How to circumvent the 417 Expectation failed behind a Squid proxy

Submitted by gionn on 07/09/2010 11:53

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Many applications rely on using a special HTTP/1.1 header (Expect: 100-continue) when doing a POST, which is not happily supported by Squid.

RFC2616 says:

The purpose of the 100 (Continue) status (see section 10.1.1) is to allow a client that is sending a request message with a request body to determine if the origin server is willing to accept the request (based on the request headers) before the client sends the request body. In some cases, it might either be inappropriate or highly inefficient for the client to send the body if the server will reject the message without looking at the body.

We can configure Squid to simply ignore that request header, and usually client with poor error handling will fallback without even notice it.

Add in squid.conf:
ignore_expect_100 on

Android application like AppBrain and Facebook Contact Sync, and BOINC client was having login issues due to this reason.

Comments

TJ

22/09/2010 14:34

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Thanks for the info. I was

Thanks for the info. I was getting 417 error when trying to access Amazon Web Services (AWS) from behind a squid proxy, and was getting frustrated about not being able to solve it. Added the line in the conf file and everything is working fine now.

Cheers.

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Jernej

24/11/2011 18:53

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Hi!

Hi!
I had the same issue with squid reverse proxy, where I have multiple webservers behind single IP. I use squid to redirect requests to appropriate webserver, but there was a problem with apps that wanted to upload files. "ignore_expect_100 on" solved the problem. Many thanks for your post!
Jernej