/*
 * ni-iface-helper.c
 * This file is part of Network Inador
 *
 * Copyright (C) 2021 - Félix Arreola Rodríguez
 *
 * Network Inador 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.
 *
 * Network Inador 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with Network Inador; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, 
 * Boston, MA  02110-1301  USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

#include <stdint.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <arpa/inet.h>

#include "network-inador-manager.h"

#define COMMAND_SOCKET_PATH "/tmp/network-inador.socket"

extern char** environ;

int debug (int argc, char *argv[]) {
	char **item;
	int fd;
	
	fd = open ("/tmp/var_dhcp.env", O_CREAT | O_WRONLY | O_TRUNC, 0644);
	
	if (fd < 0) {
		return -1;
	}
	
	for (item = environ; *item; item++) {
		char *name, *val, **p;

		/* Split on the = */
		name = strdup (*item);
		val = strchr (name, '=');
		if (!val || val == name) {
			free (name);
			continue;
		}
		*val++ = '\0';

		/* Ignore non-DCHP-related environment variables
		for (p = (char **) ignore; *p; p++) {
			if (strncmp (name, *p, strlen (*p)) == 0)
				goto next;
		}*/
		
		write (fd, "Name: <", 7);
		write (fd, name, strlen (name));
		write (fd, ">, Value: <", 11);
		write (fd, val, strlen (val));
		write (fd, ">\n", 2);
	}
	
	close (fd);
	
	return 0;
}

enum {
	DHCP_CLIENT_SELECTING,
	DHCP_CLIENT_BOUND,
	DHCP_CLIENT_RENEWED,
	
	DHCP_CLIENT_EXPIRED,
	DHCP_CLIENT_FAILED,
	
	DHCP_CLIENT_KILLED,
};

uint32_t utils_ip4_netmask_to_prefix (uint32_t netmask) {
	uint32_t prefix;
	uint8_t v;
	const uint8_t *p = (uint8_t *) &netmask;

	if (p[3]) {
		prefix = 24;
		v = p[3];
	} else if (p[2]) {
		prefix = 16;
		v = p[2];
	} else if (p[1]) {
		prefix = 8;
		v = p[1];
	} else {
		prefix = 0;
		v = p[0];
	}

	while (v) {
		prefix++;
		v <<= 1;
	}

	return prefix;
}

char *retrieve_env (const char *name) {
	char *bus, *dup, *get;
	
	get = getenv (name);
	
	if (get == NULL) {
		return NULL;
	}
	
	bus = strchr (get, '=');
	
	if (!bus || bus == get) {
		return NULL;
	}
	
	dup = strdup (&get[1]);
	
	if (dup == NULL) {
		return NULL;
	}
	
	return dup;
}

int wait_for_ack_or_error (int s) {
	unsigned char buffer[128];
	int ret;
	
	ret = recv (s, buffer, sizeof (buffer), 0);
	
	if (ret < 3) {
		return -1;
	}
	
	if (buffer[0] == NET_INADOR_TYPE_RESPONSE_ERROR) {
		return -1;
	}
	
	if (buffer[0] == NET_INADOR_TYPE_RESPONSE && buffer[1] == NET_INADOR_RESPONSE_EXECUTED) {
		return 0;
	}
	
	return -1;
}

void send_basic (int s, char *interface, int tipo) {
	unsigned char buffer[128];
	
	buffer[0] = NET_INADOR_TYPE_COMMAND;
	buffer[1] = NET_INADOR_COMMAND_DHCP_CLIENT_FEED;
	
	buffer[2] = AF_INET;
	if (tipo == DHCP_CLIENT_SELECTING) {
		buffer[3] = NET_INADOR_DHCP_STATUS_SELECTING;
	} else if (tipo == DHCP_CLIENT_EXPIRED) {
		buffer[3] = NET_INADOR_DHCP_STATUS_EXPIRED;
	} else if (tipo == DHCP_CLIENT_FAILED) {
		buffer[3] = NET_INADOR_DHCP_STATUS_FAILED;
	}
	buffer[4] = strlen (interface);
	memset (&buffer[5], 0, 11);
	
