mpls: Netlink commands to add, remove, and dump routes

This change adds two new netlink routing attributes:
RTA_VIA and RTA_NEWDST.

RTA_VIA specifies the specifies the next machine to send a packet to
like RTA_GATEWAY.  RTA_VIA differs from RTA_GATEWAY in that it
includes the address family of the address of the next machine to send
a packet to.  Currently the MPLS code supports addresses in AF_INET,
AF_INET6 and AF_PACKET.  For AF_INET and AF_INET6 the destination mac
address is acquired from the neighbour table.  For AF_PACKET the
destination mac_address is specified in the netlink configuration.

I think raw destination mac address support with the family AF_PACKET
will prove useful.  There is MPLS-TP which is defined to operate
on machines that do not support internet packets of any flavor.  Further
seem to be corner cases where it can be useful.  At this point
I don't care much either way.

RTA_NEWDST specifies the destination address to forward the packet
with.  MPLS typically changes it's destination address at every hop.
For a swap operation RTA_NEWDST is specified with a length of one label.
For a push operation RTA_NEWDST is specified with two or more labels.
For a pop operation RTA_NEWDST is not specified or equivalently an emtpy
RTAN_NEWDST is specified.

Those new netlink attributes are used to implement handling of rt-netlink
RTM_NEWROUTE, RTM_DELROUTE, and RTM_GETROUTE messages, to maintain the
MPLS label table.

rtm_to_route_config parses a netlink RTM_NEWROUTE or RTM_DELROUTE message,
verify no unhandled attributes or unhandled values are present and sets
up the data structures for mpls_route_add and mpls_route_del.

I did my best to match up with the existing conventions with the caveats
that MPLS addresses are all destination-specific-addresses, and so
don't properly have a scope.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 5cc5d66bf519..bad65550ae3e 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -303,6 +303,8 @@ enum rtattr_type_t {
 	RTA_TABLE,
 	RTA_MARK,
 	RTA_MFC_STATS,
+	RTA_VIA,
+	RTA_NEWDST,
 	__RTA_MAX
 };
 
@@ -344,6 +346,12 @@ struct rtnexthop {
 #define RTNH_SPACE(len)	RTNH_ALIGN(RTNH_LENGTH(len))
 #define RTNH_DATA(rtnh)   ((struct rtattr*)(((char*)(rtnh)) + RTNH_LENGTH(0)))
 
+/* RTA_VIA */
+struct rtvia {
+	__kernel_sa_family_t	rtvia_family;
+	__u8			rtvia_addr[0];
+};
+
 /* RTM_CACHEINFO */
 
 struct rta_cacheinfo {