MPLS subsystem

The MPLS subsystem manages MPLS labels and handles their allocation to
MPLS-aware routing protocols. These labels are then attached to IP or VPN
routes representing label switched paths -- LSPs.

There was already a preliminary MPLS support consisting of MPLS label
net_addr, MPLS routing tables with static MPLS routes, remote labels in
next hops, and kernel protocol support.

This patch adds the MPLS domain as a basic structure representing local
label space with dynamic label allocator and configurable label ranges.
To represent LSPs, allocated local labels can be attached as route
attributes to IP or VPN routes with local labels as attributes.

There are several steps for handling LSP routes in routing protocols --
deciding to which forwarding equivalence class (FEC) the LSP route
belongs, allocating labels for new FECs, announcing MPLS routes for new
FECs, attaching labels to LSP routes. The FEC map structure implements
basic code for managing FECs in routing protocols, therefore existing
protocols can be made MPLS-aware by adding FEC map and delegating
most work related to local label management to it.

1 files changed, 170 insertions, 0 deletions

diff --git a/nest/mpls.h b/nest/mpls.h
new file mode 100644
index 00000000..a84ede14
--- /dev/null
+++ b/nest/mpls.h
@@ -0,0 +1,170 @@
+/*
+ *	BIRD Internet Routing Daemon -- MPLS Structures
+ *
+ *	(c) 2022 Ondrej Zajicek <santiago@crfreenet.org>
+ *	(c) 2022 CZ.NIC z.s.p.o.
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#ifndef _BIRD_MPLS_H_
+#define _BIRD_MPLS_H_
+
+#include "nest/bird.h"
+#include "lib/bitmap.h"
+#include "lib/hash.h"
+#include "nest/route.h"
+#include "nest/protocol.h"
+
+
+#define MPLS_POLICY_NONE	0
+#define MPLS_POLICY_STATIC	1
+#define MPLS_POLICY_PREFIX	2
+#define MPLS_POLICY_AGGREGATE	3
+
+#define MPLS_FEC_DOWN		0
+#define MPLS_FEC_CLEAN		1
+#define MPLS_FEC_DIRTY		2
+
+
+struct mpls_domain_config {
+  node n;				/* Node in config.mpls_domains */
+  struct mpls_domain *domain;		/* Our instance */
+  const char *name;
+
+  list ranges;				/* List of label ranges (struct mpls_range_config) */
+  struct mpls_range_config *static_range;  /* Default static label range */
+  struct mpls_range_config *dynamic_range; /* Default dynamic label range */
+};
+
+struct mpls_domain {
+  node n;				/* Node in global list of MPLS domains (mpls_domains) */
+  struct mpls_domain_config *cf;	/* Our config */
+  const char *name;
+  pool *pool;				/* Pool for the domain and associated objects */
+
+  struct lmap labels;			/* Bitmap of allocated labels */
+  uint label_count;			/* Number of allocated labels */
+  uint use_count;			/* Reference counter */
+
+  struct config *removed;		/* Deconfigured, waiting for zero use_count,
+					   while keeping config obstacle */
+
+  list ranges;				/* List of label ranges (struct mpls_range) */
+  list handles;				/* List of label handles (struct mpls_handle) */
+};
+
+struct mpls_range_config {
+  node n;				/* Node in mpls_domain_config.ranges */
+  struct mpls_range *range;		/* Our instance */
+  struct mpls_domain_config *domain;	/* Parent MPLS domain */
+  const char *name;
+
+  uint start;				/* Label range start, (uint) -1 for undefined */
+  uint length;				/* Label range length, (uint) -1 for undefined */
+};
+
+struct mpls_range {
+  node n;				/* Node in mpls_domain.ranges */
+  struct mpls_range_config *cf;		/* Our config */
+  const char *name;
+
+  uint lo, hi;				/* Label range interval */
+  uint label_count;			/* Number of allocated labels */
