cond %{SEND_REQUEST_HDR_HOOK} [AND]
cond %{NEXT-HOP:HOST} ="parent.example.com"
    set-header X-Via-Parent "yes"

cond %{SEND_RESPONSE_HDR_HOOK} [AND]
cond %{SERVER-HEADER:X-Via-Parent} ="yes"
    set-header X-Next-Host "%{NEXT-HOP:HOST}"
    set-header X-Next-Port "%{NEXT-HOP:PORT}"
    set-header X-Next-Strategy "%{NEXT-HOP:STRATEGY}"
