[PATCH net-next 2/8] netfilter: add API to manage NAT helpers.

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The API allows a conntrack helper to indicate its corresponding
NAT helper which then can be loaded and reference counted.

Signed-off-by: Flavio Leitner <fbl@xxxxxxxxxxxx>
---
 include/net/netfilter/nf_conntrack_helper.h |  19 +++-
 net/netfilter/nf_conntrack_amanda.c         |   2 +
 net/netfilter/nf_conntrack_ftp.c            |   6 +-
 net/netfilter/nf_conntrack_helper.c         | 108 +++++++++++++++++++-
 net/netfilter/nf_conntrack_irc.c            |   3 +-
 net/netfilter/nf_conntrack_sane.c           |   4 +-
 net/netfilter/nf_conntrack_sip.c            |  12 ++-
 net/netfilter/nf_conntrack_tftp.c           |   6 +-
 8 files changed, 147 insertions(+), 13 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index e86fadf7e7c5..0d36d6bfb522 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -58,6 +58,8 @@ struct nf_conntrack_helper {
 	unsigned int queue_num;
 	/* length of userspace private data stored in nf_conn_help->data */
 	u16 data_len;
+	/* name of NAT helper module */
+	char nat_mod_name[NF_CT_HELPER_NAME_LEN];
 };
 
 /* Must be kept in sync with the classes defined by helpers */
@@ -98,7 +100,8 @@ void nf_ct_helper_init(struct nf_conntrack_helper *helper,
 				   enum ip_conntrack_info ctinfo),
 		       int (*from_nlattr)(struct nlattr *attr,
 					  struct nf_conn *ct),
-		       struct module *module);
+		       struct module *module,
+		       const char *nat_mod_name);
 
 int nf_conntrack_helper_register(struct nf_conntrack_helper *);
 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);
@@ -157,4 +160,18 @@ nf_ct_helper_expectfn_find_by_symbol(const void *symbol);
 extern struct hlist_head *nf_ct_helper_hash;
 extern unsigned int nf_ct_helper_hsize;
 
+struct nf_conntrack_helper_nat {
+	struct list_head list;
+	char name[NF_CT_HELPER_NAME_LEN];
+	struct module *module;		/* pointer to self */
+};
+
+void nf_ct_helper_nat_init(struct nf_conntrack_helper_nat *nat,
+			   const char *name, struct module *module);
+
+void nf_conntrack_helper_nat_register(struct nf_conntrack_helper_nat *nat);
+void nf_conntrack_helper_nat_unregister(struct nf_conntrack_helper_nat *nat);
+int nf_conntrack_helper_nat_try_module_get(const char *name, u16 l3num,
+					   u8 protonum);
+void nf_conntrack_helper_nat_put(struct nf_conntrack_helper *helper);
 #endif /*_NF_CONNTRACK_HELPER_H*/
diff --git a/net/netfilter/nf_conntrack_amanda.c b/net/netfilter/nf_conntrack_amanda.c
index f2681ec5b5f6..b5d255897d9e 100644
--- a/net/netfilter/nf_conntrack_amanda.c
+++ b/net/netfilter/nf_conntrack_amanda.c
@@ -186,6 +186,7 @@ static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 		.tuple.src.u.udp.port	= cpu_to_be16(10080),
 		.tuple.dst.protonum	= IPPROTO_UDP,
 		.expect_policy		= &amanda_exp_policy,
+		.nat_mod_name		= NF_CT_NAT_HELPER_MOD_NAME("amanda"),
 	},
 	{
 		.name			= "amanda",
@@ -195,6 +196,7 @@ static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 		.tuple.src.u.udp.port	= cpu_to_be16(10080),
 		.tuple.dst.protonum	= IPPROTO_UDP,
 		.expect_policy		= &amanda_exp_policy,
+		.nat_mod_name		= NF_CT_NAT_HELPER_MOD_NAME("amanda"),
 	},
 };
 
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index a11c304fb771..fec9bb462071 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -590,10 +590,12 @@ static int __init nf_conntrack_ftp_init(void)
 	for (i = 0; i < ports_c; i++) {
 		nf_ct_helper_init(&ftp[2 * i], AF_INET, IPPROTO_TCP, "ftp",
 				  FTP_PORT, ports[i], ports[i], &ftp_exp_policy,
-				  0, help, nf_ct_ftp_from_nlattr, THIS_MODULE);
+				  0, help, nf_ct_ftp_from_nlattr, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("ftp"));
 		nf_ct_helper_init(&ftp[2 * i + 1], AF_INET6, IPPROTO_TCP, "ftp",
 				  FTP_PORT, ports[i], ports[i], &ftp_exp_policy,
-				  0, help, nf_ct_ftp_from_nlattr, THIS_MODULE);
+				  0, help, nf_ct_ftp_from_nlattr, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("ftp"));
 	}
 
 	ret = nf_conntrack_helpers_register(ftp, ports_c * 2);
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 274baf1dab87..883a8d438503 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -42,6 +42,9 @@ 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 struct list_head nf_ct_nat_helpers __read_mostly;
+static DEFINE_SPINLOCK(nf_ct_nat_helpers_lock);
+
 /* 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)
@@ -130,6 +133,75 @@ void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
 
