kernel / tools / testing / selftests / net / ovpn / ovpn-cli.c

// SPDX-License-Identifier: GPL-2.0
/*  OpenVPN data channel accelerator
 *
 *  Copyright (C) 2020-2025 OpenVPN, Inc.
 *
 *  Author:	Antonio Quartulli <[e-mail]>
 */

#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <time.h>

#include <linux/ovpn.h>
#include <linux/types.h>
#include <linux/netlink.h>

#include <netlink/socket.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <netlink/genl/family.h>
#include <netlink/genl/ctrl.h>

#include <mbedtls/base64.h>
#include <mbedtls/error.h>

#include <sys/socket.h>

#include "kselftest.h"

/* defines to make checkpatch happy */
#define strscpy strncpy

/* libnl < 3.5.0 does not set the NLA_F_NESTED on its own, therefore we
 * have to explicitly do it to prevent the kernel from failing upon
 * parsing of the message
 */
#define nla_nest_start(_msg, _type) \
	nla_nest_start(_msg, (_type) | NLA_F_NESTED)

/* libnl < 3.11.0 does not implement nla_get_uint() */
uint64_t ovpn_nla_get_uint(struct nlattr *attr)
{
	if (nla_len(attr) == sizeof(uint32_t))
		return nla_get_u32(attr);
	else
		return nla_get_u64(attr);
}

typedef int (*ovpn_nl_cb)(struct nl_msg *msg, void *arg);

enum ovpn_key_direction {
	KEY_DIR_IN = 0,
	KEY_DIR_OUT,
};

#define KEY_LEN (256 / 8)
#define NONCE_LEN 8

#define PEER_ID_UNDEF 0x00FFFFFF
#define MAX_PEERS 10

struct nl_ctx {
	struct nl_sock *nl_sock;
	struct nl_msg *nl_msg;
	struct nl_cb *nl_cb;

	int ovpn_dco_id;
};

enum ovpn_cmd {
	CMD_INVALID,
	CMD_NEW_IFACE,
	CMD_DEL_IFACE,
	CMD_LISTEN,
	CMD_CONNECT,
	CMD_NEW_PEER,
	CMD_NEW_MULTI_PEER,
	CMD_SET_PEER,
	CMD_DEL_PEER,
	CMD_GET_PEER,
	CMD_NEW_KEY,
	CMD_DEL_KEY,
	CMD_GET_KEY,
	CMD_SWAP_KEYS,
	CMD_LISTEN_MCAST,
};

struct ovpn_ctx {
	enum ovpn_cmd cmd;

	__u8 key_enc[KEY_LEN];
	__u8 key_dec[KEY_LEN];
	__u8 nonce[NONCE_LEN];

	enum ovpn_cipher_alg cipher;

	sa_family_t sa_family;

	unsigned long peer_id, tx_id;
	unsigned long lport;

	union {
		struct sockaddr_in in4;
		struct sockaddr_in6 in6;
	} remote;

	union {
		struct sockaddr_in in4;
		struct sockaddr_in6 in6;
	} peer_ip;

	bool peer_ip_set;

	unsigned int ifindex;
	char ifname[IFNAMSIZ];
	enum ovpn_mode mode;
	bool mode_set;

	int socket;
	int cli_sockets[MAX_PEERS];

	__u32 keepalive_interval;
	__u32 keepalive_timeout;

	enum ovpn_key_direction key_dir;
	enum ovpn_key_slot key_slot;
	int key_id;

	uint32_t mark;
	bool asymm_id;

	const char *peers_file;
};

static int ovpn_nl_recvmsgs(struct nl_ctx *ctx)
{
	int ret;

	ret = nl_recvmsgs(ctx->nl_sock, ctx->nl_cb);

	switch (ret) {
	case -NLE_INTR:
		fprintf(stderr,
			"netlink received interrupt due to signal - ignoring\n");
		break;
	case -NLE_NOMEM:
		fprintf(stderr, "netlink out of memory error\n");
		break;
	case -NLE_AGAIN:
		fprintf(stderr,
			"netlink reports blocking read - aborting wait\n");
		break;
	default:
		if (ret)
			fprintf(stderr, "netlink reports error (%d): %s\n",
				ret, nl_geterror(-ret));
		break;
	}

	return ret;
}

static struct nl_ctx *nl_ctx_alloc_flags(struct ovpn_ctx *ovpn, int cmd,
					 int flags)
{
	struct nl_ctx *ctx;
	int err, ret;

	ctx = calloc(1, sizeof(*ctx));
	if (!ctx)
		return NULL;

	ctx->nl_sock = nl_socket_alloc();
	if (!ctx->nl_sock) {
		fprintf(stderr, "cannot allocate netlink socket\n");
		goto err_free;
	}

	nl_socket_set_buffer_size(ctx->nl_sock, 8192, 8192);

	ret = genl_connect(ctx->nl_sock);
	if (ret) {
		fprintf(stderr, "cannot connect to generic netlink: %s\n",
			nl_geterror(ret));
		goto err_sock;
	}

	/* enable Extended ACK for detailed error reporting */
	err = 1;
	setsockopt(nl_socket_get_fd(ctx->nl_sock), SOL_NETLINK, NETLINK_EXT_ACK,
		   &err, sizeof(err));

	ctx->ovpn_dco_id = genl_ctrl_resolve(ctx->nl_sock, OVPN_FAMILY_NAME);
	if (ctx->ovpn_dco_id < 0) {
		fprintf(stderr, "cannot find ovpn_dco netlink component: %d\n",
			ctx->ovpn_dco_id);
		goto err_free;
	}

	ctx->nl_msg = nlmsg_alloc();
	if (!ctx->nl_msg) {
		fprintf(stderr, "cannot allocate netlink message\n");
		goto err_sock;
	}

	ctx->nl_cb = nl_cb_alloc(NL_CB_DEFAULT);
	if (!ctx->nl_cb) {
		fprintf(stderr, "failed to allocate netlink callback\n");
		goto err_msg;
	}

	nl_socket_set_cb(ctx->nl_sock, ctx->nl_cb);

	genlmsg_put(ctx->nl_msg, 0, 0, ctx->ovpn_dco_id, 0, flags, cmd, 0);

	if (ovpn->ifindex > 0)
		NLA_PUT_U32(ctx->nl_msg, OVPN_A_IFINDEX, ovpn->ifindex);

	return ctx;
nla_put_failure:
err_msg:
	nlmsg_free(ctx->nl_msg);
err_sock:
	nl_socket_free(ctx->nl_sock);
err_free:
	free(ctx);
	return NULL;
}

static struct nl_ctx *nl_ctx_alloc(struct ovpn_ctx *ovpn, int cmd)
{
	return nl_ctx_alloc_flags(ovpn, cmd, 0);
}

static void nl_ctx_free(struct nl_ctx *ctx)
{
	if (!ctx)
		return;

	nl_socket_free(ctx->nl_sock);
	nlmsg_free(ctx->nl_msg);
	nl_cb_put(ctx->nl_cb);
	free(ctx);
}

static int ovpn_nl_cb_error(struct sockaddr_nl (*nla)__always_unused,
			    struct nlmsgerr *err, void *arg)
{
	struct nlmsghdr *nlh = (struct nlmsghdr *)err - 1;
	struct nlattr *tb_msg[NLMSGERR_ATTR_MAX + 1];
	int len = nlh->nlmsg_len;
	struct nlattr *attrs;
	int *ret = arg;
	int ack_len = sizeof(*nlh) + sizeof(int) + sizeof(*nlh);

	*ret = err->error;

	if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
		return NL_STOP;

	if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
		ack_len += err->msg.nlmsg_len - sizeof(*nlh);

	if (len <= ack_len)
		return NL_STOP;

	attrs = (void *)((uint8_t *)nlh + ack_len);
	len -= ack_len;

	nla_parse(tb_msg, NLMSGERR_ATTR_MAX, attrs, len, NULL);
	if (tb_msg[NLMSGERR_ATTR_MSG]) {
		len = strnlen((char *)nla_data(tb_msg[NLMSGERR_ATTR_MSG]),
			      nla_len(tb_msg[NLMSGERR_ATTR_MSG]));
		fprintf(stderr, "kernel error: %*s\n", len,
			(char *)nla_data(tb_msg[NLMSGERR_ATTR_MSG]));
	}

	if (tb_msg[NLMSGERR_ATTR_MISS_NEST]) {
		fprintf(stderr, "missing required nesting type %u\n",
			nla_get_u32(tb_msg[NLMSGERR_ATTR_MISS_NEST]));
	}

	if (tb_msg[NLMSGERR_ATTR_MISS_TYPE]) {
		fprintf(stderr, "missing required attribute type %u\n",
			nla_get_u32(tb_msg[NLMSGERR_ATTR_MISS_TYPE]));
	}

	return NL_STOP;
}

static int ovpn_nl_cb_finish(struct nl_msg (*msg)__always_unused,
			     void *arg)
{
	int *status = arg;

	*status = 0;
	return NL_SKIP;
}

static int ovpn_nl_cb_ack(struct nl_msg (*msg)__always_unused,
			  void *arg)
{
	int *status = arg;

