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/export.h> 12#include <linux/ip.h> 13#include <linux/icmp.h> 14 15#include <linux/netfilter.h> 16#include <net/netfilter/nf_nat.h> 17#include <net/netfilter/nf_nat_core.h> 18#include <net/netfilter/nf_nat_l4proto.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(const struct nf_nat_l3proto *l3proto, 32 struct nf_conntrack_tuple *tuple, 33 const struct nf_nat_range *range, 34 enum nf_nat_manip_type maniptype, 35 const struct nf_conn *ct) 36{ 37 static u_int16_t id; 38 unsigned int range_size; 39 unsigned int i; 40 41 range_size = ntohs(range->max_proto.icmp.id) - 42 ntohs(range->min_proto.icmp.id) + 1; 43 /* If no range specified... */ 44 if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) 45 range_size = 0xFFFF; 46 47 for (i = 0; ; ++id) { 48 tuple->src.u.icmp.id = htons(ntohs(range->min_proto.icmp.id) + 49 (id % range_size)); 50 if (++i == range_size || !nf_nat_used_tuple(tuple, ct)) 51 return; 52 } 53 return; 54} 55 56static bool 57icmp_manip_pkt(struct sk_buff *skb, 58 const struct nf_nat_l3proto *l3proto, 59 unsigned int iphdroff, unsigned int hdroff, 60 const struct nf_conntrack_tuple *tuple, 61 enum nf_nat_manip_type maniptype) 62{ 63 struct icmphdr *hdr; 64 65 if (!skb_make_writable(skb, hdroff + sizeof(*hdr))) 66 return false; 67 68 hdr = (struct icmphdr *)(skb->data + hdroff); 69 inet_proto_csum_replace2(&hdr->checksum, skb, 70 hdr->un.echo.id, tuple->src.u.icmp.id, 0); 71 hdr->un.echo.id = tuple->src.u.icmp.id; 72 return true; 73} 74 75const struct nf_nat_l4proto nf_nat_l4proto_icmp = { 76 .l4proto = IPPROTO_ICMP, 77 .manip_pkt = icmp_manip_pkt, 78 .in_range = icmp_in_range, 79 .unique_tuple = icmp_unique_tuple, 80#if IS_ENABLED(CONFIG_NF_CT_NETLINK) 81 .nlattr_to_range = nf_nat_l4proto_nlattr_to_range, 82#endif 83}; 84