Bug 1885414

Description of problem: 

Recently, the ability to enable HTTP/2 for ingress controllers (which are based on HAProxy) was added.  Enabling HAProxy to use HTTP/2 to connect to backend servers required enabling HAProxy's "HTX" option.  However, enabling HTX causes HAProxy to down-case HTTP header names.  HAProxy's behavior is standards-compliant because HTTP header names are case-insensitive.  However, some non-compliant legacy HTTP clients and servers require that case be preserved in HTTP header names.  

In order to provide temporary backwards compatibility with these non-compliant clients and servers, we should turn off HTX when HTTP/2 is not enabled, so that the case of HTTP header names is preserved.  


Version-Release number of selected component (if applicable): 

HTX was first enabled in OCP 4.4.  


How reproducible: 

Reliably.  


Steps to Reproduce: 

1. Launch an OCP 4.4, 4.5, or 4.6 cluster.  

2. Create an HTTP echo server: 

    oc adm new-project echo
    oc -n echo create -f https://raw.githubusercontent.com/openshift/origin/release-3.11/test/extended/testdata/router-http-echo-server.yaml

3. Curl the echo server, specifying some custom headers that include non-lowercase characters in the headers' names: 

    INGRESS_DOMAIN="$(oc get ingress.config/cluster -o 'jsonpath={.spec.domain}')"
    ADDR="$(dig "xyz.$INGRESS_DOMAIN" +short)"
    curl http://router-headers.example.com --resolve "router-headers.example.com:80:$ADDR" -H X-foo:foo -H X-Bar:Bar -H X-BaZ:BaZ


Actual results:

The output of Step 3 shows that the header names are down-cased:

    % curl http://router-headers.example.com --resolve "router-headers.example.com:80:$ADDR" -H X-foo:foo -H X-Bar:Bar -H X-BaZ:BaZ
    GET / HTTP/1.1
    user-agent: curl/7.29.0
    accept: */*
    x-foo: foo
    x-bar: Bar
    x-baz: BaZ
    host: router-headers.example.com
    x-forwarded-host: router-headers.example.com
    x-forwarded-port: 80
    x-forwarded-proto: http
    forwarded: for=75.170.24.197;host=router-headers.example.com;proto=http
    x-forwarded-for: 75.170.24.197


Expected results:

The output of Step 3 should show that the case of the header names is preserved:

    % curl http://router-headers.example.com --resolve "router-headers.example.com:80:$ADDR" -H X-foo:foo -H X-Bar:Bar -H X-BaZ:BaZ
    GET / HTTP/1.1
    User-Agent: curl/7.29.0
    Accept: */*
    X-foo:foo
    X-Bar:Bar
    X-BaZ:BaZ
    Host: router-headers.example.com
    X-Forwarded-Host: router-headers.example.com
    X-Forwarded-Port: 80
    X-Forwarded-Proto: http
    Forwarded: for=75.170.24.197;host=router-headers.example.com;proto=http
    X-Forwarded-For: 75.170.24.197


Additional info:

RFC 7230 states that HTTP header names are case-insensitive:

>   Each header field consists of a case-insensitive field name followed
>   by a colon (":"), optional leading whitespace, the field value, and
>   optional trailing whitespace.

https://tools.ietf.org/html/rfc7230#section-3.2

HTX becomes non-configurable in HAProxy 2.2, so turning off HTX is an interim solution.  Ideally, legacy applications need to be updated to bring them into conformance.  Alternatively, we can use HAProxy 2.2's h1-case-adjust option to preserve case for specific HTTP headers.