	*status = 0;
	return NL_STOP;
}

static int ovpn_nl_msg_send(struct nl_ctx *ctx, ovpn_nl_cb cb)
{
	int status = 1;

	nl_cb_err(ctx->nl_cb, NL_CB_CUSTOM, ovpn_nl_cb_error, &status);
	nl_cb_set(ctx->nl_cb, NL_CB_FINISH, NL_CB_CUSTOM, ovpn_nl_cb_finish,
		  &status);
	nl_cb_set(ctx->nl_cb, NL_CB_ACK, NL_CB_CUSTOM, ovpn_nl_cb_ack, &status);

	if (cb)
		nl_cb_set(ctx->nl_cb, NL_CB_VALID, NL_CB_CUSTOM, cb, ctx);

	nl_send_auto_complete(ctx->nl_sock, ctx->nl_msg);

	while (status == 1)
		ovpn_nl_recvmsgs(ctx);

	if (status < 0)
		fprintf(stderr, "failed to send netlink message: %s (%d)\n",
			strerror(-status), status);

	return status;
}

static int ovpn_parse_key(const char *file, struct ovpn_ctx *ctx)
{
	int idx_enc, idx_dec, ret = -1;
	unsigned char *ckey = NULL;
	__u8 *bkey = NULL;
	size_t olen = 0;
	long ckey_len;
	FILE *fp;

	fp = fopen(file, "r");
	if (!fp) {
		fprintf(stderr, "cannot open: %s\n", file);
		return -1;
	}

	/* get file size */
	fseek(fp, 0L, SEEK_END);
	ckey_len = ftell(fp);
	rewind(fp);

	/* if the file is longer, let's just read a portion */
	if (ckey_len > 256)
		ckey_len = 256;

	ckey = malloc(ckey_len);
	if (!ckey)
		goto err;

	ret = fread(ckey, 1, ckey_len, fp);
	if (ret != ckey_len) {
		fprintf(stderr,
			"couldn't read enough data from key file: %dbytes read\n",
			ret);
		goto err;
	}

	olen = 0;
	ret = mbedtls_base64_decode(NULL, 0, &olen, ckey, ckey_len);
	if (ret != MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL) {
		char buf[256];

		mbedtls_strerror(ret, buf, sizeof(buf));
		fprintf(stderr, "unexpected base64 error1: %s (%d)\n", buf,
			ret);

		goto err;
	}

	bkey = malloc(olen);
	if (!bkey) {
		fprintf(stderr, "cannot allocate binary key buffer\n");
		goto err;
	}

	ret = mbedtls_base64_decode(bkey, olen, &olen, ckey, ckey_len);
	if (ret) {
		char buf[256];

		mbedtls_strerror(ret, buf, sizeof(buf));
		fprintf(stderr, "unexpected base64 error2: %s (%d)\n", buf,
			ret);

		goto err;
	}

	if (olen < 2 * KEY_LEN + NONCE_LEN) {
		fprintf(stderr,
			"not enough data in key file, found %zdB but needs %dB\n",
			olen, 2 * KEY_LEN + NONCE_LEN);
		goto err;
	}

	switch (ctx->key_dir) {
	case KEY_DIR_IN:
		idx_enc = 0;
		idx_dec = 1;
		break;
	case KEY_DIR_OUT:
		idx_enc = 1;
		idx_dec = 0;
		break;
	default:
		goto err;
	}

	memcpy(ctx->key_enc, bkey + KEY_LEN * idx_enc, KEY_LEN);
	memcpy(ctx->key_dec, bkey + KEY_LEN * idx_dec, KEY_LEN);
	memcpy(ctx->nonce, bkey + 2 * KEY_LEN, NONCE_LEN);

	ret = 0;

err:
	fclose(fp);
	free(bkey);
	free(ckey);

	return ret;
}

static int ovpn_parse_cipher(const char *cipher, struct ovpn_ctx *ctx)
{
	if (strcmp(cipher, "aes") == 0)
		ctx->cipher = OVPN_CIPHER_ALG_AES_GCM;
	else if (strcmp(cipher, "chachapoly") == 0)
		ctx->cipher = OVPN_CIPHER_ALG_CHACHA20_POLY1305;
	else if (strcmp(cipher, "none") == 0)
		ctx->cipher = OVPN_CIPHER_ALG_NONE;
	else
		return -ENOTSUP;

	return 0;
}

static int ovpn_parse_key_direction(const char *dir, struct ovpn_ctx *ctx)
{
	int in_dir;

	in_dir = strtoll(dir, NULL, 10);
	switch (in_dir) {
	case KEY_DIR_IN:
	case KEY_DIR_OUT:
		ctx->key_dir = in_dir;
		break;
	default:
		fprintf(stderr,
			"invalid key direction provided. Can be 0 or 1 only\n");
		return -1;
	}

	return 0;
}

static int ovpn_socket(struct ovpn_ctx *ctx, sa_family_t family, int proto)
{
	struct sockaddr_storage local_sock = { 0 };
	struct sockaddr_in6 *in6;
	struct sockaddr_in *in;
	int ret, s, sock_type;
	size_t sock_len;

	if (proto == IPPROTO_UDP)
		sock_type = SOCK_DGRAM;
	else if (proto == IPPROTO_TCP)
		sock_type = SOCK_STREAM;
	else
		return -EINVAL;

	s = socket(family, sock_type, 0);
	if (s < 0) {
		perror("cannot create socket");
		return -1;
	}

	switch (family) {
	case AF_INET:
		in = (struct sockaddr_in *)&local_sock;
		in->sin_family = family;
		in->sin_port = htons(ctx->lport);
		in->sin_addr.s_addr = htonl(INADDR_ANY);
		sock_len = sizeof(*in);
		break;
	case AF_INET6:
		in6 = (struct sockaddr_in6 *)&local_sock;
		in6->sin6_family = family;
		in6->sin6_port = htons(ctx->lport);
		in6->sin6_addr = in6addr_any;
		sock_len = sizeof(*in6);
		break;
	default:
		return -1;
	}

	int opt = 1;

	ret = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	if (ret < 0) {
		perror("setsockopt for SO_REUSEADDR");
		return ret;
	}

	ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &opt, sizeof(opt));
	if (ret < 0) {
		perror("setsockopt for SO_REUSEPORT");
		return ret;
	}

	if (ctx->mark != 0) {
		ret = setsockopt(s, SOL_SOCKET, SO_MARK, (void *)&ctx->mark,
				 sizeof(ctx->mark));
		if (ret < 0) {
			perror("setsockopt for SO_MARK");
			return ret;
		}
	}

	if (family == AF_INET6) {
		opt = 0;
		if (setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &opt,
			       sizeof(opt))) {
			perror("failed to set IPV6_V6ONLY");
			return -1;
		}
	}

	ret = bind(s, (struct sockaddr *)&local_sock, sock_len);
	if (ret < 0) {
		perror("cannot bind socket");
		goto err_socket;
	}

	ctx->socket = s;
	ctx->sa_family = family;
	return 0;

err_socket:
	close(s);
	return -1;
}

static int ovpn_udp_socket(struct ovpn_ctx *ctx, sa_family_t family)
{
	return ovpn_socket(ctx, family, IPPROTO_UDP);
}

static int ovpn_listen(struct ovpn_ctx *ctx, sa_family_t family)
{
	int ret;

	ret = ovpn_socket(ctx, family, IPPROTO_TCP);
	if (ret < 0)
		return ret;

	ret = listen(ctx->socket, 10);
	if (ret < 0) {
		perror("listen");
		close(ctx->socket);
		return -1;
	}

	return 0;
}

static int ovpn_accept(struct ovpn_ctx *ctx)
{
	socklen_t socklen;
	int ret;

	socklen = sizeof(ctx->remote);
	ret = accept(ctx->socket, (struct sockaddr *)&ctx->remote, &socklen);
	if (ret < 0) {
		perror("accept");
		goto err;
	}

	fprintf(stderr, "Connection received!\n");

	switch (socklen) {
	case sizeof(struct sockaddr_in):
	case sizeof(struct sockaddr_in6):
		break;
	default:
		fprintf(stderr, "error: expecting IPv4 or IPv6 connection\n");
		close(ret);
		ret = -EINVAL;
		goto err;
	}

	return ret;
err:
	close(ctx->socket);
	return ret;
}

static int ovpn_connect(struct ovpn_ctx *ovpn)
{
	socklen_t socklen;
	int s, ret;

	s = socket(ovpn->remote.in4.sin_family, SOCK_STREAM, 0);
	if (s < 0) {
		perror("cannot create socket");
		return -1;
	}

	switch (ovpn->remote.in4.sin_family) {
	case AF_INET:
		socklen = sizeof(struct sockaddr_in);
		break;
	case AF_INET6:
		socklen = sizeof(struct sockaddr_in6);
		break;
	default:
		return -EOPNOTSUPP;
	}

	ret = connect(s, (struct sockaddr *)&ovpn->remote, socklen);
	if (ret < 0) {
		perror("connect");
		goto err;
	}

	fprintf(stderr, "connected\n");

	ovpn->socket = s;

	return 0;
err:
	close(s);
	return ret;
}

static int ovpn_new_peer(struct ovpn_ctx *ovpn, bool is_tcp)
{
	struct nlattr *attr;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_PEER_NEW);
	if (!ctx)
		return -ENOMEM;

	attr = nla_nest_start(ctx->nl_msg, OVPN_A_PEER);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_ID, ovpn->peer_id);
	if (ovpn->asymm_id)
		NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_TX_ID, ovpn->tx_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_SOCKET, ovpn->socket);

