swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Tip revision: d8c3291c73b958243b33f8509d4507e76dafd055 authored by Linus Torvalds on 11 May 2006, 23:31:53 UTC
Linux v2.6.17-rc4
Linux v2.6.17-rc4
Tip revision: d8c3291
ip_nat_core.c
/* NAT for netfilter; shared with compatibility layer. */
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 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/module.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4.h>
#include <linux/vmalloc.h>
#include <net/checksum.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/tcp.h> /* For tcp_prot in getorigdst */
#include <linux/icmp.h>
#include <linux/udp.h>
#include <linux/jhash.h>
#define ASSERT_READ_LOCK(x)
#define ASSERT_WRITE_LOCK(x)
#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_conntrack_core.h>
#include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_nat_protocol.h>
#include <linux/netfilter_ipv4/ip_nat_core.h>
#include <linux/netfilter_ipv4/ip_nat_helper.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/listhelp.h>
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
DEFINE_RWLOCK(ip_nat_lock);
/* Calculated at init based on memory size */
static unsigned int ip_nat_htable_size;
static struct list_head *bysource;
#define MAX_IP_NAT_PROTO 256
static struct ip_nat_protocol *ip_nat_protos[MAX_IP_NAT_PROTO];
static inline struct ip_nat_protocol *
__ip_nat_proto_find(u_int8_t protonum)
{
return ip_nat_protos[protonum];
}
struct ip_nat_protocol *
ip_nat_proto_find_get(u_int8_t protonum)
{
struct ip_nat_protocol *p;
/* we need to disable preemption to make sure 'p' doesn't get
* removed until we've grabbed the reference */
preempt_disable();
p = __ip_nat_proto_find(protonum);
if (!try_module_get(p->me))
p = &ip_nat_unknown_protocol;
preempt_enable();
return p;
}
EXPORT_SYMBOL_GPL(ip_nat_proto_find_get);
void
ip_nat_proto_put(struct ip_nat_protocol *p)
{
module_put(p->me);
}
EXPORT_SYMBOL_GPL(ip_nat_proto_put);
/* We keep an extra hash for each conntrack, for fast searching. */
static inline unsigned int
hash_by_src(const struct ip_conntrack_tuple *tuple)
{
/* Original src, to ensure we map it consistently if poss. */
return jhash_3words(tuple->src.ip, tuple->src.u.all,
tuple->dst.protonum, 0) % ip_nat_htable_size;
}
/* Noone using conntrack by the time this called. */
static void ip_nat_cleanup_conntrack(struct ip_conntrack *conn)
{
if (!(conn->status & IPS_NAT_DONE_MASK))
return;
write_lock_bh(&ip_nat_lock);
list_del(&conn->nat.info.bysource);
write_unlock_bh(&ip_nat_lock);
}
/* We do checksum mangling, so if they were wrong before they're still
* wrong. Also works for incomplete packets (eg. ICMP dest
* unreachables.) */
u_int16_t
ip_nat_cheat_check(u_int32_t oldvalinv, u_int32_t newval, u_int16_t oldcheck)
{
u_int32_t diffs[] = { oldvalinv, newval };
return csum_fold(csum_partial((char *)diffs, sizeof(diffs),
oldcheck^0xFFFF));
}
EXPORT_SYMBOL(ip_nat_cheat_check);
/* Is this tuple already taken? (not by us) */
int
ip_nat_used_tuple(const struct ip_conntrack_tuple *tuple,
const struct ip_conntrack *ignored_conntrack)
{
/* Conntrack tracking doesn't keep track of outgoing tuples; only
incoming ones. NAT means they don't have a fixed mapping,
so we invert the tuple and look for the incoming reply.
