Re: Avoid a redirect loop in url-http

[Chong Yidong <cyd@stupidchicken.com>]

Diane Murray <disumu@x3y2z1.net> writes:

> On occasion url-http gets stuck in an endless redirect loop.  This can
> be fixed by simply checking if the number of redirected URLs in
> `url-callback-arguments' hasn't gone over a certain number (which
> could be a customizable variable).  If it has been redirected too many
> times, rather than call `url-retrieve-internal' again,
> `url-http-parse-headers' should just let the callback function get
> activated - after adding a redirect error to `url-callback-arguments',
> so that the callback knows that the maximum number of redirects was
> reached.

Thanks.

How about this patch?  It doesn't implement a defcustom as you
suggested; it simply searches for a redirect loop.  It also simply
signals an error if a loop is found.

(The indentation of existing code is left unchanged to make the patch
easier to read.)

*** emacs/lisp/url/url-http.el.~1.52.~	2007-04-01 11:32:35.000000000 -0400
--- emacs/lisp/url/url-http.el	2007-04-12 00:17:40.000000000 -0400
***************
*** 555,561 ****
  		     (url-expand-file-name redirect-uri url-http-target-url)))
             (let ((url-request-method url-http-method)
  		 (url-request-data url-http-data)
! 		 (url-request-extra-headers url-http-extra-headers))
  	     ;; Remember that the request was redirected.
  	     (setf (car url-callback-arguments)
  		   (nconc (list :redirect redirect-uri)
--- 555,571 ----
  		     (url-expand-file-name redirect-uri url-http-target-url)))
             (let ((url-request-method url-http-method)
  		 (url-request-data url-http-data)
! 		 (url-request-extra-headers url-http-extra-headers)
! 		 (events (car url-callback-arguments)))
! 	     ;; Check for redirect loops
! 	     (while events
! 	       (if (eq (car events) :redirect)
! 		   (and (setq events (cdr events))
! 			(if (eq (car events) redirect-uri)
! 			    (error "HTTP redirect loop detected")
! 			  (setq events (cdr events))))
! 		 (and (setq events (cdr events))
! 		      (setq events (cdr events)))))
  	     ;; Remember that the request was redirected.
  	     (setf (car url-callback-arguments)
  		   (nconc (list :redirect redirect-uri)
***************
*** 570,576 ****
  		   (url-retrieve-internal
  		    redirect-uri url-callback-function
  		    url-callback-arguments))
! 	      (url-mark-buffer-as-dead (current-buffer))))))
        (4				; Client error
         ;; 400 Bad Request
         ;; 401 Unauthorized
--- 580,586 ----
  		   (url-retrieve-internal
  		    redirect-uri url-callback-function
  		    url-callback-arguments))
! 	      (url-mark-buffer-as-dead (current-buffer)))))))
        (4				; Client error
         ;; 400 Bad Request
         ;; 401 Unauthorized