include/linux/netfilter_bridge/ebt_arp.h

Maybe I'm wrong again, but I see there is a difference between file
ebtables-v2.0.5/include/linux/netfilter_bridge/ebt_arp.h in the user-space
utility package ebtables-v2.0.5.tar.gz and
/usr/src/linux/include/linux/netfilter_bridge/ebt_arp.h, generated by the
kernel patch ebtables-v2.0.003_vs_2.4.20.diff.gz. In user-space, it is:

struct ebt_arp_info
{
	uint16_t htype;
	uint16_t ptype;
	uint16_t opcode;
	uint32_t saddr;
	uint32_t smsk;
	uint32_t daddr;
	uint32_t dmsk;
	unsigned char smaddr[ETH_ALEN];
	unsigned char smmsk[ETH_ALEN];
	unsigned char dmaddr[ETH_ALEN];
	unsigned char dmmsk[ETH_ALEN];
	uint8_t  bitmask;
	uint8_t  invflags;
};

while in kernel it is:

struct ebt_arp_info
{
	uint16_t htype;
	uint16_t ptype;
	uint16_t opcode;
	uint32_t saddr;
	uint32_t smsk;
	uint32_t daddr;
	uint32_t dmsk;
	uint8_t  bitmask;
	uint8_t  invflags;
};

It prevents --arp-* options from working. Function ebt_arp_check from file
eth_arp.c in kernel finds a difference between sizes:

static int ebt_arp_check(const char *tablename, unsigned int hookmask,
   const struct ebt_entry *e, void *data, unsigned int datalen)
{
	struct ebt_arp_info *info = (struct ebt_arp_info *)data;

	if (datalen != sizeof(struct ebt_arp_info))

		/**** it comes here ****/

		return -EINVAL;
	if ((e->ethproto != __constant_htons(ETH_P_ARP) &&
	   e->ethproto != __constant_htons(ETH_P_RARP)) ||
	   e->invflags & EBT_IPROTO)
		return -EINVAL;
	if (info->bitmask & ~EBT_ARP_MASK || info->invflags &
~EBT_ARP_MASK)
		return -EINVAL;
	return 0;
}

I just copied the former ebt_arp.h onto the latter and it works so far.

BTW I'm implementing some contribs to ebtables, include arp-replyer
(replies with arbitrary mac address) and indexed snat/dnat (a large
target, which does MAC snatting/dnatting the packets dependently of their
IP addresses). I'll publish them ASAP. I hope You will enjoy it.

-- 
Grzesław


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