We could keep a separate hash if this proves too slow. */
struct ip_conntrack_tuple reply;
invert_tuplepr(&reply, tuple);
return ip_conntrack_tuple_taken(&reply, ignored_conntrack);
}
EXPORT_SYMBOL(ip_nat_used_tuple);
/* If we source map this tuple so reply looks like reply_tuple, will
* that meet the constraints of range. */
static int
in_range(const struct ip_conntrack_tuple *tuple,
const struct ip_nat_range *range)
{
struct ip_nat_protocol *proto =
__ip_nat_proto_find(tuple->dst.protonum);
/* If we are supposed to map IPs, then we must be in the
range specified, otherwise let this drag us onto a new src IP. */
if (range->flags & IP_NAT_RANGE_MAP_IPS) {
if (ntohl(tuple->src.ip) < ntohl(range->min_ip)
|| ntohl(tuple->src.ip) > ntohl(range->max_ip))
return 0;
}
if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)
|| proto->in_range(tuple, IP_NAT_MANIP_SRC,
&range->min, &range->max))
return 1;
return 0;
}
static inline int
same_src(const struct ip_conntrack *ct,
const struct ip_conntrack_tuple *tuple)
{
return (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum
== tuple->dst.protonum
&& ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip
== tuple->src.ip
&& ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.all
== tuple->src.u.all);
}
/* Only called for SRC manip */
static int
find_appropriate_src(const struct ip_conntrack_tuple *tuple,
struct ip_conntrack_tuple *result,
const struct ip_nat_range *range)
{
unsigned int h = hash_by_src(tuple);
struct ip_conntrack *ct;
read_lock_bh(&ip_nat_lock);
list_for_each_entry(ct, &bysource[h], nat.info.bysource) {
if (same_src(ct, tuple)) {
/* Copy source part from reply tuple. */
invert_tuplepr(result,
&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
result->dst = tuple->dst;
if (in_range(result, range)) {
read_unlock_bh(&ip_nat_lock);
return 1;
}
}
}
read_unlock_bh(&ip_nat_lock);
return 0;
}
/* For [FUTURE] fragmentation handling, we want the least-used
src-ip/dst-ip/proto triple. Fairness doesn't come into it. Thus
if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports
1-65535, we don't do pro-rata allocation based on ports; we choose
the ip with the lowest src-ip/dst-ip/proto usage.
*/
static void
find_best_ips_proto(struct ip_conntrack_tuple *tuple,
const struct ip_nat_range *range,
const struct ip_conntrack *conntrack,
enum ip_nat_manip_type maniptype)
{
u_int32_t *var_ipp;
/* Host order */
u_int32_t minip, maxip, j;
/* No IP mapping? Do nothing. */
if (!(range->flags & IP_NAT_RANGE_MAP_IPS))
return;
if (maniptype == IP_NAT_MANIP_SRC)
var_ipp = &tuple->src.ip;
else
var_ipp = &tuple->dst.ip;
/* Fast path: only one choice. */
if (range->min_ip == range->max_ip) {
*var_ipp = range->min_ip;
return;
}
/* Hashing source and destination IPs gives a fairly even
* spread in practice (if there are a small number of IPs
* involved, there usually aren't that many connections
* anyway). The consistency means that servers see the same
* client coming from the same IP (some Internet Banking sites
* like this), even across reboots. */
minip = ntohl(range->min_ip);
maxip = ntohl(range->max_ip);
j = jhash_2words(tuple->src.ip, tuple->dst.ip, 0);
*var_ipp = htonl(minip + j % (maxip - minip + 1));
}
/* Manipulate the tuple into the range given. For NF_IP_POST_ROUTING,
* we change the source to map into the range. For NF_IP_PRE_ROUTING
* and NF_IP_LOCAL_OUT, we change the destination to map into the
* range. It might not be possible to get a unique tuple, but we try.
* At worst (or if we race), we will end up with a final duplicate in
* __ip_conntrack_confirm and drop the packet. */
static void
get_unique_tuple(struct ip_conntrack_tuple *tuple,
const struct ip_conntrack_tuple *orig_tuple,
const struct ip_nat_range *range,
struct ip_conntrack *conntrack,
enum ip_nat_manip_type maniptype)
{
struct ip_nat_protocol *proto;
/* 1) If this srcip/proto/src-proto-part is currently mapped,
and that same mapping gives a unique tuple within the given
range, use that.
This is only required for source (ie. NAT/masq) mappings.