+static struct nf_conntrack_helper_nat *
+nf_conntrack_helper_nat_find(const char *name)
+{
+	struct nf_conntrack_helper_nat *cur;
+	bool found = false;
+
+	list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
+		if (!strcmp(cur->name, name)) {
+			found = true;
+			break;
+		}
+	}
+	return found ? cur : NULL;
+}
+
+int
+nf_conntrack_helper_nat_try_module_get(const char *name, u16 l3num, u8 protonum)
+{
+	struct nf_conntrack_helper *h;
+	struct nf_conntrack_helper_nat *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 == NULL) {
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	if (!strlen(h->nat_mod_name)) {
+		rcu_read_unlock();
+		return -EOPNOTSUPP;
+	}
+
+	nat = nf_conntrack_helper_nat_find(h->nat_mod_name);
+	if (nat == NULL) {
+		snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
+		rcu_read_unlock();
+		ret = request_module(mod_name);
+		if (ret != 0)
+			return ret;
+
+		rcu_read_lock();
+		nat = nf_conntrack_helper_nat_find(mod_name);
+		if (nat == NULL) {
+			rcu_read_unlock();
+			return -EINVAL;
+		}
+	}
+
+	if (!try_module_get(nat->module))
+		ret = -EINVAL;
+
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_nat_try_module_get);
+
+void nf_conntrack_helper_nat_put(struct nf_conntrack_helper *helper)
+{
+	struct nf_conntrack_helper_nat *nat;
+
+	nat = nf_conntrack_helper_nat_find(helper->nat_mod_name);
+	BUG_ON(nat == NULL);
+	module_put(nat->module);
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_nat_put);
+
 struct nf_conn_help *
 nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 {
@@ -420,7 +492,8 @@ void nf_ct_helper_init(struct nf_conntrack_helper *helper,
 				   enum ip_conntrack_info ctinfo),
 		       int (*from_nlattr)(struct nlattr *attr,
 					  struct nf_conn *ct),
-		       struct module *module)
+		       struct module *module,
+		       const char *nat_mod_name)
 {
 	helper->tuple.src.l3num = l3num;
 	helper->tuple.dst.protonum = protonum;
@@ -430,6 +503,10 @@ void nf_ct_helper_init(struct nf_conntrack_helper *helper,
 	helper->help = help;
 	helper->from_nlattr = from_nlattr;
 	helper->me = module;
+	helper->nat_mod_name[0] = '\0';
+	if (nat_mod_name)
+		snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
+			 "%s", nat_mod_name);
 
 	if (spec_port == default_port)
 		snprintf(helper->name, sizeof(helper->name), "%s", name);
@@ -466,6 +543,34 @@ void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
 
+void nf_conntrack_helper_nat_register(struct nf_conntrack_helper_nat *nat)
+{
+	BUG_ON(nat->module == NULL);
+
+	spin_lock(&nf_ct_nat_helpers_lock);
+	list_add_rcu(&nat->list, &nf_ct_nat_helpers);
+	spin_unlock(&nf_ct_nat_helpers_lock);
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_nat_register);
+
+void nf_conntrack_helper_nat_unregister(struct nf_conntrack_helper_nat *nat)
+{
+	BUG_ON(nat->module == NULL);
+
+	spin_lock(&nf_ct_nat_helpers_lock);
+	list_del_rcu(&nat->list);
+	spin_unlock(&nf_ct_nat_helpers_lock);
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_nat_unregister);
+
+void nf_ct_helper_nat_init(struct nf_conntrack_helper_nat *nat,
+			   const char *name, struct module *module)
+{
+	nat->module = module;
+	snprintf(nat->name, sizeof(nat->name), "%s", name);
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_nat_init);
+
 static const struct nf_ct_ext_type helper_extend = {
 	.len	= sizeof(struct nf_conn_help),
 	.align	= __alignof__(struct nf_conn_help),
@@ -493,6 +598,7 @@ int nf_conntrack_helper_init(void)
 		goto out_extend;
 	}
 