+  uint use_count;			/* Reference counter */
+  u8 removed;				/* Deconfigured, waiting for zero use_count */
+};
+
+struct mpls_handle {
+  node n;				/* Node in mpls_domain.handles */
+
+  struct mpls_range *range;		/* Associated range, keeping reference */
+  uint label_count;			/* Number of allocated labels */
+};
+
+
+void mpls_init(void);
+struct mpls_domain_config * mpls_domain_config_new(struct symbol *s);
+void mpls_domain_postconfig(struct mpls_domain_config *cf);
+struct mpls_range_config * mpls_range_config_new(struct mpls_domain_config *m, struct symbol *s);
+void mpls_preconfig(struct config *c);
+void mpls_commit(struct config *new, struct config *old);
+uint mpls_new_label(struct mpls_domain *m, struct mpls_handle *h);
+void mpls_free_label(struct mpls_domain *m, struct mpls_handle *h, uint n);
+
+static inline struct mpls_domain_config *cf_default_mpls_domain(struct config *cfg)
+{ return EMPTY_LIST(cfg->mpls_domains) ? NULL : HEAD(cfg->mpls_domains); }
+
+
+struct mpls_channel_config {
+  struct channel_config c;
+
+  struct mpls_domain_config *domain;
+  struct mpls_range_config *range;
+
+  uint label_policy;
+};
+
+struct mpls_channel {
+  struct channel c;
+
+  struct mpls_domain *domain;
+  struct mpls_range *range;
+
+  uint label_policy;
+};
+
+
+void mpls_channel_postconfig(struct channel_config *CF);
+extern struct channel_class channel_mpls;
+
+
+struct mpls_fec {
+  u32 label;				/* Label for FEC */
+  u32 hash;				/* Hash for primary key (net / rta) */
+  u32 uc;				/* Number of LSPs for FEC */
+  union {				/* Extension part of key */
+    u32 path_id;			/* Source path_id */
+    u32 class_id;			/* Aaggregation class */
+  };
+
+  u8 state;				/* FEC state (MPLS_FEC_*) */
+  u8 policy;				/* Label policy (MPLS_POLICY_*) */
+
+  struct mpls_fec *next_k;		/* Next in mpls_fec.net_hash/rta_hash */
+  struct mpls_fec *next_l;		/* Next in mpls_fec.label_hash */
+  union {				/* Primary key */
+    struct rta *rta;
+    net_addr net[0];
+  };
+};
+
+struct mpls_fec_map {
+  pool *pool;				/* Pool for FEC map */
+  slab *slabs[4];			/* Slabs for FEC allocation */
+  HASH(struct mpls_fec) net_hash;	/* Hash table for MPLS_POLICY_PREFIX FECs */
+  HASH(struct mpls_fec) rta_hash;	/* Hash table for MPLS_POLICY_AGGREGATE FECs */
+  HASH(struct mpls_fec) label_hash;	/* Hash table for FEC lookup by label */
+
+  struct channel *channel;		/* MPLS channel for FEC announcement */
+  struct mpls_domain *domain;		/* MPLS domain, keeping reference */
+  struct mpls_handle *handle;		/* Handle for allocation of labels */
+
+  u8 mpls_rts;				/* Source value used for MPLS routes (RTS_*) */
+  u8 mpls_scope;			/* Scope  value used for MPLS routes () */
+};
+
+
+struct mpls_fec_map *mpls_fec_map_new(pool *p, struct channel *c, uint rts);
+void mpls_fec_map_free(struct mpls_fec_map *m);
+struct mpls_fec *mpls_find_fec_by_label(struct mpls_fec_map *x, u32 label);
+struct mpls_fec *mpls_get_fec_by_label(struct mpls_fec_map *m, u32 label);
+struct mpls_fec *mpls_get_fec_by_net(struct mpls_fec_map *m, const net_addr *net, u32 path_id);
+struct mpls_fec *mpls_get_fec_by_rta(struct mpls_fec_map *m, const rta *src, u32 class_id);
+void mpls_free_fec(struct mpls_fec_map *x, struct mpls_fec *fec);
+void mpls_handle_rte(struct mpls_fec_map *m, const net_addr *n, rte *r, linpool *lp, struct mpls_fec **locked_fec);
+void mpls_handle_rte_cleanup(struct mpls_fec_map *m, struct mpls_fec **locked_fec);
+void mpls_rte_insert(net *n UNUSED, rte *r);
+void mpls_rte_remove(net *n UNUSED, rte *r);
+
+#endif