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/*
* (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_str(r, NFTNL_RULE_TABLE, table);
nftnl_rule_set_str(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 if (strcmp(argv[1], "inet") == 0)
family = NFPROTO_INET;
else {
fprintf(stderr, "Unknown family: ip, ip6, inet\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_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;
}
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