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- // SPDX-License-Identifier: GPL-2.0-only
- /* Helper handling for netfilter. */
- /* (C) 1999-2001 Paul `Rusty' Russell
- * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
- * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
- * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
- */
- #include <linux/types.h>
- #include <linux/netfilter.h>
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/vmalloc.h>
- #include <linux/stddef.h>
- #include <linux/random.h>
- #include <linux/err.h>
- #include <linux/kernel.h>
- #include <linux/netdevice.h>
- #include <linux/rculist.h>
- #include <linux/rtnetlink.h>
- #include <net/netfilter/nf_conntrack.h>
- #include <net/netfilter/nf_conntrack_core.h>
- #include <net/netfilter/nf_conntrack_ecache.h>
- #include <net/netfilter/nf_conntrack_extend.h>
- #include <net/netfilter/nf_conntrack_helper.h>
- #include <net/netfilter/nf_conntrack_l4proto.h>
- #include <net/netfilter/nf_log.h>
- static DEFINE_MUTEX(nf_ct_helper_mutex);
- struct hlist_head *nf_ct_helper_hash __read_mostly;
- EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
- unsigned int nf_ct_helper_hsize __read_mostly;
- EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
- static unsigned int nf_ct_helper_count __read_mostly;
- static bool nf_ct_auto_assign_helper __read_mostly = false;
- module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
- MODULE_PARM_DESC(nf_conntrack_helper,
- "Enable automatic conntrack helper assignment (default 0)");
- static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
- static struct list_head nf_ct_nat_helpers __read_mostly;
- /* Stupid hash, but collision free for the default registrations of the
- * helpers currently in the kernel. */
- static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
- {
- return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
- (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
- }
- static struct nf_conntrack_helper *
- __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
- {
- struct nf_conntrack_helper *helper;
- struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
- unsigned int h;
- if (!nf_ct_helper_count)
- return NULL;
- h = helper_hash(tuple);
- hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
- if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
- return helper;
- }
- return NULL;
- }
- struct nf_conntrack_helper *
- __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
- {
- struct nf_conntrack_helper *h;
- unsigned int i;
- for (i = 0; i < nf_ct_helper_hsize; i++) {
- hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
- if (strcmp(h->name, name))
- continue;
- if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
- h->tuple.src.l3num != l3num)
- continue;
- if (h->tuple.dst.protonum == protonum)
- return h;
- }
- }
- return NULL;
- }
- EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
- struct nf_conntrack_helper *
- nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
- {
- struct nf_conntrack_helper *h;
- rcu_read_lock();
- h = __nf_conntrack_helper_find(name, l3num, protonum);
- #ifdef CONFIG_MODULES
- if (h == NULL) {
- rcu_read_unlock();
- if (request_module("nfct-helper-%s", name) == 0) {
- rcu_read_lock();
- h = __nf_conntrack_helper_find(name, l3num, protonum);
- } else {
- return h;
- }
- }
- #endif
- if (h != NULL && !try_module_get(h->me))
- h = NULL;
- if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
- module_put(h->me);
- h = NULL;
- }
- rcu_read_unlock();
- return h;
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
- void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
- {
- refcount_dec(&helper->refcnt);
- module_put(helper->me);
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
- static struct nf_conntrack_nat_helper *
- nf_conntrack_nat_helper_find(const char *mod_name)
- {
- struct nf_conntrack_nat_helper *cur;
- bool found = false;
- list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
- if (!strcmp(cur->mod_name, mod_name)) {
- found = true;
- break;
- }
- }
- return found ? cur : NULL;
- }
- int
- nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
- {
- struct nf_conntrack_helper *h;
- struct nf_conntrack_nat_helper *nat;
- char mod_name[NF_CT_HELPER_NAME_LEN];
- int ret = 0;
- rcu_read_lock();
- h = __nf_conntrack_helper_find(name, l3num, protonum);
- if (!h) {
- rcu_read_unlock();
- return -ENOENT;
- }
- nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
- if (!nat) {
- snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
- rcu_read_unlock();
- request_module(mod_name);
- rcu_read_lock();
- nat = nf_conntrack_nat_helper_find(mod_name);
- if (!nat) {
- rcu_read_unlock();
- return -ENOENT;
- }
- }
- if (!try_module_get(nat->module))
- ret = -ENOENT;
- rcu_read_unlock();
- return ret;
- }
- EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
- void nf_nat_helper_put(struct nf_conntrack_helper *helper)
- {
- struct nf_conntrack_nat_helper *nat;
- nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
- if (WARN_ON_ONCE(!nat))
- return;
- module_put(nat->module);
- }
- EXPORT_SYMBOL_GPL(nf_nat_helper_put);
- struct nf_conn_help *
- nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
- {
- struct nf_conn_help *help;
- help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
- if (help)
- INIT_HLIST_HEAD(&help->expectations);
- else
- pr_debug("failed to add helper extension area");
- return help;
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
- static struct nf_conntrack_helper *
- nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
- {
- if (!net->ct.sysctl_auto_assign_helper) {
- if (net->ct.auto_assign_helper_warned)
- return NULL;
- if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
- return NULL;
- pr_info("nf_conntrack: default automatic helper assignment "
- "has been turned off for security reasons and CT-based "
- " firewall rule not found. Use the iptables CT target "
- "to attach helpers instead.\n");
- net->ct.auto_assign_helper_warned = 1;
- return NULL;
- }
- return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
- }
- int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
- gfp_t flags)
- {
- struct nf_conntrack_helper *helper = NULL;
- struct nf_conn_help *help;
- struct net *net = nf_ct_net(ct);
- /* We already got a helper explicitly attached. The function
- * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
- * the helper up again. Since now the user is in full control of
- * making consistent helper configurations, skip this automatic
- * re-lookup, otherwise we'll lose the helper.
