This patch adds on-request module loading for helpers via ctnetlink.
To do so, we release the locks, load the module and check. If the
helper is present, then it returns EAGAIN to re-start the operation.
With this patch, we support explicit and implicit helper assignment.
This patch also modifies nfnetlink to handle EAGAIN appropriately.
This all is based on a suggestion from Patrick McHardy.
This patch also provides a refactorized function to lookup-and-set
the connection tracking helper. The function removes the exported
symbol __nf_ct_helper_find as it has not clients anymore.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
include/linux/netfilter/nfnetlink.h | 3 +
include/net/netfilter/nf_conntrack_helper.h | 5 +-
net/netfilter/nf_conntrack_core.c | 28 +---------
net/netfilter/nf_conntrack_helper.c | 33 +++++++++++-
net/netfilter/nf_conntrack_netlink.c | 73 ++++++++++++++++++++++++---
net/netfilter/nfnetlink.c | 12 +++-
6 files changed, 111 insertions(+), 43 deletions(-)
diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index 0d8424f..7d8e045 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -78,6 +78,9 @@ extern int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group,
int echo);
extern int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags);
+extern void nfnl_lock(void);
+extern void nfnl_unlock(void);
+
#define MODULE_ALIAS_NFNL_SUBSYS(subsys) \
MODULE_ALIAS("nfnetlink-subsys-" __stringify(subsys))
diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index f8060ab..8eebf6e 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -39,9 +39,6 @@ struct nf_conntrack_helper
};
extern struct nf_conntrack_helper *
-__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple);
-
-extern struct nf_conntrack_helper *
__nf_conntrack_helper_find_byname(const char *name);
extern int nf_conntrack_helper_register(struct nf_conntrack_helper *);
@@ -49,6 +46,8 @@ extern void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);
extern struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp);
+extern int __nf_ct_set_helper(struct nf_conn *ct, gfp_t flags);
+
static inline struct nf_conn_help *nfct_help(const struct nf_conn *ct)
{
return nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 27de3c7..54e35f3 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -581,14 +581,7 @@ init_conntrack(struct net *net,
nf_conntrack_get(&ct->master->ct_general);
NF_CT_STAT_INC(net, expect_new);
} else {
- struct nf_conntrack_helper *helper;
-
- helper = __nf_ct_helper_find(&repl_tuple);
- if (helper) {
- help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
- if (help)
- rcu_assign_pointer(help->helper, helper);
- }
+ __nf_ct_set_helper(ct, GFP_ATOMIC);
NF_CT_STAT_INC(net, new);
}
@@ -765,7 +758,6 @@ void nf_conntrack_alter_reply(struct nf_conn *ct,
const struct nf_conntrack_tuple *newreply)
{
struct nf_conn_help *help = nfct_help(ct);
- struct nf_conntrack_helper *helper;
/* Should be unconfirmed, so not in hash table yet */
NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
@@ -778,23 +770,7 @@ void nf_conntrack_alter_reply(struct nf_conn *ct,
return;
rcu_read_lock();
- helper = __nf_ct_helper_find(newreply);
- if (helper == NULL) {
- if (help)
- rcu_assign_pointer(help->helper, NULL);
- goto out;
- }
-
- if (help == NULL) {
- help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
- if (help == NULL)
- goto out;
- } else {
- memset(&help->help, 0, sizeof(help->help));
- }
-
- rcu_assign_pointer(help->helper, helper);
-out:
+ __nf_ct_set_helper(ct, GFP_ATOMIC);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 9c06b9f..86cdbde 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -44,7 +44,7 @@ static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
}
-struct nf_conntrack_helper *
+static struct nf_conntrack_helper *
__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
{
struct nf_conntrack_helper *helper;
@@ -62,7 +62,6 @@ __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
}
return NULL;
}
-EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
struct nf_conntrack_helper *
__nf_conntrack_helper_find_byname(const char *name)
@@ -94,6 +93,36 @@ struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
}
EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
