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, 15 insertions, 0 deletions

diff --git a/nest/route.h b/nest/route.h
index a1732bc7..102ea0ea 100644
--- a/nest/route.h
+++ b/nest/route.h
@@ -192,6 +192,8 @@ typedef struct rtable {
 
   list subscribers;			/* Subscribers for notifications */
   struct timer *settle_timer;		/* Settle time for notifications */
+  list flowspec_links;			/* List of flowspec links, src for NET_IPx and dst for NET_FLOWx */
+  struct f_trie *flowspec_trie;		/* Trie for evaluation of flowspec notifications */
 } rtable;
 
 struct rt_subscription {
@@ -201,6 +203,13 @@ struct rt_subscription {
   void *data;
 };
 
+struct rt_flowspec_link {
+  node n;
+  rtable *src;
+  rtable *dst;
+  u32 uc;
+};
+
 #define NHU_CLEAN	0
 #define NHU_SCHEDULED	1
 #define NHU_RUNNING	2
@@ -267,6 +276,7 @@ typedef struct rte {
     struct {
       u8 suppressed;			/* Used for deterministic MED comparison */
       s8 stale;				/* Route is LLGR_STALE, -1 if unknown */
+      struct rtable *base_table;	/* Base table for Flowspec validation */
     } bgp;
 #endif
 #ifdef CONFIG_BABEL
@@ -322,6 +332,8 @@ void rt_lock_table(rtable *);
 void rt_unlock_table(rtable *);
 void rt_subscribe(rtable *tab, struct rt_subscription *s);
 void rt_unsubscribe(struct rt_subscription *s);
+void rt_flowspec_link(rtable *src, rtable *dst);
+void rt_flowspec_unlink(rtable *src, rtable *dst);
 rtable *rt_setup(pool *, struct rtable_config *);
 static inline void rt_shutdown(rtable *r) { rfree(r->rp); }
 
@@ -743,6 +755,9 @@ rta_set_recursive_next_hop(rtable *dep, rta *a, rtable *tab, ip_addr gw, ip_addr
 static inline void rt_lock_hostentry(struct hostentry *he) { if (he) he->uc++; }
 static inline void rt_unlock_hostentry(struct hostentry *he) { if (he) he->uc--; }
 
+int rt_flowspec_check(rtable *tab_ip, rtable *tab_flow, const net_addr *n, rta *a, int interior);
+
+
 /*
  *	Default protocol preferences
  */