Re: [lwip-users] two logical ethernet interfaces on the same, physical port?

[Kamil Khoury]

Hi,

I was able to find something on the internet which allows to implement layer 2 protocols in a socket using the SOCK_RAW. Unfortunately, this is a linux library which is described here:
http://man7.org/linux/man-pages/man7/packet.7.html

Packet sockets are used to receive or send raw packets at the device
       driver (OSI Layer 2) level.  They allow the user to implement
       protocol modules in user space on top of the physical layer.

I know that the SOCK_RAW option is also available in LWIP but I think it only allows a socket over IPv4 not layer 2. Am I correct? Do you think I can use this library in LWIP to do a layer 2 socket?

Thanks.

On Thu, Jun 14, 2018 at 5:10 PM, goldsimon <address@hidden> wrote:

Unless you want to use VLANs, I guess pretty much everything has been said here :-)

Simon

Am 14. Juni 2018 17:04:04 MESZ schrieb Kamil Khoury <address@hidden>:

Thank you both for your response. 
To be specific, all received messages have the same multicast address. the only difference between the two types of messages is contained in the message header that should be unpacked later at the protocol engine (over layer 2) not at the port. So the port should not have authority to decide the type of the message or to handle it. The job of the port is to receive the message and forward it up. 
In my case, the logical port should not even receive the message at all unless it belongs to its (virtual domain). To put it in simple words, I'm looking for two separate logical Ethernet connections on the same physical port that can be identified somehow by an ID. Just like how UDP identifies sessions by port numbers.

Is this even realistic? because that's the only way I could understand this paragraph:
"the node communicates with the network via two logical interfaces based on a single physical port"

On Thu, Jun 14, 2018 at 4:32 PM, Sergio R. Caprile <address@hidden> wrote:

Regarding your image, it didn't get through my mail, "An HTML attachment
was scrubbed..." and I'm too lazy to go dig it. Anyway... it belongs
here now:
http://lists.nongnu.org/archive/html/lwip-users/2018-06/msg00050.html

So you still want two hosts.
And as far as I can see, you need a bridge among them and the physical
port. How would a bridge respond to an incoming multicast frame on the
physical port? It will forward to both netifs, and the interested one
will answer... Does it help ?

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