HI also supports defining custom "x-forwarded-for" type headers. In a multi-vendor world, it is
quite possible that the header name carrying the original client IP could be vendor-specific. This
is due to the absence of standardization which would otherwise standardize the header name. In such
a scenario, it is important to provide a configuration with which such x-forwarded-for type headers
can be introduced to HI. The headers can be introduced with the xff_headers configuration. The
default value of this configuration is "x-forwarded-for true-client-ip". The default definition
introduces the two commonly known "x-forwarded-for" type headers and is preferred in the same order
by the inspector as they are defined, e.g "x-forwarded-for" will be preferred than "true-client-ip"
if both headers are present in the stream. Every HTTP Header is mapped to an ID internally. The
custom headers are mapped to a dynamically generated ID and the mapping is appended at the end
of the mapping of the known HTTP headers. Every HI instance can have its own list of custom
headers and thus an instance of HTTP header mapping list is also associated with an HI instance.
