![Toke Høiland-Jørgensen](/assets/img/avatar_default.png)
This adds a global netfilter function to extract a conntrack tuple from an skb. The function uses a new function added to nf_ct_hook, which will try to get the tuple from skb->_nfct, and do a full lookup if that fails. This makes it possible to use the lookup function before the skb has passed through the conntrack init hooks (e.g., in an ingress qdisc). The tuple is copied to the caller to avoid issues with reference counting. The function returns false if conntrack is not loaded, allowing it to be used without incurring a module dependency on conntrack. This is used by the NAT mode in sch_cake. Cc: netfilter-devel@vger.kernel.org Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk> Signed-off-by: David S. Miller <davem@davemloft.net>
694 lines
16 KiB
C
694 lines
16 KiB
C
/* netfilter.c: look after the filters for various protocols.
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* Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
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*
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* Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
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* way.
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*
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* This code is GPL.
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*/
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#include <linux/kernel.h>
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#include <linux/netfilter.h>
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#include <net/protocol.h>
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#include <linux/init.h>
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#include <linux/skbuff.h>
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#include <linux/wait.h>
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#include <linux/module.h>
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#include <linux/interrupt.h>
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#include <linux/if.h>
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#include <linux/netdevice.h>
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#include <linux/netfilter_ipv6.h>
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#include <linux/inetdevice.h>
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#include <linux/proc_fs.h>
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#include <linux/mutex.h>
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#include <linux/mm.h>
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#include <linux/rcupdate.h>
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#include <net/net_namespace.h>
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#include <net/sock.h>
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#include "nf_internals.h"
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const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
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EXPORT_SYMBOL_GPL(nf_ipv6_ops);
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DEFINE_PER_CPU(bool, nf_skb_duplicated);
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EXPORT_SYMBOL_GPL(nf_skb_duplicated);
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#ifdef HAVE_JUMP_LABEL
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struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
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EXPORT_SYMBOL(nf_hooks_needed);
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#endif
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static DEFINE_MUTEX(nf_hook_mutex);
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/* max hooks per family/hooknum */
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#define MAX_HOOK_COUNT 1024
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#define nf_entry_dereference(e) \
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rcu_dereference_protected(e, lockdep_is_held(&nf_hook_mutex))
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static struct nf_hook_entries *allocate_hook_entries_size(u16 num)
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{
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struct nf_hook_entries *e;
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size_t alloc = sizeof(*e) +
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sizeof(struct nf_hook_entry) * num +
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sizeof(struct nf_hook_ops *) * num +
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sizeof(struct nf_hook_entries_rcu_head);
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if (num == 0)
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return NULL;
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e = kvzalloc(alloc, GFP_KERNEL);
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if (e)
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e->num_hook_entries = num;
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return e;
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}
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static void __nf_hook_entries_free(struct rcu_head *h)
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{
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struct nf_hook_entries_rcu_head *head;
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head = container_of(h, struct nf_hook_entries_rcu_head, head);
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kvfree(head->allocation);
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}
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static void nf_hook_entries_free(struct nf_hook_entries *e)
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{
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struct nf_hook_entries_rcu_head *head;
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struct nf_hook_ops **ops;
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unsigned int num;
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if (!e)
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return;
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num = e->num_hook_entries;
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ops = nf_hook_entries_get_hook_ops(e);
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head = (void *)&ops[num];
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head->allocation = e;
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call_rcu(&head->head, __nf_hook_entries_free);
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}
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static unsigned int accept_all(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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return NF_ACCEPT; /* ACCEPT makes nf_hook_slow call next hook */
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}
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static const struct nf_hook_ops dummy_ops = {
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.hook = accept_all,
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.priority = INT_MIN,
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};
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static struct nf_hook_entries *
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nf_hook_entries_grow(const struct nf_hook_entries *old,
