Re: [mpls-linux-general] I need some help to read the codes related with MPLS patches

[Olivier D. <Oli...@rd...>]

Hi,

Look at document joint. It's an update of the packet journey inside the
kernel for MPLS.

Hope you this help.

Olivier

=C1=A4=B1=E2=BF=B5 wrote:

>=20
> I've looked at the code, and i think that the binding point of=20
> mpls_output() is in route.c
>=20
> After patching mpls codes, in ./net/ipv4/route.c
>=20
> void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 =
itag)
> {
>       struct fib_info *fi =3D res->fi;
> =20
> =A1=A6
> =20
> #ifdef CONFIG_MPLS
>       /* JLEU: we need to do this here because both
>       * ip_route_output_slow() and ip_route_output_slow()
>       * us this to finish the next hop calculations
>       */
>       if(res->proto_data[AUX_PROTO_DATA_MPLS]) {
>           struct mpls_out_info *moi;
>           int i;
> =20
>           MPLS_DEBUG(("rt_set_nexthop: adding label to dst\n"));
>           MPLS_DEBUG(("rt_set_nexthop: before - mtu =3D %d\n",
>             rt->u.dst.pmtu));
>           rt->u.dst.output =3D mpls_output; /* HERE */
>           rt->u.dst.dst_proto_data[AUX_PROTO_DATA_MPLS] =3D
>             res->proto_data[AUX_PROTO_DATA_MPLS];
>           moi =3D res->proto_data[AUX_PROTO_DATA_MPLS];
> mpls_again:
>           for(i=3D0;imoi_instruction_length;i++) {
>             switch(moi->moi_instruction[i].mi_opcode) {
>                 case MPLS_OP_FWD:
>                   moi =3D (struct mpls_out_info*)
>                     moi->moi_instruction[i].mi_data;
>                   goto mpls_again;
>                   break;
>                 case MPLS_OP_PUSH:
>                   rt->u.dst.pmtu -=3D 4;
>                   break;
>             }
>           }
>           MPLS_DEBUG(("rt_set_nexthop: after - mtu =3D %d\n",
>             rt->u.dst.pmtu));
>       }
> =20
> =A1=A6
> =20
> }
> =20
> If res->proto_data[AUX_PROTO_DATA_MPLS] have a value (not zero)
> then the output related function is binded with mpls_output()
> so the function is invoked.
> =20
> But I still try to find work that describes the structures or methods =
of=20
> MPLS in Linux .
> Is there anyone who know this? I hope to learn from him or her.
> =20
> Especially, I want to know the semantics of=20
> proto_data[AUX_PROTO_DATA_MPLS].
> =20
> Thanks, in advance.
> =20
> B.E.
> =20
> Kiyoung Jung
> -------------------------------------------------------
> Ki Young Jung (jj...@ic...)
> Information and Communications University(ICU)
> Broadband Network Laboratory(http://bnlab.icu.ac.kr)
> 58-4 Hwaam-dong, Yusong-gu, Taejon, 305-732, KOREA
> Tel)+82-42-866-6182, 016-370-1751 Fax)+82-42-866-6110
> -------------------------------------------------------
>=20
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