[Bloat] Issue with negotiating ECN with Cloudflare hosts?

Fri Sep 20 05:41:29 EDT 2019

Jesper Dangaard Brouer <brouer at redhat.com> writes:

> On Thu, 19 Sep 2019 19:50:45 +0200 Toke Høiland-Jørgensen <toke at toke.dk> wrote:
>
>> Is anyone else experiencing problems negotiating ECN when connecting to
>> Cloudflare? I see this for most sites protected by Cloudflare (such as
>> bufferbloat.net), but only when using IPv4:
>> 
>> # sysctl -w net.ipv4.tcp_ecn=1
>> net.ipv4.tcp_ecn = 1
>> # curl -v 1.1.1.1
>> *   Trying 1.1.1.1:80...
>> * TCP_NODELAY set
>> * Connected to 1.1.1.1 (1.1.1.1) port 80 (#0)
>> > GET / HTTP/1.1
>> > Host: 1.1.1.1
>> > User-Agent: curl/7.66.0
>> > Accept: */*
>> >   
>> * Recv failure: Connection reset by peer
>> * Closing connection 0
>> curl: (56) Recv failure: Connection reset by peer
>
> It works for me when repeating your experiment:
>
> $ sysctl -w net.ipv4.tcp_ecn=1
> net.ipv4.tcp_ecn = 1
>
> $ curl -v 1.1.1.1
> * Rebuilt URL to: 1.1.1.1/
> *   Trying 1.1.1.1...
> * TCP_NODELAY set
> * Connected to 1.1.1.1 (1.1.1.1) port 80 (#0)
>> GET / HTTP/1.1
>> Host: 1.1.1.1
>> User-Agent: curl/7.61.1
>> Accept: */*
>> 
> < HTTP/1.1 301 Moved Permanently
> < Date: Fri, 20 Sep 2019 07:19:48 GMT
> < Content-Type: text/html
> < Transfer-Encoding: chunked
> < Connection: keep-alive
> < Location: https://1.1.1.1/
> < Served-In-Seconds: 0.000
> < CF-Cache-Status: HIT
> < Age: 5944
> < Expires: Fri, 20 Sep 2019 11:19:48 GMT
> < Cache-Control: public, max-age=14400
> < Server: cloudflare
> < CF-RAY: 519208830aced891-CPH
> [...]
>  
>  
>> # sysctl -w net.ipv4.tcp_ecn=0
>> net.ipv4.tcp_ecn = 0
>> # curl -v 1.1.1.1
>> *   Trying 1.1.1.1:80...
>> * TCP_NODELAY set
>> * Connected to 1.1.1.1 (1.1.1.1) port 80 (#0)
>> > GET / HTTP/1.1
>> > Host: 1.1.1.1
>> > User-Agent: curl/7.66.0
>> > Accept: */*
>> >   
>> * Mark bundle as not supporting multiuse
>> < HTTP/1.1 301 Moved Permanently
>> < Date: Thu, 19 Sep 2019 17:42:22 GMT
>> < Content-Type: text/html
>> < Transfer-Encoding: chunked
>> < Connection: keep-alive
>> < Location: https://1.1.1.1/
>> < Served-In-Seconds: 0.000
>> < CF-Cache-Status: HIT
>> < Age: 4442
>> < Expires: Thu, 19 Sep 2019 21:42:22 GMT
>> < Cache-Control: public, max-age=14400
>> < Server: cloudflare
>> < CF-RAY: 518d5b13fcfcd43f-HAM
>> < 
>> <html>
>> <head><title>301 Moved Permanently</title></head>
>> <body bgcolor="white">
>> <center><h1>301 Moved Permanently</h1></center>
>> <hr><center>cloudflare-lb</center>
>> </body>
>> </html>
>> * Connection #0 to host 1.1.1.1 left intact
>> 
>> 
>> I've opened a support request with my ISP, but thought I'd ask if anyone
>> else was seeing this? (Is anyone else running with ECN enabled?)
>
> I'm not seeing it, so it might be your ISP?

Yeah, guess I'll get to see if my ISP support knows what ECN is...
Should be fun :P

-Toke