Date: Sat, 01 Nov 2008 19:14:19 -0700 From: Julian Elischer <julian@elischer.org> To: Joe Pellegrino <jdp@elvis.rowan.edu> Cc: freebsd-net@freebsd.org Subject: Re: A netgraph question. Message-ID: <490D0CFB.5040102@elischer.org> In-Reply-To: <Pine.GSO.4.64.0811012107200.7887@elvis.rowan.edu> References: <Pine.GSO.4.64.0811011759200.4676@elvis.rowan.edu> <490CEF11.4010007@elischer.org> <Pine.GSO.4.64.0811012107200.7887@elvis.rowan.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
Joe Pellegrino wrote:
> On Sat, 1 Nov 2008, Julian Elischer wrote:
>
>> I'll try answer your questions..
>>
>> Hooks are created on demand..
>> you need to send a 'connect' or 'mkpeer' message to the node(s)
>> on which you want t script level, you just use the ngctl program
>> to do it for you.
>>
>> Hooks are always made in pairs. so you need two nodes to connect.
>> The mkpeer message does this for you, and creates a new node and
>> connects them together by two hooks of the names you specify.
>>
>> Have you looked at the sample netgraph scripts in
>> /usr/share/examples/netgraph?
>>
>
> Yep, I've looked at those but if I recall they are all scripts. I am
> looking for some C or C++ example. Basically on the userland side I have
> something like:
>
> #include <..>
> #include <netgraph/ng_socket.h>
>
> int main () {
> int s1 = socket (PF_NETGRAPH, SOCK_DGRAM, NG_CONTROL)
> int s2 = socket (PF_NETGRAPH, SOCK_DGRAM, NG_DATA)
> bind(...);
>
> }
>
> This gives me a node with a name, set with bind, of type socket and no
> hooks.
>
> The kernel module I don't have any netgraph code yet but I figure it
> will involve a set of calls similar to the userland program. So if I
> want to interact with the socket the userland program created, what kind
> of node do I create in the module? Another ng_socket or a ng_ksocket or
> something different. Then how do I go about connecting the two hooks?
>
>>> Of course I realize that I proabably need to create a node on the
>>> kernel side so which type of netgraph node would be suggested? How is
>>> it created and then hooked to the ng_socket?
>>
>> for fun you could use the ng_echo node type which would send
>> everything you want back to you..
>>
>> Alternatively when you kldload the ng-ether node type, then all the
>> ethernets will grow nodes to match them so you can connect to them
>> directly.
>>
>> You could connect an ng_bpf (packet filter) node to the ng_ether node
>> and pass specific packets only on to the socket.
>>
>
> I'll look into this for the other half of what I am playing with. I
> looked at bpf by itself and it seemed to me it made a copy of the
> packet, with the original continuing up the stack rather than diverting
> the packet. But I am getting ahead of myself. I'd like to get the
> userland <-> module part together first. :) And all the example code are
> scripts. Am I missing someting?
have you done man 3 netgraph to look at the netgraph management library?
for example programs, see:
/usr/src/usr.sbin/nghook
/usr/src/usr.sbin/ngctl
/usr/ports/net/mpd (you'll need to download the sources with "make")
>
>>> pages and can't seem to find a lot of good documentation or example
>>> code so I am hoping to get some pointers here. BTW If this is the
>>> wrong list please directly to the right place to ask. Thanks in advance.
>>
>> not sure what netlink does..
>> (will look on google :-)
>>
>
> Thanks for your help, there is a reasonable entry in the wiki about it.
>
> ---jdp
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?490D0CFB.5040102>