If the client sent chunks, then it is safe to assume that the proxy can send chunks as well. Generally speaking, user agents only send chunks to applications that they know will accept chunks.
The client could be sending chunks precisely because it's designed to work with a proxy that is known to accept them. That doesn't imply any knowledge of the backend(s) proxied, which might be anything up to and including the 'net in general.
Theoretically, yes. However, in practice, that is never the case. Either a user agent is using generic stuff like HTML forms, which will always result in a content-length if there is a body, or it is using custom software designed to work with custom server apps. There are no other real-world examples, and thus it is safe to use chunks if the client used chunks.
Also bear in mind that we were discussing (also) the case where the request came with C-L but an input filter invalidated it.
I was not discussing that case. The answer to that case is "don't do that".
Fix the input filter if it is doing something stupid.
....Roy