	if (!is_tcp) {
		switch (ovpn->remote.in4.sin_family) {
		case AF_INET:
			NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_REMOTE_IPV4,
				    ovpn->remote.in4.sin_addr.s_addr);
			NLA_PUT_U16(ctx->nl_msg, OVPN_A_PEER_REMOTE_PORT,
				    ovpn->remote.in4.sin_port);
			break;
		case AF_INET6:
			NLA_PUT(ctx->nl_msg, OVPN_A_PEER_REMOTE_IPV6,
				sizeof(ovpn->remote.in6.sin6_addr),
				&ovpn->remote.in6.sin6_addr);
			NLA_PUT_U32(ctx->nl_msg,
				    OVPN_A_PEER_REMOTE_IPV6_SCOPE_ID,
				    ovpn->remote.in6.sin6_scope_id);
			NLA_PUT_U16(ctx->nl_msg, OVPN_A_PEER_REMOTE_PORT,
				    ovpn->remote.in6.sin6_port);
			break;
		default:
			fprintf(stderr,
				"Invalid family for remote socket address\n");
			goto nla_put_failure;
		}
	}

	if (ovpn->peer_ip_set) {
		switch (ovpn->peer_ip.in4.sin_family) {
		case AF_INET:
			NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_VPN_IPV4,
				    ovpn->peer_ip.in4.sin_addr.s_addr);
			break;
		case AF_INET6:
			NLA_PUT(ctx->nl_msg, OVPN_A_PEER_VPN_IPV6,
				sizeof(struct in6_addr),
				&ovpn->peer_ip.in6.sin6_addr);
			break;
		default:
			fprintf(stderr, "Invalid family for peer address\n");
			goto nla_put_failure;
		}
	}

	nla_nest_end(ctx->nl_msg, attr);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_set_peer(struct ovpn_ctx *ovpn)
{
	struct nlattr *attr;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_PEER_SET);
	if (!ctx)
		return -ENOMEM;

	attr = nla_nest_start(ctx->nl_msg, OVPN_A_PEER);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_ID, ovpn->peer_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_KEEPALIVE_INTERVAL,
		    ovpn->keepalive_interval);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_KEEPALIVE_TIMEOUT,
		    ovpn->keepalive_timeout);
	nla_nest_end(ctx->nl_msg, attr);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_del_peer(struct ovpn_ctx *ovpn)
{
	struct nlattr *attr;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_PEER_DEL);
	if (!ctx)
		return -ENOMEM;

	attr = nla_nest_start(ctx->nl_msg, OVPN_A_PEER);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_ID, ovpn->peer_id);
	nla_nest_end(ctx->nl_msg, attr);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_handle_peer(struct nl_msg *msg, void (*arg)__always_unused)
{
	struct nlattr *pattrs[OVPN_A_PEER_MAX + 1];
	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *attrs[OVPN_A_MAX + 1];
	__u16 rport = 0, lport = 0;

	nla_parse(attrs, OVPN_A_MAX, genlmsg_attrdata(gnlh, 0),
		  genlmsg_attrlen(gnlh, 0), NULL);

	if (!attrs[OVPN_A_PEER]) {
		fprintf(stderr, "no packet content in netlink message\n");
		return NL_SKIP;
	}

	nla_parse(pattrs, OVPN_A_PEER_MAX, nla_data(attrs[OVPN_A_PEER]),
		  nla_len(attrs[OVPN_A_PEER]), NULL);

	if (pattrs[OVPN_A_PEER_ID])
		fprintf(stderr, "* Peer %u\n",
			nla_get_u32(pattrs[OVPN_A_PEER_ID]));

	if (pattrs[OVPN_A_PEER_TX_ID])
		fprintf(stderr, "\tTX peer ID %u\n",
			nla_get_u32(pattrs[OVPN_A_PEER_TX_ID]));

	if (pattrs[OVPN_A_PEER_SOCKET_NETNSID])
		fprintf(stderr, "\tsocket NetNS ID: %d\n",
			nla_get_s32(pattrs[OVPN_A_PEER_SOCKET_NETNSID]));

	if (pattrs[OVPN_A_PEER_VPN_IPV4]) {
		char buf[INET_ADDRSTRLEN];

		inet_ntop(AF_INET, nla_data(pattrs[OVPN_A_PEER_VPN_IPV4]),
			  buf, sizeof(buf));
		fprintf(stderr, "\tVPN IPv4: %s\n", buf);
	}

	if (pattrs[OVPN_A_PEER_VPN_IPV6]) {
		char buf[INET6_ADDRSTRLEN];

		inet_ntop(AF_INET6, nla_data(pattrs[OVPN_A_PEER_VPN_IPV6]),
			  buf, sizeof(buf));
		fprintf(stderr, "\tVPN IPv6: %s\n", buf);
	}

	if (pattrs[OVPN_A_PEER_LOCAL_PORT])
		lport = ntohs(nla_get_u16(pattrs[OVPN_A_PEER_LOCAL_PORT]));

	if (pattrs[OVPN_A_PEER_REMOTE_PORT])
		rport = ntohs(nla_get_u16(pattrs[OVPN_A_PEER_REMOTE_PORT]));

	if (pattrs[OVPN_A_PEER_REMOTE_IPV6]) {
		void *ip = pattrs[OVPN_A_PEER_REMOTE_IPV6];
		char buf[INET6_ADDRSTRLEN];
		int scope_id = -1;

		if (pattrs[OVPN_A_PEER_REMOTE_IPV6_SCOPE_ID]) {
			void *p = pattrs[OVPN_A_PEER_REMOTE_IPV6_SCOPE_ID];

			scope_id = nla_get_u32(p);
		}

		inet_ntop(AF_INET6, nla_data(ip), buf, sizeof(buf));
		fprintf(stderr, "\tRemote: %s:%hu (scope-id: %u)\n", buf, rport,
			scope_id);

		if (pattrs[OVPN_A_PEER_LOCAL_IPV6]) {
			void *ip = pattrs[OVPN_A_PEER_LOCAL_IPV6];

			inet_ntop(AF_INET6, nla_data(ip), buf, sizeof(buf));
			fprintf(stderr, "\tLocal: %s:%hu\n", buf, lport);
		}
	}

	if (pattrs[OVPN_A_PEER_REMOTE_IPV4]) {
		void *ip = pattrs[OVPN_A_PEER_REMOTE_IPV4];
		char buf[INET_ADDRSTRLEN];

		inet_ntop(AF_INET, nla_data(ip), buf, sizeof(buf));
		fprintf(stderr, "\tRemote: %s:%hu\n", buf, rport);

		if (pattrs[OVPN_A_PEER_LOCAL_IPV4]) {
			void *p = pattrs[OVPN_A_PEER_LOCAL_IPV4];

			inet_ntop(AF_INET, nla_data(p), buf, sizeof(buf));
			fprintf(stderr, "\tLocal: %s:%hu\n", buf, lport);
		}
	}

	if (pattrs[OVPN_A_PEER_KEEPALIVE_INTERVAL]) {
		void *p = pattrs[OVPN_A_PEER_KEEPALIVE_INTERVAL];

		fprintf(stderr, "\tKeepalive interval: %u sec\n",
			nla_get_u32(p));
	}

	if (pattrs[OVPN_A_PEER_KEEPALIVE_TIMEOUT])
		fprintf(stderr, "\tKeepalive timeout: %u sec\n",
			nla_get_u32(pattrs[OVPN_A_PEER_KEEPALIVE_TIMEOUT]));

	if (pattrs[OVPN_A_PEER_VPN_RX_BYTES])
		fprintf(stderr, "\tVPN RX bytes: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_VPN_RX_BYTES]));

	if (pattrs[OVPN_A_PEER_VPN_TX_BYTES])
		fprintf(stderr, "\tVPN TX bytes: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_VPN_TX_BYTES]));

	if (pattrs[OVPN_A_PEER_VPN_RX_PACKETS])
		fprintf(stderr, "\tVPN RX packets: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_VPN_RX_PACKETS]));

	if (pattrs[OVPN_A_PEER_VPN_TX_PACKETS])
		fprintf(stderr, "\tVPN TX packets: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_VPN_TX_PACKETS]));

	if (pattrs[OVPN_A_PEER_LINK_RX_BYTES])
		fprintf(stderr, "\tLINK RX bytes: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_LINK_RX_BYTES]));

	if (pattrs[OVPN_A_PEER_LINK_TX_BYTES])
		fprintf(stderr, "\tLINK TX bytes: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_LINK_TX_BYTES]));

	if (pattrs[OVPN_A_PEER_LINK_RX_PACKETS])
		fprintf(stderr, "\tLINK RX packets: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_LINK_RX_PACKETS]));

	if (pattrs[OVPN_A_PEER_LINK_TX_PACKETS])
		fprintf(stderr, "\tLINK TX packets: %" PRIu64 "\n",
			ovpn_nla_get_uint(pattrs[OVPN_A_PEER_LINK_TX_PACKETS]));

	return NL_SKIP;
}

static int ovpn_get_peer(struct ovpn_ctx *ovpn)
{
	int flags = 0, ret = -1;
	struct nlattr *attr;
	struct nl_ctx *ctx;

	if (ovpn->peer_id == PEER_ID_UNDEF)
		flags = NLM_F_DUMP;

	ctx = nl_ctx_alloc_flags(ovpn, OVPN_CMD_PEER_GET, flags);
	if (!ctx)
		return -ENOMEM;

	if (ovpn->peer_id != PEER_ID_UNDEF) {
		attr = nla_nest_start(ctx->nl_msg, OVPN_A_PEER);
		NLA_PUT_U32(ctx->nl_msg, OVPN_A_PEER_ID, ovpn->peer_id);
		nla_nest_end(ctx->nl_msg, attr);
	}

	ret = ovpn_nl_msg_send(ctx, ovpn_handle_peer);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_new_key(struct ovpn_ctx *ovpn)
{
	struct nlattr *keyconf, *key_dir;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_KEY_NEW);
	if (!ctx)
		return -ENOMEM;