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const struct nf_hook_ops *reg)
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{
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unsigned int i, alloc_entries, nhooks, old_entries;
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struct nf_hook_ops **orig_ops = NULL;
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struct nf_hook_ops **new_ops;
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struct nf_hook_entries *new;
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bool inserted = false;
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alloc_entries = 1;
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old_entries = old ? old->num_hook_entries : 0;
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if (old) {
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orig_ops = nf_hook_entries_get_hook_ops(old);
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for (i = 0; i < old_entries; i++) {
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if (orig_ops[i] != &dummy_ops)
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alloc_entries++;
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}
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}
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if (alloc_entries > MAX_HOOK_COUNT)
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return ERR_PTR(-E2BIG);
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new = allocate_hook_entries_size(alloc_entries);
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if (!new)
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return ERR_PTR(-ENOMEM);
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new_ops = nf_hook_entries_get_hook_ops(new);
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i = 0;
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nhooks = 0;
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while (i < old_entries) {
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if (orig_ops[i] == &dummy_ops) {
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++i;
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continue;
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}
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if (inserted || reg->priority > orig_ops[i]->priority) {
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new_ops[nhooks] = (void *)orig_ops[i];
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new->hooks[nhooks] = old->hooks[i];
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i++;
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} else {
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new_ops[nhooks] = (void *)reg;
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new->hooks[nhooks].hook = reg->hook;
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new->hooks[nhooks].priv = reg->priv;
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inserted = true;
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}
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nhooks++;
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}
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if (!inserted) {
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new_ops[nhooks] = (void *)reg;
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new->hooks[nhooks].hook = reg->hook;
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new->hooks[nhooks].priv = reg->priv;
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}
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return new;
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}
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static void hooks_validate(const struct nf_hook_entries *hooks)
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{
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#ifdef CONFIG_DEBUG_KERNEL
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struct nf_hook_ops **orig_ops;
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int prio = INT_MIN;
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size_t i = 0;
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orig_ops = nf_hook_entries_get_hook_ops(hooks);
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for (i = 0; i < hooks->num_hook_entries; i++) {
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if (orig_ops[i] == &dummy_ops)
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continue;
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WARN_ON(orig_ops[i]->priority < prio);
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if (orig_ops[i]->priority > prio)
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prio = orig_ops[i]->priority;
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}
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#endif
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}
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int nf_hook_entries_insert_raw(struct nf_hook_entries __rcu **pp,
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const struct nf_hook_ops *reg)
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{
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struct nf_hook_entries *new_hooks;
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struct nf_hook_entries *p;
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p = rcu_dereference_raw(*pp);
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new_hooks = nf_hook_entries_grow(p, reg);
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if (IS_ERR(new_hooks))
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return PTR_ERR(new_hooks);
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hooks_validate(new_hooks);
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rcu_assign_pointer(*pp, new_hooks);
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BUG_ON(p == new_hooks);
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nf_hook_entries_free(p);
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return 0;
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}
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EXPORT_SYMBOL_GPL(nf_hook_entries_insert_raw);
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/*
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* __nf_hook_entries_try_shrink - try to shrink hook array
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*
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* @old -- current hook blob at @pp
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* @pp -- location of hook blob
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*
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* Hook unregistration must always succeed, so to-be-removed hooks
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* are replaced by a dummy one that will just move to next hook.
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*
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* This counts the current dummy hooks, attempts to allocate new blob,
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* copies the live hooks, then replaces and discards old one.
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*
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* return values:
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*
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* Returns address to free, or NULL.
