On 29 Sep 2015, at 11:40 AM, Daniil Iaitskov <[email protected]> wrote:

> I am patching HTTP proxy module to pass trailing headers from a client to an 
> origin server.
> 
> I want it to be compatible with RFCs, and I was stumbled with 2 statements 
> from 
> them.
> 
> 1. Trailer header is hop-by-hop so it cannot be transferred to outgoing 
> connection 
>     (RFC2616 13.5.1 - it's obsolete by RFC7230, RFC7231, RFC7232, 
>     RFC7233, RFC7234, RFC7235, but they don't mention the ban list anymore).

You may not transfer a hop-by-hop header end to end, but you can certainly 
generate a new hop-by-hop header on the next connection that happens to have 
the same name and value as the hop-by-hop header on the earlier connection. The 
key thing is that the Trailer header and the trailers are addressing the next 
link in the chain only.

In other words, a trailer can be passed from A to B, then passed from B to C, 
but if trailers aren’t supported from C to D that’s fine too.

Regards,
Graham
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