1/* (C) 1999-2001 Paul `Rusty' Russell 2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 9#include <linux/types.h> 10#include <linux/init.h> 11#include <linux/ip.h> 12#include <linux/icmp.h> 13 14#include <linux/netfilter.h> 15#include <net/netfilter/nf_nat.h> 16#include <net/netfilter/nf_nat_core.h> 17#include <net/netfilter/nf_nat_rule.h> 18#include <net/netfilter/nf_nat_protocol.h> 19 20static bool 21icmp_in_range(const struct nf_conntrack_tuple *tuple, 22 enum nf_nat_manip_type maniptype, 23 const union nf_conntrack_man_proto *min, 24 const union nf_conntrack_man_proto *max) 25{ 26 return ntohs(tuple->src.u.icmp.id) >= ntohs(min->icmp.id) && 27 ntohs(tuple->src.u.icmp.id) <= ntohs(max->icmp.id); 28} 29 30static void 31icmp_unique_tuple(struct nf_conntrack_tuple *tuple, 32 const struct nf_nat_range *range, 33 enum nf_nat_manip_type maniptype, 34 const struct nf_conn *ct) 35{ 36 static u_int16_t id; 37 unsigned int range_size; 38 unsigned int i; 39 40 range_size = ntohs(range->max.icmp.id) - ntohs(range->min.icmp.id) + 1; 41 /* If no range specified... */ 42 if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) 43 range_size = 0xFFFF; 44 45 for (i = 0; ; ++id) { 46 tuple->src.u.icmp.id = htons(ntohs(range->min.icmp.id) + 47 (id % range_size)); 48 if (++i == range_size || !nf_nat_used_tuple(tuple, ct)) 49 return; 50 } 51 return; 52} 53 54static bool 55icmp_manip_pkt(struct sk_buff *skb, 56 unsigned int iphdroff, 57 const struct nf_conntrack_tuple *tuple, 58 enum nf_nat_manip_type maniptype) 59{ 60 const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff); 61 struct icmphdr *hdr; 62 unsigned int hdroff = iphdroff + iph->ihl*4; 63 64 if (!skb_make_writable(skb, hdroff + sizeof(*hdr))) 65 return false; 66 67 hdr = (struct icmphdr *)(skb->data + hdroff); 68 inet_proto_csum_replace2(&hdr->checksum, skb, 69 hdr->un.echo.id, tuple->src.u.icmp.id, 0); 70 hdr->un.echo.id = tuple->src.u.icmp.id; 71 return true; 72} 73 74const struct nf_nat_protocol nf_nat_protocol_icmp = { 75 .protonum = IPPROTO_ICMP, 76 .me = THIS_MODULE, 77 .manip_pkt = icmp_manip_pkt, 78 .in_range = icmp_in_range, 79 .unique_tuple = icmp_unique_tuple, 80#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE) 81 .range_to_nlattr = nf_nat_proto_range_to_nlattr, 82 .nlattr_to_range = nf_nat_proto_nlattr_to_range, 83#endif 84}; 85