	strncpy (&buffer[16], interface, buffer[4]);
	
	send (s, buffer, 16 + buffer[4], 0);
	
	if (wait_for_ack_or_error (s) < 0) {
		return;
	}
}

void send_bound_renew (int s, int is_bound, char *interface, struct in_addr *ip, int prefix, struct in_addr *gateways, int gw_c, struct in_addr *broadcast, struct in_addr *dhcp_server, uint32_t lease_time, struct in_addr *dns, int dns_c, char *domain_name) {
	unsigned char buffer[128];
	struct in_addr empty;
	int pos, g;
	
	memset (&empty, 0, sizeof (empty));
	
	buffer[0] = NET_INADOR_TYPE_COMMAND;
	buffer[1] = NET_INADOR_COMMAND_DHCP_CLIENT_FEED;
	
	buffer[2] = AF_INET;
	if (is_bound) {
		buffer[3] = NET_INADOR_DHCP_STATUS_BOUND;
	} else {
		buffer[3] = NET_INADOR_DHCP_STATUS_RENEWED;
	}
	buffer[4] = strlen (interface);
	memset (&buffer[5], 0, 11);
	
	buffer[6] = prefix;
	
	if (lease_time != 0) {
		memcpy (&buffer[12], &lease_time, 4);
	}
	
	pos = 16;
	
	/* Copiar el nombre de la interfaz */
	strncpy (&buffer[16], interface, buffer[4]);
	pos = 16 + buffer[4];
	
	if (memcmp (&empty, ip, sizeof (empty)) != 0) {
		/* Tenemos una IP */
		buffer[5] = 4;
		memcpy (&buffer[pos], ip, 4);
		pos += 4;
	}
	
	/* Procesar las múltiples rutas posibles */
	buffer[7] = 4 * gw_c;
	for (g = 0; g < gw_c; g++) {
		memcpy (&buffer[pos], &gateways[g], 4);
		pos += 4;
	}
	
	if (memcmp (&empty, broadcast, sizeof (empty)) != 0) {
		/* Tenemos broadcast */
		buffer[8] = 4;
		memcpy (&buffer[pos], broadcast, 4);
		pos += 4;
	}
	
	if (memcmp (&empty, dhcp_server, sizeof (empty)) != 0) {
		/* Tenemos IP del servidor DHCP */
		buffer[9] = 4;
		memcpy (&buffer[pos], dhcp_server, 4);
		pos += 4;
	}
	
	/* Procesar los múltiples dns */
	buffer[10] = 4 * dns_c;
	for (g = 0; g < dns_c; g++) {
		memcpy (&buffer[pos], &dns[g], 4);
		pos += 4;
	}
	
	/* Procesar el nombre de dominio */
	if (domain_name != NULL && domain_name[0] != 0) {
		buffer[11] = strlen (domain_name);
		memcpy (&buffer[pos], domain_name, buffer[11]);
		pos += buffer[11];
	}
	send (s, buffer, pos, 0);
	
	if (wait_for_ack_or_error (s) < 0) {
		return;
	}
}

int parse_ip (char *var, struct in_addr *addr) {
	int res;
	
	if (var == NULL) {
		return -1;
	}
	
	res = inet_pton (AF_INET, var, addr);
	
	if (res <= 0) {
		memset (addr, 0, sizeof (*addr));
		
		return -1;
	}
	
	return 0;
}

int parse_multiple_ip (char *var, struct in_addr *addr, int max) {
	int res;
	char buffer[512];
	char *inicio, *bus;
	int c = 0;
	size_t offset;
	
	if (var == NULL) return 0;
	
	inicio = var;
	while (inicio[0] != 0) {
		bus = strchr (inicio, ' ');
		
		if (bus == NULL) break;
		
