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<div dir="auto">I don't think NGINX has any default duplicate header handing and hasn't really. My guess is that you've simply not seen this behavior in the past.</div>
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<div dir="auto">You can suppress the backend header:</div>
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<div dir="auto">proxy_hide_header Content-Length;</div>
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<div dir="auto">Note that the behavior hasnt changed and only *certain* headers remain default-hidden from the backend - I don't believe Content-Length was ever one of them.</div>
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<div dir="auto" style="font-size:12px; color:#575757">Sent from my Galaxy</div>
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<div>-------- Original message --------</div>
<div>From: Jesse Stimpson <jstimpson@relaypro.com> </div>
<div>Date: 4/19/23 09:09 (GMT-05:00) </div>
<div>To: Thomas Ward <teward@thomas-ward.net> </div>
<div>Cc: nginx@nginx.org </div>
<div>Subject: Re: Duplicate Content-Length header with same value, recent change in behavior intentional?
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<div dir="ltr">Yes, apologies for being unclear. Indeed, the upstream proxy is the one generating the duplicate header. My message is primarily concerning the behavior of nginx upon recognizing such a duplicate from the upstream. In order to complete my testing,
I wrote an http server as my upstream that purposefully sent duplicate headers. I realize this consider misbehavior of an upstream.</div>
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<div dir="ltr" class="gmail_attr">On Wed, Apr 19, 2023 at 9:06 AM Thomas Ward <<a href="mailto:teward@thomas-ward.net">teward@thomas-ward.net</a>> wrote:<br>
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<div dir="auto">This sounds like your backend and nginx are both generating the header. NGINX hasn't changed to the point it would create two headers, but if your backend is adding the header as well as nginx then there's your problem.</div>
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<div dir="auto" style="font-size:12px; color:rgb(87,87,87)">Sent from my Galaxy</div>
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<div>-------- Original message --------</div>
<div>From: Jesse Stimpson via nginx <<a href="mailto:nginx@nginx.org" target="_blank">nginx@nginx.org</a>>
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<div>Date: 4/19/23 08:57 (GMT-05:00) </div>
<div>To: <a href="mailto:nginx@nginx.org" target="_blank">nginx@nginx.org</a> </div>
<div>Cc: Jesse Stimpson <<a href="mailto:jstimpson@relaypro.com" target="_blank">jstimpson@relaypro.com</a>>
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<div>Subject: Duplicate Content-Length header with same value, recent change in behavior intentional?
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<div dir="ltr">Hello,
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<div>I've noticed a recent change in behavior that occurred between releases 1.22.1 and 1.23.4, and I'm unable to find this particular change documented.</div>
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<div>If an upstream proxy sends a response with duplicate Content-Length headers, both of the same value, nginx 1.22.1 allows the response to be sent to the client, removing the duplicate. However, nginx 1.23.4 (and 1.24.0) responds to the client with a 502.
I did not explicitly test with any other versions.</div>
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<div>I won't try to make any claims on the correctness of either behavior, but it is a change that may affect some workloads.</div>
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<div>Here is an example response that exhibits the change:</div>
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<div>"""</div>
<div>HTTP/1.1 200 OK</div>
<div>Server: http_tcp</div>
<div>Content-Length: 12</div>
<div>Content-Length: 12</div>
<div>Connection: Closed</div>
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<div>Hello World\n<br>
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<div>"""</div>
<div>------</div>
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<div>jstimpson:[~/dev/c/nginx-1.22.1]: curl -i localhost<br>
HTTP/1.1 200 OK<br>
Server: nginx/1.22.1<br>
Date: Wed, 19 Apr 2023 12:17:05 GMT<br>
Content-Length: 12<br>
Connection: keep-alive<br>
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Hello World<br>
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<div>-----</div>
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<div>jstimpson:[~/dev/c/nginx-1.23.4]: curl -i localhost<br>
HTTP/1.1 502 Bad Gateway<br>
Server: nginx/1.23.4<br>
Date: Wed, 19 Apr 2023 12:13:09 GMT<br>
Content-Type: text/html<br>
Content-Length: 497<br>
Connection: keep-alive<br>
ETag: "643fd39e-1f1"<br>
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<div>...<snip>...</div>
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<div>---------</div>
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<div>These tests were done with this simple config, the rest of the conf is defaults.</div>
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<div> location / {<br>
proxy_pass <a href="http://localhost:4040" target="_blank">http://localhost:4040</a>;<br>
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<div> }</div>
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<div>Is this change intentional? Did I overlook it in the Changelog?</div>
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<div>Thanks,</div>
<div>Jesse</div>
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