Both TCP and IP include checksums to validate packets have not been corrupted https://locklessinc.com/articles/tcp_checksum/ https://en.wikipedia.org/wiki/IPv4_header_checksum. For your question "Can I send messages back to my own NIC" I would say it probably depends on the NIC but I wouldn't rely on it working for most NICs.
Overall I think this would be significantly easier for you if you didn't use winpcap at all, why not just change the IP and MAC of your adapter directly and receive the packets straight to the HTTP server https://docs.microsoft.com/en-us/powershell/module/netadapter/set-netadapter?view=win10-ps? Even if you wanted to do other things it's significantly easier to combine adapter mac spoofing & Windows IP sockets than it is to do everything manually at layer 2 from winpcap. If you insist on using winpcap I'd first make sure you test sending a customized TCP packet between 2 PCs before trying to do it all local as it will be easier to troubleshoot where things are getting dropped. Daniel Smith On Sat, Sep 22, 2018 at 5:24 PM Reznicencu Sergiu < [email protected]> wrote: > Hi. I am trying to divert all traffic from a pc to my own. But when doing > so I will modify the receiving packets to look as if the request was > specially made for my computer on which I run a http server. To do this I > receive spoofed packets, I change mac and ip to my own and resend them back > with pcap_sendpacket(). But the computer just refuses to accept the first > SYN packet. I made a side by side comparison between an authentic request > to my webserver and a fake one. I couldn’t see much of a difference. Is > there any problem with theory? Can I send messages back to my own NIC? > Thanks in advance. > _______________________________________________ > Winpcap-users mailing list > [email protected] > https://www.winpcap.org/mailman/listinfo/winpcap-users >
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