bug#37044: 27.0.50; url-http breaks behind proxy when reusing existing connection

bug#37044: 27.0.50; url-http breaks behind proxy when reusing existing connection

[David Ringo]

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When trying to make more than one HTTPS request to the same host via
`url-retrieve-synchronously' behind my work proxy, only the first request
succeeds.  Depending on the host, subsequent requests result in 400/404/302
and perhaps a couple other response codes.  There's some minimal code below
that can be run with emacs -Q, but I don't know how to replicate the proxy.

It seems that commit 84613dae5c3 is at least partially responsible for
this.  It's a small change to `url-https-proxy-after-change-function' that
binds `url-http-proxy' around the call to `url-http-create-request'.
Without that binding, I see no errors.  I tested this both in 26.2.90 which
does not include that commit, and the revision in this report by simply
redefining the function to the older version.

This happens both when `url-proxy-services' is set manually and when it is
set from environment variables.

I'm not sure if this is a problem with Emacs, the proxy I'm behind, or if
there is some configuration I should be aware of that already addresses
this.  Please let me know if there's any other useful information I can
provide.

Sample code and the corresponding url-http buffer headers follow.  The
specific URLs don't seem to matter as long they are HTTPS.  The optional
arguments also don't seem to make a difference.

- David

Code:
(url-retrieve-synchronously "https://xkcd.com/1/")
(url-retrieve-synchronously "https://xkcd.com/2/")

First request (success):
HTTP/1.1 200 OK
Server: nginx
Content-Type: text/html; charset=UTF-8
Last-Modified: Thu, 15 Aug 2019 11:24:39 GMT
Expires: Thu, 15 Aug 2019 21:22:11 GMT
Cache-Control: max-age=300
Content-Length: 3012
Accept-Ranges: bytes
Date: Fri, 16 Aug 2019 01:32:01 GMT
Via: 1.1 varnish
Age: 142
Connection: keep-alive
X-Served-By: cache-mdw17348-MDW
X-Cache: HIT
X-Cache-Hits: 1
X-Timer: S1565919121.298692,VS0,VE0
Vary: Accept-Encoding

Second request (failuer):
HTTP/1.1 400 Bad Request
Server: nginx
Content-Type: text/html; charset=UTF-8
Content-Length: 166
Accept-Ranges: bytes
Date: Fri, 16 Aug 2019 01:32:01 GMT
Via: 1.1 varnish
Connection: keep-alive
X-Served-By: cache-mdw17348-MDW
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1565919121.349321,VS0,VE26


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu)
 of 2019-08-07 built on slartibartfast
Repository revision: d5622eb6fff94714c5d5a64c98c5e02bc1be478c
Repository branch: master
Windowing system distributor 'Fedora Project', version 11.0.12005000
System Description: Fedora 30 (Workstation Edition)

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bug#37044: 27.0.50; url-http breaks behind proxy when reusing existing connection

[Thomas Fitzsimmons]

Hi David,

David Ringo <davidmringo@gmail.com> writes:

> It seems that commit 84613dae5c3 is at least partially responsible for
> this.  It's a small change to `url-https-proxy-after-change-function'
> that binds `url-http-proxy' around the call to
> `url-http-create-request'.

This might be addressed by the fix for bug#35969 that I pushed last
night, can you retry with master tip?

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=35969

Thanks,
Thomas

bug#37044: 27.0.50; url-http breaks behind proxy when reusing existing connection

[David Ringo]

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Hi Thomas,

I haven't been able to test on the machine I submitted the report from, but
on some other shared machines behind the proxy, it looks like your fix
seems to work (while the revision I was on is still broken on those
machines). Thanks for all the work on the other bug -- that seemed like a
long process.

I'm not super familiar with debbugs, but if there's anything I should do to
mark this as closed or resolved, please let me know.

- David

On Fri, Aug 16, 2019 at 11:06 AM Thomas Fitzsimmons <fitzsim@fitzsim.org>
wrote:

> Hi David,
>
> David Ringo <davidmringo@gmail.com> writes:
>
> > It seems that commit 84613dae5c3 is at least partially responsible for
> > this.  It's a small change to `url-https-proxy-after-change-function'
> > that binds `url-http-proxy' around the call to
> > `url-http-create-request'.
>
> This might be addressed by the fix for bug#35969 that I pushed last
> night, can you retry with master tip?
>
> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=35969
>
> Thanks,
> Thomas
>

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bug#37044: 27.0.50; url-http breaks behind proxy when reusing existing connection

[Thomas Fitzsimmons]

Hi David,

David Ringo <davidmringo@gmail.com> writes:

> Hi Thomas,
>
> I haven't been able to test on the machine I submitted the report
> from, but on some other shared machines behind the proxy, it looks
> like your fix seems to work (while the revision I was on is still
> broken on those machines). Thanks for all the work on the other bug --
> that seemed like a long process.
>
> I'm not super familiar with debbugs, but if there's anything I should
> do to mark this as closed or resolved, please let me know.

Thanks for the bug report and for confirming the fix.  I'm marking this
"done".

Thomas