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diff --git a/lib/cspf.h b/lib/cspf.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Constraints Shortest Path First algorithms definition - cspf.h
+ *
+ * Author: Olivier Dugeon <olivier.dugeon@orange.com>
+ *
+ * Copyright (C) 2022 Orange http://www.orange.com
+ *
+ * This file is part of Free Range Routing (FRR).
+ */
+
+#ifndef _FRR_CSPF_H_
+#define _FRR_CSPF_H_
+
+#include "typesafe.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * This file defines the different structure used for Path Computation with
+ * various constrained. Up to now, standard metric, TE metric, delay and
+ * bandwidth constraints are supported.
+ * All proposed algorithms used the same principle:
+ *  - A pruning function that keeps only links that meet constraints
+ *  - A priority Queue that keeps the shortest on-going computed path
+ *  - A main loop over all vertices to find the shortest path
+ */
+
+#define MAX_COST	0xFFFFFFFF
+
+/* Status of the path */
+enum path_status {
+	FAILED = 0,
+	NO_SOURCE,
+	NO_DESTINATION,
+	SAME_SRC_DST,
+	IN_PROGRESS,
+	SUCCESS
+};
+enum path_type {RSVP_TE = 1, SR_TE, SRV6_TE};
+enum metric_type {CSPF_METRIC = 1, CSPF_TE_METRIC, CSPF_DELAY};
+
+/* Constrained metrics structure */
+struct constraints {
+	uint32_t cost;		/* total cost (metric) of the path */
+	enum metric_type ctype;	/* Metric Type: standard, TE or Delay */
+	float bw;		/* bandwidth of the path */
+	uint8_t cos;		/* Class of Service of the path */
+	enum path_type type;	/* RSVP-TE or SR-TE path */
+	uint8_t family;		/* AF_INET or AF_INET6 address family */
+};
+
+/* Priority Queue for Constrained Path Computation */
+PREDECL_RBTREE_NONUNIQ(pqueue);
+
+/* Processed Path for Constrained Path Computation */
+PREDECL_RBTREE_UNIQ(processed);
+
+/* Constrained Path structure */
+struct c_path {
+	struct pqueue_item q_itm;    /* entry in the Priority Queue */
+	uint32_t weight;             /* Weight to sort path in Priority Queue */
+	struct processed_item p_itm; /* entry in the Processed RB Tree */
+	uint64_t dst;                /* Destination vertex key of this path */
+	struct list *edges;          /* List of Edges that compose this path */
+	enum path_status status;     /* status of the computed path */
+};
+
+macro_inline int q_cmp(const struct c_path *p1, const struct c_path *p2)
+{
+	return numcmp(p1->weight, p2->weight);
+}
+DECLARE_RBTREE_NONUNIQ(pqueue, struct c_path, q_itm, q_cmp);
+
+macro_inline int p_cmp(const struct c_path *p1, const struct c_path *p2)
+{
+	return numcmp(p1->dst, p2->dst);
+}
+DECLARE_RBTREE_UNIQ(processed, struct c_path, p_itm, p_cmp);
+
+/* List of visited node */
+PREDECL_RBTREE_UNIQ(visited);
+struct v_node {
+	struct visited_item item; /* entry in the Processed RB Tree */
+	uint64_t key;
+	struct ls_vertex *vertex;
+};
+
+macro_inline int v_cmp(const struct v_node *p1, const struct v_node *p2)
+{
+	return numcmp(p1->key, p2->key);
+}
+DECLARE_RBTREE_UNIQ(visited, struct v_node, item, v_cmp);
+
+/* Path Computation algorithms structure */
+struct cspf {
+	struct pqueue_head pqueue;       /* Priority Queue */
+	struct processed_head processed; /* Paths that have been processed */
+	struct visited_head visited;     /* Vertices that have been visited */
+	struct constraints csts;         /* Constraints of the path */
+	struct c_path *path;             /* Current Computed Path */
+	struct c_path *pdst;             /* Computed Path to the destination */
+};
+
+/**
+ * Create a new CSPF structure. Memory is dynamically allocated.
+ *
+ * @return	pointer to the new cspf structure
+ */
+extern struct cspf *cspf_new(void);
+
+/**
+ * Initialize CSPF structure prior to compute a constrained path. If CSPF
+ * structure is NULL, a new CSPF is dynamically allocated prior to the
+ * configuration itself.
+ *
+ * @param algo	CSPF structure, may be null if a new CSPF must be created
+ * @param src	Source vertex of the requested path
+ * @param dst	Destination vertex of the requested path
+ * @param csts	Constraints of the requested path
+ *
+ * @return	pointer to the initialized CSPF structure
+ */
+extern struct cspf *cspf_init(struct cspf *algo, const struct ls_vertex *src,
+			      const struct ls_vertex *dst,
+			      struct constraints *csts);
+
+/**
+ * Initialize CSPF structure prior to compute a constrained path. If CSPF
+ * structure is NULL, a new CSPF is dynamically allocated prior to the
+ * configuration itself. This function starts by searching source and
+ * destination vertices from the IPv4 addresses in the provided TED.
+ *
+ * @param algo	CSPF structure, may be null if a new CSPF must be created
+ * @param ted	Traffic Engineering Database
+ * @param src	Source IPv4 address of the requested path
+ * @param dst	Destination IPv4 address of the requested path
+ * @param csts	Constraints of the requested path
+ *
+ * @return	pointer to the initialized CSPF structure
+ */
+extern struct cspf *cspf_init_v4(struct cspf *algo, struct ls_ted *ted,
+				 const struct in_addr src,
+				 const struct in_addr dst,
+				 struct constraints *csts);
+
+/**
+ * Initialize CSPF structure prior to compute a constrained path. If CSPF
+ * structure is NULL, a new CSPF is dynamically allocated prior to the
+ * configuration itself. This function starts by searching source and
+ * destination vertices from the IPv6 addresses in the provided TED.
+ *
+ * @param algo	CSPF structure, may be null if a new CSPF must be created
+ * @param ted	Traffic Engineering Database
+ * @param src	Source IPv6 address of the requested path
+ * @param dst	Destination IPv6 address of the requested path
+ * @param csts	Constraints of the requested path
+ *
+ * @return	pointer to the initialized CSPF structure
+ */
+extern struct cspf *cspf_init_v6(struct cspf *algo, struct ls_ted *ted,
+				 const struct in6_addr src,
+				 const struct in6_addr dst,
+				 struct constraints *csts);
+
+/**
+ * Clean CSPF structure. Reset all internal list and priority queue for latter
+ * initialization of the CSPF structure and new path computation.
+ *
+ * @param algo	CSPF structure
+ */
+extern void cspf_clean(struct cspf *algo);
+
+/**
+ * Delete CSPF structure, internal list and priority queue.
+ *
+ * @param algo	CSPF structure
+ */
+extern void cspf_del(struct cspf *algo);
+
+/**
+ * Compute point-to-point constrained path. cspf_init() function must be call
+ * prior to call this function.
+ *
+ * @param algo	CSPF structure
+ * @param ted	Traffic Engineering Database
+ *
+ * @return	Constrained Path with status to indicate computation success
+ */
+extern struct c_path *compute_p2p_path(struct cspf *algo, struct ls_ted *ted);
+
+extern void cpath_del(struct c_path *path);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _FRR_CSPF_H_ */