Simple HTTP Proxy with haproxy (POC - not recommended)

haproxy.cfg

global
  log stdout local0

defaults
    log global
    log-format "%ci:%cp [%tr] %ft %b/%s %TR/%Tw/%Tc/%Tr/%Ta %ST %B %CC %CS %tsc %ac/%fc/%bc/%sc/%rc %sq/%bq %hr %hs %{+Q}r %si:%sp"

frontend proxy
  bind :3128

  mode http
  http-request do-resolve(txn.myip,mydns,ipv4) hdr(Host),lower unless { url_ip -m found }
  http-request set-var(txn.myip) url_ip if { url_ip -m found }
  http-request set-var(txn.myport) url_port

  use_backend b_503 unless { var(txn.myip) -m found }
  use_backend forwardproxy

resolvers mydns
  parse-resolv-conf

backend b_503
  mode http

backend forwardproxy
  mode http
  option httpclose
  http-request set-dst var(txn.myip)
  http-request set-dst-port int(80)
  http-request set-dst-port var(txn.myport) if { var(txn.myport) -m found }
  server clear 0.0.0.0:0