/*
 *  tayga.h -- main header file
 *
 *  part of TAYGA <http://www.litech.org/tayga/>
 *  Copyright (C) 2010  Nathan Lutchansky <lutchann@litech.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <poll.h>
#include <fcntl.h>
#include <syslog.h>
#include <errno.h>
#include <time.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include <linux/if_ether.h>

#include "list.h"
#include "config.h"


/* Configuration knobs */

/* Number of seconds of silence before a map ages out of the cache */
#define CACHE_MAX_AGE		120

/* Number of seconds between cache ageing passes */
#define CACHE_CHECK_INTERVAL	5

/* Number of seconds between dynamic pool ageing passes */
#define POOL_CHECK_INTERVAL	45

/* Valid token delimiters in config file and dynamic map file */
#define DELIM		" \t\r\n"


/* Protocol structures */

struct ip4 {
	uint8_t ver_ihl; /* 7-4: ver==4, 3-0: IHL */
	uint8_t tos;
	uint16_t length;
	uint16_t ident;
	uint16_t flags_offset; /* 15-13: flags, 12-0: frag offset */
	uint8_t ttl;
	uint8_t proto;
	uint16_t cksum;
	struct in_addr src;
	struct in_addr dest;
} __attribute__ ((__packed__));

#define IP4_F_DF	0x4000
#define IP4_F_MF	0x2000
#define IP4_F_MASK	0x1fff

struct ip6 {
	uint32_t ver_tc_fl; /* 31-28: ver==6, 27-20: traf cl, 19-0: flow lbl */
	uint16_t payload_length;
	uint8_t next_header;
	uint8_t hop_limit;
	struct in6_addr src;
	struct in6_addr dest;
} __attribute__ ((__packed__));

struct ip6_frag {
	uint8_t next_header;
	uint8_t reserved;
	uint16_t offset_flags; /* 15-3: frag offset, 2-0: flags */
	uint32_t ident;
} __attribute__ ((__packed__));

#define IP6_F_MF	0x0001
#define IP6_F_MASK	0xfff8

struct icmp {
	uint8_t type;
	uint8_t code;
	uint16_t cksum;
	uint32_t word;
} __attribute__ ((__packed__));

#define	WKPF	(htonl(0x0064ff9b))

/* Adjusting the MTU by 20 does not leave room for the IP6 fragmentation
   header, for fragments with the DF bit set.  Follow up with BEHAVE on this.

   (See http://www.ietf.org/mail-archive/web/behave/current/msg08499.html)
 */
#define MTU_ADJ		20


/* TAYGA data definitions */

struct pkt {
	struct ip4 *ip4;
	struct ip6 *ip6;
	struct ip6_frag *ip6_frag;
	struct icmp *icmp;
	uint8_t data_proto;
	uint8_t *data;
	uint32_t data_len;
	uint32_t header_len; /* inc IP hdr for v4 but excl IP hdr for v6 */
};

enum {
	MAP_TYPE_STATIC,
	MAP_TYPE_RFC6052,
	MAP_TYPE_DYNAMIC_POOL,
	MAP_TYPE_DYNAMIC_HOST,
};

struct map4 {
	struct in_addr addr;
	struct in_addr mask;
	int prefix_len;
	int type;
	struct list_head list;
};

struct map6 {
	struct in6_addr addr;
	struct in6_addr mask;
	int prefix_len;
	int type;
	struct list_head list;
};

struct map_static {
	struct map4 map4;
	struct map6 map6;
	int conffile_lineno;
};

struct free_addr {
	uint32_t addr; /* in-use address (host order) */
	uint32_t count; /* num of free addresses after addr */
	struct list_head list;
};

struct map_dynamic {
	struct map4 map4;
	struct map6 map6;
	struct cache_entry *cache_entry;
	time_t last_use;
	struct list_head list;
	struct free_addr free;
};

struct dynamic_pool {
	struct map4 map4;
	struct list_head mapped_list;
	struct list_head dormant_list;
	struct list_head free_list;
	struct free_addr free_head;
};

struct cache_entry {
	struct in6_addr addr6;
	struct in_addr addr4;
	time_t last_use;
	uint32_t flags;
	uint16_t ip4_ident;
	struct list_head list;
	struct list_head hash4;
	struct list_head hash6;
};

