401 lines
10 KiB
C
401 lines
10 KiB
C
/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/icmp.h>
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#include <linux/ip.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv4.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/proc_fs.h>
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#include <net/ip.h>
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#include <net/checksum.h>
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#include <linux/spinlock.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_rule.h>
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#include <net/netfilter/nf_nat_protocol.h>
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#include <net/netfilter/nf_nat_core.h>
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#include <net/netfilter/nf_nat_helper.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(format, args...)
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#endif
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#ifdef CONFIG_XFRM
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static void nat_decode_session(struct sk_buff *skb, struct flowi *fl)
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{
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struct nf_conn *ct;
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struct nf_conntrack_tuple *t;
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enum ip_conntrack_info ctinfo;
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enum ip_conntrack_dir dir;
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unsigned long statusbit;
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ct = nf_ct_get(skb, &ctinfo);
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if (ct == NULL)
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return;
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dir = CTINFO2DIR(ctinfo);
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t = &ct->tuplehash[dir].tuple;
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if (dir == IP_CT_DIR_ORIGINAL)
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statusbit = IPS_DST_NAT;
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else
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statusbit = IPS_SRC_NAT;
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if (ct->status & statusbit) {
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fl->fl4_dst = t->dst.u3.ip;
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if (t->dst.protonum == IPPROTO_TCP ||
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t->dst.protonum == IPPROTO_UDP)
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fl->fl_ip_dport = t->dst.u.tcp.port;
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}
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statusbit ^= IPS_NAT_MASK;
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if (ct->status & statusbit) {
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fl->fl4_src = t->src.u3.ip;
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if (t->dst.protonum == IPPROTO_TCP ||
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t->dst.protonum == IPPROTO_UDP)
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fl->fl_ip_sport = t->src.u.tcp.port;
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}
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}
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#endif
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static unsigned int
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nf_nat_fn(unsigned int hooknum,
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struct sk_buff **pskb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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struct nf_conn_nat *nat;
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struct nf_nat_info *info;
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/* maniptype == SRC for postrouting. */
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enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
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/* We never see fragments: conntrack defrags on pre-routing
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and local-out, and nf_nat_out protects post-routing. */
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NF_CT_ASSERT(!(ip_hdr(*pskb)->frag_off & htons(IP_MF | IP_OFFSET)));
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ct = nf_ct_get(*pskb, &ctinfo);
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/* Can't track? It's not due to stress, or conntrack would
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have dropped it. Hence it's the user's responsibilty to
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packet filter it out, or implement conntrack/NAT for that
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protocol. 8) --RR */
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if (!ct) {
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/* Exception: ICMP redirect to new connection (not in
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hash table yet). We must not let this through, in
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case we're doing NAT to the same network. */
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if (ip_hdr(*pskb)->protocol == IPPROTO_ICMP) {
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struct icmphdr _hdr, *hp;
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hp = skb_header_pointer(*pskb, ip_hdrlen(*pskb),
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sizeof(_hdr), &_hdr);
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if (hp != NULL &&
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hp->type == ICMP_REDIRECT)
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return NF_DROP;
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}
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return NF_ACCEPT;
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}
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/* Don't try to NAT if this packet is not conntracked */
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if (ct == &nf_conntrack_untracked)
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return NF_ACCEPT;
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nat = nfct_nat(ct);
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if (!nat)
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return NF_ACCEPT;
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switch (ctinfo) {
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case IP_CT_RELATED:
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case IP_CT_RELATED+IP_CT_IS_REPLY:
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if (ip_hdr(*pskb)->protocol == IPPROTO_ICMP) {
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if (!nf_nat_icmp_reply_translation(ct, ctinfo,
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hooknum, pskb))
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return NF_DROP;
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else
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return NF_ACCEPT;
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}
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/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
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case IP_CT_NEW:
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info = &nat->info;
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/* Seen it before? This can happen for loopback, retrans,
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or local packets.. */
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if (!nf_nat_initialized(ct, maniptype)) {
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unsigned int ret;
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if (unlikely(nf_ct_is_confirmed(ct)))
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/* NAT module was loaded late */
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ret = alloc_null_binding_confirmed(ct, info,
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hooknum);
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else if (hooknum == NF_IP_LOCAL_IN)
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/* LOCAL_IN hook doesn't have a chain! */
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ret = alloc_null_binding(ct, info, hooknum);
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else
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ret = nf_nat_rule_find(pskb, hooknum, in, out,
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ct, info);
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if (ret != NF_ACCEPT) {
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return ret;
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}
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} else
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DEBUGP("Already setup manip %s for ct %p\n",
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maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
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ct);
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break;
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default:
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/* ESTABLISHED */
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NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
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ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
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info = &nat->info;
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}
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NF_CT_ASSERT(info);
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return nf_nat_packet(ct, ctinfo, hooknum, pskb);
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}
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static unsigned int
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nf_nat_in(unsigned int hooknum,
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struct sk_buff **pskb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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unsigned int ret;
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__be32 daddr = ip_hdr(*pskb)->daddr;
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ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
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if (ret != NF_DROP && ret != NF_STOLEN &&
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daddr != ip_hdr(*pskb)->daddr) {
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dst_release((*pskb)->dst);
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(*pskb)->dst = NULL;
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}
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return ret;
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}
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static unsigned int
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nf_nat_out(unsigned int hooknum,
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struct sk_buff **pskb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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#ifdef CONFIG_XFRM
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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#endif
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unsigned int ret;
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/* root is playing with raw sockets. */
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if ((*pskb)->len < sizeof(struct iphdr) ||
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ip_hdrlen(*pskb) < sizeof(struct iphdr))
