Following ->hook values are valid on master in warp_recv:
- WARP_FORWARD
      -> packet contines through netfilter and is sent out.
- WARP_LOCAL_OUT
      -> packets to be sent out, eg. httpproxy running on slave, dns
      requests from slave, ipsec packets encrypted on slave....
- WARP_PRE_ROUTING:
      -> ipsec packets that have been encrypted on the slave.

Following ->hook values are valid in warp_recv on slave:
- WARP_LOCAL_IN (ips, local proxies...)
       --> will be consumed by slave, not warped back.
- IPSEC_DECRYPT (ipsec)
       -> warped back with WARP_PRE_ROUTING
- IPSEC_ENCRYPT (ipsec)
       -> warped back with NF_INET_LOCAL_OUT
- WARP_FORWARD
      -> warped back with WARP_FORWARD (and higher priority to avoid loop)

WARP_POST_ROUTING is not used as a reinjection point at this time.
