netfilter: ctnetlink: add support for user-space expectation helpers

This patch adds the basic infrastructure to support user-space
expectation helpers via ctnetlink and the netfilter queuing
infrastructure NFQUEUE. Basically, this patch:

* adds NF_CT_EXPECT_USERSPACE flag to identify user-space
  created expectations. I have also added a sanity check in
  __nf_ct_expect_check() to avoid that kernel-space helpers
  may create an expectation if the master conntrack has no
  helper assigned.
* adds some branches to check if the master conntrack helper
  exists, otherwise we skip the code that refers to kernel-space
  helper such as the local expectation list and the expectation
  policy.
* allows to set the timeout for user-space expectations with
  no helper assigned.
* a list of expectations created from user-space that depends
  on ctnetlink (if this module is removed, they are deleted).
* includes USERSPACE in the /proc output for expectations
  that have been created by a user-space helper.

This patch also modifies ctnetlink to skip including the helper
name in the Netlink messages if no kernel-space helper is set
(since no user-space expectation has not kernel-space kernel
assigned).

You can access an example user-space FTP conntrack helper at:
http://people.netfilter.org/pablo/userspace-conntrack-helpers/nf-ftp-helper-userspace-POC.tar.bz

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/include/linux/netfilter/nf_conntrack_common.h b/include/linux/netfilter/nf_conntrack_common.h
index fdc50ca..23a1a08 100644 (file)
--- a/include/linux/netfilter/nf_conntrack_common.h
+++ b/include/linux/netfilter/nf_conntrack_common.h
@@ -103,6 +103,7 @@ enum ip_conntrack_expect_events {
 /* expectation flags */
 #define NF_CT_EXPECT_PERMANENT         0x1
 #define NF_CT_EXPECT_INACTIVE          0x2
+#define NF_CT_EXPECT_USERSPACE         0x4
 
 #ifdef __KERNEL__
 struct ip_conntrack_stat {

diff --git a/include/net/netfilter/nf_conntrack_expect.h b/include/net/netfilter/nf_conntrack_expect.h
index 96bb42a..416b838 100644 (file)
--- a/include/net/netfilter/nf_conntrack_expect.h
+++ b/include/net/netfilter/nf_conntrack_expect.h
@@ -85,6 +85,7 @@ nf_ct_find_expectation(struct net *net, u16 zone,
 void nf_ct_unlink_expect(struct nf_conntrack_expect *exp);
 void nf_ct_remove_expectations(struct nf_conn *ct);
 void nf_ct_unexpect_related(struct nf_conntrack_expect *exp);
+void nf_ct_remove_userspace_expectations(void);
 
 /* Allocate space for an expectation: this is mandatory before calling
    nf_ct_expect_related.  You will have to call put afterwards. */

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index acb29cc..b30a1f2 100644 (file)
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -38,20 +38,23 @@ static int nf_ct_expect_hash_rnd_initted __read_mostly;
 
 static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
 
+static HLIST_HEAD(nf_ct_userspace_expect_list);
+
 /* 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);
        struct net *net = nf_ct_exp_net(exp);
 
-       NF_CT_ASSERT(master_help);
        NF_CT_ASSERT(!timer_pending(&exp->timeout));
 
        hlist_del_rcu(&exp->hnode);
        net->ct.expect_count--;
 
        hlist_del(&exp->lnode);
-       master_help->expecting[exp->class]--;
+       if (!(exp->flags & NF_CT_EXPECT_USERSPACE))
+               master_help->expecting[exp->class]--;
+
        nf_ct_expect_put(exp);
 
        NF_CT_STAT_INC(net, expect_delete);
@@ -320,16 +323,21 @@ static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
 
        atomic_inc(&exp->use);
 
-       hlist_add_head(&exp->lnode, &master_help->expectations);
-       master_help->expecting[exp->class]++;
+       if (master_help) {
+               hlist_add_head(&exp->lnode, &master_help->expectations);
+               master_help->expecting[exp->class]++;
+       } else if (exp->flags & NF_CT_EXPECT_USERSPACE)
+               hlist_add_head(&exp->lnode, &nf_ct_userspace_expect_list);
 
        hlist_add_head_rcu(&exp->hnode, &net->ct.expect_hash[h]);
        net->ct.expect_count++;
 
        setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
                    (unsigned long)exp);
-       p = &master_help->helper->expect_policy[exp->class];
-       exp->timeout.expires = jiffies + p->timeout * HZ;
+       if (master_help) {
+               p = &master_help->helper->expect_policy[exp->class];
+               exp->timeout.expires = jiffies + p->timeout * HZ;
+       }
        add_timer(&exp->timeout);
 
        atomic_inc(&exp->use);
@@ -380,7 +388,9 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
        unsigned int h;
        int ret = 1;
 
