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/udp.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 u_int16_t udp_port_rover; 21 22static void 23udp_unique_tuple(struct nf_conntrack_tuple *tuple, 24 const struct nf_nat_range *range, 25 enum nf_nat_manip_type maniptype, 26 const struct nf_conn *ct) 27{ 28 nf_nat_proto_unique_tuple(tuple, range, maniptype, ct, &udp_port_rover); 29} 30 31static bool 32udp_manip_pkt(struct sk_buff *skb, 33 unsigned int iphdroff, 34 const struct nf_conntrack_tuple *tuple, 35 enum nf_nat_manip_type maniptype) 36{ 37 const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff); 38 struct udphdr *hdr; 39 unsigned int hdroff = iphdroff + iph->ihl*4; 40 __be32 oldip, newip; 41 __be16 *portptr, newport; 42 43 if (!skb_make_writable(skb, hdroff + sizeof(*hdr))) 44 return false; 45 46 iph = (struct iphdr *)(skb->data + iphdroff); 47 hdr = (struct udphdr *)(skb->data + hdroff); 48 49 if (maniptype == IP_NAT_MANIP_SRC) { 50 /* Get rid of src ip and src pt */ 51 oldip = iph->saddr; 52 newip = tuple->src.u3.ip; 53 newport = tuple->src.u.udp.port; 54 portptr = &hdr->source; 55 } else { 56 /* Get rid of dst ip and dst pt */ 57 oldip = iph->daddr; 58 newip = tuple->dst.u3.ip; 59 newport = tuple->dst.u.udp.port; 60 portptr = &hdr->dest; 61 } 62 if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) { 63 inet_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1); 64 inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport, 65 0); 66 if (!hdr->check) 67 hdr->check = CSUM_MANGLED_0; 68 } 69 *portptr = newport; 70 return true; 71} 72 73const struct nf_nat_protocol nf_nat_protocol_udp = { 74 .protonum = IPPROTO_UDP, 75 .me = THIS_MODULE, 76 .manip_pkt = udp_manip_pkt, 77 .in_range = nf_nat_proto_in_range, 78 .unique_tuple = udp_unique_tuple, 79#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE) 80 .range_to_nlattr = nf_nat_proto_range_to_nlattr, 81 .nlattr_to_range = nf_nat_proto_nlattr_to_range, 82#endif 83}; 84