// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/inetdevice.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_nat_masquerade.h>
struct masq_dev_work {
struct work_struct work;
struct net *net;
netns_tracker ns_tracker;
union nf_inet_addr addr;
int ifindex;
int (*iter)(struct nf_conn *i, void *data);
};
#define MAX_MASQ_WORKER_COUNT 16
static DEFINE_MUTEX(masq_mutex);
static unsigned int masq_refcnt __read_mostly;
static atomic_t masq_worker_count __read_mostly;
unsigned int
nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
const struct nf_nat_range2 *range,
const struct net_device *out)
{
struct nf_conn *ct;
struct nf_conn_nat *nat;
enum ip_conntrack_info ctinfo;
struct nf_nat_range2 newrange;
const struct rtable *rt;
__be32 newsrc, nh;
WARN_ON(hooknum != NF_INET_POST_ROUTING);
ct = nf_ct_get(skb, &ctinfo);
WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED_REPLY)));
/* Source address is 0.0.0.0 - locally generated packet that is
* probably not supposed to be masqueraded.
*/
if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
return NF_ACCEPT;
rt = skb_rtable(skb);
nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE);
if (!newsrc) {
pr_info("%s ate my IP address\n", out->name);
return NF_DROP;
}
nat = nf_ct_nat_ext_add(ct);
if (nat)
nat->masq_index = out->ifindex;
/* Transfer from original range. */
memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.ip = newsrc;
newrange.max_addr.ip = newsrc;
newrange.min_proto = range->min_proto;
newrange.max_proto = range->max_proto;
/* Hand modified range to generic setup. */
return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
static void iterate_cleanup_work(struct work_struct *work)
{
struct nf_ct_iter_data iter_data = {};
struct masq_dev_work *w;
w = container_of(work, struct masq_dev_work, work);
iter_data.net = w->net;
iter_data.data = (void *)w;
nf_ct_iterate_cleanup_net(w->iter, &iter_data);
put_net_track(w->net, &w->ns_tracker);
kfree(w);
atomic_dec(&masq_worker_count);
module_put(THIS_MODULE);
}
/* Iterate conntrack table in the background and remove conntrack entries
* that use the device/address being removed.
*
* In case too many work items have been queued already or memory allocation
* fails iteration is skipped, conntrack entries will time out eventually.
*/
static void nf_nat_masq_schedule(struct net *net, union nf_inet_addr *addr,
int ifindex,
int (*iter)(struct nf_conn *i, void *data),
gfp_t gfp_flags)
{
struct masq_dev_work *w;
if (atomic_read(&masq_worker_count) > MAX_MASQ_WORKER_COUNT)
return;
net = maybe_get_net(net);
if (!net)
return;
if (!try_module_get(THIS_MODULE))
goto err_module;
w = kzalloc(sizeof(*w), gfp_flags);
if (w) {
/* We can overshoot MAX_MASQ_WORKER_COUNT, no big deal */
atomic_inc(&masq_worker_count);
INIT_WORK(&w->work, iterate_cleanup_work);
w->ifindex = ifindex;
w->net = net;
netns_tracker_alloc(net, &w->ns_tracker, gfp_flags);
w->iter = iter;
if (addr)
w->addr = *addr;
schedule_work(&w->work);
return;
}
module_put(THIS_MODULE);
err_module:
put_net(net);
}
static int device_cmp(struct nf_conn *i, void *arg)
{
const struct nf_conn_nat *nat = nfct_nat(i);
const struct masq_dev_work *w = arg;
if (!nat)
return 0;
return nat->masq_index == w->ifindex;
}
static int masq_device_event(struct notifier_block *this,
unsigned long event,
void *ptr)
{
const struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);
if (event == NETDEV_DOWN) {
/* Device was downed. Search entire table for
* conntracks which were associated with that device,
* and forget them.
*/
nf_nat_masq_schedule(net, NULL, dev->ifindex,
device_cmp, GFP_KERNEL);
}
return NOTIFY_DONE;
}
static int inet_cmp(struct nf_conn *ct, void *ptr)
{
struct nf_conntrack_tuple *tuple;
struct masq_dev_work *w = ptr;
if (!device_cmp(ct, ptr))
return 0;
tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
return nf_inet_addr_cmp(&w->addr, &tuple->dst.u3);
}
static int masq_inet_event(struct notifier_block *this,
unsigned long event,
void *ptr)
{
const struct in_ifaddr *ifa = ptr;
const struct in_device *idev;
const struct net_device *dev;
union nf_inet_addr addr;
if (event != NETDEV_DOWN)
return NOTIFY_DONE;
/* The masq_dev_notifier will catch the case of the device going
* down. So if the inetdev is dead and being destroyed we have
* no work to do. Otherwise this is an individual address removal
* and we have to perform the flush.
