first step for import dhcp pacit

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
add dhcp helper functions

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
merging
Merge branch 'master' of github.com:vtolstov/pacit into ip
add checksum calc

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>