BGP: Support for MPLS labels and VPN SAFI

Basic support for SAFI 4 and 128 (MPLS labeled IP and VPN) for IPv4 and
IPv6. Should work for route reflector, but does not properly handle
originating routes with next hop self.

Based on patches from Jan Matejka.

1 files changed, 80 insertions, 4 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index f2a8e8b5..cf9db1c8 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -629,6 +629,75 @@ bgp_decode_large_community(struct bgp_parse_state *s, uint code UNUSED, uint fla
   bgp_set_attr_ptr(to, s->pool, BA_LARGE_COMMUNITY, flags, ad);
 }
 
+static void
+bgp_export_mpls_label_stack(struct bgp_export_state *s, eattr *a)
+{
+  net_addr *n = s->route->net->n.addr;
+  u32 *labels = (u32 *) a->u.ptr->data;
+  uint lnum = a->u.ptr->length / 4;
+
+  /* Perhaps we should just ignore it? */
+  if (!s->mpls)
+    WITHDRAW("Unexpected MPLS stack");
+
+  /* Empty MPLS stack is not allowed */
+  if (!lnum)
+    WITHDRAW("Malformed MPLS stack - empty");
+
+  /* This is ugly, but we must ensure that labels fit into NLRI field */
+  if ((24*lnum + (net_is_vpn(n) ? 64 : 0) + net_pxlen(n)) > 255)
+    WITHDRAW("Malformed MPLS stack - too many labels (%u)", lnum);
+
+  for (uint i = 0; i < lnum; i++)
+  {
+    if (labels[i] > 0xfffff)
+      WITHDRAW("Malformed MPLS stack - invalid label (%u)", labels[i]);
+
+    /* TODO: Check for special-purpose label values? */
+  }
+}
+
+static int
+bgp_encode_mpls_label_stack(struct bgp_write_state *s, eattr *a, byte *buf UNUSED, uint size UNUSED)
+{
+  /*
+   * MPLS labels are encoded as a part of the NLRI in MP_REACH_NLRI attribute,
+   * so we store MPLS_LABEL_STACK and encode it later by AFI-specific hooks.
+   */
+
+  s->mpls_labels = a->u.ptr;
+  return 0;
+}
+
+static void
+bgp_decode_mpls_label_stack(struct bgp_parse_state *s, uint code UNUSED, uint flags UNUSED, byte *data UNUSED, uint len UNUSED, ea_list **to UNUSED)
+{
+  DISCARD("Discarding received attribute #0");
+}
+
+static void
+bgp_format_mpls_label_stack(eattr *a, byte *buf, uint size)
+{
+  u32 *labels = (u32 *) a->u.ptr->data;
+  uint lnum = a->u.ptr->length / 4;
+  char *pos = buf;
+
+  for (uint i = 0; i < lnum; i++)
+  {
+    if (size < 20)
+    {
+      bsprintf(pos, "...");
+      return;
+    }
+
+    uint l = bsprintf(pos, "%d/", labels[i]);
+    ADVANCE(pos, size, l);
+  }
+
+  /* Clear last slash or terminate empty string */
+  pos[lnum ? -1 : 0] = 0;
+}
+
 static inline void
 bgp_decode_unknown(struct bgp_parse_state *s, uint code, uint flags, byte *data, uint len, ea_list **to)
 {
@@ -763,6 +832,14 @@ static const struct bgp_attr_desc bgp_attr_table[] = {
     .encode = bgp_encode_u32s,
     .decode = bgp_decode_large_community,
   },
+  [BA_MPLS_LABEL_STACK] = {
+    .name = "mpls_label_stack",
+    .type = EAF_TYPE_INT_SET,
+    .export = bgp_export_mpls_label_stack,
+    .encode = bgp_encode_mpls_label_stack,
+    .decode = bgp_decode_mpls_label_stack,
+    .format = bgp_format_mpls_label_stack,
+  },
 };
 
 static inline int
@@ -849,7 +926,6 @@ bgp_export_attrs(struct bgp_export_state *s, ea_list *attrs)
     return NULL;
 
   return new;
-
 }
 
 
@@ -1340,7 +1416,7 @@ bgp_update_attrs(struct bgp_proto *p, struct bgp_channel *c, rte *e, ea_list *at
 {
   struct proto *SRC = e->attrs->src->proto;
   struct bgp_proto *src = (SRC->proto == &proto_bgp) ? (void *) SRC : NULL;
-  struct bgp_export_state s = { .proto = p, .channel =c, .pool = pool, .src = src, .route = e };
+  struct bgp_export_state s = { .proto = p, .channel = c, .pool = pool, .src = src, .route = e, .mpls = c->desc->mpls };
   ea_list *attrs = attrs0;
   eattr *a;
   adata *ad;
@@ -1453,13 +1529,13 @@ bgp_rt_notify(struct proto *P, struct channel *C, net *n, rte *new, rte *old, ea
 
   if (new)
   {
-    attrs = bgp_update_attrs(p, c, new, attrs, bgp_linpool);
+    attrs = bgp_update_attrs(p, c, new, attrs, bgp_linpool2);
 
     /* If attributes are invalid, we fail back to withdraw */
     buck = attrs ? bgp_get_bucket(c, attrs) : bgp_get_withdraw_bucket(c);
     path = new->attrs->src->global_id;
 
-    lp_flush(bgp_linpool);
+    lp_flush(bgp_linpool2);
   }
   else
   {