Anyone,

Yet another mysterious question, at least to me.

I have written to simple utilities to send and receive a file / data through a newly created driver, HDLC using an MPC8360E.

Though I doubt this question is limited to that specific HW.

The main question is that everything I send though device HDLC0 I can immediately read from HDLC0 even though logically there is no connection there. It as if the kernel is immediately allowing me to read from the same device, what a separate application just wrote.???

HOW CAN THIS BE?

Details:

I have two applications: send and receive.  (pseudo code as follows)

Send opens a socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)).

And binds it (AF_PACKET, ETH_P_HLDC, if_index(hdlc0))

Receive opens a socket to the same device

socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))

bind(AF_PACKET, ETH_P_ALL, if_index(hdlc0)

Note they are opening the same device.

Now if I send anything through the send application, I immediately receive it via the receive application??

Note, entirely separate processes!

Note, there is NO hardware loopback, this should be a dead end, and I should get nothing back at least as far as HW is concerned.

What am I missing, that causes all my TX data to show up immediately in the RX app? Note I have verified my HDLC drier is not actually receiving anything, so is there something in the kernel that is bridging the TX / RX paths, or am I just missing the function of this? If so how can I use RAW mode, while not mixing this, or at least keeping them separate in the applications?

-Russ