[Winpcap-users] Sending packets to own NIC

[Guy Harris]

On Sep 22, 2018, at 4:39 PM, Daniel Smith <zamadatix at gmail.com> wrote:

> 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.

Most if not all Ethernet adapters will *NOT* receive packets they transmit.

Most if not all Internet-protocol stacks will, if you're sending a packet to an IP address for the machine sending the packet, won't even other transmitting the packet on any physical network adapter, and will, instead, just loop it back internally.  On UN*Xes, this may result in the packet being "transmitted" on the loopback adapter (lo0 on some UN*Xes, lo on others); on Windows, it's just wrapped around without appearing on a particular adapter.