[NETFILTER]: nf_conntrack: split out expectation handling

This patch splits out expectation handling into its own file
nf_conntrack_expect.c

Signed-off-by: Martin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 365 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
new file mode 100644
index 000000000000..076e678b3188
--- /dev/null
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -0,0 +1,365 @@
+/* Expectation handling for nf_conntrack. */
+
+/* (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>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/netfilter.h>
+#include <linux/skbuff.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/stddef.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/percpu.h>
+#include <linux/kernel.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+
+LIST_HEAD(nf_conntrack_expect_list);
+kmem_cache_t *nf_conntrack_expect_cachep __read_mostly;
+DECLARE_PER_CPU(struct ip_conntrack_stat, nf_conntrack_stat);
+static unsigned int nf_conntrack_expect_next_id;
+
+/* nf_conntrack_expect helper functions */
+void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
+{
+	struct nf_conn_help *master_help = nfct_help(exp->master);
+
+	NF_CT_ASSERT(master_help);
+	NF_CT_ASSERT(!timer_pending(&exp->timeout));
+
+	list_del(&exp->list);
+	NF_CT_STAT_INC(expect_delete);
+	master_help->expecting--;
+	nf_conntrack_expect_put(exp);
+}
+
+static void expectation_timed_out(unsigned long ul_expect)
+{
+	struct nf_conntrack_expect *exp = (void *)ul_expect;
+
+	write_lock_bh(&nf_conntrack_lock);
+	nf_ct_unlink_expect(exp);
+	write_unlock_bh(&nf_conntrack_lock);
+	nf_conntrack_expect_put(exp);
+}
+
+struct nf_conntrack_expect *
+__nf_conntrack_expect_find(const struct nf_conntrack_tuple *tuple)
+{
+	struct nf_conntrack_expect *i;
+
+	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
+		if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
+			return i;
+	}
+	return NULL;
+}
+
+/* Just find a expectation corresponding to a tuple. */
+struct nf_conntrack_expect *
+nf_conntrack_expect_find(const struct nf_conntrack_tuple *tuple)
+{
+	struct nf_conntrack_expect *i;
+
+	read_lock_bh(&nf_conntrack_lock);
+	i = __nf_conntrack_expect_find(tuple);
+	if (i)
+		atomic_inc(&i->use);
+	read_unlock_bh(&nf_conntrack_lock);
+
+	return i;
+}
+
+/* If an expectation for this connection is found, it gets delete from
+ * global list then returned. */
+struct nf_conntrack_expect *
+find_expectation(const struct nf_conntrack_tuple *tuple)
+{
+	struct nf_conntrack_expect *i;
+
+	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
+	/* If master is not in hash table yet (ie. packet hasn't left
+	   this machine yet), how can other end know about expected?
+	   Hence these are not the droids you are looking for (if
+	   master ct never got confirmed, we'd hold a reference to it
+	   and weird things would happen to future packets). */
+		if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask)
+		    && nf_ct_is_confirmed(i->master)) {
+			if (i->flags & NF_CT_EXPECT_PERMANENT) {
+				atomic_inc(&i->use);
+				return i;
+			} else if (del_timer(&i->timeout)) {
+				nf_ct_unlink_expect(i);
+				return i;
+			}
+		}
+	}
+	return NULL;
+}
+
+/* delete all expectations for this conntrack */
+void nf_ct_remove_expectations(struct nf_conn *ct)
+{
+	struct nf_conntrack_expect *i, *tmp;
+	struct nf_conn_help *help = nfct_help(ct);
+
+	/* Optimization: most connection never expect any others. */
+	if (!help || help->expecting == 0)
+		return;
+
+	list_for_each_entry_safe(i, tmp, &nf_conntrack_expect_list, list) {
+		if (i->master == ct && del_timer(&i->timeout)) {
+			nf_ct_unlink_expect(i);
+			nf_conntrack_expect_put(i);
+ 		}
+	}
+}
+
+/* Would two expected things clash? */
+static inline int expect_clash(const struct nf_conntrack_expect *a,
+			       const struct nf_conntrack_expect *b)
+{
+	/* Part covered by intersection of masks must be unequal,
+	   otherwise they clash */
+	struct nf_conntrack_tuple intersect_mask;
+	int count;
+
+	intersect_mask.src.l3num = a->mask.src.l3num & b->mask.src.l3num;
+	intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
+	intersect_mask.dst.u.all = a->mask.dst.u.all & b->mask.dst.u.all;
+	intersect_mask.dst.protonum = a->mask.dst.protonum
+					& b->mask.dst.protonum;
+
+	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
+		intersect_mask.src.u3.all[count] =
+			a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
+	}
+
+	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
+		intersect_mask.dst.u3.all[count] =
+			a->mask.dst.u3.all[count] & b->mask.dst.u3.all[count];
+	}
+
+	return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
+}
+
+static inline int expect_matches(const struct nf_conntrack_expect *a,
+				 const struct nf_conntrack_expect *b)
+{
+	return a->master == b->master
+		&& nf_ct_tuple_equal(&a->tuple, &b->tuple)
+		&& nf_ct_tuple_equal(&a->mask, &b->mask);
+}
+
+/* Generally a bad idea to call this: could have matched already. */
