netfilter: ctnetlink: allow to set expectfn for expectations

This patch allows you to set expectfn which is specifically used
by the NAT side of most of the existing conntrack helpers.

I have added a symbol map that uses a string as key to look up for
the function that is attached to the expectation object. This is
the best solution I came out with to solve this issue.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

7 files changed, 115 insertions, 1 deletions

diff --git a/include/linux/netfilter/nfnetlink_conntrack.h b/include/linux/netfilter/nfnetlink_conntrack.h
index a2f1f483ecc9..e58e4b93c108 100644
--- a/include/linux/netfilter/nfnetlink_conntrack.h
+++ b/include/linux/netfilter/nfnetlink_conntrack.h
@@ -175,6 +175,7 @@ enum ctattr_expect {
         CTA_EXPECT_FLAGS,
         CTA_EXPECT_CLASS,
         CTA_EXPECT_NAT,
+        CTA_EXPECT_FN,
         __CTA_EXPECT_MAX
 };
 #define CTA_EXPECT_MAX (__CTA_EXPECT_MAX - 1)
diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index f1c1311adc2c..5767dc242dee 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -69,4 +69,17 @@ extern int nf_conntrack_broadcast_help(struct sk_buff *skb,
                                        enum ip_conntrack_info ctinfo,
                                        unsigned int timeout);
 
+struct nf_ct_helper_expectfn {
+        struct list_head head;
+        const char *name;
+        void (*expectfn)(struct nf_conn *ct, struct nf_conntrack_expect *exp);
+};
+
+void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n);
+void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n);
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_name(const char *name);
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_symbol(const void *symbol);
+
 #endif /*_NF_CONNTRACK_HELPER_H*/
diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
index a708933dc230..abb52adf5acd 100644
--- a/net/ipv4/netfilter/nf_nat_core.c
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -686,6 +686,11 @@ static struct pernet_operations nf_nat_net_ops = {
         .exit = nf_nat_net_exit,
 };
 
+static struct nf_ct_helper_expectfn follow_master_nat = {
+        .name           = "nat-follow-master",
+        .expectfn       = nf_nat_follow_master,
+};
+
 static int __init nf_nat_init(void)
 {
         size_t i;
@@ -717,6 +722,8 @@ static int __init nf_nat_init(void)
 
         l3proto = nf_ct_l3proto_find_get((u_int16_t)AF_INET);
 
+        nf_ct_helper_expectfn_register(&follow_master_nat);
+
         BUG_ON(nf_nat_seq_adjust_hook != NULL);
         RCU_INIT_POINTER(nf_nat_seq_adjust_hook, nf_nat_seq_adjust);
         BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
@@ -736,6 +743,7 @@ static void __exit nf_nat_cleanup(void)
         unregister_pernet_subsys(&nf_nat_net_ops);
         nf_ct_l3proto_put(l3proto);
         nf_ct_extend_unregister(&nat_extend);
+        nf_ct_helper_expectfn_unregister(&follow_master_nat);
         RCU_INIT_POINTER(nf_nat_seq_adjust_hook, NULL);
         RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, NULL);
         RCU_INIT_POINTER(nf_ct_nat_offset, NULL);
diff --git a/net/ipv4/netfilter/nf_nat_h323.c b/net/ipv4/netfilter/nf_nat_h323.c
index dc1dd912baf4..82536701e3a3 100644
--- a/net/ipv4/netfilter/nf_nat_h323.c
+++ b/net/ipv4/netfilter/nf_nat_h323.c
@@ -568,6 +568,16 @@ static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
         return 0;
 }
 
+static struct nf_ct_helper_expectfn q931_nat = {
+        .name           = "Q.931",
+        .expectfn       = ip_nat_q931_expect,
+};
+
+static struct nf_ct_helper_expectfn callforwarding_nat = {
+        .name           = "callforwarding",
+        .expectfn       = ip_nat_callforwarding_expect,
+};
+
 /****************************************************************************/
 static int __init init(void)
 {
@@ -590,6 +600,8 @@ static int __init init(void)
         RCU_INIT_POINTER(nat_h245_hook, nat_h245);
         RCU_INIT_POINTER(nat_callforwarding_hook, nat_callforwarding);
         RCU_INIT_POINTER(nat_q931_hook, nat_q931);
+        nf_ct_helper_expectfn_register(&q931_nat);
+        nf_ct_helper_expectfn_register(&callforwarding_nat);
         return 0;
 }
 
