/* Command line utility to create GTP link */

/* (C) 2014 by sysmocom - s.f.m.c. GmbH
 * (C) 2016 by Pablo Neira Ayuso <pablo@netfilter.org>
 *
 * Author: Pablo Neira Ayuso <pablo@gnumonks.org>
 *
 * All Rights Reserved
 *
 * 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <libmnl/libmnl.h>
#include <linux/if.h>
#include <linux/if_link.h>
#include <linux/rtnetlink.h>

#include <linux/gtp.h>
#include <linux/if_link.h>

#include <libgtpnl/gtpnl.h>

int main(int argc, char *argv[])
{
	struct mnl_socket *nl;
	char buf[MNL_SOCKET_BUFFER_SIZE];
	struct nlmsghdr *nlh;
	struct ifinfomsg *ifm;
	int ret;
	unsigned int seq, portid;
	struct nlattr *nest, *nest2;

	if (argc != 3) {
		printf("Usage: %s <add|del> <device>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	if (!strcmp(argv[1], "del")) {
		printf("destroying gtp interface...\n");
		if (gtp_dev_destroy(argv[2]) < 0)
			perror("gtp_dev_destroy");

		return 0;
	}

	nlh = mnl_nlmsg_put_header(buf);
	nlh->nlmsg_type	= RTM_NEWLINK;
	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL |NLM_F_ACK;
	nlh->nlmsg_seq = seq = time(NULL);
	ifm = mnl_nlmsg_put_extra_header(nlh, sizeof(*ifm));
	ifm->ifi_family = AF_INET;
	ifm->ifi_change |= IFF_UP;
	ifm->ifi_flags |= IFF_UP;

	int fd1 = socket(AF_INET, SOCK_DGRAM, 0);
	int fd2 = socket(AF_INET, SOCK_DGRAM, 0);
	struct sockaddr_in sockaddr_fd1 = {
		.sin_family	= AF_INET,
		.sin_port	= htons(3386),
		.sin_addr	= {
			.s_addr 	= INADDR_ANY,
		},
	};
	struct sockaddr_in sockaddr_fd2 = {
		.sin_family	= AF_INET,
		.sin_port	= htons(2152),
		.sin_addr	= {
			.s_addr 	= INADDR_ANY,
		},
	};

	if (bind(fd1, (struct sockaddr *) &sockaddr_fd1,
		 sizeof(sockaddr_fd1)) < 0) {
		perror("bind");
		exit(EXIT_FAILURE);
	}
	if (bind(fd2, (struct sockaddr *) &sockaddr_fd2,
		 sizeof(sockaddr_fd2)) < 0) {
		perror("bind");
		exit(EXIT_FAILURE);
	}

	mnl_attr_put_str(nlh, IFLA_IFNAME, argv[2]);
	nest = mnl_attr_nest_start(nlh, IFLA_LINKINFO);
	mnl_attr_put_str(nlh, IFLA_INFO_KIND, "gtp");
	nest2 = mnl_attr_nest_start(nlh, IFLA_INFO_DATA);
	mnl_attr_put_u32(nlh, IFLA_GTP_FD0, fd1);
	mnl_attr_put_u32(nlh, IFLA_GTP_FD1, fd2);
	mnl_attr_put_u32(nlh, IFLA_GTP_PDP_HASHSIZE, 131072);
	mnl_attr_nest_end(nlh, nest2);
	mnl_attr_nest_end(nlh, nest);

	nl = mnl_socket_open(NETLINK_ROUTE);
	if (nl == NULL) {
		perror("mnl_socket_open");
		exit(EXIT_FAILURE);
	}

	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
		perror("mnl_socket_bind");
		exit(EXIT_FAILURE);
	}
	portid = mnl_socket_get_portid(nl);

	mnl_nlmsg_fprintf(stdout, nlh, nlh->nlmsg_len,
			  sizeof(struct ifinfomsg));

	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
		perror("mnl_socket_send");
		exit(EXIT_FAILURE);
	}

	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
	if (ret == -1) {
		perror("read");
		exit(EXIT_FAILURE);
	}

	ret = mnl_cb_run(buf, ret, seq, portid, NULL, NULL);
	if (ret == -1){
		perror("callback");
		exit(EXIT_FAILURE);
	}

	mnl_socket_close(nl);

	fprintf(stderr, "WARNING: attaching dummy socket descriptors. Keep "
			"this process running for testing purposes.\n");

	while (1) {
		struct sockaddr_in addr;
		socklen_t len = sizeof(addr);

		ret = recvfrom(fd1, buf, sizeof(buf), 0,
			       (struct sockaddr *)&addr, &len);
		printf("received %d bytes via UDP socket\n", ret);
	}

	return 0;
}