root/net/ipv4/netfilter/nf_nat_proto_icmp.c

DEFINITIONS

1. icmp_in_range
2. icmp_unique_tuple
3. icmp_manip_pkt

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@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/types.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/icmp.h>

#include <linux/netfilter.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_rule.h>
#include <net/netfilter/nf_nat_protocol.h>

static bool
icmp_in_range(const struct nf_conntrack_tuple *tuple,
              enum nf_nat_manip_type maniptype,
              const union nf_conntrack_man_proto *min,
              const union nf_conntrack_man_proto *max)
{
        return ntohs(tuple->src.u.icmp.id) >= ntohs(min->icmp.id) &&
               ntohs(tuple->src.u.icmp.id) <= ntohs(max->icmp.id);
}

static bool
icmp_unique_tuple(struct nf_conntrack_tuple *tuple,
                  const struct nf_nat_range *range,
                  enum nf_nat_manip_type maniptype,
                  const struct nf_conn *ct)
{
        static u_int16_t id;
        unsigned int range_size;
        unsigned int i;

        range_size = ntohs(range->max.icmp.id) - ntohs(range->min.icmp.id) + 1;
        /* 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 = htons(ntohs(range->min.icmp.id) +
                                             (id % range_size));
                if (!nf_nat_used_tuple(tuple, ct))
                        return true;
        }
        return false;
}

static bool
icmp_manip_pkt(struct sk_buff *skb,
               unsigned int iphdroff,
               const struct nf_conntrack_tuple *tuple,
               enum nf_nat_manip_type maniptype)
{
        const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
        struct icmphdr *hdr;
        unsigned int hdroff = iphdroff + iph->ihl*4;

        if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
                return false;

        hdr = (struct icmphdr *)(skb->data + hdroff);
        inet_proto_csum_replace2(&hdr->checksum, skb,
                                 hdr->un.echo.id, tuple->src.u.icmp.id, 0);
        hdr->un.echo.id = tuple->src.u.icmp.id;
        return true;
}

const struct nf_nat_protocol nf_nat_protocol_icmp = {
        .protonum               = IPPROTO_ICMP,
        .me                     = THIS_MODULE,
        .manip_pkt              = icmp_manip_pkt,
        .in_range               = icmp_in_range,
        .unique_tuple           = icmp_unique_tuple,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
        .range_to_nlattr        = nf_nat_proto_range_to_nlattr,
        .nlattr_to_range        = nf_nat_proto_nlattr_to_range,
#endif
};