// SPDX-License-Identifier: GPL-2.0 #include #include #include #include #include #include #include struct masq_dev_work { struct work_struct work; struct net *net; 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 masq_dev_work *w; w = container_of(work, struct masq_dev_work, work); nf_ct_iterate_cleanup_net(w->net, w->iter, (void *)w, 0, 0); put_net(w->net); 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; 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);