iproute2/ip/iptuntap.c

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * iptunnel.c	       "ip tuntap"
 *
 * Authors:	David Woodhouse <David.Woodhouse@intel.com>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include <linux/if_arp.h>
#include <pwd.h>
#include <grp.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <glob.h>

#include "rt_names.h"
#include "utils.h"
#include "ip_common.h"

static const char drv_name[] = "tun";

#define TUNDEV "/dev/net/tun"

static void usage(void) __attribute__((noreturn));

static void usage(void)
{
	fprintf(stderr,
		"Usage: ip tuntap { add | del | show | list | lst | help } [ dev PHYS_DEV ]\n"
		"       [ mode { tun | tap } ] [ user USER ] [ group GROUP ]\n"
		"       [ one_queue ] [ pi ] [ vnet_hdr ] [ multi_queue ] [ name NAME ]\n"
		"\n"
		"Where: USER  := { STRING | NUMBER }\n"
		"       GROUP := { STRING | NUMBER }\n");
	exit(-1);
}

static int tap_add_ioctl(struct ifreq *ifr, uid_t uid, gid_t gid)
{
	int fd;
	int ret = -1;

#ifdef IFF_TUN_EXCL
	ifr->ifr_flags |= IFF_TUN_EXCL;
#endif

	fd = open(TUNDEV, O_RDWR);
	if (fd < 0) {
		perror("open");
		return -1;
	}
	if (ioctl(fd, TUNSETIFF, ifr)) {
		perror("ioctl(TUNSETIFF)");
		goto out;
	}
	if (uid != -1 && ioctl(fd, TUNSETOWNER, uid)) {
		perror("ioctl(TUNSETOWNER)");
		goto out;
	}
	if (gid != -1 && ioctl(fd, TUNSETGROUP, gid)) {
		perror("ioctl(TUNSETGROUP)");
		goto out;
	}
	if (ioctl(fd, TUNSETPERSIST, 1)) {
		perror("ioctl(TUNSETPERSIST)");
		goto out;
	}
	ret = 0;
 out:
	close(fd);
	return ret;
}

static int tap_del_ioctl(struct ifreq *ifr)
{
	int fd = open(TUNDEV, O_RDWR);
	int ret = -1;

	if (fd < 0) {
		perror("open");
		return -1;
	}
	if (ioctl(fd, TUNSETIFF, ifr)) {
		perror("ioctl(TUNSETIFF)");
		goto out;
	}
	if (ioctl(fd, TUNSETPERSIST, 0)) {
		perror("ioctl(TUNSETPERSIST)");
		goto out;
	}
	ret = 0;
 out:
	close(fd);
	return ret;

}
static int parse_args(int argc, char **argv,
		      struct ifreq *ifr, uid_t *uid, gid_t *gid)
{
	memset(ifr, 0, sizeof(*ifr));

	ifr->ifr_flags |= IFF_NO_PI;

	while (argc > 0) {
		if (matches(*argv, "mode") == 0) {
			NEXT_ARG();
			if (matches(*argv, "tun") == 0) {
				if (ifr->ifr_flags & IFF_TAP) {
					fprintf(stderr, "You managed to ask for more than one tunnel mode.\n");
					exit(-1);
				}
				ifr->ifr_flags |= IFF_TUN;
			} else if (matches(*argv, "tap") == 0) {
				if (ifr->ifr_flags & IFF_TUN) {
					fprintf(stderr, "You managed to ask for more than one tunnel mode.\n");
					exit(-1);
				}
				ifr->ifr_flags |= IFF_TAP;
			} else {
				fprintf(stderr, "Unknown tunnel mode \"%s\"\n", *argv);
				exit(-1);
			}
		} else if (uid && matches(*argv, "user") == 0) {
			char *end;
			unsigned long user;

			NEXT_ARG();
			if (**argv && ((user = strtol(*argv, &end, 10)), !*end))
				*uid = user;
			else {
				struct passwd *pw = getpwnam(*argv);

				if (!pw) {
					fprintf(stderr, "invalid user \"%s\"\n", *argv);
					exit(-1);
				}
				*uid = pw->pw_uid;
			}
		} else if (gid && matches(*argv, "group") == 0) {
			char *end;
			unsigned long group;