		/* Desboardamiento */
		offset = bus - inicio;
		
		if (offset + 1 > sizeof (buffer)) {
			return 0;
		}
		strncpy (buffer, inicio, offset);
		buffer[offset] = 0;
		inicio = &var[offset + 1];
		
		res = parse_ip (buffer, &addr[c]);
		if (res < 0) continue;
		
		c++;
		if (c == max) return c;
	}
	
	/* Parsear lo último, si es que queda algo */
	if (inicio[0] != 0) {
		res = parse_ip (inicio, &addr[c]);
		if (res < 0) {
			return c;
		}
		
		c++;
	}
	
	return c;
}

int parse_int (char *var, int *entero) {
	int res;
	
	if (var == NULL) {
		return -1;
	}
	
	res = sscanf (var, "%i", entero);
	
	if (res <= 0) {
		*entero = 0;
		
		return -1;
	}
	
	return 0;
}

enum {
	IFACE_ISC_DHCLIENT = 1,
	IFACE_BUSYBOX_UDHCPC
};

const char *isc_dhcp_reasons[] = {
	"MEDIUM",
	"PREINIT",
	"BOUND",
	"RENEW",
	"REBIND",
	"REBOOT",
	"EXPIRE",
	"FAIL",
	"STOP",
	"RELEASE",
	"NBI",
	"TIMEOUT",
	NULL
};

const char *busybox_dhcp_argv[] = {
	"deconfig",
	"bound",
	"renew",
	"nak"
};

int main (int argc, char *argv[]) {
	char *reason, *interface;
	int s, ret, tipo;
	struct sockaddr_un path_dest;
	struct in_addr ip, netmask, broadcast, dhcp_server;
	struct in_addr gateways[7];
	struct in_addr dns[7];
	int gw_c, dns_c;
	
	int prefix, lease_time;
	
	debug (argc, argv);
	tipo = 0;
	
	/* Tratar de determinar si estamos siendo corridos por un el DHCP del ISC o por el udhcpc busybox */
	reason = getenv ("reason");
	
	if (reason != NULL) {
		s = 0;
		while (isc_dhcp_reasons[s] != NULL) {
			if (strcmp (reason, isc_dhcp_reasons[s]) == 0) {
				/* Es un ISC DHCP Client */
				tipo = IFACE_ISC_DHCLIENT;
				break;
			}
			s++;
		}
	}
	
	if (tipo == 0 && argc > 1) {
		/* Intentar revisar si es un busybox udhcpc */
		s = 0;
		while (busybox_dhcp_argv[s] != NULL) {
			if (strcmp (argv[1], busybox_dhcp_argv[s]) == 0) {
				tipo = IFACE_BUSYBOX_UDHCPC;
				reason = argv[1];
				break;
			}
			s++;
		}
	}
	
	if (tipo == 0) {
		return 1;
	}
	
	interface = getenv ("interface");
	
	if (reason == NULL || interface == NULL) {
		return 1;
	}
	
	/* Intentar abrir el socket a la escucha */
	s = socket (AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0);
	
	if (s < 0) {
		return 1;
	}
	
	path_dest.sun_family = AF_UNIX;
	strncpy (path_dest.sun_path, COMMAND_SOCKET_PATH, sizeof (path_dest.sun_path));
	ret = connect (s, (struct sockaddr *) &path_dest, sizeof (path_dest));
	
