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netfilter: nat: move specific NAT IPv4 to core
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Move the specific NAT IPv4 core functions that are called from the
hooks from iptable_nat.c to nf_nat_l3proto_ipv4.c. This prepares the
ground to allow iptables and nft to use the same NAT engine code that
comes in a follow up patch.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Pablo Neira Ayuso committed Sep 2, 2014
1 parent f111f78 commit 30766f4
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Showing 3 changed files with 271 additions and 199 deletions.
38 changes: 38 additions & 0 deletions include/net/netfilter/nf_nat_l3proto.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,44 @@ const struct nf_nat_l3proto *__nf_nat_l3proto_find(u8 l3proto);
int nf_nat_icmp_reply_translation(struct sk_buff *skb, struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int hooknum);

unsigned int nf_nat_ipv4_in(const struct nf_hook_ops *ops, struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int (*do_chain)(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct));

unsigned int nf_nat_ipv4_out(const struct nf_hook_ops *ops, struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int (*do_chain)(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct));

unsigned int nf_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int (*do_chain)(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct));

unsigned int nf_nat_ipv4_fn(const struct nf_hook_ops *ops, struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int (*do_chain)(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct));

int nf_nat_icmpv6_reply_translation(struct sk_buff *skb, struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int hooknum, unsigned int hdrlen);
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233 changes: 34 additions & 199 deletions net/ipv4/netfilter/iptable_nat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,246 +28,81 @@ static const struct xt_table nf_nat_ipv4_table = {
.af = NFPROTO_IPV4,
};

static unsigned int alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
{
/* Force range to this IP; let proto decide mapping for
* per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
*/
struct nf_nat_range range;

range.flags = 0;
pr_debug("Allocating NULL binding for %p (%pI4)\n", ct,
HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip :
&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);

return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
}

static unsigned int nf_nat_rule_find(struct sk_buff *skb, unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct)
static unsigned int iptable_nat_do_chain(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct)
{
struct net *net = nf_ct_net(ct);
unsigned int ret;

ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
if (ret == NF_ACCEPT) {
if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
ret = alloc_null_binding(ct, hooknum);
}
return ret;
return ipt_do_table(skb, ops->hooknum, in, out, net->ipv4.nat_table);
}

static unsigned int
nf_nat_ipv4_fn(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
static unsigned int iptable_nat_ipv4_fn(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
struct nf_conn_nat *nat;
/* maniptype == SRC for postrouting. */
enum nf_nat_manip_type maniptype = HOOK2MANIP(ops->hooknum);

/* We never see fragments: conntrack defrags on pre-routing
* and local-out, and nf_nat_out protects post-routing.
*/
NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));

ct = nf_ct_get(skb, &ctinfo);
/* Can't track? It's not due to stress, or conntrack would
* have dropped it. Hence it's the user's responsibilty to
* packet filter it out, or implement conntrack/NAT for that
* protocol. 8) --RR
*/
if (!ct)
return NF_ACCEPT;

/* Don't try to NAT if this packet is not conntracked */
if (nf_ct_is_untracked(ct))
return NF_ACCEPT;

nat = nf_ct_nat_ext_add(ct);
if (nat == NULL)
return NF_ACCEPT;

switch (ctinfo) {
case IP_CT_RELATED:
case IP_CT_RELATED_REPLY:
if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
ops->hooknum))
return NF_DROP;
else
return NF_ACCEPT;
}
/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
case IP_CT_NEW:
/* Seen it before? This can happen for loopback, retrans,
* or local packets.
*/
if (!nf_nat_initialized(ct, maniptype)) {
unsigned int ret;

ret = nf_nat_rule_find(skb, ops->hooknum, in, out, ct);
if (ret != NF_ACCEPT)
return ret;
} else {
pr_debug("Already setup manip %s for ct %p\n",
maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
ct);
if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat, out))
goto oif_changed;
}
break;

default:
/* ESTABLISHED */
NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
ctinfo == IP_CT_ESTABLISHED_REPLY);
if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat, out))
goto oif_changed;
}

return nf_nat_packet(ct, ctinfo, ops->hooknum, skb);

oif_changed:
nf_ct_kill_acct(ct, ctinfo, skb);
return NF_DROP;
return nf_nat_ipv4_fn(ops, skb, in, out, iptable_nat_do_chain);
}

static unsigned int
nf_nat_ipv4_in(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
static unsigned int iptable_nat_ipv4_in(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
unsigned int ret;
__be32 daddr = ip_hdr(skb)->daddr;

ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
if (ret != NF_DROP && ret != NF_STOLEN &&
daddr != ip_hdr(skb)->daddr)
skb_dst_drop(skb);

return ret;
return nf_nat_ipv4_in(ops, skb, in, out, iptable_nat_do_chain);
}

static unsigned int
nf_nat_ipv4_out(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
static unsigned int iptable_nat_ipv4_out(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
#ifdef CONFIG_XFRM
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
int err;
#endif
unsigned int ret;

/* root is playing with raw sockets. */
if (skb->len < sizeof(struct iphdr) ||
ip_hdrlen(skb) < sizeof(struct iphdr))
return NF_ACCEPT;

ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
#ifdef CONFIG_XFRM
if (ret != NF_DROP && ret != NF_STOLEN &&
!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

if ((ct->tuplehash[dir].tuple.src.u3.ip !=
ct->tuplehash[!dir].tuple.dst.u3.ip) ||
(ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
ct->tuplehash[dir].tuple.src.u.all !=
ct->tuplehash[!dir].tuple.dst.u.all)) {
err = nf_xfrm_me_harder(skb, AF_INET);
if (err < 0)
ret = NF_DROP_ERR(err);
}
}
#endif
return ret;
return nf_nat_ipv4_out(ops, skb, in, out, iptable_nat_do_chain);
}

static unsigned int
nf_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
static unsigned int iptable_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int ret;
int err;

/* root is playing with raw sockets. */
if (skb->len < sizeof(struct iphdr) ||
ip_hdrlen(skb) < sizeof(struct iphdr))
return NF_ACCEPT;

ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

if (ct->tuplehash[dir].tuple.dst.u3.ip !=
ct->tuplehash[!dir].tuple.src.u3.ip) {
err = ip_route_me_harder(skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#ifdef CONFIG_XFRM
else if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
ct->tuplehash[dir].tuple.dst.u.all !=
ct->tuplehash[!dir].tuple.src.u.all) {
err = nf_xfrm_me_harder(skb, AF_INET);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#endif
}
return ret;
return nf_nat_ipv4_local_fn(ops, skb, in, out, iptable_nat_do_chain);
}

static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv4_in,
.hook = iptable_nat_ipv4_in,
.owner = THIS_MODULE,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_PRE_ROUTING,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv4_out,
.hook = iptable_nat_ipv4_out,
.owner = THIS_MODULE,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP_PRI_NAT_SRC,
},
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv4_local_fn,
.hook = iptable_nat_ipv4_local_fn,
.owner = THIS_MODULE,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_OUT,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv4_fn,
.hook = iptable_nat_ipv4_fn,
.owner = THIS_MODULE,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_IN,
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