+	INIT_LIST_HEAD(&nf_ct_nat_helpers);
 	return 0;
 out_extend:
 	kvfree(nf_ct_helper_hash);
diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c
index 4099f4d79bae..659aa2cb5493 100644
--- a/net/netfilter/nf_conntrack_irc.c
+++ b/net/netfilter/nf_conntrack_irc.c
@@ -261,7 +261,8 @@ static int __init nf_conntrack_irc_init(void)
 	for (i = 0; i < ports_c; i++) {
 		nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, "irc",
 				  IRC_PORT, ports[i], i, &irc_exp_policy,
-				  0, help, NULL, THIS_MODULE);
+				  0, help, NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("irc"));
 	}
 
 	ret = nf_conntrack_helpers_register(&irc[0], ports_c);
diff --git a/net/netfilter/nf_conntrack_sane.c b/net/netfilter/nf_conntrack_sane.c
index 5072ff96ab33..b08724b8754c 100644
--- a/net/netfilter/nf_conntrack_sane.c
+++ b/net/netfilter/nf_conntrack_sane.c
@@ -198,11 +198,11 @@ static int __init nf_conntrack_sane_init(void)
 		nf_ct_helper_init(&sane[2 * i], AF_INET, IPPROTO_TCP, "sane",
 				  SANE_PORT, ports[i], ports[i],
 				  &sane_exp_policy, 0, help, NULL,
-				  THIS_MODULE);
+				  THIS_MODULE, NULL);
 		nf_ct_helper_init(&sane[2 * i + 1], AF_INET6, IPPROTO_TCP, "sane",
 				  SANE_PORT, ports[i], ports[i],
 				  &sane_exp_policy, 0, help, NULL,
-				  THIS_MODULE);
+				  THIS_MODULE, NULL);
 	}
 
 	ret = nf_conntrack_helpers_register(sane, ports_c * 2);
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index f067c6b50857..0d4fca4a329f 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1677,19 +1677,23 @@ static int __init nf_conntrack_sip_init(void)
 		nf_ct_helper_init(&sip[4 * i], AF_INET, IPPROTO_UDP, "sip",
 				  SIP_PORT, ports[i], i, sip_exp_policy,
 				  SIP_EXPECT_MAX, sip_help_udp,
-				  NULL, THIS_MODULE);
+				  NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("sip"));
 		nf_ct_helper_init(&sip[4 * i + 1], AF_INET, IPPROTO_TCP, "sip",
 				  SIP_PORT, ports[i], i, sip_exp_policy,
 				  SIP_EXPECT_MAX, sip_help_tcp,
-				  NULL, THIS_MODULE);
+				  NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("sip"));
 		nf_ct_helper_init(&sip[4 * i + 2], AF_INET6, IPPROTO_UDP, "sip",
 				  SIP_PORT, ports[i], i, sip_exp_policy,
 				  SIP_EXPECT_MAX, sip_help_udp,
-				  NULL, THIS_MODULE);
+				  NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("sip"));
 		nf_ct_helper_init(&sip[4 * i + 3], AF_INET6, IPPROTO_TCP, "sip",
 				  SIP_PORT, ports[i], i, sip_exp_policy,
 				  SIP_EXPECT_MAX, sip_help_tcp,
-				  NULL, THIS_MODULE);
+				  NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("sip"));
 	}
 
 	ret = nf_conntrack_helpers_register(sip, ports_c * 4);
diff --git a/net/netfilter/nf_conntrack_tftp.c b/net/netfilter/nf_conntrack_tftp.c
index 548b673b3625..e1fbf892db70 100644
--- a/net/netfilter/nf_conntrack_tftp.c
+++ b/net/netfilter/nf_conntrack_tftp.c
@@ -121,10 +121,12 @@ static int __init nf_conntrack_tftp_init(void)
 	for (i = 0; i < ports_c; i++) {
 		nf_ct_helper_init(&tftp[2 * i], AF_INET, IPPROTO_UDP, "tftp",
 				  TFTP_PORT, ports[i], i, &tftp_exp_policy,
-				  0, tftp_help, NULL, THIS_MODULE);
+				  0, tftp_help, NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("tftp"));
 		nf_ct_helper_init(&tftp[2 * i + 1], AF_INET6, IPPROTO_UDP, "tftp",
 				  TFTP_PORT, ports[i], i, &tftp_exp_policy,
-				  0, tftp_help, NULL, THIS_MODULE);
+				  0, tftp_help, NULL, THIS_MODULE,
+				  NF_CT_NAT_HELPER_MOD_NAME("tftp"));
 	}
 
 	ret = nf_conntrack_helpers_register(tftp, ports_c * 2);
-- 
2.20.1







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