BGP: Implement flowspec validation procedure

Implement flowspec validation procedure as described in RFC 8955 sec. 6
and RFC 9117. The Validation procedure enforces that only routers in the
forwarding path for a network can originate flowspec rules for that
network.

The patch adds new mechanism for tracking inter-table dependencies, which
is necessary as the flowspec validation depends on IP routes, and flowspec
rules must be revalidated when best IP routes change.

The validation procedure is disabled by default and requires that
relevant IP table uses trie, as it uses interval queries for subnets.

1 files changed, 51 insertions, 3 deletions

diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index e4d754b1..58084136 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -101,6 +101,7 @@
  * RFC 8203 - BGP Administrative Shutdown Communication
  * RFC 8212 - Default EBGP Route Propagation Behavior without Policies
  * RFC 8654 - Extended Message Support for BGP
+ * RFC 9117 - Revised Validation Procedure for BGP Flow Specifications
  * draft-ietf-idr-ext-opt-param-07
  * draft-uttaro-idr-bgp-persistence-04
  * draft-walton-bgp-hostname-capability-02
@@ -1735,6 +1736,9 @@ bgp_channel_init(struct channel *C, struct channel_config *CF)
 
   if (cf->igp_table_ip6)
     c->igp_table_ip6 = cf->igp_table_ip6->table;
+
+  if (cf->base_table)
+    c->base_table = cf->base_table->table;
 }
 
 static int
@@ -1750,6 +1754,12 @@ bgp_channel_start(struct channel *C)
   if (c->igp_table_ip6)
     rt_lock_table(c->igp_table_ip6);
 
+  if (c->base_table)
+  {
+    rt_lock_table(c->base_table);
+    rt_flowspec_link(c->base_table, c->c.table);
+  }
+
   c->pool = p->p.pool; // XXXX
   bgp_init_bucket_table(c);
   bgp_init_prefix_table(c);
@@ -1834,6 +1844,12 @@ bgp_channel_cleanup(struct channel *C)
   if (c->igp_table_ip6)
     rt_unlock_table(c->igp_table_ip6);
 
+  if (c->base_table)
+  {
+    rt_flowspec_unlink(c->base_table, c->c.table);
+    rt_unlock_table(c->base_table);
+  }
+
   c->index = 0;
 
   /* Cleanup rest of bgp_channel starting at pool field */
@@ -1881,6 +1897,25 @@ bgp_default_igp_table(struct bgp_config *cf, struct bgp_channel_config *cc, u32
   cf_error("Undefined IGP table");
 }
 
+static struct rtable_config *
+bgp_default_base_table(struct bgp_config *cf, struct bgp_channel_config *cc)
+{
+  /* Expected table type */
+  u32 type = (cc->afi == BGP_AF_FLOW4) ? NET_IP4 : NET_IP6;
+
+  /* First, try appropriate IP channel */
+  u32 afi2 = BGP_AF(BGP_AFI(cc->afi), BGP_SAFI_UNICAST);
+  struct bgp_channel_config *cc2 = bgp_find_channel_config(cf, afi2);
+  if (cc2 && (cc2->c.table->addr_type == type))
+    return cc2->c.table;
+
+  /* Last, try default table of given type */
+  struct rtable_config *tab = cf->c.global->def_tables[type];
+  if (tab)
+    return tab;
+
+  cf_error("Undefined base table");
+}
 
 void
 bgp_postconfig(struct proto_config *CF)
@@ -2025,6 +2060,14 @@ bgp_postconfig(struct proto_config *CF)
 	cf_error("Mismatched IGP table type");
     }
 
+    /* Default value of base table */
+    if ((BGP_SAFI(cc->afi) == BGP_SAFI_FLOW) && cc->validate && !cc->base_table)
+      cc->base_table = bgp_default_base_table(cf, cc);
+
+    if (cc->base_table && !cc->base_table->trie_used)
+      cf_error("Flowspec validation requires base table (%s) with trie",
+	       cc->base_table->name);
+
     if (cf->multihop && (cc->gw_mode == GW_DIRECT))
       cf_error("Multihop BGP cannot use direct gateway mode");
 
@@ -2093,7 +2136,7 @@ bgp_reconfigure(struct proto *P, struct proto_config *CF)
   return same;
 }
 
-#define IGP_TABLE(cf, sym) ((cf)->igp_table_##sym ? (cf)->igp_table_##sym ->table : NULL )
+#define TABLE(cf, NAME) ((cf)->NAME ? (cf)->NAME->table : NULL )
 
 static int
 bgp_channel_reconfigure(struct channel *C, struct channel_config *CC, int *import_changed, int *export_changed)
@@ -2104,6 +2147,7 @@ bgp_channel_reconfigure(struct channel *C, struct channel_config *CC, int *impor
   struct bgp_channel_config *old = c->cf;
 
   if ((new->secondary != old->secondary) ||
+      (new->validate != old->validate) ||
       (new->gr_able != old->gr_able) ||
       (new->llgr_able != old->llgr_able) ||
       (new->llgr_time != old->llgr_time) ||
@@ -2111,8 +2155,9 @@ bgp_channel_reconfigure(struct channel *C, struct channel_config *CC, int *impor
       (new->add_path != old->add_path) ||
       (new->import_table != old->import_table) ||
       (new->export_table != old->export_table) ||
-      (IGP_TABLE(new, ip4) != IGP_TABLE(old, ip4)) ||
-      (IGP_TABLE(new, ip6) != IGP_TABLE(old, ip6)))
+      (TABLE(new, igp_table_ip4) != TABLE(old, igp_table_ip4)) ||
+      (TABLE(new, igp_table_ip6) != TABLE(old, igp_table_ip6)) ||
+      (TABLE(new, base_table) != TABLE(old, base_table)))
     return 0;
 
   if (new->mandatory && !old->mandatory && (C->channel_state != CS_UP))
@@ -2526,6 +2571,9 @@ bgp_show_proto_info(struct proto *P)
 
       if (c->igp_table_ip6)
 	cli_msg(-1006, "    IGP IPv6 table: %s", c->igp_table_ip6->name);
+
+      if (c->base_table)
+	cli_msg(-1006, "    Base table:     %s", c->base_table->name);
     }
   }
 }