			NEXT_ARG();

			if (**argv && ((group = strtol(*argv, &end, 10)), !*end))
				*gid = group;
			else {
				struct group *gr = getgrnam(*argv);

				if (!gr) {
					fprintf(stderr, "invalid group \"%s\"\n", *argv);
					exit(-1);
				}
				*gid = gr->gr_gid;
			}
		} else if (matches(*argv, "pi") == 0) {
			ifr->ifr_flags &= ~IFF_NO_PI;
		} else if (matches(*argv, "one_queue") == 0) {
			ifr->ifr_flags |= IFF_ONE_QUEUE;
		} else if (matches(*argv, "vnet_hdr") == 0) {
			ifr->ifr_flags |= IFF_VNET_HDR;
		} else if (matches(*argv, "multi_queue") == 0) {
			ifr->ifr_flags |= IFF_MULTI_QUEUE;
		} else if (matches(*argv, "dev") == 0) {
			NEXT_ARG();
			if (get_ifname(ifr->ifr_name, *argv))
				invarg("\"dev\" not a valid ifname", *argv);
		} else {
			if (matches(*argv, "name") == 0) {
				NEXT_ARG();
			} else if (matches(*argv, "help") == 0)
				usage();
			if (ifr->ifr_name[0])
				duparg2("name", *argv);
			if (get_ifname(ifr->ifr_name, *argv))
				invarg("\"name\" not a valid ifname", *argv);
		}
		argc--; argv++;
	}

	if (!(ifr->ifr_flags & TUN_TYPE_MASK)) {
		fprintf(stderr, "You failed to specify a tunnel mode\n");
		return -1;
	}

	return 0;
}


static int do_add(int argc, char **argv)
{
	struct ifreq ifr;
	uid_t uid = -1;
	gid_t gid = -1;

	if (parse_args(argc, argv, &ifr, &uid, &gid) < 0)
		return -1;

	return tap_add_ioctl(&ifr, uid, gid);
}

static int do_del(int argc, char **argv)
{
	struct ifreq ifr;

	if (parse_args(argc, argv, &ifr, NULL, NULL) < 0)
		return -1;

	return tap_del_ioctl(&ifr);
}

static void print_flags(long flags)
{
	open_json_array(PRINT_JSON, "flags");

	if (flags & IFF_TUN)
		print_string(PRINT_ANY, NULL, " %s", "tun");

	if (flags & IFF_TAP)
		print_string(PRINT_ANY, NULL, " %s", "tap");

	if (!(flags & IFF_NO_PI))
		print_string(PRINT_ANY, NULL, " %s", "pi");

	if (flags & IFF_ONE_QUEUE)
		print_string(PRINT_ANY, NULL, " %s", "one_queue");

	if (flags & IFF_MULTI_QUEUE)
		print_string(PRINT_ANY, NULL, " %s", "multi_queue");

	if (flags & IFF_VNET_HDR)
		print_string(PRINT_ANY, NULL, " %s", "vnet_hdr");

	if (flags & IFF_PERSIST)
		print_string(PRINT_ANY, NULL, " %s", "persist");

	if (!(flags & IFF_NOFILTER))
		print_string(PRINT_ANY, NULL, " %s", "filter");

	flags &= ~(IFF_TUN | IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE |
		   IFF_MULTI_QUEUE | IFF_VNET_HDR | IFF_PERSIST |
		   IFF_NOFILTER);
	if (flags)
		print_0xhex(PRINT_ANY, NULL, " %#llx", flags);

	close_json_array(PRINT_JSON, NULL);
}

static void show_processes(const char *name)
{
	glob_t globbuf = { };
	char **fd_path;
	int err;

	err = glob("/proc/[0-9]*/fd/[0-9]*", GLOB_NOSORT,
		   NULL, &globbuf);
	if (err)
		return;

	open_json_array(PRINT_JSON, "processes");

	fd_path = globbuf.gl_pathv;
	while (*fd_path) {
		const char *dev_net_tun = "/dev/net/tun";
		const size_t linkbuf_len = strlen(dev_net_tun) + 2;
		char linkbuf[linkbuf_len], *fdinfo;
		int pid, fd;
		FILE *f;