- */
- if (test_bit(IPS_HELPER_BIT, &ct->status))
- return 0;
- if (tmpl != NULL) {
- help = nfct_help(tmpl);
- if (help != NULL) {
- helper = help->helper;
- set_bit(IPS_HELPER_BIT, &ct->status);
- }
- }
- help = nfct_help(ct);
- if (helper == NULL) {
- helper = nf_ct_lookup_helper(ct, net);
- if (helper == NULL) {
- if (help)
- RCU_INIT_POINTER(help->helper, NULL);
- return 0;
- }
- }
- if (help == NULL) {
- help = nf_ct_helper_ext_add(ct, flags);
- if (help == NULL)
- return -ENOMEM;
- } else {
- /* We only allow helper re-assignment of the same sort since
- * we cannot reallocate the helper extension area.
- */
- struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
- if (tmp && tmp->help != helper->help) {
- RCU_INIT_POINTER(help->helper, NULL);
- return 0;
- }
- }
- rcu_assign_pointer(help->helper, helper);
- return 0;
- }
- EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
- /* appropriate ct lock protecting must be taken by caller */
- static int unhelp(struct nf_conn *ct, void *me)
- {
- struct nf_conn_help *help = nfct_help(ct);
- if (help && rcu_dereference_raw(help->helper) == me) {
- nf_conntrack_event(IPCT_HELPER, ct);
- RCU_INIT_POINTER(help->helper, NULL);
- }
- /* We are not intended to delete this conntrack. */
- return 0;
- }
- void nf_ct_helper_destroy(struct nf_conn *ct)
- {
- struct nf_conn_help *help = nfct_help(ct);
- struct nf_conntrack_helper *helper;
- if (help) {
- rcu_read_lock();
- helper = rcu_dereference(help->helper);
- if (helper && helper->destroy)
- helper->destroy(ct);
- rcu_read_unlock();
- }
- }
- static LIST_HEAD(nf_ct_helper_expectfn_list);
- void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
- {
- spin_lock_bh(&nf_conntrack_expect_lock);
- list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
- spin_unlock_bh(&nf_conntrack_expect_lock);
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
- void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
- {
- spin_lock_bh(&nf_conntrack_expect_lock);
- list_del_rcu(&n->head);
- spin_unlock_bh(&nf_conntrack_expect_lock);
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
- /* Caller should hold the rcu lock */
- struct nf_ct_helper_expectfn *
- nf_ct_helper_expectfn_find_by_name(const char *name)
- {
- struct nf_ct_helper_expectfn *cur;
- bool found = false;
- list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
- if (!strcmp(cur->name, name)) {
- found = true;
- break;
- }
- }
- return found ? cur : NULL;
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
- /* Caller should hold the rcu lock */
- struct nf_ct_helper_expectfn *
- nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
- {
- struct nf_ct_helper_expectfn *cur;
- bool found = false;
- list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
- if (cur->expectfn == symbol) {
- found = true;
- break;
- }
- }
- return found ? cur : NULL;
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
- __printf(3, 4)
- void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
- const char *fmt, ...)
