bgpd: Install SAFI_LABELED_UNICAST routes in SAFI_UNICAST table

Signed-off-by: Daniel Walton <dwalton@cumulusnetworks.com>

- All ipv4 labeled-unicast routes are now installed in the ipv4 unicast
  table. This allows us to do things like take routes from an ipv4
  unicast peer, allocate a label for them and TX them to a ipv4
  labeled-unicast peer. We can do the opposite where we take routes from
  a labeled-unicast peer, remove the label and advertise them to an ipv4
  unicast peer.

- Multipath over a labeled route and non-labeled route is not allowed.

- You cannot activate a peer for both 'ipv4 unicast' and 'ipv4
  labeled-unicast'

- The 'tag' variable was overloaded for zebra's route tag feature as
  well as the mpls label. I added a 'mpls_label_t mpls' variable to
  avoid this.  This is much cleaner but resulted in touching a lot of
  code.

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/mpls.h b/lib/mpls.h
index 6cf0142755..d78fcb1f57 100644
--- a/lib/mpls.h
+++ b/lib/mpls.h
@@ -76,8 +76,13 @@ typedef unsigned int mpls_lse_t;
 /* MPLS label value as a 32-bit (mostly we only care about the label value). */
 typedef unsigned int mpls_label_t;
 
-#define MPLS_NO_LABEL                      0xFFFFFFFF
-#define MPLS_INVALID_LABEL                 0xFFFFFFFF
+/* The MPLS explicit-null label is 0 which means when you memset a mpls_label_t
+ * to zero you have set that variable to explicit-null which was probably not
+ * your intent. The work-around is to use one bit to indicate if the
+ * mpls_label_t has been set by the user. MPLS_INVALID_LABEL has this bit clear
+ * so that we can use MPLS_INVALID_LABEL to initialize mpls_label_t variables.
+ */
+#define MPLS_INVALID_LABEL                 0xFFFDFFFF
 
 /* LSP types. */
 enum lsp_types_t