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#include <linux/types.h>
#include <linux/init.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/if.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
#include <linux/netfilter_ipv4/ip_nat_protocol.h>
static int
icmp_in_range(const struct ip_conntrack_tuple *tuple,
enum ip_nat_manip_type maniptype,
const union ip_conntrack_manip_proto *min,
const union ip_conntrack_manip_proto *max)
{
return (tuple->src.u.icmp.id >= min->icmp.id
&& tuple->src.u.icmp.id <= max->icmp.id);
}
static int
icmp_unique_tuple(struct ip_conntrack_tuple *tuple,
const struct ip_nat_range *range,
enum ip_nat_manip_type maniptype,
const struct ip_conntrack *conntrack)
{
static u_int16_t id = 0;
unsigned int range_size
= (unsigned int)range->max.icmp.id - range->min.icmp.id + 1;
unsigned int i;
/* If no range specified... */
if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED))
range_size = 0xFFFF;
for (i = 0; i < range_size; i++, id++) {
tuple->src.u.icmp.id = range->min.icmp.id + (id % range_size);
if (!ip_nat_used_tuple(tuple, conntrack))
return 1;
}
return 0;
}
static void
icmp_manip_pkt(struct iphdr *iph, size_t len,
const struct ip_conntrack_manip *manip,
enum ip_nat_manip_type maniptype)
{
struct icmphdr *hdr = (struct icmphdr *)((u_int32_t *)iph + iph->ihl);
hdr->checksum = ip_nat_cheat_check(hdr->un.echo.id ^ 0xFFFF,
manip->u.icmp.id,
hdr->checksum);
hdr->un.echo.id = manip->u.icmp.id;
}
static unsigned int
icmp_print(char *buffer,
const struct ip_conntrack_tuple *match,
const struct ip_conntrack_tuple *mask)
{
unsigned int len = 0;
if (mask->src.u.icmp.id)
len += sprintf(buffer + len, "id=%u ",
ntohs(match->src.u.icmp.id));
if (mask->dst.u.icmp.type)
len += sprintf(buffer + len, "type=%u ",
ntohs(match->dst.u.icmp.type));
if (mask->dst.u.icmp.code)
len += sprintf(buffer + len, "code=%u ",
ntohs(match->dst.u.icmp.code));
return len;
}
static unsigned int
icmp_print_range(char *buffer, const struct ip_nat_range *range)
{
if (range->min.icmp.id != 0 || range->max.icmp.id != 0xFFFF)
return sprintf(buffer, "id %u-%u ",
ntohs(range->min.icmp.id),
ntohs(range->max.icmp.id));
else return 0;
}
struct ip_nat_protocol ip_nat_protocol_icmp
= { { NULL, NULL }, "ICMP", IPPROTO_ICMP,
icmp_manip_pkt,
icmp_in_range,
icmp_unique_tuple,
icmp_print,
icmp_print_range
};
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