-       if (!master_help->helper) {
+       /* Don't allow expectations created from kernel-space with no helper */
+       if (!(expect->flags & NF_CT_EXPECT_USERSPACE) &&
+           (!master_help || (master_help && !master_help->helper))) {
                ret = -ESHUTDOWN;
                goto out;
        }
@@ -398,13 +408,16 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
                }
        }
        /* Will be over limit? */
-       p = &master_help->helper->expect_policy[expect->class];
-       if (p->max_expected &&
-           master_help->expecting[expect->class] >= p->max_expected) {
-               evict_oldest_expect(master, expect);
-               if (master_help->expecting[expect->class] >= p->max_expected) {
-                       ret = -EMFILE;
-                       goto out;
+       if (master_help) {
+               p = &master_help->helper->expect_policy[expect->class];
+               if (p->max_expected &&
+                   master_help->expecting[expect->class] >= p->max_expected) {
+                       evict_oldest_expect(master, expect);
+                       if (master_help->expecting[expect->class]
+                                               >= p->max_expected) {
+                               ret = -EMFILE;
+                               goto out;
+                       }
                }
        }
 
@@ -439,6 +452,21 @@ out:
 }
 EXPORT_SYMBOL_GPL(nf_ct_expect_related_report);
 
+void nf_ct_remove_userspace_expectations(void)
+{
+       struct nf_conntrack_expect *exp;
+       struct hlist_node *n, *next;
+
+       hlist_for_each_entry_safe(exp, n, next,
+                                 &nf_ct_userspace_expect_list, lnode) {
+               if (del_timer(&exp->timeout)) {
+                       nf_ct_unlink_expect(exp);
+                       nf_ct_expect_put(exp);
+               }
+       }
+}
+EXPORT_SYMBOL_GPL(nf_ct_remove_userspace_expectations);
+
 #ifdef CONFIG_PROC_FS
 struct ct_expect_iter_state {
        struct seq_net_private p;
@@ -529,8 +557,12 @@ static int exp_seq_show(struct seq_file *s, void *v)
                seq_printf(s, "PERMANENT");
                delim = ",";
        }
-       if (expect->flags & NF_CT_EXPECT_INACTIVE)
+       if (expect->flags & NF_CT_EXPECT_INACTIVE) {
                seq_printf(s, "%sINACTIVE", delim);
+               delim = ",";
+       }
+       if (expect->flags & NF_CT_EXPECT_USERSPACE)
+               seq_printf(s, "%sUSERSPACE", delim);
 
        helper = rcu_dereference(nfct_help(expect->master)->helper);
        if (helper) {

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 0804e0e..b4077be 100644 (file)
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1560,8 +1560,8 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
                          const struct nf_conntrack_expect *exp)
 {
        struct nf_conn *master = exp->master;
-       struct nf_conntrack_helper *helper;
        long timeout = (exp->timeout.expires - jiffies) / HZ;
+       struct nf_conn_help *help;
 
        if (timeout < 0)
                timeout = 0;
@@ -1578,9 +1578,14 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
        NLA_PUT_BE32(skb, CTA_EXPECT_TIMEOUT, htonl(timeout));
        NLA_PUT_BE32(skb, CTA_EXPECT_ID, htonl((unsigned long)exp));
        NLA_PUT_BE32(skb, CTA_EXPECT_FLAGS, htonl(exp->flags));
-       helper = rcu_dereference(nfct_help(master)->helper);
-       if (helper)
-               NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name);
+       help = nfct_help(master);
+       if (help) {
+               struct nf_conntrack_helper *helper;
+
+               helper = rcu_dereference(help->helper);
+               if (helper)
+                       NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name);
+       }
 
        return 0;
 
@@ -1921,24 +1926,32 @@ ctnetlink_create_expect(struct net *net, u16 zone,
        if (!h)
                return -ENOENT;
        ct = nf_ct_tuplehash_to_ctrack(h);
-       help = nfct_help(ct);
-
-       if (!help || !help->helper) {
-               /* such conntrack hasn't got any helper, abort */
-               err = -EOPNOTSUPP;
-               goto out;
-       }
-
        exp = nf_ct_expect_alloc(ct);
        if (!exp) {
                err = -ENOMEM;
                goto out;
        }
+       help = nfct_help(ct);
+       if (!help) {
+               if (!cda[CTA_EXPECT_TIMEOUT]) {
+                       err = -EINVAL;
+                       goto out;
+               }
+               exp->timeout.expires =
+                 jiffies + ntohl(nla_get_be32(cda[CTA_EXPECT_TIMEOUT])) * HZ;
 
-       if (cda[CTA_EXPECT_FLAGS])
-               exp->flags = ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
-       else
-               exp->flags = 0;
+               exp->flags = NF_CT_EXPECT_USERSPACE;
+               if (cda[CTA_EXPECT_FLAGS]) {
+                       exp->flags |=
+                               ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
+               }
+       } else {
+               if (cda[CTA_EXPECT_FLAGS]) {
+                       exp->flags = ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
+                       exp->flags &= ~NF_CT_EXPECT_USERSPACE;
+               } else
+                       exp->flags = 0;
+       }
 
        exp->class = 0;
        exp->expectfn = NULL;
@@ -2109,6 +2122,7 @@ static void __exit ctnetlink_exit(void)
 {
        pr_info("ctnetlink: unregistering from nfnetlink.\n");
 
+       nf_ct_remove_userspace_expectations();
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
        nf_ct_expect_unregister_notifier(&ctnl_notifier_exp);
        nf_conntrack_unregister_notifier(&ctnl_notifier);