	keyconf = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_PEER_ID, ovpn->peer_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_SLOT, ovpn->key_slot);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_KEY_ID, ovpn->key_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_CIPHER_ALG, ovpn->cipher);

	key_dir = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF_ENCRYPT_DIR);
	NLA_PUT(ctx->nl_msg, OVPN_A_KEYDIR_CIPHER_KEY, KEY_LEN, ovpn->key_enc);
	NLA_PUT(ctx->nl_msg, OVPN_A_KEYDIR_NONCE_TAIL, NONCE_LEN, ovpn->nonce);
	nla_nest_end(ctx->nl_msg, key_dir);

	key_dir = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF_DECRYPT_DIR);
	NLA_PUT(ctx->nl_msg, OVPN_A_KEYDIR_CIPHER_KEY, KEY_LEN, ovpn->key_dec);
	NLA_PUT(ctx->nl_msg, OVPN_A_KEYDIR_NONCE_TAIL, NONCE_LEN, ovpn->nonce);
	nla_nest_end(ctx->nl_msg, key_dir);

	nla_nest_end(ctx->nl_msg, keyconf);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_del_key(struct ovpn_ctx *ovpn)
{
	struct nlattr *keyconf;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_KEY_DEL);
	if (!ctx)
		return -ENOMEM;

	keyconf = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_PEER_ID, ovpn->peer_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_SLOT, ovpn->key_slot);
	nla_nest_end(ctx->nl_msg, keyconf);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_handle_key(struct nl_msg *msg, void (*arg)__always_unused)
{
	struct nlattr *kattrs[OVPN_A_KEYCONF_MAX + 1];
	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *attrs[OVPN_A_MAX + 1];

	nla_parse(attrs, OVPN_A_MAX, genlmsg_attrdata(gnlh, 0),
		  genlmsg_attrlen(gnlh, 0), NULL);

	if (!attrs[OVPN_A_KEYCONF]) {
		fprintf(stderr, "no packet content in netlink message\n");
		return NL_SKIP;
	}

	nla_parse(kattrs, OVPN_A_KEYCONF_MAX, nla_data(attrs[OVPN_A_KEYCONF]),
		  nla_len(attrs[OVPN_A_KEYCONF]), NULL);

	if (kattrs[OVPN_A_KEYCONF_PEER_ID])
		fprintf(stderr, "* Peer %u\n",
			nla_get_u32(kattrs[OVPN_A_KEYCONF_PEER_ID]));
	if (kattrs[OVPN_A_KEYCONF_SLOT]) {
		fprintf(stderr, "\t- Slot: ");
		switch (nla_get_u32(kattrs[OVPN_A_KEYCONF_SLOT])) {
		case OVPN_KEY_SLOT_PRIMARY:
			fprintf(stderr, "primary\n");
			break;
		case OVPN_KEY_SLOT_SECONDARY:
			fprintf(stderr, "secondary\n");
			break;
		default:
			fprintf(stderr, "invalid (%u)\n",
				nla_get_u32(kattrs[OVPN_A_KEYCONF_SLOT]));
			break;
		}
	}
	if (kattrs[OVPN_A_KEYCONF_KEY_ID])
		fprintf(stderr, "\t- Key ID: %u\n",
			nla_get_u32(kattrs[OVPN_A_KEYCONF_KEY_ID]));
	if (kattrs[OVPN_A_KEYCONF_CIPHER_ALG]) {
		fprintf(stderr, "\t- Cipher: ");
		switch (nla_get_u32(kattrs[OVPN_A_KEYCONF_CIPHER_ALG])) {
		case OVPN_CIPHER_ALG_NONE:
			fprintf(stderr, "none\n");
			break;
		case OVPN_CIPHER_ALG_AES_GCM:
			fprintf(stderr, "aes-gcm\n");
			break;
		case OVPN_CIPHER_ALG_CHACHA20_POLY1305:
			fprintf(stderr, "chacha20poly1305\n");
			break;
		default:
			fprintf(stderr, "invalid (%u)\n",
				nla_get_u32(kattrs[OVPN_A_KEYCONF_CIPHER_ALG]));
			break;
		}
	}

	return NL_SKIP;
}

static int ovpn_get_key(struct ovpn_ctx *ovpn)
{
	struct nlattr *keyconf;
	struct nl_ctx *ctx;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_KEY_GET);
	if (!ctx)
		return -ENOMEM;

	keyconf = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_PEER_ID, ovpn->peer_id);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_SLOT, ovpn->key_slot);
	nla_nest_end(ctx->nl_msg, keyconf);

	ret = ovpn_nl_msg_send(ctx, ovpn_handle_key);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

static int ovpn_swap_keys(struct ovpn_ctx *ovpn)
{
	struct nl_ctx *ctx;
	struct nlattr *kc;
	int ret = -1;

	ctx = nl_ctx_alloc(ovpn, OVPN_CMD_KEY_SWAP);
	if (!ctx)
		return -ENOMEM;

	kc = nla_nest_start(ctx->nl_msg, OVPN_A_KEYCONF);
	NLA_PUT_U32(ctx->nl_msg, OVPN_A_KEYCONF_PEER_ID, ovpn->peer_id);
	nla_nest_end(ctx->nl_msg, kc);

	ret = ovpn_nl_msg_send(ctx, NULL);
nla_put_failure:
	nl_ctx_free(ctx);
	return ret;
}

/* Helper function used to easily add attributes to a rtnl message */
static int ovpn_addattr(struct nlmsghdr *n, int maxlen, int type,
			const void *data, int alen)
{
	int len = RTA_LENGTH(alen);
	struct rtattr *rta;

	if ((int)(NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len)) > maxlen)	{
		fprintf(stderr, "%s: rtnl: message exceeded bound of %d\n",
			__func__, maxlen);
		return -EMSGSIZE;
	}

	rta = nlmsg_tail(n);
	rta->rta_type = type;
	rta->rta_len = len;

	if (!data)
		memset(RTA_DATA(rta), 0, alen);
	else
		memcpy(RTA_DATA(rta), data, alen);

	n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);

	return 0;
}

static struct rtattr *ovpn_nest_start(struct nlmsghdr *msg, size_t max_size,
				      int attr)
{
	struct rtattr *nest = nlmsg_tail(msg);

	if (ovpn_addattr(msg, max_size, attr, NULL, 0) < 0)
		return NULL;

	return nest;
}

static void ovpn_nest_end(struct nlmsghdr *msg, struct rtattr *nest)
{
	nest->rta_len = (uint8_t *)nlmsg_tail(msg) - (uint8_t *)nest;
}

#define RT_SNDBUF_SIZE (1024 * 2)
#define RT_RCVBUF_SIZE (1024 * 4)

/* Open RTNL socket */
static int ovpn_rt_socket(void)
{
	int sndbuf = RT_SNDBUF_SIZE, rcvbuf = RT_RCVBUF_SIZE, fd;

	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
	if (fd < 0) {
		fprintf(stderr, "%s: cannot open netlink socket\n", __func__);
		return fd;
	}

	if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf,
		       sizeof(sndbuf)) < 0) {
		fprintf(stderr, "%s: SO_SNDBUF\n", __func__);
		close(fd);
		return -1;
	}

	if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf,
		       sizeof(rcvbuf)) < 0) {
		fprintf(stderr, "%s: SO_RCVBUF\n", __func__);
		close(fd);
		return -1;
	}

	return fd;
}

/* Bind socket to Netlink subsystem */
static int ovpn_rt_bind(int fd, uint32_t groups)
{
	struct sockaddr_nl local = { 0 };
	socklen_t addr_len;

	local.nl_family = AF_NETLINK;
	local.nl_groups = groups;

	if (bind(fd, (struct sockaddr *)&local, sizeof(local)) < 0) {
		fprintf(stderr, "%s: cannot bind netlink socket: %d\n",
			__func__, errno);
		return -errno;
	}

	addr_len = sizeof(local);
	if (getsockname(fd, (struct sockaddr *)&local, &addr_len) < 0) {
		fprintf(stderr, "%s: cannot getsockname: %d\n", __func__,
			errno);
		return -errno;
	}

	if (addr_len != sizeof(local)) {
		fprintf(stderr, "%s: wrong address length %d\n", __func__,
			addr_len);
		return -EINVAL;
	}

	if (local.nl_family != AF_NETLINK) {
		fprintf(stderr, "%s: wrong address family %d\n", __func__,
			local.nl_family);
		return -EINVAL;
	}

	return 0;
}

typedef int (*ovpn_parse_reply_cb)(struct nlmsghdr *msg, void *arg);

/* Send Netlink message and run callback on reply (if specified) */
static int ovpn_rt_send(struct nlmsghdr *payload, pid_t peer,
			unsigned int groups, ovpn_parse_reply_cb cb,
			void *arg_cb)
{
	int len, rem_len, fd, ret, rcv_len;
	struct sockaddr_nl nladdr = { 0 };
	struct nlmsgerr *err;
	struct nlmsghdr *h;
	char buf[1024 * 16];
	struct iovec iov = {
		.iov_base = payload,
		.iov_len = payload->nlmsg_len,
	};
	struct msghdr nlmsg = {
		.msg_name = &nladdr,
		.msg_namelen = sizeof(nladdr),
		.msg_iov = &iov,
		.msg_iovlen = 1,
	};

	nladdr.nl_family = AF_NETLINK;
	nladdr.nl_pid = peer;
	nladdr.nl_groups = groups;

	payload->nlmsg_seq = time(NULL);