+int __nf_ct_set_helper(struct nf_conn *ct, gfp_t flags)
+{
+ int ret = 0;
+ struct nf_conntrack_helper *helper;
+ struct nf_conn_help *help = nfct_help(ct);
+
+ helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+ if (helper == NULL) {
+ if (help)
+ rcu_assign_pointer(help->helper, NULL);
+ ret = -ENOENT;
+ goto out;
+ }
+
+ if (help == NULL) {
+ help = nf_ct_helper_ext_add(ct, flags);
+ if (help == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ } else {
+ memset(&help->help, 0, sizeof(help->help));
+ }
+
+ rcu_assign_pointer(help->helper, helper);
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__nf_ct_set_helper);
+
static inline int unhelp(struct nf_conntrack_tuple_hash *i,
const struct nf_conntrack_helper *me)
{
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index b7a6be8..8621b48 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -952,8 +952,23 @@ ctnetlink_change_helper(struct nf_conn *ct, struct nlattr *cda[])
}
helper = __nf_conntrack_helper_find_byname(helpname);
- if (helper == NULL)
+ if (helper == NULL) {
+#ifdef CONFIG_KMOD
+ spin_unlock_bh(&nf_conntrack_lock);
+ nfnl_unlock();
+ if (request_module("nfct-helper-%s", helpname) < 0) {
+ nfnl_lock();
+ spin_lock_bh(&nf_conntrack_lock);
+ return -EOPNOTSUPP;
+ }
+ nfnl_lock();
+ spin_lock_bh(&nf_conntrack_lock);
+ helper = __nf_conntrack_helper_find_byname(helpname);
+ if (helper)
+ return -EAGAIN;
+#endif
return -EOPNOTSUPP;
+ }
if (help) {
if (help->helper == helper)
@@ -1117,7 +1132,6 @@ ctnetlink_create_conntrack(struct nlattr *cda[],
{
struct nf_conn *ct;
int err = -EINVAL;
- struct nf_conn_help *help;
struct nf_conntrack_helper *helper;
ct = nf_conntrack_alloc(&init_net, otuple, rtuple, GFP_KERNEL);
@@ -1132,16 +1146,57 @@ ctnetlink_create_conntrack(struct nlattr *cda[],
ct->status |= IPS_CONFIRMED;
rcu_read_lock();
- helper = __nf_ct_helper_find(rtuple);
- if (helper) {
- help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
- if (help == NULL) {
+ if (cda[CTA_HELP]) {
+ char *helpname;
+
+ err = ctnetlink_parse_help(cda[CTA_HELP], &helpname);
+ if (err < 0) {
+ rcu_read_unlock();
+ goto err;
+ }
+
+ helper = __nf_conntrack_helper_find_byname(helpname);
+ if (helper == NULL) {
+ rcu_read_unlock();
+#ifdef CONFIG_KMOD
+ nfnl_unlock();
+ if (request_module("nfct-helper-%s", helpname) < 0) {
+ nfnl_lock();
+ err = -EOPNOTSUPP;
+ goto err;
+ }
+ nfnl_lock();
+ rcu_read_lock();
+ helper = __nf_conntrack_helper_find_byname(helpname);
+ if (helper) {
+ rcu_read_unlock();
+ err = -EAGAIN;
+ goto err;
+ }
+ rcu_read_unlock();
+#endif
+ err = -EOPNOTSUPP;
+ goto err;
+ } else {
+ struct nf_conn_help *help;
+
+ help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
+ if (help == NULL) {
+ rcu_read_unlock();
+ err = -ENOMEM;
+ goto err;
+ }
+
+ /* not in hash table yet so not strictly necessary */
+ rcu_assign_pointer(help->helper, helper);
+ }
+ } else {
+ /* try an implicit helper assignation */
+ err = __nf_ct_set_helper(ct, GFP_ATOMIC);
+ if (err == -ENOMEM) {
rcu_read_unlock();
- err = -ENOMEM;
goto err;
}
- /* not in hash table yet so not strictly necessary */
- rcu_assign_pointer(help->helper, helper);
}
if (cda[CTA_STATUS]) {
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index b75c9c4..4739f9f 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -44,15 +44,17 @@ static struct sock *nfnl = NULL;
static const struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
static DEFINE_MUTEX(nfnl_mutex);
-static inline void nfnl_lock(void)
+void nfnl_lock(void)
{
mutex_lock(&nfnl_mutex);
}
+EXPORT_SYMBOL_GPL(nfnl_lock);
-static inline void nfnl_unlock(void)
+void nfnl_unlock(void)
{
mutex_unlock(&nfnl_mutex);
}
+EXPORT_SYMBOL_GPL(nfnl_unlock);
int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
{
@@ -132,6 +134,7 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
return 0;
type = nlh->nlmsg_type;
+replay:
ss = nfnetlink_get_subsys(type);
if (!ss) {
#ifdef CONFIG_KMOD
@@ -165,7 +168,10 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
} else
return -EINVAL;
- return nc->call(nfnl, skb, nlh, cda);
+ err = nc->call(nfnl, skb, nlh, cda);
+ if (err == -EAGAIN)
+ goto replay;
+ return err;
}
}
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