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, 5 insertions, 1 deletions

diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index cca4b448..e894d632 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -146,6 +146,7 @@ struct bgp_channel_config {
   u8 mandatory;				/* Channel is mandatory in capability negotiation */
   u8 gw_mode;				/* How we compute route gateway from next_hop attr, see GW_* */
   u8 secondary;				/* Accept also non-best routes (i.e. RA_ACCEPTED) */
+  u8 validate;				/* Validate Flowspec per RFC 8955 (6) */
   u8 gr_able;				/* Allow full graceful restart for the channel */
   u8 llgr_able;				/* Allow full long-lived GR for the channel */
   uint llgr_time;			/* Long-lived graceful restart stale time */
@@ -159,6 +160,7 @@ struct bgp_channel_config {
 
   struct rtable_config *igp_table_ip4;	/* Table for recursive IPv4 next hop lookups */
   struct rtable_config *igp_table_ip6;	/* Table for recursive IPv6 next hop lookups */
+  struct rtable_config *base_table;	/* Base table for Flowspec validation */
 };
 
 #define BGP_PT_INTERNAL		1
@@ -340,6 +342,7 @@ struct bgp_channel {
 
   rtable *igp_table_ip4;		/* Table for recursive IPv4 next hop lookups */
   rtable *igp_table_ip6;		/* Table for recursive IPv6 next hop lookups */
+  rtable *base_table;			/* Base table for Flowspec validation */
 
   /* Rest are zeroed when down */
   pool *pool;
@@ -449,6 +452,7 @@ struct bgp_parse_state {
   jmp_buf err_jmpbuf;
 
   struct hostentry *hostentry;
+  struct rtable *base_table;
   adata *mpls_labels;
 
   /* Cached state for bgp_rte_update() */
@@ -515,7 +519,7 @@ struct rte_source *bgp_get_source(struct bgp_proto *p, u32 path_id);
 static inline int
 rte_resolvable(rte *rt)
 {
-  return rt->attrs->dest == RTD_UNICAST;
+  return rt->attrs->dest != RTD_UNREACHABLE;
 }