#define CACHE_F_SEEN_4TO6	(1<<0)
#define CACHE_F_SEEN_6TO4	(1<<1)
#define CACHE_F_GEN_IDENT	(1<<2)
#define CACHE_F_REP_AGEOUT	(1<<3)

struct config {
	char tundev[IFNAMSIZ];
	char data_dir[512];
	uint32_t recv_buf_size;
	struct in_addr local_addr4;
	struct in6_addr local_addr6;
	struct list_head map4_list;
	struct list_head map6_list;
	int dyn_min_lease;
	int dyn_max_lease;
	int max_commit_delay;
	struct dynamic_pool *dynamic_pool;
	int hash_bits;
	int cache_size;
	int allow_ident_gen;
	int ipv6_offlink_mtu;
	int lazy_frag_hdr;

	int urandom_fd;
	int tun_fd;

	uint16_t mtu;
	uint8_t *recv_buf;

	uint32_t rand[8];
	struct list_head cache_pool;
	struct list_head cache_active;
	time_t last_cache_maint;
	struct list_head *hash_table4;
	struct list_head *hash_table6;

	time_t last_dynamic_maint;
	time_t last_map_write;
	int map_write_pending;
};


/* Macros and static functions */

/* Get a pointer to the object containing x, which is of type "type" and 
 * embeds x as a field called "field" */
#define container_of(x, type, field) ({ \
		const typeof( ((type *)0)->field ) *__mptr = (x); \
		(type *)( (char *)__mptr - offsetof(type, field) );})

#define IN6_IS_IN_NET(addr,net,mask) \
		((net)->s6_addr32[0] == ((addr)->s6_addr32[0] & \
						(mask)->s6_addr32[0]) && \
		 (net)->s6_addr32[1] == ((addr)->s6_addr32[1] & \
			 			(mask)->s6_addr32[1]) && \
		 (net)->s6_addr32[2] == ((addr)->s6_addr32[2] & \
			 			(mask)->s6_addr32[2]) && \
		 (net)->s6_addr32[3] == ((addr)->s6_addr32[3] & \
			 			(mask)->s6_addr32[3]))


/* TAYGA function prototypes */

/* addrmap.c */
int validate_ip4_addr(const struct in_addr *a);
int validate_ip6_addr(const struct in6_addr *a);
int is_private_ip4_addr(const struct in_addr *a);
int calc_ip4_mask(struct in_addr *mask, const struct in_addr *addr, int len);
int calc_ip6_mask(struct in6_addr *mask, const struct in6_addr *addr, int len);
void create_cache(void);
int insert_map4(struct map4 *m, struct map4 **conflict);
int insert_map6(struct map6 *m, struct map6 **conflict);
struct map4 *find_map4(const struct in_addr *addr4);
struct map6 *find_map6(const struct in6_addr *addr6);
int append_to_prefix(struct in6_addr *addr6, const struct in_addr *addr4,
		const struct in6_addr *prefix, int prefix_len);
int map_ip4_to_ip6(struct in6_addr *addr6, const struct in_addr *addr4,
		struct cache_entry **c_ptr);
int map_ip6_to_ip4(struct in_addr *addr4, const struct in6_addr *addr6,
		struct cache_entry **c_ptr, int dyn_alloc);
void addrmap_maint(void);

/* conffile.c */
void read_config(char *conffile);

/* dynamic.c */
struct map6 *assign_dynamic(const struct in6_addr *addr6);
void load_dynamic(struct dynamic_pool *pool);
void dynamic_maint(struct dynamic_pool *pool, int shutdown);

/* nat64.c */
void handle_ip4(struct pkt *p);
void handle_ip6(struct pkt *p);

/* tayga.c */
void slog(int priority, const char *format, ...);
void read_random_bytes(void *d, int len);