web scenarios now can have http proxy explicitly defined, but some documentation detail is missing.

a) do we do any sanity checking before passing proxy variable to libcurl, or do we pass it as-is ?

b) curl manpage also lists socks protocols :

socks4
socks4a
socks5
socks5h
do they work in zabbix ?

c) what happens if we specify wrong protocol ?

d) does (supported by curl) simple "proxy" work as well and default to http ?