From: Norbert van Bolhuis <nvbolhuis@aimvalley•nl>
To: rmcguire@videopresence•com
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: RAW Sockets - HDLC or Ethernet
Date: Fri, 07 Mar 2008 08:53:29 +0100 [thread overview]
Message-ID: <47D0F479.4050109@aimvalley.nl> (raw)
In-Reply-To: <000001c87f6b$e1d5e9e0$6405a8c0@absolut>
I guess this is what a raw packet socket is supposed to do.
It's not a bug it's a feature.
Can't you somehow recognize your own packet (and skip it) ?
Btw. this question can probably be better addressed in
comp.os.linux.development.system
---
N. van Bolhuis.
Russell McGuire wrote:
> 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
>
>
>
> ------------------------------------------------------------------------
>
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> Linuxppc-embedded@ozlabs•org
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prev parent reply other threads:[~2008-03-07 8:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-06 9:24 RAW Sockets - HDLC or Ethernet Russell McGuire
2008-03-07 7:53 ` Norbert van Bolhuis [this message]
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