		if (sscanf(*fd_path, "/proc/%d/fd/%d", &pid, &fd) != 2)
			goto next;

		if (pid == getpid())
			goto next;

		err = readlink(*fd_path, linkbuf, linkbuf_len - 1);
		if (err < 0) {
			perror("readlink");
			goto next;
		}
		linkbuf[err] = '\0';
		if (strcmp(dev_net_tun, linkbuf))
			goto next;

		if (asprintf(&fdinfo, "/proc/%d/fdinfo/%d", pid, fd) < 0)
			goto next;

		f = fopen(fdinfo, "r");
		free(fdinfo);
		if (!f) {
			perror("fopen");
			goto next;
		}

		while (!feof(f)) {
			char *key = NULL, *value = NULL;

			err = fscanf(f, "%m[^:]: %ms\n", &key, &value);
			if (err == EOF) {
				if (ferror(f))
					perror("fscanf");
				break;
			} else if (err == 2 &&
				   !strcmp("iff", key) &&
				   !strcmp(name, value)) {
				SPRINT_BUF(pname);

				if (get_task_name(pid, pname, sizeof(pname)))
					print_string(PRINT_ANY, "name",
						     "%s", "<NULL>");
				else
					print_string(PRINT_ANY, "name",
						     "%s", pname);

				print_uint(PRINT_ANY, "pid", "(%d)", pid);
			}

			free(key);
			free(value);
		}
		if (fclose(f))
			perror("fclose");

next:
		++fd_path;
	}
	close_json_array(PRINT_JSON, NULL);

	globfree(&globbuf);
}

static int tuntap_filter_req(struct nlmsghdr *nlh, int reqlen)
{
	struct rtattr *linkinfo;
	int err;

	linkinfo = addattr_nest(nlh, reqlen, IFLA_LINKINFO);

	err = addattr_l(nlh, reqlen, IFLA_INFO_KIND,
			drv_name, sizeof(drv_name) - 1);
	if (err)
		return err;

	addattr_nest_end(nlh, linkinfo);

	return 0;
}

static int print_tuntap(struct nlmsghdr *n, void *arg)
{
	struct ifinfomsg *ifi = NLMSG_DATA(n);
	struct rtattr *tb[IFLA_MAX+1];
	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
	const char *name, *kind;
	long flags, owner = -1, group = -1;

	if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)
		return 0;

	if (n->nlmsg_len < NLMSG_LENGTH(sizeof(*ifi)))
		return -1;

	switch (ifi->ifi_type) {
	case ARPHRD_NONE:
	case ARPHRD_ETHER:
		break;
	default:
		return 0;
	}

	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), IFLA_PAYLOAD(n));

	if (!tb[IFLA_IFNAME])
		return 0;

	if (!tb[IFLA_LINKINFO])
		return 0;

	parse_rtattr_nested(linkinfo, IFLA_INFO_MAX, tb[IFLA_LINKINFO]);

	if (!linkinfo[IFLA_INFO_KIND])
		return 0;

	kind = rta_getattr_str(linkinfo[IFLA_INFO_KIND]);
	if (strcmp(kind, drv_name))
		return 0;

	name = rta_getattr_str(tb[IFLA_IFNAME]);

	if (read_prop(name, "tun_flags", &flags))
		return 0;
	if (read_prop(name, "owner", &owner))
		return 0;
	if (read_prop(name, "group", &group))
		return 0;

	open_json_object(NULL);
	print_color_string(PRINT_ANY, COLOR_IFNAME,
			   "ifname", "%s:", name);
	print_flags(flags);
	if (owner != -1)
		print_u64(PRINT_ANY, "user",
			   " user %ld", owner);
	if (group != -1)
		print_u64(PRINT_ANY, "group",
			   " group %ld", group);

	if (show_details) {
		print_string(PRINT_FP, NULL,
			     "%s\tAttached to processes:", _SL_);
		show_processes(name);
	}
	close_json_object();
	print_string(PRINT_FP, NULL, "%s", "\n");

	return 0;
}

static int do_show(int argc, char **argv)
{
	if (rtnl_linkdump_req_filter_fn(&rth, AF_UNSPEC,
					tuntap_filter_req) < 0) {
		perror("Cannot send dump request\n");
		return -1;
	}

