s _IOFBF)
           ;; Enlarge the receive buffer.
           (setsockopt s SOL_SOCKET SO_RCVBUF (* 12 1024))
+          ;; If we're using a proxy, make a note of that.
+          (when http-proxy (set! (http-proxy-port? s) #t))
           s)
         (lambda args
           ;; Connection failed, so try one of the other addresses.
diff --git a/module/web/http.scm b/module/web/http.scm
index 35169ef..a587578 100644
--- a/module/web/http.scm
+++ b/module/web/http.scm
@@ -66,7 +66,9 @@
             write-response-line
 
             make-chunked-input-port
-            make-chunked-output-port))
+            make-chunked-output-port
+
+            http-proxy-port?))
 
 
 (define (string->header name)
@@ -1117,6 +1119,21 @@ three values: the method, the URI, and the version."
   "Write the first line of an HTTP request to PORT."
   (display method port)
   (display #\space port)
+  (when (http-proxy-port? port)
+    (let ((scheme (uri-scheme uri))
+          (host (uri-host uri))
+          (host-port (uri-port uri)))
+      (when (and scheme host)
+        (display scheme port)
+        (display "://" port)
+        (if (string-index host #\:)
+            (begin (display #\[ port)
+                   (display host port)
+                   (display #\] port))
+            (display host port))
+        (unless ((@@ (web uri) default-port?) scheme host-port)
+          (display #\: port)
+          (display host-port port)))))
   (let ((path (uri-path uri))
         (query (uri-query uri)))
     (if (not (string-null? path))
@@ -1958,3 +1975,5 @@ KEEP-ALIVE? is true."
     (unless keep-alive?
       (close-port port)))
   (make-soft-port (vector put-char put-string flush #f close) "w"))
+
+(define http-proxy-port? (make-object-property))
-- 
1.7.10.4