So far, we don't do local source mappings, so multiple
manips not an issue. */
if (maniptype == IP_NAT_MANIP_SRC) {
if (find_appropriate_src(orig_tuple, tuple, range)) {
DEBUGP("get_unique_tuple: Found current src map\n");
if (!ip_nat_used_tuple(tuple, conntrack))
return;
}
}
/* 2) Select the least-used IP/proto combination in the given
range. */
*tuple = *orig_tuple;
find_best_ips_proto(tuple, range, conntrack, maniptype);
/* 3) The per-protocol part of the manip is made to map into
the range to make a unique tuple. */
proto = ip_nat_proto_find_get(orig_tuple->dst.protonum);
/* Only bother mapping if it's not already in range and unique */
if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)
|| proto->in_range(tuple, maniptype, &range->min, &range->max))
&& !ip_nat_used_tuple(tuple, conntrack)) {
ip_nat_proto_put(proto);
return;
}
/* Last change: get protocol to try to obtain unique tuple. */
proto->unique_tuple(tuple, range, maniptype, conntrack);
ip_nat_proto_put(proto);
}
unsigned int
ip_nat_setup_info(struct ip_conntrack *conntrack,
const struct ip_nat_range *range,
unsigned int hooknum)
{
struct ip_conntrack_tuple curr_tuple, new_tuple;
struct ip_nat_info *info = &conntrack->nat.info;
int have_to_hash = !(conntrack->status & IPS_NAT_DONE_MASK);
enum ip_nat_manip_type maniptype = HOOK2MANIP(hooknum);
IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
|| hooknum == NF_IP_POST_ROUTING
|| hooknum == NF_IP_LOCAL_IN
|| hooknum == NF_IP_LOCAL_OUT);
BUG_ON(ip_nat_initialized(conntrack, maniptype));
/* What we've got will look like inverse of reply. Normally
this is what is in the conntrack, except for prior
manipulations (future optimization: if num_manips == 0,
orig_tp =
conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */
invert_tuplepr(&curr_tuple,
&conntrack->tuplehash[IP_CT_DIR_REPLY].tuple);
get_unique_tuple(&new_tuple, &curr_tuple, range, conntrack, maniptype);
if (!ip_ct_tuple_equal(&new_tuple, &curr_tuple)) {
struct ip_conntrack_tuple reply;
/* Alter conntrack table so will recognize replies. */
invert_tuplepr(&reply, &new_tuple);
ip_conntrack_alter_reply(conntrack, &reply);
/* Non-atomic: we own this at the moment. */
if (maniptype == IP_NAT_MANIP_SRC)
conntrack->status |= IPS_SRC_NAT;
else
conntrack->status |= IPS_DST_NAT;
}
/* Place in source hash if this is the first time. */
if (have_to_hash) {
unsigned int srchash
= hash_by_src(&conntrack->tuplehash[IP_CT_DIR_ORIGINAL]
.tuple);
write_lock_bh(&ip_nat_lock);
list_add(&info->bysource, &bysource[srchash]);
write_unlock_bh(&ip_nat_lock);
}
/* It's done. */
if (maniptype == IP_NAT_MANIP_DST)
set_bit(IPS_DST_NAT_DONE_BIT, &conntrack->status);
else
set_bit(IPS_SRC_NAT_DONE_BIT, &conntrack->status);
return NF_ACCEPT;
}
EXPORT_SYMBOL(ip_nat_setup_info);
/* Returns true if succeeded. */
static int
manip_pkt(u_int16_t proto,
struct sk_buff **pskb,
unsigned int iphdroff,
const struct ip_conntrack_tuple *target,
enum ip_nat_manip_type maniptype)
{
struct iphdr *iph;
struct ip_nat_protocol *p;
if (!skb_make_writable(pskb, iphdroff + sizeof(*iph)))
return 0;
iph = (void *)(*pskb)->data + iphdroff;
/* Manipulate protcol part. */
p = ip_nat_proto_find_get(proto);
if (!p->manip_pkt(pskb, iphdroff, target, maniptype)) {
ip_nat_proto_put(p);
return 0;
}
ip_nat_proto_put(p);
iph = (void *)(*pskb)->data + iphdroff;
if (maniptype == IP_NAT_MANIP_SRC) {
iph->check = ip_nat_cheat_check(~iph->saddr, target->src.ip,