	if (ret < 0) {
		perror ("Connect");
		close (s);
		return 1;
	}
	
	if (strcmp (reason, "PREINIT") == 0 || // ISC DHCP
	    strcmp (reason, "deconfig") == 0 // Busybox udhcpc
	    ) {
		send_basic (s, interface, DHCP_CLIENT_SELECTING);
	} if (strcmp (reason, "FAIL") == 0) {
		send_basic (s, interface, DHCP_CLIENT_FAILED);
	} else if (strcmp (reason, "BOUND") == 0 || strcmp (reason, "REBOOT") == 0 ||
		strcmp (reason, "RENEW") == 0 || strcmp (reason, "REBIND") == 0 || // 4 de ISC DHCP
		strcmp (reason, "bound") == 0 || strcmp (reason, "renew") == 0 // 2 de Busybox udhcpc
	) {
		/*
		 * Los valores más importantes recibidos:
		 * new_domain_name_servers -> los DNS
		 * new_expiry -> el timestamp de la hora
		 * new_domain_name -> DNS search name
		 * new_routers -> Lista de routers
		 * new_subnet_mask -> Máscara de red en formato largo
		 * new_broadcast_address -> Dirección broadcast
		 * new_ip_address -> Dirección IP
		 * new_dhcp_lease_time -> Tiempo en segundos
		 */
		/* Parsear y revisar las direcciones IP recibidas */
		char *s_ip, *s_mask, *s_gateway, *s_broadcast, *s_lease_time, *s_dhcp_server, *s_dns, *s_domain_name;
		if (tipo == IFACE_ISC_DHCLIENT) {
			s_ip = getenv ("new_ip_address");
			s_mask = getenv ("new_subnet_mask");
			s_gateway = getenv ("new_routers");
			s_broadcast = getenv ("new_broadcast_address");
			s_lease_time = getenv ("new_dhcp_lease_time");
			s_dhcp_server = getenv ("new_dhcp_server_identifier");
			s_dns = getenv ("new_domain_name_servers");
			s_domain_name = getenv ("new_domain_name");
		} else if (tipo == IFACE_BUSYBOX_UDHCPC) {
			s_ip = getenv ("ip");
			s_mask = getenv ("subnet");
			s_gateway = getenv ("router");
			s_broadcast = getenv ("broadcast");
			s_lease_time = getenv ("lease");
			s_dhcp_server = getenv ("serverid");
			s_dns = getenv ("dns");
			s_domain_name = getenv ("domain");
		}
		/* TODO: Faltan los DNS */
		
		if (parse_ip (s_ip, &ip) < 0) {
			close (s);
			return -1;
		}
		
		if (parse_ip (s_mask, &netmask) < 0) {
			close (s);
			return -1;
		}
		
		prefix = utils_ip4_netmask_to_prefix (netmask.s_addr);
		gw_c = parse_multiple_ip (s_gateway, gateways, 7);
		
		if (parse_ip (s_broadcast, &broadcast) < 0) {
			memset (&broadcast, 0, sizeof (broadcast));
		}
		
		if (parse_ip (s_dhcp_server, &dhcp_server) < 0) {
			memset (&dhcp_server, 0, sizeof (dhcp_server));
		}
		
		if (parse_int (s_lease_time, &lease_time) < 0) {
			lease_time = 0;
		}
		
		dns_c = parse_multiple_ip (s_dns, dns, 7);
		int is_bound = 0;
		if (strcmp (reason, "BOUND") == 0 || strcmp (reason, "REBOOT") == 0 || // Del ISC dhcp
		    strcmp (reason, "bound") == 0 // del busybox
		) {
			is_bound = 1;
		}
		send_bound_renew (s, is_bound, interface, &ip, prefix, gateways, gw_c, &broadcast, &dhcp_server, lease_time, dns, dns_c, s_domain_name);
	} else if (strcmp (reason, "EXPIRE") == 0 || strcmp (reason, "STOP") == 0 || strcmp (reason, "RELEASE") == 0) {
		/* Los mismos valores, pero con old_ */
		send_basic (s, interface, DHCP_CLIENT_EXPIRED);
	} else {
		send_basic (s, interface, DHCP_CLIENT_FAILED);
		close (s);
		
		return -1;
	}
	close (s);
	
	return 0;
}