the final thing we can do in wgm is to disable the rp_filter for the WAN interface. whenever we use IPSET to force packets to different route we will need to disable this.
"reverse path filter" is a very simple protection that many now days consider obsolete. whenever a packets comes in on i.e. WAN it will change place on Destination and Source and run it trough the routing table to see if a reply to this packet would be routed out the same way. it understands most rules but it will not understand that some packets will recieve a mark and be routed differently. so in this case we need to disable the rp_filter on WAN, otherwise answers from WAN will not be accepted. there are 3 values for rp_filter. 0 means "Disabled", 1 means "Enabled, strict", 2 means "Enabled loose". loose means that it does not check routing explicitly, but will accept if there are any routing ways back this interface. 2 is sufficient for us.