Commit 35b93951 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso
Browse files

netfilter: add generic ARP packet logger 



This adds the generic plain text packet loggger for ARP packets. It is
based on the ebt_log code. Nevertheless, the output has been modified
to make it consistent with the original xt_LOG output.

This is an example output:

IN=wlan0 OUT= ARP HTYPE=1 PTYPE=0x0800 OPCODE=2 MACSRC=00:ab:12:34:55:63 IPSRC=192.168.10.1 MACDST=80:09:12:70:4f:50 IPDST=192.168.10.150

This patch enables packet logging from ARP chains, eg.

  nft add rule arp filter input log prefix "input: "

Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent fab4085f

net/ipv4/netfilter/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -159,6 +159,11 @@ config IP_NF_TARGET_SYNPROXY 


	  To compile it as a module, choose M here. If unsure, say N.



config NF_LOG_ARP

	tristate "ARP packet logging"

	default m if NETFILTER_ADVANCED=n

	select NF_LOG_INET



config NF_LOG_IPV4

	tristate "IPv4 packet logging"

	default m if NETFILTER_ADVANCED=n

net/ipv4/netfilter/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ obj-$(CONFIG_NF_NAT_IPV4) += nf_nat_ipv4.o 
obj-$(CONFIG_NF_DEFRAG_IPV4) += nf_defrag_ipv4.o



# logging

obj-$(CONFIG_NF_LOG_ARP) += nf_log_arp.o

obj-$(CONFIG_NF_LOG_IPV4) += nf_log_ipv4.o



# NAT helpers (nf_conntrack)

net/ipv4/netfilter/nf_log_arp.c

0 → 100644
+149 −0
Original line number Diff line number Diff line 
/*

 * (C) 2014 by Pablo Neira Ayuso <pablo@netfilter.org>

 *

 * Based on code from ebt_log from:

 *

 * Bart De Schuymer <bdschuym@pandora.be>

 * Harald Welte <laforge@netfilter.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#include <linux/module.h>

#include <linux/spinlock.h>

#include <linux/skbuff.h>

#include <linux/if_arp.h>

#include <linux/ip.h>

#include <net/route.h>



#include <linux/netfilter.h>

#include <linux/netfilter/xt_LOG.h>

#include <net/netfilter/nf_log.h>



static struct nf_loginfo default_loginfo = {

	.type	= NF_LOG_TYPE_LOG,

	.u = {

		.log = {

			.level	  = 5,

			.logflags = NF_LOG_MASK,

		},

	},

};



struct arppayload {

	unsigned char mac_src[ETH_ALEN];

	unsigned char ip_src[4];

	unsigned char mac_dst[ETH_ALEN];

	unsigned char ip_dst[4];

};



static void dump_arp_packet(struct nf_log_buf *m,

			    const struct nf_loginfo *info,

			    const struct sk_buff *skb, unsigned int nhoff)

{

	const struct arphdr *ah;

	struct arphdr _arph;

	const struct arppayload *ap;

	struct arppayload _arpp;



	ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);

	if (ah == NULL) {

		nf_log_buf_add(m, "TRUNCATED");

		return;

	}

	nf_log_buf_add(m, "ARP HTYPE=%d PTYPE=0x%04x OPCODE=%d",

		       ntohs(ah->ar_hrd), ntohs(ah->ar_pro), ntohs(ah->ar_op));



	/* If it's for Ethernet and the lengths are OK, then log the ARP

	 * payload.

	 */

	if (ah->ar_hrd != htons(1) ||

	    ah->ar_hln != ETH_ALEN ||

	    ah->ar_pln != sizeof(__be32))

		return;



	ap = skb_header_pointer(skb, sizeof(_arph), sizeof(_arpp), &_arpp);

	if (ap == NULL) {

		nf_log_buf_add(m, " INCOMPLETE [%Zu bytes]",

			       skb->len - sizeof(_arph));

		return;

	}

	nf_log_buf_add(m, " MACSRC=%pM IPSRC=%pI4 MACDST=%pM IPDST=%pI4",

		       ap->mac_src, ap->ip_src, ap->mac_dst, ap->ip_dst);

}



void nf_log_arp_packet(struct net *net, u_int8_t pf,

		      unsigned int hooknum, const struct sk_buff *skb,

		      const struct net_device *in,

		      const struct net_device *out,

		      const struct nf_loginfo *loginfo,

		      const char *prefix)

{

	struct nf_log_buf *m;



	/* FIXME: Disabled from containers until syslog ns is supported */

	if (!net_eq(net, &init_net))

		return;



	m = nf_log_buf_open();



	if (!loginfo)

		loginfo = &default_loginfo;



	nf_log_dump_packet_common(m, pf, hooknum, skb, in, out, loginfo,

				  prefix);

	dump_arp_packet(m, loginfo, skb, 0);



	nf_log_buf_close(m);

}



static struct nf_logger nf_arp_logger __read_mostly = {

	.name		= "nf_log_arp",

	.type		= NF_LOG_TYPE_LOG,

	.logfn		= nf_log_arp_packet,

	.me		= THIS_MODULE,

};



static int __net_init nf_log_arp_net_init(struct net *net)

{

	nf_log_set(net, NFPROTO_ARP, &nf_arp_logger);

	return 0;

}



static void __net_exit nf_log_arp_net_exit(struct net *net)

{

	nf_log_unset(net, &nf_arp_logger);

}



static struct pernet_operations nf_log_arp_net_ops = {

	.init = nf_log_arp_net_init,

	.exit = nf_log_arp_net_exit,

};



static int __init nf_log_arp_init(void)

{

	int ret;



	ret = register_pernet_subsys(&nf_log_arp_net_ops);

	if (ret < 0)

		return ret;



	nf_log_register(NFPROTO_ARP, &nf_arp_logger);

	return 0;

}



static void __exit nf_log_arp_exit(void)

{

	unregister_pernet_subsys(&nf_log_arp_net_ops);

	nf_log_unregister(&nf_arp_logger);

}



module_init(nf_log_arp_init);

module_exit(nf_log_arp_exit);



MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");

MODULE_DESCRIPTION("Netfilter ARP packet logging");

MODULE_LICENSE("GPL");

MODULE_ALIAS_NF_LOGGER(3, 0);

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