Bug Report: Forum Inaccessible in Firefox with SPDY 3.1

[JSLover]

I don't know what changed, but right now I cannot access these forums (or the trac) in Firefox with SPDY 3.1 enabled. I receive the error...

406 Not Acceptable

An appropriate representation of the requested resource / could not be found on this server.

...it has worked fine in the past (that is: going to the forums in Firefox has worked fine in the past, I don't know if the server was using SPDY or SPDY 3.1 in the past tho), my browser history shows me accessing the forums on 1/20/15 at 7pm ET when it was working fine, but on 1/22/15 at around 7pm ET is when I noticed it not working (it's 9pm now, but I noticed it earlier). I imagine a server update was pushed between those times, either enabling SPDY or upgrading to SPDY 3.1.

I don't know how to debug SPDY, but perhaps someone can look at the server logs & find all the 406 errors & figure out what's wrong? If nothing else, limit the server to SPDY 3.0 until a real fix can be implemented.

███ WORKAROUND ███

• If you can't access these forums (then how are you reading this), follow these steps...
  
  • Go to about:config
  • Search for spdy
  • Double-click network.http.spdy.enabled.v3-1 so the value changes to false
  • Try loading the forums again

[thresh]

I don't know what you've done with your Firefox setup ('stop sniffing my browser Google, I'm just gonna lie to you & say Firefox/35.0, cuz Australis SUCKS ASS & I'm not gonna update to that crap', yeah, like someone cares), but please try with a fresh user profile / install.

It works just fine using spdy 3.1 here. Disabling it in prefs makes your firefox speak usual http over ssl.

[JSLover]

I don't know what you've done with your Firefox setup...

...Gmail started complaining about my Firefox, so I made it shut up.

...but please try with a fresh user profile / install.

...I did test in a new blank profile before posting.

It works just fine using spdy 3.1 here.

...I have new information!...it's not just SPDY 3.1 causing the problem (but it is involved, somehow).

Steps to Reproduce...

• Open Firefox (in a new blank profile, if desired)
• Go to https://forum.videolan.org, confirm the Forum loads just fine
• Go to https://forum.videolan.org/robots.txt, notice you get a 404 (OK, that's fine)
• Go to https://forum.videolan.org, you should now get a 406 error (press Shift+Reload to make sure you are getting a fresh load from the server).

...for some odd reason, trying to load robots.txt pisses the server off & then the server will 406 EVERYTHING until some unknown timeout occurs. Once you trigger the 406 behavior, the only way to access the forum is to disable SPDY 3.1 or wait an unknown amount of time (8+ hours?) until it's not mad at you anymore (for simply trying to load the robots.txt).

I can't test again for a few hours, but perhaps it's not just robots.txt that will trigger this?...maybe ANY 404 could trigger it?...I'll let you know whenever I can test again. This is a very strange bug, either a Firefox bug or a server-side SPDY 3.1 bug, but I'm not insane! I wish I could get a client-side & server-side debug log of this problem before & after it happens.

What I know so far: this bug ONLY happens with...

• Firefox
• SPDY 3.1
• nginx 1.7.9 (the server running on forum.videolan.org)

...it does NOT happen in Chrome or on https://www.videolan.org, but the www subdomain is on a different server than forum/trac — hmm, interesting, that (the www subdomain) is running on nginx 1.7.9 too, so something is different in the config for the server the forum/trac is on. This bug is only happening on services (subdomains) running on sirius.videolan.org, not on goldeneye.videolan.org. So something is different/wrong with the config for sirius.

[Jean-Baptiste Kempf]

I can reproduce.

[thresh]

Thank you, JSLover. You were right - I was able to reproduce it using those exact steps.

It was anti-spam protection system kicking in here. It monitors all requests to robots.txt (amongst others) and when something is not really right, it starts to behave a bit weird.

It looks like when using SPDY, some of the headers it tries to peek in are not set, therefore it thinks you're a malicious client.

Indeed, Firefox does not send Accept-Encoding header (as spdy is already supposed to be compressed)...

I've made some changes to server configuration and it looks like the problem is now fixed.

Thank you again.