STRING, can be read,
Request headers sent to the backend.
Before Fastly invokes
vcl_pass, we copy the contents of
req.http.* into a new set of headers called
bereq.http. This header list can then be modified without affecting the original request received from the client.
bereq.http.* headers are also available in
vcl_fetch, after the fetch to the backend has been made, but modifying their values in
vcl_fetch has no effect.