Re: [mpls-linux-general] How to do it?

[James R. L. <jl...@mi...>]

Hello,

On Thu, Jan 17, 2002 at 07:49:55PM +0800, =D5=C5=CE=B0=D2=BB wrote:
> Hi ALL,
>  In the README in mpls-linux-1.0\patches,Jim wrote "if you also add sup=
port for the /proc filesystem the result will be four new files in the /p=
roc/net directory".I have run "mplsadm" successfully.But I do not find th=
ose files in /proc/net.How can I add suppot for /proc filesystem?
>  There are mpls_*.c in /usr/src/linux/net/mpls.I do not clear that how =
those codes called by mplsadm? (I know using those files we can generate =
the mpls.o,but in the Makefile in mpls-linux-1.0/utils,we do not use the =
mpls.o) How does the mplsadm implement the MPLS forwarding for the Linux =
Kernel?
>   I wanna your help,thanks.:)

Since the MPLS forwarding plane is in the kernel and 'mplsadm' runs as
a userland process, their are a few mechanisms availble for transfering
information between the two:
- /proc/sys/*
- system calls ('ioctl' 'fnctl' etc..)
- netlink

Currently I use a mix of system calls and netlink (although I'm leaning m=
ore
to using less and less netlink).

If you look in the patched kernel source you can look at the two files th=
at
are the entry points for netlink and ioctl calls:  net/mpls/mpls_ioctl.c
net/mpls/mpls_netlink.c.  Both of these files end up calling functions
in differnt files (mpls_tunnel.c mpls_in_info.c mpls_out_info.c etc).

What all this about /proc?  MPLS for linux uses the proc filesystem as
a way of exposing to the user what is currently configured, they are
read only "files".  The reason I quoted "files" is that they are not file=
s
in the traditional sense.  Everything in the /proc filesystem is actually
a set of virtual files that result in kernel functions being called whenv=
er
they are accessed.  If you look in net/mpls/mpls_proc.c you will see the
functions that produce the output that you see when looking at /proc/net/=
mpls_*

I hope this helps.
Jim

> =20
> Yours Sincerely
>=20
> Zhang Weiyi
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--=20
James R. Leu