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