- {
- const struct nf_conn_help *help;
- const struct nf_conntrack_helper *helper;
- struct va_format vaf;
- va_list args;
- va_start(args, fmt);
- vaf.fmt = fmt;
- vaf.va = &args;
- /* Called from the helper function, this call never fails */
- help = nfct_help(ct);
- /* rcu_read_lock()ed by nf_hook_thresh */
- helper = rcu_dereference(help->helper);
- nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
- "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
- va_end(args);
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_log);
- int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
- {
- struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
- unsigned int h = helper_hash(&me->tuple);
- struct nf_conntrack_helper *cur;
- int ret = 0, i;
- BUG_ON(me->expect_policy == NULL);
- BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
- BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
- if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
- return -EINVAL;
- mutex_lock(&nf_ct_helper_mutex);
- for (i = 0; i < nf_ct_helper_hsize; i++) {
- hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
- if (!strcmp(cur->name, me->name) &&
- (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
- cur->tuple.src.l3num == me->tuple.src.l3num) &&
- cur->tuple.dst.protonum == me->tuple.dst.protonum) {
- ret = -EEXIST;
- goto out;
- }
- }
- }
- /* avoid unpredictable behaviour for auto_assign_helper */
- if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
- hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
- if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
- &mask)) {
- ret = -EEXIST;
- goto out;
- }
- }
- }
- refcount_set(&me->refcnt, 1);
- hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
- nf_ct_helper_count++;
- out:
- mutex_unlock(&nf_ct_helper_mutex);
- return ret;
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
- static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
- {
- struct nf_conn_help *help = nfct_help(exp->master);
- const struct nf_conntrack_helper *me = data;
- const struct nf_conntrack_helper *this;
- if (exp->helper == me)
- return true;
- this = rcu_dereference_protected(help->helper,
- lockdep_is_held(&nf_conntrack_expect_lock));
- return this == me;
- }
- void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
- {
- mutex_lock(&nf_ct_helper_mutex);
- hlist_del_rcu(&me->hnode);
- nf_ct_helper_count--;
- mutex_unlock(&nf_ct_helper_mutex);
- /* Make sure every nothing is still using the helper unless its a
- * connection in the hash.
- */
- synchronize_rcu();
- nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
- nf_ct_iterate_destroy(unhelp, me);
- /* Maybe someone has gotten the helper already when unhelp above.
- * So need to wait it.
- */
- synchronize_rcu();
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
- void nf_ct_helper_init(struct nf_conntrack_helper *helper,
- u16 l3num, u16 protonum, const char *name,
- u16 default_port, u16 spec_port, u32 id,
- const struct nf_conntrack_expect_policy *exp_pol,
- u32 expect_class_max,
- int (*help)(struct sk_buff *skb, unsigned int protoff,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo),
- int (*from_nlattr)(struct nlattr *attr,
- struct nf_conn *ct),
- struct module *module)
- {
- helper->tuple.src.l3num = l3num;
- helper->tuple.dst.protonum = protonum;
- helper->tuple.src.u.all = htons(spec_port);
- helper->expect_policy = exp_pol;
- helper->expect_class_max = expect_class_max;
- helper->help = help;
- helper->from_nlattr = from_nlattr;
- helper->me = module;
- snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
- NF_NAT_HELPER_PREFIX "%s", name);
- if (spec_port == default_port)
- snprintf(helper->name, sizeof(helper->name), "%s", name);
- else
- snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
- }
- EXPORT_SYMBOL_GPL(nf_ct_helper_init);
- int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
- unsigned int n)
- {
- unsigned int i;
- int err = 0;
- for (i = 0; i < n; i++) {
- err = nf_conntrack_helper_register(&helper[i]);
- if (err < 0)
- goto err;
- }
- return err;
- err:
- if (i > 0)
- nf_conntrack_helpers_unregister(helper, i);
- return err;
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
- void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
- unsigned int n)
- {
- while (n-- > 0)
- nf_conntrack_helper_unregister(&helper[n]);
- }
- EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
- void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
- {
- mutex_lock(&nf_ct_nat_helpers_mutex);
- list_add_rcu(&nat->list, &nf_ct_nat_helpers);
- mutex_unlock(&nf_ct_nat_helpers_mutex);
- }
- EXPORT_SYMBOL_GPL(nf_nat_helper_register);
- void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
- {
- mutex_lock(&nf_ct_nat_helpers_mutex);
- list_del_rcu(&nat->list);
- mutex_unlock(&nf_ct_nat_helpers_mutex);
- }
- EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
- static const struct nf_ct_ext_type helper_extend = {
- .len = sizeof(struct nf_conn_help),
- .align = __alignof__(struct nf_conn_help),
- .id = NF_CT_EXT_HELPER,
- };
- void nf_conntrack_helper_pernet_init(struct net *net)
- {
- net->ct.auto_assign_helper_warned = false;
- net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
- }
- int nf_conntrack_helper_init(void)
- {
- int ret;
- nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
- nf_ct_helper_hash =
- nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
- if (!nf_ct_helper_hash)
- return -ENOMEM;
- ret = nf_ct_extend_register(&helper_extend);
- if (ret < 0) {
- pr_err("nf_ct_helper: Unable to register helper extension.\n");
- goto out_extend;
- }
- INIT_LIST_HEAD(&nf_ct_nat_helpers);
- return 0;
- out_extend:
- kvfree(nf_ct_helper_hash);
- return ret;
- }
- void nf_conntrack_helper_fini(void)
- {
- nf_ct_extend_unregister(&helper_extend);
- kvfree(nf_ct_helper_hash);
- }
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