iph->check);
iph->saddr = target->src.ip;
} else {
iph->check = ip_nat_cheat_check(~iph->daddr, target->dst.ip,
iph->check);
iph->daddr = target->dst.ip;
}
return 1;
}
/* Do packet manipulations according to ip_nat_setup_info. */
unsigned int ip_nat_packet(struct ip_conntrack *ct,
enum ip_conntrack_info ctinfo,
unsigned int hooknum,
struct sk_buff **pskb)
{
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
unsigned long statusbit;
enum ip_nat_manip_type mtype = HOOK2MANIP(hooknum);
if (mtype == IP_NAT_MANIP_SRC)
statusbit = IPS_SRC_NAT;
else
statusbit = IPS_DST_NAT;
/* Invert if this is reply dir. */
if (dir == IP_CT_DIR_REPLY)
statusbit ^= IPS_NAT_MASK;
/* Non-atomic: these bits don't change. */
if (ct->status & statusbit) {
struct ip_conntrack_tuple target;
/* We are aiming to look like inverse of other direction. */
invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
if (!manip_pkt(target.dst.protonum, pskb, 0, &target, mtype))
return NF_DROP;
}
return NF_ACCEPT;
}
EXPORT_SYMBOL_GPL(ip_nat_packet);
/* Dir is direction ICMP is coming from (opposite to packet it contains) */
int ip_nat_icmp_reply_translation(struct sk_buff **pskb,
struct ip_conntrack *ct,
enum ip_nat_manip_type manip,
enum ip_conntrack_dir dir)
{
struct {
struct icmphdr icmp;
struct iphdr ip;
} *inside;
struct ip_conntrack_tuple inner, target;
int hdrlen = (*pskb)->nh.iph->ihl * 4;
unsigned long statusbit;
if (!skb_make_writable(pskb, hdrlen + sizeof(*inside)))
return 0;
inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
/* We're actually going to mangle it beyond trivial checksum
adjustment, so make sure the current checksum is correct. */
if ((*pskb)->ip_summed != CHECKSUM_UNNECESSARY) {
hdrlen = (*pskb)->nh.iph->ihl * 4;
if ((u16)csum_fold(skb_checksum(*pskb, hdrlen,
(*pskb)->len - hdrlen, 0)))
return 0;
}
/* Must be RELATED */
IP_NF_ASSERT((*pskb)->nfctinfo == IP_CT_RELATED ||
(*pskb)->nfctinfo == IP_CT_RELATED+IP_CT_IS_REPLY);
/* Redirects on non-null nats must be dropped, else they'll
start talking to each other without our translation, and be
confused... --RR */
if (inside->icmp.type == ICMP_REDIRECT) {
/* If NAT isn't finished, assume it and drop. */
if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
return 0;
if (ct->status & IPS_NAT_MASK)
return 0;
}
DEBUGP("icmp_reply_translation: translating error %p manp %u dir %s\n",
*pskb, manip, dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY");
if (!ip_ct_get_tuple(&inside->ip, *pskb, (*pskb)->nh.iph->ihl*4 +
sizeof(struct icmphdr) + inside->ip.ihl*4,
&inner,
__ip_conntrack_proto_find(inside->ip.protocol)))
return 0;
/* Change inner back to look like incoming packet. We do the
opposite manip on this hook to normal, because it might not
pass all hooks (locally-generated ICMP). Consider incoming
packet: PREROUTING (DST manip), routing produces ICMP, goes
through POSTROUTING (which must correct the DST manip). */
if (!manip_pkt(inside->ip.protocol, pskb,
(*pskb)->nh.iph->ihl*4
+ sizeof(inside->icmp),
&ct->tuplehash[!dir].tuple,
!manip))
return 0;
/* Reloading "inside" here since manip_pkt inner. */
inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
inside->icmp.checksum = 0;
inside->icmp.checksum = csum_fold(skb_checksum(*pskb, hdrlen,
(*pskb)->len - hdrlen,
0));
/* Change outer to look the reply to an incoming packet
* (proto 0 means don't invert per-proto part). */
if (manip == IP_NAT_MANIP_SRC)
