delivery: http1 chunked encoding trailers support & other improvements #4
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- select chunked encoding if Trailers present - mark where trailers start - update trailer start for unset - assert elsewhere
Analogous to req_top, we add resp_top to access the top-level response headers from esi_level > 0. Write access produces chunked trailers if allowed as indicated by resp.http.Trailer on esi level 0. This requires a fundamental change to error handling: We cannot allow writes to resp_top from esi_level 0 outside vcl_deliver / synth (it does not exist yet), so we introduce runtime error checking for header access: Callers of vrt have to acquire permission before using a struct http, which might fail. Foreseeing concurrent access to headers, the new interface is ref/deref via VRT_http_(de)?ref_(ro|rw). Added benefit is that VRT_http_ref_ro, the successor of VRT_selecthttp() now returns a const. Reflecting on the run-time access: we current do allow writes to resp.http from esi_level > 0, which I guess has been counter-intuitive to almost any varnish user at some point because any such changes have zero effect. So most likely, our users run a lot of vcl_deliver code with esi for just nothing except confusion. Should we go for runtime access checking, we might as well forbid write access to resp.http for esi_level > 0. (see #ifdef XXX_CONSIDER_THIS in cache_vrt.c)
So if it happened to have been set before, make it a trailer. This actually enables Unsetting trailers
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continued in #6 |
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Continuing and based upon #3
Please read the individual commit messages. Overall, the changes are:
commits most relevant regarding interfaces:
resp_top.http.*The latter requires introduction of run time header access control to VRT which is suggested as a reference/dereference pattern replacing
VRT_selecthttp()