bgpd: Convert bgp_packet_mpattr_prefix_size to use an enum

The function bgp_packet_mpattr_prefix_size had an if/else
body that allowed people to add encoding types to bgpd
such that we could build the wrong size packets.  This
was exposed recently in commit:
0a9705a1e07c1d8176fd21f8f1bde2a9a155331b

Where it was discovered flowspec was causing bgp update
messages to exceed the maximum size and the peer to
drop the connection.  Let's be proscriptive about this
and hopefully make it so that things don't work when
someone adds a new safi to the system ( and they'll have
to update this function ).

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index 337a82b9456ce93d0424eacf0c99ea0416da6433..47baed5af538d0537ae4cb0925f4e53e62208195 100644 (file)
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -3979,15 +3979,39 @@ size_t bgp_packet_mpattr_prefix_size(afi_t afi, safi_t safi,
                                     const struct prefix *p)
 {
        int size = PSIZE(p->prefixlen);
-       if (safi == SAFI_MPLS_VPN)
+
+       switch (safi) {
+       case SAFI_UNSPEC:
+       case SAFI_MAX:
+               assert(!"Attempting to figure size for a SAFI_UNSPEC/SAFI_MAX this is a DEV ESCAPE");
+               break;
+       case SAFI_UNICAST:
+       case SAFI_MULTICAST:
+               break;
+       case SAFI_MPLS_VPN:
                size += 88;
-       else if (safi == SAFI_LABELED_UNICAST)
+               break;
+       case SAFI_ENCAP:
+               /* This has to be wrong, but I don't know what to put here */
+               assert(!"Do we try to use this?");
+               break;
+       case SAFI_LABELED_UNICAST:
                size += BGP_LABEL_BYTES;
-       else if (afi == AFI_L2VPN && safi == SAFI_EVPN)
-               size += 232; // TODO: Maximum possible for type-2, type-3 and
-                            // type-5
-       else if (safi == SAFI_FLOWSPEC)
+               break;
+       case SAFI_EVPN:
+               /*
+                * TODO: Maximum possible for type-2, type-3 and type-5
+                */
+               if (afi == AFI_L2VPN)
+                       size += 232;
+               else
+                       assert(!"Attempting to figure size for SAFI_EVPN and !AFI_L2VPN and FRR will not have the proper values");
+               break;
+       case SAFI_FLOWSPEC:
                size = ((struct prefix_fs *)p)->prefix.prefixlen;
+               break;
+       }
+
        return size;
 }