+void nf_conntrack_unexpect_related(struct nf_conntrack_expect *exp)
+{
+	struct nf_conntrack_expect *i;
+
+	write_lock_bh(&nf_conntrack_lock);
+	/* choose the the oldest expectation to evict */
+	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
+		if (expect_matches(i, exp) && del_timer(&i->timeout)) {
+			nf_ct_unlink_expect(i);
+			write_unlock_bh(&nf_conntrack_lock);
+			nf_conntrack_expect_put(i);
+			return;
+		}
+	}
+	write_unlock_bh(&nf_conntrack_lock);
+}
+
+/* We don't increase the master conntrack refcount for non-fulfilled
+ * conntracks. During the conntrack destruction, the expectations are
+ * always killed before the conntrack itself */
+struct nf_conntrack_expect *nf_conntrack_expect_alloc(struct nf_conn *me)
+{
+	struct nf_conntrack_expect *new;
+
+	new = kmem_cache_alloc(nf_conntrack_expect_cachep, GFP_ATOMIC);
+	if (!new)
+		return NULL;
+
+	new->master = me;
+	atomic_set(&new->use, 1);
+	return new;
+}
+
+void nf_conntrack_expect_put(struct nf_conntrack_expect *exp)
+{
+	if (atomic_dec_and_test(&exp->use))
+		kmem_cache_free(nf_conntrack_expect_cachep, exp);
+}
+
+static void nf_conntrack_expect_insert(struct nf_conntrack_expect *exp)
+{
+	struct nf_conn_help *master_help = nfct_help(exp->master);
+
+	atomic_inc(&exp->use);
+	master_help->expecting++;
+	list_add(&exp->list, &nf_conntrack_expect_list);
+
+	init_timer(&exp->timeout);
+	exp->timeout.data = (unsigned long)exp;
+	exp->timeout.function = expectation_timed_out;
+	exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
+	add_timer(&exp->timeout);
+
+	exp->id = ++nf_conntrack_expect_next_id;
+	atomic_inc(&exp->use);
+	NF_CT_STAT_INC(expect_create);
+}
+
+/* Race with expectations being used means we could have none to find; OK. */
+static void evict_oldest_expect(struct nf_conn *master)
+{
+	struct nf_conntrack_expect *i;
+
+	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
+		if (i->master == master) {
+			if (del_timer(&i->timeout)) {
+				nf_ct_unlink_expect(i);
+				nf_conntrack_expect_put(i);
+			}
+			break;
+		}
+	}
+}
+
+static inline int refresh_timer(struct nf_conntrack_expect *i)
+{
+	struct nf_conn_help *master_help = nfct_help(i->master);
+
+	if (!del_timer(&i->timeout))
+		return 0;
+
+	i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
+	add_timer(&i->timeout);
+	return 1;
+}
+
+int nf_conntrack_expect_related(struct nf_conntrack_expect *expect)
+{
+	struct nf_conntrack_expect *i;
+	struct nf_conn *master = expect->master;
+	struct nf_conn_help *master_help = nfct_help(master);
+	int ret;
+
+	NF_CT_ASSERT(master_help);
+
+	write_lock_bh(&nf_conntrack_lock);
+	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
+		if (expect_matches(i, expect)) {
+			/* Refresh timer: if it's dying, ignore.. */
+			if (refresh_timer(i)) {
+				ret = 0;
+				goto out;
+			}
+		} else if (expect_clash(i, expect)) {
+			ret = -EBUSY;
+			goto out;
+		}
+	}
+	/* Will be over limit? */
+	if (master_help->helper->max_expected &&
+	    master_help->expecting >= master_help->helper->max_expected)
+		evict_oldest_expect(master);
+
+	nf_conntrack_expect_insert(expect);
+	nf_conntrack_expect_event(IPEXP_NEW, expect);
+	ret = 0;
+out:
+	write_unlock_bh(&nf_conntrack_lock);
+	return ret;
+}
+
+#ifdef CONFIG_PROC_FS
+static void *exp_seq_start(struct seq_file *s, loff_t *pos)
+{
+	struct list_head *e = &nf_conntrack_expect_list;
+	loff_t i;
+
+	/* strange seq_file api calls stop even if we fail,
+	 * thus we need to grab lock since stop unlocks */
+	read_lock_bh(&nf_conntrack_lock);
+
+	if (list_empty(e))
+		return NULL;
+
+	for (i = 0; i <= *pos; i++) {
+		e = e->next;
+		if (e == &nf_conntrack_expect_list)
+			return NULL;
+	}
+	return e;
+}
+
+static void *exp_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	struct list_head *e = v;
+
+	++*pos;
+	e = e->next;
+
+	if (e == &nf_conntrack_expect_list)
+		return NULL;
+
+	return e;
+}
+
+static void exp_seq_stop(struct seq_file *s, void *v)
+{
+	read_unlock_bh(&nf_conntrack_lock);
+}
+
+static int exp_seq_show(struct seq_file *s, void *v)
+{
+	struct nf_conntrack_expect *expect = v;
+
+	if (expect->timeout.function)
+		seq_printf(s, "%ld ", timer_pending(&expect->timeout)
+			   ? (long)(expect->timeout.expires - jiffies)/HZ : 0);
+	else
+		seq_printf(s, "- ");
+	seq_printf(s, "l3proto = %u proto=%u ",
+		   expect->tuple.src.l3num,
+		   expect->tuple.dst.protonum);
+	print_tuple(s, &expect->tuple,
+		    __nf_ct_l3proto_find(expect->tuple.src.l3num),
+		    __nf_ct_proto_find(expect->tuple.src.l3num,
+				       expect->tuple.dst.protonum));
+	return seq_putc(s, '\n');
+}
+
+static struct seq_operations exp_seq_ops = {
+	.start = exp_seq_start,
+	.next = exp_seq_next,
+	.stop = exp_seq_stop,
+	.show = exp_seq_show
+};
+
+static int exp_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &exp_seq_ops);
+}
+
+struct file_operations exp_file_ops = {
+	.owner   = THIS_MODULE,
+	.open    = exp_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release
+};
+#endif /* CONFIG_PROC_FS */