@@ -605,6 +617,8 @@ static void __exit fini(void)
         RCU_INIT_POINTER(nat_h245_hook, NULL);
         RCU_INIT_POINTER(nat_callforwarding_hook, NULL);
         RCU_INIT_POINTER(nat_q931_hook, NULL);
+        nf_ct_helper_expectfn_unregister(&q931_nat);
+        nf_ct_helper_expectfn_unregister(&callforwarding_nat);
         synchronize_rcu();
 }
 
diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index d0319f96269f..57932c43960e 100644
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -526,6 +526,11 @@ err1:
         return NF_DROP;
 }
 
+static struct nf_ct_helper_expectfn sip_nat = {
+        .name           = "sip",
+        .expectfn       = ip_nat_sip_expected,
+};
+
 static void __exit nf_nat_sip_fini(void)
 {
         RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
@@ -535,6 +540,7 @@ static void __exit nf_nat_sip_fini(void)
         RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
         RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
         RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
+        nf_ct_helper_expectfn_unregister(&sip_nat);
         synchronize_rcu();
 }
 
@@ -554,6 +560,7 @@ static int __init nf_nat_sip_init(void)
         RCU_INIT_POINTER(nf_nat_sdp_port_hook, ip_nat_sdp_port);
         RCU_INIT_POINTER(nf_nat_sdp_session_hook, ip_nat_sdp_session);
         RCU_INIT_POINTER(nf_nat_sdp_media_hook, ip_nat_sdp_media);
+        nf_ct_helper_expectfn_register(&sip_nat);
         return 0;
 }
 
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index bbe23baa19b6..436b7cb79ba4 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -181,6 +181,60 @@ void nf_ct_helper_destroy(struct nf_conn *ct)
         }
 }
 
+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_lock);
+        list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
+        spin_unlock_bh(&nf_conntrack_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_lock);
+        list_del_rcu(&n->head);
+        spin_unlock_bh(&nf_conntrack_lock);
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
+
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_name(const char *name)
+{
+        struct nf_ct_helper_expectfn *cur;
+        bool found = false;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
+                if (!strcmp(cur->name, name)) {
+                        found = true;
+                        break;
+                }
+        }
+        rcu_read_unlock();
+        return found ? cur : NULL;
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
+
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
+{
+        struct nf_ct_helper_expectfn *cur;
+        bool found = false;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
+                if (cur->expectfn == symbol) {
+                        found = true;
+                        break;
+                }
+        }
+        rcu_read_unlock();
+        return found ? cur : NULL;
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
+
 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 {
         unsigned int h = helper_hash(&me->tuple);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 845c8ca28563..b8827e8a11fe 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1679,6 +1679,8 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
         struct nlattr *nest_parms;
         struct nf_conntrack_tuple nat_tuple = {};
 #endif
+        struct nf_ct_helper_expectfn *expfn;
+
         if (timeout < 0)
                 timeout = 0;
 
@@ -1722,6 +1724,9 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
                 if (helper)
                         NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name);
         }
+        expfn = nf_ct_helper_expectfn_find_by_symbol(exp->expectfn);
+        if (expfn != NULL)
+                NLA_PUT_STRING(skb, CTA_EXPECT_FN, expfn->name);
 
         return 0;
 
@@ -1881,6 +1886,7 @@ static const struct nla_policy exp_nla_policy[CTA_EXPECT_MAX+1] = {
         [CTA_EXPECT_FLAGS]      = { .type = NLA_U32 },
         [CTA_EXPECT_CLASS]      = { .type = NLA_U32 },
         [CTA_EXPECT_NAT]        = { .type = NLA_NESTED },
+        [CTA_EXPECT_FN]         = { .type = NLA_NUL_STRING },
 };
 
 static int
@@ -2182,9 +2188,20 @@ ctnetlink_create_expect(struct net *net, u16 zone,
                 } else
                         exp->flags = 0;
         }
+        if (cda[CTA_EXPECT_FN]) {
+                const char *name = nla_data(cda[CTA_EXPECT_FN]);
+                struct nf_ct_helper_expectfn *expfn;
+
+                expfn = nf_ct_helper_expectfn_find_by_name(name);
+                if (expfn == NULL) {
+                        err = -EINVAL;
+                        goto err_out;
+                }
+                exp->expectfn = expfn->expectfn;
+        } else
+                exp->expectfn = NULL;
 
         exp->class = class;
-        exp->expectfn = NULL;
         exp->master = ct;
         exp->helper = helper;
         memcpy(&exp->tuple, &tuple, sizeof(struct nf_conntrack_tuple));