[Winpcap-users] Sending packets to own NIC

Reznicencu Sergiu sergiureznicencu at gmail.com
Sun Sep 23 11:37:14 UTC 2018

I forgot to mention that I already recalculate the ip checksum. It is weird
that I cann see in wireshark the packets that I modified and resnt.
Shouldn't the packets be in "loopback"?
Pe 23.09.2018 02:41, "Daniel Smith" <zamadatix at gmail.com> a scris:

> Both TCP and IP include checksums to validate packets have not been
> corrupted https://locklessinc.com/articles/tcp_checksum/ htt
> ps://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 <
> sergiureznicencu at gmail.com> 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.
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