address translation

[hex]

Hi,

I am trying to use your pkacet filter for writing a nat. But i am not sure sure how to do it.

I have laready downloaded and read the rfc on nat.

However, are there any special thinks to consider when using your pkt filter ??

❓

[Vadim Smirnov]

However, are there any special thinks to consider when using your pkt filter ??

I’m not sure what you actually mean here, but there is no technical problems to realize NAT using WinpkFilter.

[bk]

To NAT you must change the source or destination IP in a direction and do the opposite in the other direction. Remember to recalculate the checksum of the packets. You’ll have no problems using winpkfilter driver to NAT, I’ve done it without problems.

[wed3460]

HI BK:
my architecture like following

Client(WLAN)<---><--->Server(WLAN)-NAT-Server(WAN)<--->Internet

i can receive the packet from Client and modify packet ,recauclate checksum(it’s ok),but i cant forward to other NIC(WAN)

so i got trouble to implement NAT
the problem:
how to bind the different nic and translate packet to other NIC
and i confuse the how to used the “SendPacketToAdapter” and
“SendPacketToMstcp”
or have else procedure i havt to notice. please help me , thanks

[Vadim Smirnov]

One of the approaches (the easiest from my point of view) is filtering Server(WAN) interface substituting the original IP (if it is from LAN) in the outgoing packet with Server WAN card IP (port substitution also should be done in order to perform backward mapping). For incoming packets on the Server (WAN) interface you should match against NAT table and perform the reversed operation. Please note that packet forwarding should be enabled on the Server. You don’t need to route packets youself, TCP/IP will do it for you.

[Author]

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