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*/
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static void *__nf_hook_entries_try_shrink(struct nf_hook_entries *old,
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struct nf_hook_entries __rcu **pp)
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{
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unsigned int i, j, skip = 0, hook_entries;
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struct nf_hook_entries *new = NULL;
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struct nf_hook_ops **orig_ops;
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struct nf_hook_ops **new_ops;
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if (WARN_ON_ONCE(!old))
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return NULL;
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orig_ops = nf_hook_entries_get_hook_ops(old);
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for (i = 0; i < old->num_hook_entries; i++) {
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if (orig_ops[i] == &dummy_ops)
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skip++;
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}
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/* if skip == hook_entries all hooks have been removed */
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hook_entries = old->num_hook_entries;
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if (skip == hook_entries)
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goto out_assign;
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if (skip == 0)
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return NULL;
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hook_entries -= skip;
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new = allocate_hook_entries_size(hook_entries);
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if (!new)
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return NULL;
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new_ops = nf_hook_entries_get_hook_ops(new);
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for (i = 0, j = 0; i < old->num_hook_entries; i++) {
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if (orig_ops[i] == &dummy_ops)
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continue;
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new->hooks[j] = old->hooks[i];
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new_ops[j] = (void *)orig_ops[i];
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j++;
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}
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hooks_validate(new);
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out_assign:
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rcu_assign_pointer(*pp, new);
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return old;
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}
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static struct nf_hook_entries __rcu **
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nf_hook_entry_head(struct net *net, int pf, unsigned int hooknum,
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struct net_device *dev)
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{
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switch (pf) {
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case NFPROTO_NETDEV:
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break;
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#ifdef CONFIG_NETFILTER_FAMILY_ARP
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case NFPROTO_ARP:
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if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_arp) <= hooknum))
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return NULL;
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return net->nf.hooks_arp + hooknum;
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#endif
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#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
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case NFPROTO_BRIDGE:
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if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_bridge) <= hooknum))
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return NULL;
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return net->nf.hooks_bridge + hooknum;
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#endif
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case NFPROTO_IPV4:
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if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_ipv4) <= hooknum))
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return NULL;
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return net->nf.hooks_ipv4 + hooknum;
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case NFPROTO_IPV6:
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if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_ipv6) <= hooknum))
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return NULL;
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return net->nf.hooks_ipv6 + hooknum;
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#if IS_ENABLED(CONFIG_DECNET)
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case NFPROTO_DECNET:
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if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_decnet) <= hooknum))
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return NULL;
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return net->nf.hooks_decnet + hooknum;
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#endif
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default:
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WARN_ON_ONCE(1);
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return NULL;
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}
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#ifdef CONFIG_NETFILTER_INGRESS
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if (hooknum == NF_NETDEV_INGRESS) {
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if (dev && dev_net(dev) == net)
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return &dev->nf_hooks_ingress;
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}
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#endif
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WARN_ON_ONCE(1);
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return NULL;
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}
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static int __nf_register_net_hook(struct net *net, int pf,
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const struct nf_hook_ops *reg)
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{
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struct nf_hook_entries *p, *new_hooks;
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struct nf_hook_entries __rcu **pp;
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if (pf == NFPROTO_NETDEV) {
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#ifndef CONFIG_NETFILTER_INGRESS
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if (reg->hooknum == NF_NETDEV_INGRESS)
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return -EOPNOTSUPP;
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#endif
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if (reg->hooknum != NF_NETDEV_INGRESS ||
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!reg->dev || dev_net(reg->dev) != net)
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return -EINVAL;
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}
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pp = nf_hook_entry_head(net, pf, reg->hooknum, reg->dev);
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if (!pp)
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return -EINVAL;
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mutex_lock(&nf_hook_mutex);
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p = nf_entry_dereference(*pp);
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new_hooks = nf_hook_entries_grow(p, reg);
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if (!IS_ERR(new_hooks))
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rcu_assign_pointer(*pp, new_hooks);
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mutex_unlock(&nf_hook_mutex);
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if (IS_ERR(new_hooks))
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return PTR_ERR(new_hooks);
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hooks_validate(new_hooks);
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#ifdef CONFIG_NETFILTER_INGRESS
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if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
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net_inc_ingress_queue();
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#endif
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#ifdef HAVE_JUMP_LABEL
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static_key_slow_inc(&nf_hooks_needed[pf][reg->hooknum]);
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#endif
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BUG_ON(p == new_hooks);
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nf_hook_entries_free(p);
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return 0;
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}
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/*
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* nf_remove_net_hook - remove a hook from blob
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*
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* @oldp: current address of hook blob
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* @unreg: hook to unregister
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*
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* This cannot fail, hook unregistration must always succeed.