	/* no need to send reply */
	if (!cb)
		payload->nlmsg_flags |= NLM_F_ACK;

	fd = ovpn_rt_socket();
	if (fd < 0) {
		fprintf(stderr, "%s: can't open rtnl socket\n", __func__);
		return -errno;
	}

	ret = ovpn_rt_bind(fd, 0);
	if (ret < 0) {
		fprintf(stderr, "%s: can't bind rtnl socket\n", __func__);
		ret = -errno;
		goto out;
	}

	ret = sendmsg(fd, &nlmsg, 0);
	if (ret < 0) {
		fprintf(stderr, "%s: rtnl: error on sendmsg()\n", __func__);
		ret = -errno;
		goto out;
	}

	/* prepare buffer to store RTNL replies */
	memset(buf, 0, sizeof(buf));
	iov.iov_base = buf;

	while (1) {
		/*
		 * iov_len is modified by recvmsg(), therefore has to be initialized before
		 * using it again
		 */
		iov.iov_len = sizeof(buf);
		rcv_len = recvmsg(fd, &nlmsg, 0);
		if (rcv_len < 0) {
			if (errno == EINTR || errno == EAGAIN) {
				fprintf(stderr, "%s: interrupted call\n",
					__func__);
				continue;
			}
			fprintf(stderr, "%s: rtnl: error on recvmsg()\n",
				__func__);
			ret = -errno;
			goto out;
		}

		if (rcv_len == 0) {
			fprintf(stderr,
				"%s: rtnl: socket reached unexpected EOF\n",
				__func__);
			ret = -EIO;
			goto out;
		}

		if (nlmsg.msg_namelen != sizeof(nladdr)) {
			fprintf(stderr,
				"%s: sender address length: %u (expected %zu)\n",
				__func__, nlmsg.msg_namelen, sizeof(nladdr));
			ret = -EIO;
			goto out;
		}

		h = (struct nlmsghdr *)buf;
		while (rcv_len >= (int)sizeof(*h)) {
			len = h->nlmsg_len;
			rem_len = len - sizeof(*h);

			if (rem_len < 0 || len > rcv_len) {
				if (nlmsg.msg_flags & MSG_TRUNC) {
					fprintf(stderr, "%s: truncated message\n",
						__func__);
					ret = -EIO;
					goto out;
				}
				fprintf(stderr, "%s: malformed message: len=%d\n",
					__func__, len);
				ret = -EIO;
				goto out;
			}

			if (h->nlmsg_type == NLMSG_DONE) {
				ret = 0;
				goto out;
			}

			if (h->nlmsg_type == NLMSG_ERROR) {
				err = (struct nlmsgerr *)NLMSG_DATA(h);
				if (rem_len < (int)sizeof(struct nlmsgerr)) {
					fprintf(stderr, "%s: ERROR truncated\n",
						__func__);
					ret = -EIO;
					goto out;
				}

				if (err->error) {
					fprintf(stderr, "%s: (%d) %s\n",
						__func__, err->error,
						strerror(-err->error));
					ret = err->error;
					goto out;
				}

				ret = 0;
				if (cb)	{
					int r = cb(h, arg_cb);

					if (r <= 0)
						ret = r;
				}
				goto out;
			}

			if (cb) {
				int r = cb(h, arg_cb);

				if (r <= 0) {
					ret = r;
					goto out;
				}
			} else {
				fprintf(stderr, "%s: RTNL: unexpected reply\n",
					__func__);
			}

			rcv_len -= NLMSG_ALIGN(len);
			h = (struct nlmsghdr *)((uint8_t *)h +
						NLMSG_ALIGN(len));
		}

		if (nlmsg.msg_flags & MSG_TRUNC) {
			fprintf(stderr, "%s: message truncated\n", __func__);
			continue;
		}

		if (rcv_len) {
			fprintf(stderr, "%s: rtnl: %d not parsed bytes\n",
				__func__, rcv_len);
			ret = -1;
			goto out;
		}
	}
out:
	close(fd);

	return ret;
}

struct ovpn_link_req {
	struct nlmsghdr n;
	struct ifinfomsg i;
	char buf[256];
};

static int ovpn_new_iface(struct ovpn_ctx *ovpn)
{
	struct rtattr *linkinfo, *data;
	struct ovpn_link_req req = { 0 };
	int ret = -1;

	fprintf(stdout, "Creating interface %s with mode %u\n", ovpn->ifname,
		ovpn->mode);

	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.i));
	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
	req.n.nlmsg_type = RTM_NEWLINK;

	if (ovpn_addattr(&req.n, sizeof(req), IFLA_IFNAME, ovpn->ifname,
			 strlen(ovpn->ifname) + 1) < 0)
		goto err;

	linkinfo = ovpn_nest_start(&req.n, sizeof(req), IFLA_LINKINFO);
	if (!linkinfo)
		goto err;

	if (ovpn_addattr(&req.n, sizeof(req), IFLA_INFO_KIND, OVPN_FAMILY_NAME,
			 strlen(OVPN_FAMILY_NAME) + 1) < 0)
		goto err;

	if (ovpn->mode_set) {
		data = ovpn_nest_start(&req.n, sizeof(req), IFLA_INFO_DATA);
		if (!data)
			goto err;

		if (ovpn_addattr(&req.n, sizeof(req), IFLA_OVPN_MODE,
				 &ovpn->mode, sizeof(uint8_t)) < 0)
			goto err;

		ovpn_nest_end(&req.n, data);
	}

	ovpn_nest_end(&req.n, linkinfo);

	req.i.ifi_family = AF_PACKET;

	ret = ovpn_rt_send(&req.n, 0, 0, NULL, NULL);
err:
	return ret;
}

static int ovpn_del_iface(struct ovpn_ctx *ovpn)
{
	struct ovpn_link_req req = { 0 };

	fprintf(stdout, "Deleting interface %s ifindex %u\n", ovpn->ifname,
		ovpn->ifindex);

	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.i));
	req.n.nlmsg_flags = NLM_F_REQUEST;
	req.n.nlmsg_type = RTM_DELLINK;

	req.i.ifi_family = AF_PACKET;
	req.i.ifi_index = ovpn->ifindex;

	return ovpn_rt_send(&req.n, 0, 0, NULL, NULL);
}

static int nl_seq_check(struct nl_msg (*msg)__always_unused,
			void (*arg)__always_unused)
{
	return NL_OK;
}

struct mcast_handler_args {
	const char *group;
	int id;
};

static int mcast_family_handler(struct nl_msg *msg, void *arg)
{
	struct mcast_handler_args *grp = arg;
	struct nlattr *tb[CTRL_ATTR_MAX + 1];
	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *mcgrp;
	int rem_mcgrp;

	nla_parse(tb, CTRL_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
		  genlmsg_attrlen(gnlh, 0), NULL);

	if (!tb[CTRL_ATTR_MCAST_GROUPS])
		return NL_SKIP;

	nla_for_each_nested(mcgrp, tb[CTRL_ATTR_MCAST_GROUPS], rem_mcgrp) {
		struct nlattr *tb_mcgrp[CTRL_ATTR_MCAST_GRP_MAX + 1];

		nla_parse(tb_mcgrp, CTRL_ATTR_MCAST_GRP_MAX,
			  nla_data(mcgrp), nla_len(mcgrp), NULL);

		if (!tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME] ||
		    !tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID])
			continue;
		if (strncmp(nla_data(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME]),
			    grp->group, nla_len(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME])))
			continue;
		grp->id = nla_get_u32(tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID]);
		break;
	}

	return NL_SKIP;
}

static int mcast_error_handler(struct sockaddr_nl (*nla)__always_unused,
			       struct nlmsgerr *err, void *arg)
{
	int *ret = arg;

	*ret = err->error;
	return NL_STOP;
}

static int mcast_ack_handler(struct nl_msg (*msg)__always_unused, void *arg)
{
	int *ret = arg;

	*ret = 0;
	return NL_STOP;
}

static int ovpn_handle_msg(struct nl_msg *msg, void *arg)
{
	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *attrs[OVPN_A_MAX + 1];
	struct nlmsghdr *nlh = nlmsg_hdr(msg);
	char ifname[IF_NAMESIZE];
	int *ret = arg;
	__u32 ifindex;

	fprintf(stderr, "received message from ovpn-dco\n");

	*ret = -1;

	if (!genlmsg_valid_hdr(nlh, 0)) {
		fprintf(stderr, "invalid header\n");
		return NL_STOP;
	}

	if (nla_parse(attrs, OVPN_A_MAX, genlmsg_attrdata(gnlh, 0),
		      genlmsg_attrlen(gnlh, 0), NULL)) {
		fprintf(stderr, "received bogus data from ovpn-dco\n");
		return NL_STOP;
	}

	if (!attrs[OVPN_A_IFINDEX]) {
		fprintf(stderr, "no ifindex in this message\n");
		return NL_STOP;
	}

	ifindex = nla_get_u32(attrs[OVPN_A_IFINDEX]);
	if (!if_indextoname(ifindex, ifname)) {
		fprintf(stderr, "cannot resolve ifname for ifindex: %u\n",
			ifindex);
		return NL_STOP;
	}

	switch (gnlh->cmd) {
	case OVPN_CMD_PEER_DEL_NTF:
		fprintf(stdout, "received CMD_PEER_DEL_NTF\n");
		break;
	case OVPN_CMD_PEER_FLOAT_NTF:
		fprintf(stdout, "received CMD_PEER_FLOAT_NTF\n");
		break;
	case OVPN_CMD_KEY_SWAP_NTF:
		fprintf(stdout, "received CMD_KEY_SWAP_NTF\n");
		break;
	default:
		fprintf(stderr, "received unknown command: %d\n", gnlh->cmd);
		return NL_STOP;
	}

