Commit 7a847c00 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso
Browse files

netfilter: nf_log: incorrect offset to network header 



NFPROTO_ARP is expecting to find the ARP header at the network offset.

In the particular case of ARP, HTYPE= field shows the initial bytes of
the ethernet header destination MAC address.

 netdev out: IN= OUT=bridge0 MACSRC=c2:76:e5:71:e1:de MACDST=36:b0:4a:e2:72:ea MACPROTO=0806 ARP HTYPE=14000 PTYPE=0x4ae2 OPCODE=49782

NFPROTO_NETDEV egress hook is also expecting to find the IP headers at
the network offset.

Fixes: 35b93951 ("netfilter: add generic ARP packet logger")
Reported-by: default avatarTom Yan <tom.ty89@gmail.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 0ed8f619

net/netfilter/nf_log_syslog.c

+4 −4
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ dump_arp_packet(struct nf_log_buf *m, 
	unsigned int logflags;

	struct arphdr _arph;



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

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

	if (!ah) {

		nf_log_buf_add(m, "TRUNCATED");

		return;
@@ -96,7 +96,7 @@ dump_arp_packet(struct nf_log_buf *m, 
	    ah->ar_pln != sizeof(__be32))

		return;



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

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

	if (!ap) {

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

			       skb->len - sizeof(_arph));
@@ -149,7 +149,7 @@ static void nf_log_arp_packet(struct net *net, u_int8_t pf, 


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

				  prefix);

	dump_arp_packet(m, loginfo, skb, 0);

	dump_arp_packet(m, loginfo, skb, skb_network_offset(skb));



	nf_log_buf_close(m);

}
@@ -850,7 +850,7 @@ static void nf_log_ip_packet(struct net *net, u_int8_t pf, 
	if (in)

		dump_mac_header(m, loginfo, skb);



	dump_ipv4_packet(net, m, loginfo, skb, 0);

	dump_ipv4_packet(net, m, loginfo, skb, skb_network_offset(skb));



	nf_log_buf_close(m);

}