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* Therefore replace the to-be-removed hook with a dummy hook.
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*/
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static bool nf_remove_net_hook(struct nf_hook_entries *old,
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const struct nf_hook_ops *unreg)
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{
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struct nf_hook_ops **orig_ops;
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unsigned int i;
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orig_ops = nf_hook_entries_get_hook_ops(old);
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for (i = 0; i < old->num_hook_entries; i++) {
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if (orig_ops[i] != unreg)
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continue;
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WRITE_ONCE(old->hooks[i].hook, accept_all);
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WRITE_ONCE(orig_ops[i], &dummy_ops);
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return true;
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}
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return false;
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}
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static void __nf_unregister_net_hook(struct net *net, int pf,
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const struct nf_hook_ops *reg)
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{
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struct nf_hook_entries __rcu **pp;
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struct nf_hook_entries *p;
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pp = nf_hook_entry_head(net, pf, reg->hooknum, reg->dev);
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if (!pp)
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return;
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mutex_lock(&nf_hook_mutex);
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p = nf_entry_dereference(*pp);
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if (WARN_ON_ONCE(!p)) {
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mutex_unlock(&nf_hook_mutex);
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return;
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}
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if (nf_remove_net_hook(p, reg)) {
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#ifdef CONFIG_NETFILTER_INGRESS
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if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
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net_dec_ingress_queue();
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#endif
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#ifdef HAVE_JUMP_LABEL
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static_key_slow_dec(&nf_hooks_needed[pf][reg->hooknum]);
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#endif
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} else {
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WARN_ONCE(1, "hook not found, pf %d num %d", pf, reg->hooknum);
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}
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p = __nf_hook_entries_try_shrink(p, pp);
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mutex_unlock(&nf_hook_mutex);
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if (!p)
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return;
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nf_queue_nf_hook_drop(net);
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nf_hook_entries_free(p);
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}
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void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg)
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{
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if (reg->pf == NFPROTO_INET) {
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__nf_unregister_net_hook(net, NFPROTO_IPV4, reg);
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__nf_unregister_net_hook(net, NFPROTO_IPV6, reg);
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} else {
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__nf_unregister_net_hook(net, reg->pf, reg);
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}
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}
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EXPORT_SYMBOL(nf_unregister_net_hook);
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void nf_hook_entries_delete_raw(struct nf_hook_entries __rcu **pp,