	*ret = 0;
	return NL_OK;
}

static int ovpn_get_mcast_id(struct nl_sock *sock, const char *family,
			     const char *group)
{
	struct nl_msg *msg;
	struct nl_cb *cb;
	int ret, ctrlid;
	struct mcast_handler_args grp = {
		.group = group,
		.id = -ENOENT,
	};

	msg = nlmsg_alloc();
	if (!msg)
		return -ENOMEM;

	cb = nl_cb_alloc(NL_CB_DEFAULT);
	if (!cb) {
		ret = -ENOMEM;
		goto out_fail_cb;
	}

	ctrlid = genl_ctrl_resolve(sock, "nlctrl");

	genlmsg_put(msg, 0, 0, ctrlid, 0, 0, CTRL_CMD_GETFAMILY, 0);

	ret = -ENOBUFS;
	NLA_PUT_STRING(msg, CTRL_ATTR_FAMILY_NAME, family);

	ret = nl_send_auto_complete(sock, msg);
	if (ret < 0)
		goto nla_put_failure;

	ret = 1;

	nl_cb_err(cb, NL_CB_CUSTOM, mcast_error_handler, &ret);
	nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, mcast_ack_handler, &ret);
	nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, mcast_family_handler, &grp);

	while (ret > 0)
		nl_recvmsgs(sock, cb);

	if (ret == 0)
		ret = grp.id;
 nla_put_failure:
	nl_cb_put(cb);
 out_fail_cb:
	nlmsg_free(msg);
	return ret;
}

static int ovpn_listen_mcast(void)
{
	struct nl_sock *sock;
	struct nl_cb *cb;
	int mcid, ret;

	sock = nl_socket_alloc();
	if (!sock) {
		fprintf(stderr, "cannot allocate netlink socket\n");
		ret = -ENOMEM;
		goto err_free;
	}

	nl_socket_set_buffer_size(sock, 8192, 8192);

	ret = genl_connect(sock);
	if (ret < 0) {
		fprintf(stderr, "cannot connect to generic netlink: %s\n",
			nl_geterror(ret));
		goto err_free;
	}

	mcid = ovpn_get_mcast_id(sock, OVPN_FAMILY_NAME, OVPN_MCGRP_PEERS);
	if (mcid < 0) {
		fprintf(stderr, "cannot get mcast group: %s\n",
			nl_geterror(mcid));
		goto err_free;
	}

	ret = nl_socket_add_membership(sock, mcid);
	if (ret) {
		fprintf(stderr, "failed to join mcast group: %d\n", ret);
		goto err_free;
	}

	ret = 1;
	cb = nl_cb_alloc(NL_CB_DEFAULT);
	nl_cb_set(cb, NL_CB_SEQ_CHECK, NL_CB_CUSTOM, nl_seq_check, NULL);
	nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, ovpn_handle_msg, &ret);
	nl_cb_err(cb, NL_CB_CUSTOM, ovpn_nl_cb_error, &ret);

	while (ret == 1) {
		int err = nl_recvmsgs(sock, cb);

		if (err < 0) {
			fprintf(stderr,
				"cannot receive netlink message: (%d) %s\n",
				err, nl_geterror(-err));
			ret = -1;
			break;
		}
	}

	nl_cb_put(cb);
err_free:
	nl_socket_free(sock);
	return ret;
}

static void usage(const char *cmd)
{
	fprintf(stderr,
		"Usage %s <command> <iface> [arguments..]\n",
		cmd);
	fprintf(stderr, "where <command> can be one of the following\n\n");

	fprintf(stderr, "* new_iface <iface> [mode]: create new ovpn interface\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tmode:\n");
	fprintf(stderr, "\t\t- P2P for peer-to-peer mode (i.e. client)\n");
	fprintf(stderr, "\t\t- MP for multi-peer mode (i.e. server)\n");

	fprintf(stderr, "* del_iface <iface>: delete ovpn interface\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");

	fprintf(stderr,
		"* listen <iface> <lport> <id_type> <peers_file> [ipv6]: listen for incoming peer TCP connections\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tlport: TCP port to listen to\n");
	fprintf(stderr, "\tid_type:\n");
	fprintf(stderr,
		"\t\t- SYMM for ignoring the TX peer ID from the peers_file\n");
	fprintf(stderr,
		"\t\t- ASYMM for using the TX peer ID from the peers_file\n");
	fprintf(stderr,
		"\tpeers_file: file containing one peer per line: Line format:\n");
	fprintf(stderr, "\t\t<peer_id> <tx_id> <vpnaddr>\n");
	fprintf(stderr,
		"\tipv6: whether the socket should listen to the IPv6 wildcard address\n");

	fprintf(stderr,
		"* connect <iface> <peer_id> <tx_id> <raddr> <rport> [key_file]: start connecting peer of TCP-based VPN session\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr,
		"\tpeer_id: peer ID found in data packets received from this peer\n");
	fprintf(stderr,
		"\ttx_id: peer ID to be used when sending to this peer, 'none' for symmetric peer ID\n");
	fprintf(stderr, "\traddr: peer IP address to connect to\n");
	fprintf(stderr, "\trport: peer TCP port to connect to\n");
	fprintf(stderr,
		"\tkey_file: file containing the symmetric key for encryption\n");

	fprintf(stderr,
		"* new_peer <iface> <peer_id> <tx_id> <lport> <raddr> <rport> [vpnaddr]: add new peer\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr,
		"\tpeer_id: peer ID found in data packets received from this peer\n");
	fprintf(stderr,
		"\ttx_id: peer ID to be used when sending to this peer, 'none' for symmetric peer ID\n");
	fprintf(stderr, "\tlport: local UDP port to bind to\n");
	fprintf(stderr, "\traddr: peer IP address\n");
	fprintf(stderr, "\trport: peer UDP port\n");
	fprintf(stderr, "\tvpnaddr: peer VPN IP\n");

	fprintf(stderr,
		"* new_multi_peer <iface> <lport> <id_type> <peers_file> [mark]: add multiple peers as listed in the file\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tlport: local UDP port to bind to\n");
	fprintf(stderr, "\tid_type:\n");
	fprintf(stderr,
		"\t\t- SYMM for ignoring the TX peer ID from the peers_file\n");
	fprintf(stderr,
		"\t\t- ASYMM for using the TX peer ID from the peers_file\n");
	fprintf(stderr,
		"\tpeers_file: text file containing one peer per line. Line format:\n");
	fprintf(stderr,
		"\t\t<peer_id> <tx_id> <raddr> <rport> <laddr> <lport> <vpnaddr>\n");
	fprintf(stderr, "\tmark: socket FW mark value\n");

	fprintf(stderr,
		"* set_peer <iface> <peer_id> <keepalive_interval> <keepalive_timeout>: set peer attributes\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tpeer_id: peer ID of the peer to modify\n");
	fprintf(stderr,
		"\tkeepalive_interval: interval for sending ping messages\n");
	fprintf(stderr,
		"\tkeepalive_timeout: time after which a peer is timed out\n");

	fprintf(stderr, "* del_peer <iface> <peer_id>: delete peer\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tpeer_id: peer ID of the peer to delete\n");

	fprintf(stderr, "* get_peer <iface> [peer_id]: retrieve peer(s) status\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr,
		"\tpeer_id: peer ID of the peer to query. All peers are returned if omitted\n");

	fprintf(stderr,
		"* new_key <iface> <peer_id> <slot> <key_id> <cipher> <key_dir> <key_file>: set data channel key\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr,
		"\tpeer_id: peer ID of the peer to configure the key for\n");
	fprintf(stderr, "\tslot: either 1 (primary) or 2 (secondary)\n");
	fprintf(stderr, "\tkey_id: an ID from 0 to 7\n");
	fprintf(stderr,
		"\tcipher: cipher to use, supported: aes (AES-GCM), chachapoly (CHACHA20POLY1305)\n");
	fprintf(stderr,
		"\tkey_dir: key direction, must 0 on one host and 1 on the other\n");
	fprintf(stderr, "\tkey_file: file containing the pre-shared key\n");

	fprintf(stderr,
		"* del_key <iface> <peer_id> [slot]: erase existing data channel key\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tpeer_id: peer ID of the peer to modify\n");
	fprintf(stderr, "\tslot: slot to erase. PRIMARY if omitted\n");

	fprintf(stderr,
		"* get_key <iface> <peer_id> <slot>: retrieve non sensible key data\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tpeer_id: peer ID of the peer to query\n");
	fprintf(stderr, "\tslot: either 1 (primary) or 2 (secondary)\n");

	fprintf(stderr,
		"* swap_keys <iface> <peer_id>: swap content of primary and secondary key slots\n");
	fprintf(stderr, "\tiface: ovpn interface name\n");
	fprintf(stderr, "\tpeer_id: peer ID of the peer to modify\n");

	fprintf(stderr,
		"* listen_mcast: listen to ovpn netlink multicast messages\n");
}

static int ovpn_parse_remote(struct ovpn_ctx *ovpn, const char *host,
			     const char *service, const char *vpnip)
{
	int ret;
	struct addrinfo *result;
	struct addrinfo hints = {
		.ai_family = ovpn->sa_family,
		.ai_socktype = SOCK_DGRAM,
		.ai_protocol = IPPROTO_UDP
	};