*/
idev = ifa->ifa_dev;
if (idev->dead)
return NOTIFY_DONE;
memset(&addr, 0, sizeof(addr));
addr.ip = ifa->ifa_address;
dev = idev->dev;
nf_nat_masq_schedule(dev_net(idev->dev), &addr, dev->ifindex,
inet_cmp, GFP_KERNEL);
return NOTIFY_DONE;
}
static struct notifier_block masq_dev_notifier = {
.notifier_call = masq_device_event,
};
static struct notifier_block masq_inet_notifier = {
.notifier_call = masq_inet_event,
};
#if IS_ENABLED(CONFIG_IPV6)
static int
nat_ipv6_dev_get_saddr(struct net *net, const struct net_device *dev,
const struct in6_addr *daddr, unsigned int srcprefs,
struct in6_addr *saddr)
{
#ifdef CONFIG_IPV6_MODULE
const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
if (!v6_ops)
return -EHOSTUNREACH;
return v6_ops->dev_get_saddr(net, dev, daddr, srcprefs, saddr);
#else
return ipv6_dev_get_saddr(net, dev, daddr, srcprefs, saddr);
#endif
}
unsigned int
nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
const struct net_device *out)
{
enum ip_conntrack_info ctinfo;
struct nf_conn_nat *nat;
struct in6_addr src;
struct nf_conn *ct;
struct nf_nat_range2 newrange;
ct = nf_ct_get(skb, &ctinfo);
WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED_REPLY)));
if (nat_ipv6_dev_get_saddr(nf_ct_net(ct), out,
&ipv6_hdr(skb)->daddr, 0, &src) < 0)
return NF_DROP;
nat = nf_ct_nat_ext_add(ct);
if (nat)
nat->masq_index = out->ifindex;
newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.in6 = src;
newrange.max_addr.in6 = src;
newrange.min_proto = range->min_proto;
newrange.max_proto = range->max_proto;
return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6);
/* atomic notifier; can't call nf_ct_iterate_cleanup_net (it can sleep).
*
* Defer it to the system workqueue.
*
* As we can have 'a lot' of inet_events (depending on amount of ipv6
* addresses being deleted), we also need to limit work item queue.
*/
static int masq_inet6_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct inet6_ifaddr *ifa = ptr;
const struct net_device *dev;
union nf_inet_addr addr;
if (event != NETDEV_DOWN)
return NOTIFY_DONE;
dev = ifa->idev->dev;
memset(&addr, 0, sizeof(addr));
addr.in6 = ifa->addr;
nf_nat_masq_schedule(dev_net(dev), &addr, dev->ifindex, inet_cmp,
GFP_ATOMIC);
return NOTIFY_DONE;
}
static struct notifier_block masq_inet6_notifier = {
.notifier_call = masq_inet6_event,
};
static int nf_nat_masquerade_ipv6_register_notifier(void)
{
return register_inet6addr_notifier(&masq_inet6_notifier);
}
#else
static inline int nf_nat_masquerade_ipv6_register_notifier(void) { return 0; }
#endif
int nf_nat_masquerade_inet_register_notifiers(void)
{
int ret = 0;
mutex_lock(&masq_mutex);
if (WARN_ON_ONCE(masq_refcnt == UINT_MAX)) {
ret = -EOVERFLOW;
goto out_unlock;
}
/* check if the notifier was already set */
if (++masq_refcnt > 1)
goto out_unlock;
/* Register for device down reports */
ret = register_netdevice_notifier(&masq_dev_notifier);
if (ret)
goto err_dec;
/* Register IP address change reports */
ret = register_inetaddr_notifier(&masq_inet_notifier);
if (ret)
goto err_unregister;
ret = nf_nat_masquerade_ipv6_register_notifier();
if (ret)
goto err_unreg_inet;
mutex_unlock(&masq_mutex);
return ret;
err_unreg_inet:
unregister_inetaddr_notifier(&masq_inet_notifier);
err_unregister:
unregister_netdevice_notifier(&masq_dev_notifier);
err_dec:
masq_refcnt--;
out_unlock:
mutex_unlock(&masq_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_register_notifiers);
void nf_nat_masquerade_inet_unregister_notifiers(void)
{
mutex_lock(&masq_mutex);
/* check if the notifiers still have clients */
if (--masq_refcnt > 0)
goto out_unlock;
unregister_netdevice_notifier(&masq_dev_notifier);
unregister_inetaddr_notifier(&masq_inet_notifier);
#if IS_ENABLED(CONFIG_IPV6)
unregister_inet6addr_notifier(&masq_inet6_notifier);
#endif
out_unlock:
mutex_unlock(&masq_mutex);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_unregister_notifiers);
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