statusbit = IPS_SRC_NAT;
else
statusbit = IPS_DST_NAT;
/* Invert if this is reply dir. */
if (dir == IP_CT_DIR_REPLY)
statusbit ^= IPS_NAT_MASK;
if (ct->status & statusbit) {
invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
if (!manip_pkt(0, pskb, 0, &target, manip))
return 0;
}
return 1;
}
EXPORT_SYMBOL_GPL(ip_nat_icmp_reply_translation);
/* Protocol registration. */
int ip_nat_protocol_register(struct ip_nat_protocol *proto)
{
int ret = 0;
write_lock_bh(&ip_nat_lock);
if (ip_nat_protos[proto->protonum] != &ip_nat_unknown_protocol) {
ret = -EBUSY;
goto out;
}
ip_nat_protos[proto->protonum] = proto;
out:
write_unlock_bh(&ip_nat_lock);
return ret;
}
EXPORT_SYMBOL(ip_nat_protocol_register);
/* Noone stores the protocol anywhere; simply delete it. */
void ip_nat_protocol_unregister(struct ip_nat_protocol *proto)
{
write_lock_bh(&ip_nat_lock);
ip_nat_protos[proto->protonum] = &ip_nat_unknown_protocol;
write_unlock_bh(&ip_nat_lock);
/* Someone could be still looking at the proto in a bh. */
synchronize_net();
}
EXPORT_SYMBOL(ip_nat_protocol_unregister);
#if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
int
ip_nat_port_range_to_nfattr(struct sk_buff *skb,
const struct ip_nat_range *range)
{
NFA_PUT(skb, CTA_PROTONAT_PORT_MIN, sizeof(u_int16_t),
&range->min.tcp.port);
NFA_PUT(skb, CTA_PROTONAT_PORT_MAX, sizeof(u_int16_t),
&range->max.tcp.port);
return 0;
nfattr_failure:
return -1;
}
int
ip_nat_port_nfattr_to_range(struct nfattr *tb[], struct ip_nat_range *range)
{
int ret = 0;
/* we have to return whether we actually parsed something or not */
if (tb[CTA_PROTONAT_PORT_MIN-1]) {
ret = 1;
range->min.tcp.port =
*(u_int16_t *)NFA_DATA(tb[CTA_PROTONAT_PORT_MIN-1]);
}
if (!tb[CTA_PROTONAT_PORT_MAX-1]) {
if (ret)
range->max.tcp.port = range->min.tcp.port;
} else {
ret = 1;
range->max.tcp.port =
*(u_int16_t *)NFA_DATA(tb[CTA_PROTONAT_PORT_MAX-1]);
}
return ret;
}
EXPORT_SYMBOL_GPL(ip_nat_port_nfattr_to_range);
EXPORT_SYMBOL_GPL(ip_nat_port_range_to_nfattr);
#endif
static int __init ip_nat_init(void)
{
size_t i;
/* Leave them the same for the moment. */
ip_nat_htable_size = ip_conntrack_htable_size;
/* One vmalloc for both hash tables */
bysource = vmalloc(sizeof(struct list_head) * ip_nat_htable_size);
if (!bysource)
return -ENOMEM;
/* Sew in builtin protocols. */
write_lock_bh(&ip_nat_lock);
for (i = 0; i < MAX_IP_NAT_PROTO; i++)
ip_nat_protos[i] = &ip_nat_unknown_protocol;
ip_nat_protos[IPPROTO_TCP] = &ip_nat_protocol_tcp;
ip_nat_protos[IPPROTO_UDP] = &ip_nat_protocol_udp;
ip_nat_protos[IPPROTO_ICMP] = &ip_nat_protocol_icmp;
write_unlock_bh(&ip_nat_lock);
for (i = 0; i < ip_nat_htable_size; i++) {
INIT_LIST_HEAD(&bysource[i]);
}
/* FIXME: Man, this is a hack. <SIGH> */
IP_NF_ASSERT(ip_conntrack_destroyed == NULL);
ip_conntrack_destroyed = &ip_nat_cleanup_conntrack;
/* Initialize fake conntrack so that NAT will skip it */
ip_conntrack_untracked.status |= IPS_NAT_DONE_MASK;
return 0;
}
/* Clear NAT section of all conntracks, in case we're loaded again. */
static int clean_nat(struct ip_conntrack *i, void *data)
{
memset(&i->nat, 0, sizeof(i->nat));
i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK | IPS_SEQ_ADJUST);
return 0;
}
static void __exit ip_nat_cleanup(void)
{
ip_ct_iterate_cleanup(&clean_nat, NULL);
ip_conntrack_destroyed = NULL;
vfree(bysource);
}
MODULE_LICENSE("GPL");
module_init(ip_nat_init);
module_exit(ip_nat_cleanup);