	if (host) {
		ret = getaddrinfo(host, service, &hints, &result);
		if (ret) {
			fprintf(stderr, "getaddrinfo on remote error: %s\n",
				gai_strerror(ret));
			return -1;
		}

		if (!(result->ai_family == AF_INET &&
		      result->ai_addrlen == sizeof(struct sockaddr_in)) &&
		    !(result->ai_family == AF_INET6 &&
		      result->ai_addrlen == sizeof(struct sockaddr_in6))) {
			ret = -EINVAL;
			goto out;
		}

		memcpy(&ovpn->remote, result->ai_addr, result->ai_addrlen);
	}

	if (vpnip) {
		ret = getaddrinfo(vpnip, NULL, &hints, &result);
		if (ret) {
			fprintf(stderr, "getaddrinfo on vpnip error: %s\n",
				gai_strerror(ret));
			return -1;
		}

		if (!(result->ai_family == AF_INET &&
		      result->ai_addrlen == sizeof(struct sockaddr_in)) &&
		    !(result->ai_family == AF_INET6 &&
		      result->ai_addrlen == sizeof(struct sockaddr_in6))) {
			ret = -EINVAL;
			goto out;
		}

		memcpy(&ovpn->peer_ip, result->ai_addr, result->ai_addrlen);
		ovpn->sa_family = result->ai_family;

		ovpn->peer_ip_set = true;
	}

	ret = 0;
out:
	freeaddrinfo(result);
	return ret;
}

static int ovpn_parse_new_peer(struct ovpn_ctx *ovpn, const char *peer_id,
			       const char *tx_id, const char *raddr,
			       const char *rport, const char *vpnip)
{
	ovpn->peer_id = strtoul(peer_id, NULL, 10);
	if (errno == ERANGE || ovpn->peer_id > PEER_ID_UNDEF) {
		fprintf(stderr, "rx peer ID value out of range\n");
		return -1;
	}

	if (ovpn->asymm_id) {
		ovpn->tx_id = strtoul(tx_id, NULL, 10);
		if (errno == ERANGE || ovpn->tx_id > PEER_ID_UNDEF) {
			fprintf(stderr, "tx peer ID value out of range\n");
			return -1;
		}
	}

	return ovpn_parse_remote(ovpn, raddr, rport, vpnip);
}

static int ovpn_parse_key_slot(const char *arg, struct ovpn_ctx *ovpn)
{
	int slot = strtoul(arg, NULL, 10);

	if (errno == ERANGE || slot < 1 || slot > 2) {
		fprintf(stderr, "key slot out of range\n");
		return -1;
	}

	switch (slot) {
	case 1:
		ovpn->key_slot = OVPN_KEY_SLOT_PRIMARY;
		break;
	case 2:
		ovpn->key_slot = OVPN_KEY_SLOT_SECONDARY;
		break;
	}

	return 0;
}

static int ovpn_send_tcp_data(int socket)
{
	uint16_t len = htons(1000);
	uint8_t buf[1002];
	int ret;

	memcpy(buf, &len, sizeof(len));
	memset(buf + sizeof(len), 0x86, sizeof(buf) - sizeof(len));

	ret = send(socket, buf, sizeof(buf), MSG_NOSIGNAL);

	fprintf(stdout, "Sent %u bytes over TCP socket\n", ret);

	return ret > 0 ? 0 : ret;
}

static int ovpn_recv_tcp_data(int socket)
{
	uint8_t buf[1002];
	uint16_t len;
	int ret;

	ret = recv(socket, buf, sizeof(buf), MSG_NOSIGNAL);

	if (ret < 2) {
		fprintf(stderr, ">>>> Error while reading TCP data: %d\n", ret);
		return ret;
	}

	memcpy(&len, buf, sizeof(len));
	len = ntohs(len);

	fprintf(stdout, ">>>> Received %u bytes over TCP socket, header: %u\n",
		ret, len);

	return 0;
}

static enum ovpn_cmd ovpn_parse_cmd(const char *cmd)
{
	if (!strcmp(cmd, "new_iface"))
		return CMD_NEW_IFACE;

	if (!strcmp(cmd, "del_iface"))
		return CMD_DEL_IFACE;

	if (!strcmp(cmd, "listen"))
		return CMD_LISTEN;

	if (!strcmp(cmd, "connect"))
		return CMD_CONNECT;

	if (!strcmp(cmd, "new_peer"))
		return CMD_NEW_PEER;

	if (!strcmp(cmd, "new_multi_peer"))
		return CMD_NEW_MULTI_PEER;

	if (!strcmp(cmd, "set_peer"))
		return CMD_SET_PEER;

	if (!strcmp(cmd, "del_peer"))
		return CMD_DEL_PEER;

	if (!strcmp(cmd, "get_peer"))
		return CMD_GET_PEER;

	if (!strcmp(cmd, "new_key"))
		return CMD_NEW_KEY;

	if (!strcmp(cmd, "del_key"))
		return CMD_DEL_KEY;

	if (!strcmp(cmd, "get_key"))
		return CMD_GET_KEY;

	if (!strcmp(cmd, "swap_keys"))
		return CMD_SWAP_KEYS;

	if (!strcmp(cmd, "listen_mcast"))
		return CMD_LISTEN_MCAST;

	return CMD_INVALID;
}

/* Send process to background and waits for signal.
 *
 * This helper is called at the end of commands
 * creating sockets, so that the latter stay alive
 * along with the process that created them.
 *
 * A signal is expected to be delivered in order to
 * terminate the waiting processes
 */
static void ovpn_waitbg(void)
{
	daemon(1, 1);
	pause();
}

static int ovpn_run_cmd(struct ovpn_ctx *ovpn)
{
	char peer_id[10], tx_id[10], vpnip[INET6_ADDRSTRLEN], laddr[128];
	char lport[10], raddr[128], rport[10];
	int n, ret;
	FILE *fp;

	switch (ovpn->cmd) {
	case CMD_NEW_IFACE:
		ret = ovpn_new_iface(ovpn);
		break;
	case CMD_DEL_IFACE:
		ret = ovpn_del_iface(ovpn);
		break;
	case CMD_LISTEN:
		ret = ovpn_listen(ovpn, ovpn->sa_family);
		if (ret < 0) {
			fprintf(stderr, "cannot listen on TCP socket\n");
			return ret;
		}

		fp = fopen(ovpn->peers_file, "r");
		if (!fp) {
			fprintf(stderr, "cannot open file: %s\n",
				ovpn->peers_file);
			return -1;
		}

		int num_peers = 0;

		while ((n = fscanf(fp, "%s %s %s\n", peer_id, tx_id,
				   vpnip)) == 3) {
			struct ovpn_ctx peer_ctx = { 0 };

			if (num_peers == MAX_PEERS) {
				fprintf(stderr, "max peers reached!\n");
				return -E2BIG;
			}

			peer_ctx.ifindex = ovpn->ifindex;
			peer_ctx.sa_family = ovpn->sa_family;
			peer_ctx.asymm_id = ovpn->asymm_id;

			peer_ctx.socket = ovpn_accept(ovpn);
			if (peer_ctx.socket < 0) {
				fprintf(stderr, "cannot accept connection!\n");
				return -1;
			}

			/* store peer sockets to test TCP I/O */
			ovpn->cli_sockets[num_peers] = peer_ctx.socket;

			ret = ovpn_parse_new_peer(&peer_ctx, peer_id, tx_id,
						  NULL, NULL, vpnip);
			if (ret < 0) {
				fprintf(stderr, "error while parsing line\n");
				return -1;
			}

			ret = ovpn_new_peer(&peer_ctx, true);
			if (ret < 0) {
				fprintf(stderr,
					"cannot add peer to VPN: %s %s\n",
					peer_id, vpnip);
				return ret;
			}
			num_peers++;
		}

		for (int i = 0; i < num_peers; i++) {
			ret = ovpn_recv_tcp_data(ovpn->cli_sockets[i]);
			if (ret < 0)
				break;
		}
		ovpn_waitbg();
		break;
	case CMD_CONNECT:
		ret = ovpn_connect(ovpn);
		if (ret < 0) {
			fprintf(stderr, "cannot connect TCP socket\n");
			return ret;
		}

		ret = ovpn_new_peer(ovpn, true);
		if (ret < 0) {
			fprintf(stderr, "cannot add peer to VPN\n");
			close(ovpn->socket);
			return ret;
		}

		if (ovpn->cipher != OVPN_CIPHER_ALG_NONE) {
			ret = ovpn_new_key(ovpn);
			if (ret < 0) {
				fprintf(stderr, "cannot set key\n");
				return ret;
			}
		}

		ret = ovpn_send_tcp_data(ovpn->socket);
		ovpn_waitbg();
		break;
	case CMD_NEW_PEER:
		ret = ovpn_udp_socket(ovpn, AF_INET6);
		if (ret < 0)
			return ret;

		ret = ovpn_new_peer(ovpn, false);
		ovpn_waitbg();
		break;
	case CMD_NEW_MULTI_PEER:
		ret = ovpn_udp_socket(ovpn, AF_INET6);
		if (ret < 0)
			return ret;

		fp = fopen(ovpn->peers_file, "r");
		if (!fp) {
			fprintf(stderr, "cannot open file: %s\n",
				ovpn->peers_file);
			return -1;
		}

		while ((n = fscanf(fp, "%s %s %s %s %s %s %s\n", peer_id, tx_id,
				   laddr, lport, raddr, rport, vpnip)) == 7) {
			struct ovpn_ctx peer_ctx = { 0 };

			peer_ctx.ifindex = ovpn->ifindex;
			peer_ctx.socket = ovpn->socket;
			peer_ctx.sa_family = AF_UNSPEC;
			peer_ctx.asymm_id = ovpn->asymm_id;

