[Linux-disciples] Recognizing a new NIC

[Adam Rosi-Kessel]

Um, maybe something about block devices?  Ethernet is not a block device?

Stephen R Laniel wrote:
> On Wed, Jan 26, 2005 at 10:11:27AM -0500, Adam Rosi-Kessel wrote:
> 
>>They're not devices. They're interfaces.  My handwaving understanding is 
>>that there is an additional layer with an interface: bits going in and 
>>out of a network interface like eth0 are processed by the linux 
>>networking subsystem before they're actually passed on to the real 
>>'device', which is the network card.
>>
>>For comparison, you can output bits directly to, e.g., your serial or 
>>parallel ports, which are devices.  The kernel just sends the bits out 
>>the device as it gets them.
> 
> 
> I've been thinking about this today. I guess I still don't
> really get it. There's no reason why I couldn't send a
> stream of bits directly to my network card. Those bits would
> be nonsense, most likely, and the network card would
> silently dispose of them. As far as I understand it, most of
> the processing that turns raw bits into intelligible
> network-interface traffic happens in software: I put
> together an HTTP request for bostoncoop.net, which gets
> turned through a long sequence of calls into a bunch of
> Ethernet packets. The only thing that the NIC sees are
> Ethernet packets; it doesn't care that there's TCP inside of
> the Ethernet header or HTTP inside of the TCP.
> 
> So I don't see why I shouldn't just be able to do
> 
> echo foo > /dev/eth0
> 
> If 'foo' is meaningless to the Ethernet interface, either
> this fails silently or I get some kind of error. But in
> principle I see no reason why I shouldn't be able to pump
> bits right to the card.
> 
> The argument's the same as being able to send raw bits to a
> printer. Most raw bits will produce garbage in the printer,
> whereas some will contain (for instance) meaningful
> PostScript. But there's no reason why I shouldn't be able to
> send junk if such is my wont.
> 
> 
> 
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