1/*
2 * (C) 2014 by Pablo Neira Ayuso <pablo@netfilter.org>
3 *
4 * Based on code from ebt_log from:
5 *
6 * Bart De Schuymer <bdschuym@pandora.be>
7 * Harald Welte <laforge@netfilter.org>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
16#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/spinlock.h>
19#include <linux/skbuff.h>
20#include <linux/if_arp.h>
21#include <linux/ip.h>
22#include <net/route.h>
23
24#include <linux/netfilter.h>
25#include <linux/netfilter/xt_LOG.h>
26#include <net/netfilter/nf_log.h>
27
28static const struct nf_loginfo default_loginfo = {
29 .type = NF_LOG_TYPE_LOG,
30 .u = {
31 .log = {
32 .level = LOGLEVEL_NOTICE,
33 .logflags = NF_LOG_DEFAULT_MASK,
34 },
35 },
36};
37
38struct arppayload {
39 unsigned char mac_src[ETH_ALEN];
40 unsigned char ip_src[4];
41 unsigned char mac_dst[ETH_ALEN];
42 unsigned char ip_dst[4];
43};
44
45static void dump_arp_packet(struct nf_log_buf *m,
46 const struct nf_loginfo *info,
47 const struct sk_buff *skb, unsigned int nhoff)
48{
49 const struct arphdr *ah;
50 struct arphdr _arph;
51 const struct arppayload *ap;
52 struct arppayload _arpp;
53
54 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
55 if (ah == NULL) {
56 nf_log_buf_add(m, "TRUNCATED");
57 return;
58 }
59 nf_log_buf_add(m, "ARP HTYPE=%d PTYPE=0x%04x OPCODE=%d",
60 ntohs(ah->ar_hrd), ntohs(ah->ar_pro), ntohs(ah->ar_op));
61
62 /* If it's for Ethernet and the lengths are OK, then log the ARP
63 * payload.
64 */
65 if (ah->ar_hrd != htons(ARPHRD_ETHER) ||
66 ah->ar_hln != ETH_ALEN ||
67 ah->ar_pln != sizeof(__be32))
68 return;
69
70 ap = skb_header_pointer(skb, sizeof(_arph), sizeof(_arpp), &_arpp);
71 if (ap == NULL) {
72 nf_log_buf_add(m, " INCOMPLETE [%zu bytes]",
73 skb->len - sizeof(_arph));
74 return;
75 }
76 nf_log_buf_add(m, " MACSRC=%pM IPSRC=%pI4 MACDST=%pM IPDST=%pI4",
77 ap->mac_src, ap->ip_src, ap->mac_dst, ap->ip_dst);
78}
79
80static void nf_log_arp_packet(struct net *net, u_int8_t pf,
81 unsigned int hooknum, const struct sk_buff *skb,
82 const struct net_device *in,
83 const struct net_device *out,
84 const struct nf_loginfo *loginfo,
85 const char *prefix)
86{
87 struct nf_log_buf *m;
88
89 /* FIXME: Disabled from containers until syslog ns is supported */
90 if (!net_eq(net, &init_net) && !sysctl_nf_log_all_netns)
91 return;
92
93 m = nf_log_buf_open();
94
95 if (!loginfo)
96 loginfo = &default_loginfo;
97
98 nf_log_dump_packet_common(m, pf, hooknum, skb, in, out, loginfo,
99 prefix);
100 dump_arp_packet(m, loginfo, skb, 0);
101
102 nf_log_buf_close(m);
103}
104
105static struct nf_logger nf_arp_logger __read_mostly = {
106 .name = "nf_log_arp",
107 .type = NF_LOG_TYPE_LOG,
108 .logfn = nf_log_arp_packet,
109 .me = THIS_MODULE,
110};
111
112static int __net_init nf_log_arp_net_init(struct net *net)
113{
114 return nf_log_set(net, NFPROTO_ARP, &nf_arp_logger);
115}
116
117static void __net_exit nf_log_arp_net_exit(struct net *net)
118{
119 nf_log_unset(net, &nf_arp_logger);
120}
121
122static struct pernet_operations nf_log_arp_net_ops = {
123 .init = nf_log_arp_net_init,
124 .exit = nf_log_arp_net_exit,
125};
126
127static int __init nf_log_arp_init(void)
128{
129 int ret;
130
131 ret = register_pernet_subsys(&nf_log_arp_net_ops);
132 if (ret < 0)
133 return ret;
134
135 ret = nf_log_register(NFPROTO_ARP, &nf_arp_logger);
136 if (ret < 0) {
137 pr_err("failed to register logger\n");
138 goto err1;
139 }
140
141 return 0;
142
143err1:
144 unregister_pernet_subsys(&nf_log_arp_net_ops);
145 return ret;
146}
147
148static void __exit nf_log_arp_exit(void)
149{
150 unregister_pernet_subsys(&nf_log_arp_net_ops);
151 nf_log_unregister(&nf_arp_logger);
152}
153
154module_init(nf_log_arp_init);
155module_exit(nf_log_arp_exit);
156
157MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
158MODULE_DESCRIPTION("Netfilter ARP packet logging");
159MODULE_LICENSE("GPL");
160MODULE_ALIAS_NF_LOGGER(3, 0);
161