linux PF_PACKET compatibility

[Julian Elischer]

On 2/11/11 5:40 AM, Da Rock wrote:
> On 02/11/11 19:54, Vlad Galu wrote:
>>
>>
>> On Fri, Feb 11, 2011 at 11:36 AM, Da Rock 
>> <freebsd-hackers at herveybayaustralia.com.au 
>> <mailto:freebsd-hackers at herveybayaustralia.com.au>> wrote:
>>
>>     On 02/11/11 18:17, Julian Elischer wrote:
>>
>>         On 2/10/11 11:22 PM, Da Rock wrote:
>>
>>             "In recent versions of the Linux kernel (post-2.0
>>             releases) a new protocol family has been introduced,
>>             named PF_PACKET. This family allows an application to
>>             send and receive packets dealing directly with the
>>             network card driver, thus avoiding the usual protocol
>>             stack-handling (e.g., IP/TCP or IP/UDP processing).
>>             That is, any packet sent through the socket will be
>>             directly passed to the Ethernet interface, and any
>>             packet received through the interface will be directly
>>             passed to the application."
>>
>>             I've been chasing the answer to a FreeBSD version of
>>             this (approx. anyway), but I needed to find out what
>>             exactly PF_PACKET was first. Finally found this answer
>>             here: http://www.linuxjournal.com/article/4659
>>
>>             I looked up man socket and I can see possibilities (in
>>             my mind anyway), but I thought I'd be best to check if
>>             the gurus here might have a better idea. My reason for
>>             this is I'm attempting to build l2tpns (which
>>             supposedly builds on 7.3?! with no trouble), and I'm
>>             chasing the errors which appear to be linuxisms mostly.
>>
>>             So in man socket simply looking at the list of protocol
>>             families I'd say network driver level would be similar
>>             to PF_LINK link layer interface? Is there another man
>>             page I should be looking at as well?
>>
>>
>>         We don't have an exact equivalent.. but we have ways of
>>         doing the same  thing.
>>         one way that is suggested is to use pcap and bpf which I am
>>         pretty certain has been enhanced to allow sending as
>>         well as receiving.
>>         you can also hook directly to the interface using netgraph(4)
>>         there are other ways too but those are the two that came to
>>         mind immediately.
>>
>>     So I'm going to have to rewrite that interface entirely?
>>     Bugger! I just can't fathom how this howto could even exist for
>>     l2tpns on FreeBSD if it isn't even close to buildable... weird!
>>
>>     http://kuapp.com/2010/07/14/how-to-setup-l2tpipsec-vpn-on-freebsd.html
>>
>>     Thanks guys. I'll probably come back with more problems as I
>>     slowly crack this one... :)
>>
>>
>> I suppose you could just use mpd :)
> I could, I guess. But where's the fun in that? :)
>
> Seriously, though, mpd didn't quite cut it (I thought) for me. I 
> need a l2tp vpn server with the capability to handle multiple 
> clients with only one interface. The server is behind a firewall, 
> and I'm trying for a "walled garden" variety I guess. So far my 
> research has brought me here, but I'm open to suggestions.

why do you think you need only one interface?

>
> One other that has my attention is l2tpd (in ports). I want radius 
> auth, so IF I can use pppd in base and radius (which as I 
> understand- so far anyway- it needs), and only uses a single 
> interface, then maybe.

pppd in base will I think give you multiple interfaces..
>
> I'm still hunting and playing- learning on the fly. From what I read 
> mpd uses an ng interface for every single client. L2tpns doesn't, 
> and from what I've read so far neither does l2tpd (I was actually 
> looking at another fork of that xl2tpd). I could use some advice 
> from someone with experience with this, but my feelers on -questions 
> didn't get much response. I may try on -net if this fails...

again, whats' with the single interface?
>
> Aside from that I also wanted to get a bit more of a hands on feel 
> for the FreeBSD core. I can't sit on the sidelines yelling at the 
> players any more :) I'm not much for spectator sport either...