	new_json_obj(json);

	if (rtnl_dump_filter(&rth, print_tuntap, NULL) < 0) {
		fprintf(stderr, "Dump terminated\n");
		delete_json_obj();
		return -1;
	}

	delete_json_obj();
	fflush(stdout);

	return 0;
}

int do_iptuntap(int argc, char **argv)
{
	if (argc > 0) {
		if (matches(*argv, "add") == 0)
			return do_add(argc-1, argv+1);
		if (matches(*argv, "delete") == 0)
			return do_del(argc-1, argv+1);
		if (matches(*argv, "show") == 0 ||
		    matches(*argv, "lst") == 0 ||
		    matches(*argv, "list") == 0)
			return do_show(argc-1, argv+1);
		if (matches(*argv, "help") == 0)
			usage();
	} else
		return do_show(0, NULL);

	fprintf(stderr, "Command \"%s\" is unknown, try \"ip tuntap help\".\n",
		*argv);
	exit(-1);
}

static void print_owner(FILE *f, uid_t uid)
{
	struct passwd *pw = getpwuid(uid);

	if (pw)
		print_string(PRINT_ANY, "user", "user %s ", pw->pw_name);
	else
		print_uint(PRINT_ANY, "user", "user %u ", uid);
}

static void print_group(FILE *f, gid_t gid)
{
	struct group *group = getgrgid(gid);

	if (group)
		print_string(PRINT_ANY, "group", "group %s ", group->gr_name);
	else
		print_uint(PRINT_ANY, "group", "group %u ", gid);
}

static void print_mq(FILE *f, struct rtattr *tb[])
{
	if (!tb[IFLA_TUN_MULTI_QUEUE] ||
	    !rta_getattr_u8(tb[IFLA_TUN_MULTI_QUEUE])) {
		if (is_json_context())
			print_bool(PRINT_JSON, "multi_queue", NULL, false);
		return;
	}

	print_bool(PRINT_ANY, "multi_queue", "multi_queue ", true);

	if (tb[IFLA_TUN_NUM_QUEUES]) {
		print_uint(PRINT_ANY, "numqueues", "numqueues %u ",
			   rta_getattr_u32(tb[IFLA_TUN_NUM_QUEUES]));
	}

	if (tb[IFLA_TUN_NUM_DISABLED_QUEUES]) {
		print_uint(PRINT_ANY, "numdisabled", "numdisabled %u ",
			   rta_getattr_u32(tb[IFLA_TUN_NUM_DISABLED_QUEUES]));
	}
}

static void print_type(FILE *f, __u8 type)
{
	SPRINT_BUF(buf);
	const char *str = buf;

	if (type == IFF_TUN)
		str = "tun";
	else if (type == IFF_TAP)
		str = "tap";
	else
		snprintf(buf, sizeof(buf), "UNKNOWN:%hhu", type);

	print_string(PRINT_ANY, "type", "type %s ", str);
}

static void tun_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
{
	if (!tb)
		return;

	if (tb[IFLA_TUN_TYPE])
		print_type(f, rta_getattr_u8(tb[IFLA_TUN_TYPE]));

	if (tb[IFLA_TUN_PI])
		print_on_off(PRINT_ANY, "pi", "pi %s ",
			     rta_getattr_u8(tb[IFLA_TUN_PI]));

	if (tb[IFLA_TUN_VNET_HDR]) {
		print_on_off(PRINT_ANY, "vnet_hdr", "vnet_hdr %s ",
			     rta_getattr_u8(tb[IFLA_TUN_VNET_HDR]));
	}

	print_mq(f, tb);

	if (tb[IFLA_TUN_PERSIST])
		print_on_off(PRINT_ANY, "persist", "persist %s ",
			     rta_getattr_u8(tb[IFLA_TUN_PERSIST]));

	if (tb[IFLA_TUN_OWNER])
		print_owner(f, rta_getattr_u32(tb[IFLA_TUN_OWNER]));

	if (tb[IFLA_TUN_GROUP])
		print_group(f, rta_getattr_u32(tb[IFLA_TUN_GROUP]));
}

struct link_util tun_link_util = {
	.id = "tun",
	.maxattr = IFLA_TUN_MAX,
	.print_opt = tun_print_opt,
};