			ret = ovpn_parse_new_peer(&peer_ctx, peer_id, tx_id,
						  raddr, rport, vpnip);
			if (ret < 0) {
				fprintf(stderr, "error while parsing line\n");
				return -1;
			}

			ret = ovpn_new_peer(&peer_ctx, false);
			if (ret < 0) {
				fprintf(stderr,
					"cannot add peer to VPN: %s %s %s %s\n",
					peer_id, raddr, rport, vpnip);
				return ret;
			}
		}
		ovpn_waitbg();
		break;
	case CMD_SET_PEER:
		ret = ovpn_set_peer(ovpn);
		break;
	case CMD_DEL_PEER:
		ret = ovpn_del_peer(ovpn);
		break;
	case CMD_GET_PEER:
		if (ovpn->peer_id == PEER_ID_UNDEF)
			fprintf(stderr, "List of peers connected to: %s\n",
				ovpn->ifname);

		ret = ovpn_get_peer(ovpn);
		break;
	case CMD_NEW_KEY:
		ret = ovpn_new_key(ovpn);
		break;
	case CMD_DEL_KEY:
		ret = ovpn_del_key(ovpn);
		break;
	case CMD_GET_KEY:
		ret = ovpn_get_key(ovpn);
		break;
	case CMD_SWAP_KEYS:
		ret = ovpn_swap_keys(ovpn);
		break;
	case CMD_LISTEN_MCAST:
		ret = ovpn_listen_mcast();
		break;
	case CMD_INVALID:
		ret = -EINVAL;
		break;
	}

	return ret;
}

static int ovpn_parse_cmd_args(struct ovpn_ctx *ovpn, int argc, char *argv[])
{
	int ret;

	/* no args required for LISTEN_MCAST */
	if (ovpn->cmd == CMD_LISTEN_MCAST)
		return 0;

	/* all commands need an ifname */
	if (argc < 3)
		return -EINVAL;

	strscpy(ovpn->ifname, argv[2], IFNAMSIZ - 1);
	ovpn->ifname[IFNAMSIZ - 1] = '\0';

	/* all commands, except NEW_IFNAME, needs an ifindex */
	if (ovpn->cmd != CMD_NEW_IFACE) {
		ovpn->ifindex = if_nametoindex(ovpn->ifname);
		if (!ovpn->ifindex) {
			fprintf(stderr, "cannot find interface: %s\n",
				strerror(errno));
			return -1;
		}
	}

	switch (ovpn->cmd) {
	case CMD_NEW_IFACE:
		if (argc < 4)
			break;

		if (!strcmp(argv[3], "P2P")) {
			ovpn->mode = OVPN_MODE_P2P;
		} else if (!strcmp(argv[3], "MP")) {
			ovpn->mode = OVPN_MODE_MP;
		} else {
			fprintf(stderr, "Cannot parse iface mode: %s\n",
				argv[3]);
			return -1;
		}
		ovpn->mode_set = true;
		break;
	case CMD_DEL_IFACE:
		break;
	case CMD_LISTEN:
		if (argc < 6)
			return -EINVAL;

		ovpn->lport = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE || ovpn->lport > 65535) {
			fprintf(stderr, "lport value out of range\n");
			return -1;
		}

		if (strcmp(argv[4], "SYMM") == 0) {
			ovpn->asymm_id = false;
		} else if (strcmp(argv[4], "ASYMM") == 0) {
			ovpn->asymm_id = true;
		} else {
			fprintf(stderr, "Cannot parse id type: %s\n", argv[4]);
			return -1;
		}

		ovpn->peers_file = argv[5];

		ovpn->sa_family = AF_INET;
		if (argc > 6 && !strcmp(argv[6], "ipv6"))
			ovpn->sa_family = AF_INET6;
		break;
	case CMD_CONNECT:
		if (argc < 7)
			return -EINVAL;

		ovpn->sa_family = AF_INET;
		ovpn->asymm_id = strcmp(argv[4], "none");

		ret = ovpn_parse_new_peer(ovpn, argv[3], argv[4], argv[5],
					  argv[6], NULL);
		if (ret < 0) {
			fprintf(stderr, "Cannot parse remote peer data\n");
			return -1;
		}

		if (argc > 7) {
			ovpn->key_slot = OVPN_KEY_SLOT_PRIMARY;
			ovpn->key_id = 0;
			ovpn->cipher = OVPN_CIPHER_ALG_AES_GCM;
			ovpn->key_dir = KEY_DIR_OUT;

			ret = ovpn_parse_key(argv[7], ovpn);
			if (ret)
				return -1;
		}
		break;
	case CMD_NEW_PEER:
		if (argc < 8)
			return -EINVAL;

		ovpn->asymm_id = strcmp(argv[4], "none");

		ovpn->lport = strtoul(argv[5], NULL, 10);
		if (errno == ERANGE || ovpn->lport > 65535) {
			fprintf(stderr, "lport value out of range\n");
			return -1;
		}

		const char *vpnip = (argc > 8) ? argv[8] : NULL;

		ret = ovpn_parse_new_peer(ovpn, argv[3], argv[4], argv[6],
					  argv[7], vpnip);
		if (ret < 0)
			return -1;
		break;
	case CMD_NEW_MULTI_PEER:
		if (argc < 6)
			return -EINVAL;

		ovpn->lport = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE || ovpn->lport > 65535) {
			fprintf(stderr, "lport value out of range\n");
			return -1;
		}

		if (!strcmp(argv[4], "SYMM")) {
			ovpn->asymm_id = false;
		} else if (!strcmp(argv[4], "ASYMM")) {
			ovpn->asymm_id = true;
		} else {
			fprintf(stderr, "Cannot parse id type: %s\n", argv[4]);
			return -1;
		}

		ovpn->peers_file = argv[5];

		ovpn->mark = 0;
		if (argc > 6) {
			ovpn->mark = strtoul(argv[6], NULL, 10);
			if (errno == ERANGE || ovpn->mark > UINT32_MAX) {
				fprintf(stderr, "mark value out of range\n");
				return -1;
			}
		}
		break;
	case CMD_SET_PEER:
		if (argc < 6)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE || ovpn->peer_id > PEER_ID_UNDEF) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}

		ovpn->keepalive_interval = strtoul(argv[4], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr,
				"keepalive interval value out of range\n");
			return -1;
		}

		ovpn->keepalive_timeout = strtoul(argv[5], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr,
				"keepalive interval value out of range\n");
			return -1;
		}
		break;
	case CMD_DEL_PEER:
		if (argc < 4)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE || ovpn->peer_id > PEER_ID_UNDEF) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}
		break;
	case CMD_GET_PEER:
		ovpn->peer_id = PEER_ID_UNDEF;
		if (argc > 3) {
			ovpn->peer_id = strtoul(argv[3], NULL, 10);
			if (errno == ERANGE || ovpn->peer_id > PEER_ID_UNDEF) {
				fprintf(stderr, "peer ID value out of range\n");
				return -1;
			}
		}
		break;
	case CMD_NEW_KEY:
		if (argc < 9)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}

		ret = ovpn_parse_key_slot(argv[4], ovpn);
		if (ret)
			return -1;

		ovpn->key_id = strtoul(argv[5], NULL, 10);
		if (errno == ERANGE || ovpn->key_id > 2) {
			fprintf(stderr, "key ID out of range\n");
			return -1;
		}

		ret = ovpn_parse_cipher(argv[6], ovpn);
		if (ret < 0)
			return -1;

		ret = ovpn_parse_key_direction(argv[7], ovpn);
		if (ret < 0)
			return -1;

		ret = ovpn_parse_key(argv[8], ovpn);
		if (ret)
			return -1;
		break;
	case CMD_DEL_KEY:
		if (argc < 4)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}

		ret = ovpn_parse_key_slot(argv[4], ovpn);
		if (ret)
			return ret;
		break;
	case CMD_GET_KEY:
		if (argc < 5)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}

		ret = ovpn_parse_key_slot(argv[4], ovpn);
		if (ret)
			return ret;
		break;
	case CMD_SWAP_KEYS:
		if (argc < 4)
			return -EINVAL;

		ovpn->peer_id = strtoul(argv[3], NULL, 10);
		if (errno == ERANGE) {
			fprintf(stderr, "peer ID value out of range\n");
			return -1;
		}
		break;
	case CMD_LISTEN_MCAST:
		break;
	case CMD_INVALID:
		break;
	}

	return 0;
}

int main(int argc, char *argv[])
{
	struct ovpn_ctx ovpn;
	int ret;

	if (argc < 2) {
		usage(argv[0]);
		return -1;
	}

	memset(&ovpn, 0, sizeof(ovpn));
	ovpn.sa_family = AF_UNSPEC;
	ovpn.cipher = OVPN_CIPHER_ALG_NONE;

	ovpn.cmd = ovpn_parse_cmd(argv[1]);
	if (ovpn.cmd == CMD_INVALID) {
		fprintf(stderr, "Error: unknown command.\n\n");
		usage(argv[0]);
		return -1;
	}

	ret = ovpn_parse_cmd_args(&ovpn, argc, argv);
	if (ret < 0) {
		fprintf(stderr, "Error: invalid arguments.\n\n");
		if (ret == -EINVAL)
			usage(argv[0]);
		return ret;
	}

	ret = ovpn_run_cmd(&ovpn);
	if (ret)
		fprintf(stderr, "Cannot execute command: %s (%d)\n",
			strerror(-ret), ret);

	return ret;
}