Date: Sat, 16 Oct 2010 21:56:52 -0700 From: Nerius Landys <nlandys@gmail.com> To: FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: UDP packet spoofed LAN source address? Message-ID: <AANLkTinHyF_dXB-qBsJZ8=jRo9mX8vhSzddo4PTJjh52@mail.gmail.com>
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This is really more of a networking question. I'm wondering, in a typical scenario, for example my server is in a data center with a typical colocation company. I am editing someone else's code, and this code handles incoming UDP packets. The code handles UDP packets that have a source address being from the LAN differently. It gives those packets special treatment. To check whether a source address is a LAN address, it does the typical checks for 10.0.0.0, 172.16.0.0, 192.168.0.0, 127.0.0.0, and it also checks every assinged IP address with netmask to see if the source address on the UDP packet came from that network. My question is - how possible (in these typical environments) is it to send a UDP packet from far away that claims to have a source address being a LAN address? Will such a packet typically make it to my server, or will a router along the way stop it from arriving? Maybe, is there a simple 10 line C program that I can run and compile to check if this scenario is possible on _my_ server? - Nerius
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