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const struct nf_hook_ops *reg)
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{
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struct nf_hook_entries *p;
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p = rcu_dereference_raw(*pp);
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if (nf_remove_net_hook(p, reg)) {
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p = __nf_hook_entries_try_shrink(p, pp);
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nf_hook_entries_free(p);
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}
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}
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EXPORT_SYMBOL_GPL(nf_hook_entries_delete_raw);
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int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg)
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{
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int err;
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if (reg->pf == NFPROTO_INET) {
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err = __nf_register_net_hook(net, NFPROTO_IPV4, reg);
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if (err < 0)
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return err;
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err = __nf_register_net_hook(net, NFPROTO_IPV6, reg);
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if (err < 0) {
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__nf_unregister_net_hook(net, NFPROTO_IPV4, reg);
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return err;
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}
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} else {
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err = __nf_register_net_hook(net, reg->pf, reg);
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if (err < 0)
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return err;
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}
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return 0;
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}
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EXPORT_SYMBOL(nf_register_net_hook);
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int nf_register_net_hooks(struct net *net, const struct nf_hook_ops *reg,
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unsigned int n)
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{
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unsigned int i;
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int err = 0;
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for (i = 0; i < n; i++) {
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err = nf_register_net_hook(net, ®[i]);
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if (err)
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goto err;
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}
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return err;
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err:
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if (i > 0)
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nf_unregister_net_hooks(net, reg, i);
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return err;
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}
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EXPORT_SYMBOL(nf_register_net_hooks);
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void nf_unregister_net_hooks(struct net *net, const struct nf_hook_ops *reg,
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unsigned int hookcount)
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{
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unsigned int i;
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for (i = 0; i < hookcount; i++)
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nf_unregister_net_hook(net, ®[i]);
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}
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EXPORT_SYMBOL(nf_unregister_net_hooks);
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/* Returns 1 if okfn() needs to be executed by the caller,
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* -EPERM for NF_DROP, 0 otherwise. Caller must hold rcu_read_lock. */
|
|
int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state,
|
|
const struct nf_hook_entries *e, unsigned int s)
|
|
{
|
|
unsigned int verdict;
|
|
int ret;
|
|
|
|
for (; s < e->num_hook_entries; s++) {
|
|
verdict = nf_hook_entry_hookfn(&e->hooks[s], skb, state);
|
|
switch (verdict & NF_VERDICT_MASK) {
|
|
case NF_ACCEPT:
|
|
break;
|
|
case NF_DROP:
|
|
kfree_skb(skb);
|
|
ret = NF_DROP_GETERR(verdict);
|
|
if (ret == 0)
|
|
ret = -EPERM;
|
|
return ret;
|
|
case NF_QUEUE:
|
|
ret = nf_queue(skb, state, e, s, verdict);
|
|
if (ret == 1)
|
|
continue;
|
|
return ret;
|
|
default:
|
|
/* Implicit handling for NF_STOLEN, as well as any other
|
|
* non conventional verdicts.
|
|
*/
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(nf_hook_slow);
|
|
|
|
|
|
int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
|
|
{
|
|
if (writable_len > skb->len)
|
|
return 0;
|
|
|
|
/* Not exclusive use of packet? Must copy. */
|
|
if (!skb_cloned(skb)) {
|
|
if (writable_len <= skb_headlen(skb))
|
|
return 1;
|
|
} else if (skb_clone_writable(skb, writable_len))
|
|
return 1;
|
|
|
|
if (writable_len <= skb_headlen(skb))
|
|
writable_len = 0;
|
|
else
|
|
writable_len -= skb_headlen(skb);
|
|
|
|
return !!__pskb_pull_tail(skb, writable_len);
|
|
}
|
|
EXPORT_SYMBOL(skb_make_writable);
|
|
|
|
/* This needs to be compiled in any case to avoid dependencies between the
|
|
* nfnetlink_queue code and nf_conntrack.
|
|
*/
|
|
struct nfnl_ct_hook __rcu *nfnl_ct_hook __read_mostly;
|
|
EXPORT_SYMBOL_GPL(nfnl_ct_hook);
|
|
|
|
struct nf_ct_hook __rcu *nf_ct_hook __read_mostly;
|
|
EXPORT_SYMBOL_GPL(nf_ct_hook);
|
|
|
|
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
|
|
/* This does not belong here, but locally generated errors need it if connection
|
|
tracking in use: without this, connection may not be in hash table, and hence
|
|
manufactured ICMP or RST packets will not be associated with it. */
|
|
void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
|
|
__rcu __read_mostly;
|
|
EXPORT_SYMBOL(ip_ct_attach);
|
|
|
|
struct nf_nat_hook __rcu *nf_nat_hook __read_mostly;
|
|
EXPORT_SYMBOL_GPL(nf_nat_hook);
|
|
|
|
void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
|
|
{
|
|
void (*attach)(struct sk_buff *, const struct sk_buff *);
|
|
|
|
if (skb->_nfct) {
|
|
rcu_read_lock();
|
|
attach = rcu_dereference(ip_ct_attach);
|
|
if (attach)
|
|
attach(new, skb);
|
|
rcu_read_unlock();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(nf_ct_attach);
|
|
|
|
void nf_conntrack_destroy(struct nf_conntrack *nfct)
|
|
{
|
|
struct nf_ct_hook *ct_hook;
|
|
|
|
rcu_read_lock();
|
|
ct_hook = rcu_dereference(nf_ct_hook);
|
|
BUG_ON(ct_hook == NULL);
|
|
ct_hook->destroy(nfct);
|
|
rcu_read_unlock();
|
|
}
|
|
EXPORT_SYMBOL(nf_conntrack_destroy);
|
|
|
|
bool nf_ct_get_tuple_skb(struct nf_conntrack_tuple *dst_tuple,
|
|
const struct sk_buff *skb)
|
|
{
|
|
struct nf_ct_hook *ct_hook;
|
|
bool ret = false;
|
|
|
|
rcu_read_lock();
|
|
ct_hook = rcu_dereference(nf_ct_hook);
|
|
if (ct_hook)
|
|
ret = ct_hook->get_tuple_skb(dst_tuple, skb);
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(nf_ct_get_tuple_skb);
|
|
|
|
/* Built-in default zone used e.g. by modules. */
|
|
const struct nf_conntrack_zone nf_ct_zone_dflt = {
|
|
.id = NF_CT_DEFAULT_ZONE_ID,
|
|
.dir = NF_CT_DEFAULT_ZONE_DIR,
|
|
};
|
|
EXPORT_SYMBOL_GPL(nf_ct_zone_dflt);
|
|
#endif /* CONFIG_NF_CONNTRACK */
|
|
|
|
static void __net_init
|
|
__netfilter_net_init(struct nf_hook_entries __rcu **e, int max)
|
|
{
|
|
int h;
|
|
|
|
for (h = 0; h < max; h++)
|
|
RCU_INIT_POINTER(e[h], NULL);
|
|
}
|
|
|
|
static int __net_init netfilter_net_init(struct net *net)
|
|
{
|
|
__netfilter_net_init(net->nf.hooks_ipv4, ARRAY_SIZE(net->nf.hooks_ipv4));
|
|
__netfilter_net_init(net->nf.hooks_ipv6, ARRAY_SIZE(net->nf.hooks_ipv6));
|
|
#ifdef CONFIG_NETFILTER_FAMILY_ARP
|
|
__netfilter_net_init(net->nf.hooks_arp, ARRAY_SIZE(net->nf.hooks_arp));
|
|
#endif
|
|
#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
|
|
__netfilter_net_init(net->nf.hooks_bridge, ARRAY_SIZE(net->nf.hooks_bridge));
|
|
#endif
|
|
#if IS_ENABLED(CONFIG_DECNET)
|
|
__netfilter_net_init(net->nf.hooks_decnet, ARRAY_SIZE(net->nf.hooks_decnet));
|
|
#endif
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
|
|
net->proc_net);
|
|
if (!net->nf.proc_netfilter) {
|
|
if (!net_eq(net, &init_net))
|
|
pr_err("cannot create netfilter proc entry");
|
|
|
|
return -ENOMEM;
|
|
}
|
|
#endif
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void __net_exit netfilter_net_exit(struct net *net)
|
|
{
|
|
remove_proc_entry("netfilter", net->proc_net);
|
|
}
|
|
|
|
static struct pernet_operations netfilter_net_ops = {
|
|
.init = netfilter_net_init,
|
|
.exit = netfilter_net_exit,
|
|
};
|
|
|
|
int __init netfilter_init(void)
|
|
{
|
|
int ret;
|
|
|
|
ret = register_pernet_subsys(&netfilter_net_ops);
|
|
if (ret < 0)
|
|
goto err;
|
|
|
|
ret = netfilter_log_init();
|
|
if (ret < 0)
|
|
goto err_pernet;
|
|
|
|
return 0;
|
|
err_pernet:
|
|
unregister_pernet_subsys(&netfilter_net_ops);
|
|
err:
|
|
return ret;
|
|
}
|