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return NF_ACCEPT;
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ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
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#ifdef CONFIG_XFRM
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if (ret != NF_DROP && ret != NF_STOLEN &&
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(ct = nf_ct_get(*pskb, &ctinfo)) != NULL) {
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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if (ct->tuplehash[dir].tuple.src.u3.ip !=
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ct->tuplehash[!dir].tuple.dst.u3.ip
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|| ct->tuplehash[dir].tuple.src.u.all !=
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ct->tuplehash[!dir].tuple.dst.u.all
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)
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return ip_xfrm_me_harder(pskb) == 0 ? ret : NF_DROP;
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}
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#endif
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return ret;
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}
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static unsigned int
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nf_nat_local_fn(unsigned int hooknum,
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struct sk_buff **pskb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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unsigned int ret;
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/* root is playing with raw sockets. */
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if ((*pskb)->len < sizeof(struct iphdr) ||
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ip_hdrlen(*pskb) < sizeof(struct iphdr))
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return NF_ACCEPT;
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ret = nf_nat_fn(hooknum, pskb, in, out, okfn);
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if (ret != NF_DROP && ret != NF_STOLEN &&
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(ct = nf_ct_get(*pskb, &ctinfo)) != NULL) {
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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if (ct->tuplehash[dir].tuple.dst.u3.ip !=
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ct->tuplehash[!dir].tuple.src.u3.ip) {
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if (ip_route_me_harder(pskb, RTN_UNSPEC))
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ret = NF_DROP;
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}
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#ifdef CONFIG_XFRM
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else if (ct->tuplehash[dir].tuple.dst.u.all !=
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ct->tuplehash[!dir].tuple.src.u.all)
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if (ip_xfrm_me_harder(pskb))
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ret = NF_DROP;
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#endif
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}
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return ret;
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}
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static unsigned int
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nf_nat_adjust(unsigned int hooknum,
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struct sk_buff **pskb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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ct = nf_ct_get(*pskb, &ctinfo);
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if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
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DEBUGP("nf_nat_standalone: adjusting sequence number\n");
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if (!nf_nat_seq_adjust(pskb, ct, ctinfo))
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return NF_DROP;
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}
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return NF_ACCEPT;
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}
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/* We must be after connection tracking and before packet filtering. */
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static struct nf_hook_ops nf_nat_ops[] = {
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/* Before packet filtering, change destination */
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{
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.hook = nf_nat_in,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_PRE_ROUTING,
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.priority = NF_IP_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = nf_nat_out,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_POST_ROUTING,
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.priority = NF_IP_PRI_NAT_SRC,
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},
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/* After conntrack, adjust sequence number */
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{
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.hook = nf_nat_adjust,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_POST_ROUTING,
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.priority = NF_IP_PRI_NAT_SEQ_ADJUST,
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},
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/* Before packet filtering, change destination */
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{
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.hook = nf_nat_local_fn,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_LOCAL_OUT,
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.priority = NF_IP_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = nf_nat_fn,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_LOCAL_IN,
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.priority = NF_IP_PRI_NAT_SRC,
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},
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/* After conntrack, adjust sequence number */
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{
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.hook = nf_nat_adjust,
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.owner = THIS_MODULE,
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.pf = PF_INET,
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.hooknum = NF_IP_LOCAL_IN,
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.priority = NF_IP_PRI_NAT_SEQ_ADJUST,
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},
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};
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static int __init nf_nat_standalone_init(void)
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{
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int size, ret = 0;
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need_conntrack();
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size = ALIGN(sizeof(struct nf_conn), __alignof__(struct nf_conn_nat)) +
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sizeof(struct nf_conn_nat);
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ret = nf_conntrack_register_cache(NF_CT_F_NAT, "nf_nat:base", size);
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if (ret < 0) {
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printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n");
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return ret;
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}
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size = ALIGN(size, __alignof__(struct nf_conn_help)) +
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sizeof(struct nf_conn_help);
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ret = nf_conntrack_register_cache(NF_CT_F_NAT|NF_CT_F_HELP,
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"nf_nat:help", size);
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if (ret < 0) {
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printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n");
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goto cleanup_register_cache;
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}
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#ifdef CONFIG_XFRM
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BUG_ON(ip_nat_decode_session != NULL);
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ip_nat_decode_session = nat_decode_session;
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#endif
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ret = nf_nat_rule_init();
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if (ret < 0) {
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printk("nf_nat_init: can't setup rules.\n");
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goto cleanup_decode_session;
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}
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ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
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if (ret < 0) {
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printk("nf_nat_init: can't register hooks.\n");
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goto cleanup_rule_init;
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}
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nf_nat_module_is_loaded = 1;
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return ret;
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cleanup_rule_init:
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nf_nat_rule_cleanup();
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cleanup_decode_session:
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#ifdef CONFIG_XFRM
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ip_nat_decode_session = NULL;
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synchronize_net();
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#endif
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nf_conntrack_unregister_cache(NF_CT_F_NAT|NF_CT_F_HELP);
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cleanup_register_cache:
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nf_conntrack_unregister_cache(NF_CT_F_NAT);
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return ret;
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}
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static void __exit nf_nat_standalone_fini(void)
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{
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nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
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nf_nat_rule_cleanup();
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nf_nat_module_is_loaded = 0;
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#ifdef CONFIG_XFRM
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ip_nat_decode_session = NULL;
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synchronize_net();
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#endif
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/* Conntrack caches are unregistered in nf_conntrack_cleanup */
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}
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module_init(nf_nat_standalone_init);
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module_exit(nf_nat_standalone_fini);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ip_nat");
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