summaryrefslogtreecommitdiffstats
path: root/examples/nft-rule-add.c
blob: 6aaf5a0650f8a99a19b27e444389a056fead954c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
/*
 * (C) 2012 by Pablo Neira Ayuso <pablo@netfilter.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 software has been sponsored by Sophos Astaro <http://www.sophos.com>
 */

#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stddef.h>	/* for offsetof */
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>

#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nf_tables.h>

#include <libmnl/libmnl.h>
#include <libnftnl/rule.h>
#include <libnftnl/expr.h>

static void add_payload(struct nftnl_rule *r, uint32_t base, uint32_t dreg,
			uint32_t offset, uint32_t len)
{
	struct nftnl_expr *e;

	e = nftnl_expr_alloc("payload");
	if (e == NULL) {
		perror("expr payload oom");
		exit(EXIT_FAILURE);
	}

	nftnl_expr_set_u32(e, NFTNL_EXPR_PAYLOAD_BASE, base);
	nftnl_expr_set_u32(e, NFTNL_EXPR_PAYLOAD_DREG, dreg);
	nftnl_expr_set_u32(e, NFTNL_EXPR_PAYLOAD_OFFSET, offset);
	nftnl_expr_set_u32(e, NFTNL_EXPR_PAYLOAD_LEN, len);

	nftnl_rule_add_expr(r, e);
}

static void add_cmp(struct nftnl_rule *r, uint32_t sreg, uint32_t op,
		    const void *data, uint32_t data_len)
{
	struct nftnl_expr *e;

	e = nftnl_expr_alloc("cmp");
	if (e == NULL) {
		perror("expr cmp oom");
		exit(EXIT_FAILURE);
	}

	nftnl_expr_set_u32(e, NFTNL_EXPR_CMP_SREG, sreg);
	nftnl_expr_set_u32(e, NFTNL_EXPR_CMP_OP, op);
	nftnl_expr_set(e, NFTNL_EXPR_CMP_DATA, data, data_len);

	nftnl_rule_add_expr(r, e);
}

static void add_counter(struct nftnl_rule *r)
{
	struct nftnl_expr *e;

	e = nftnl_expr_alloc("counter");
	if (e == NULL) {
		perror("expr counter oom");
		exit(EXIT_FAILURE);
	}

	nftnl_rule_add_expr(r, e);
}

static struct nftnl_rule *setup_rule(uint8_t family, const char *table,
				   const char *chain, const char *handle)
{
	struct nftnl_rule *r = NULL;
	uint8_t proto;
	uint16_t dport;
	uint64_t handle_num;

	r = nftnl_rule_alloc();
	if (r == NULL) {
		perror("OOM");
		exit(EXIT_FAILURE);
	}

	nftnl_rule_set(r, NFTNL_RULE_TABLE, table);
	nftnl_rule_set(r, NFTNL_RULE_CHAIN, chain);
	nftnl_rule_set_u32(r, NFTNL_RULE_FAMILY, family);

	if (handle != NULL) {
		handle_num = atoll(handle);
		nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, handle_num);
	}

	proto = IPPROTO_TCP;
	add_payload(r, NFT_PAYLOAD_NETWORK_HEADER, NFT_REG_1,
		    offsetof(struct iphdr, protocol), sizeof(uint8_t));
	add_cmp(r, NFT_REG_1, NFT_CMP_EQ, &proto, sizeof(uint8_t));

	dport = htons(22);
	add_payload(r, NFT_PAYLOAD_TRANSPORT_HEADER, NFT_REG_1,
		    offsetof(struct tcphdr, dest), sizeof(uint16_t));
	add_cmp(r, NFT_REG_1, NFT_CMP_EQ, &dport, sizeof(uint16_t));

	add_counter(r);

	return r;
}

int main(int argc, char *argv[])
{
	struct mnl_socket *nl;
	struct nftnl_rule *r;
	struct nlmsghdr *nlh;
	struct mnl_nlmsg_batch *batch;
	uint8_t family;
	char buf[MNL_SOCKET_BUFFER_SIZE];
	uint32_t seq = time(NULL);
	int ret;

	if (argc < 4 || argc > 5) {
		fprintf(stderr, "Usage: %s <family> <table> <chain>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	if (strcmp(argv[1], "ip") == 0)
		family = NFPROTO_IPV4;
	else if (strcmp(argv[1], "ip6") == 0)
		family = NFPROTO_IPV6;
	else {
		fprintf(stderr, "Unknown family: ip, ip6\n");
		exit(EXIT_FAILURE);
	}

	if (argc != 5)
		r = setup_rule(family, argv[2], argv[3], NULL);
	else
		r = setup_rule(family, argv[2], argv[3], argv[4]);

	nl = mnl_socket_open(NETLINK_NETFILTER);
	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);
	}

	batch = mnl_nlmsg_batch_start(buf, sizeof(buf));

	nftnl_batch_begin(mnl_nlmsg_batch_current(batch), seq++);
	mnl_nlmsg_batch_next(batch);

	nlh = nftnl_rule_nlmsg_build_hdr(mnl_nlmsg_batch_current(batch),
			NFT_MSG_NEWRULE,
			nftnl_rule_get_u32(r, NFTNL_RULE_FAMILY),
			NLM_F_APPEND|NLM_F_CREATE|NLM_F_ACK, seq++);

	nftnl_rule_nlmsg_build_payload(nlh, r);
	nftnl_rule_free(r);
	mnl_nlmsg_batch_next(batch);

	nftnl_batch_end(mnl_nlmsg_batch_current(batch), seq++);
	mnl_nlmsg_batch_next(batch);

	ret = mnl_socket_sendto(nl, mnl_nlmsg_batch_head(batch),
				mnl_nlmsg_batch_size(batch));
	if (ret == -1) {
		perror("mnl_socket_sendto");
		exit(EXIT_FAILURE);
	}

	mnl_nlmsg_batch_stop(batch);

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

	ret = mnl_cb_run(buf, ret, 0, mnl_socket_get_portid(nl), NULL, NULL);
	if (ret < 0) {
		perror("mnl_cb_run");
		exit(EXIT_FAILURE);
	}

	mnl_socket_close(nl);

	return EXIT_SUCCESS;
}