@@ -145,4 +145,14 @@ static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
return __netlink_dump_start(ssk, skb, nlh, control);
}
+struct netlink_tap {
+ struct net_device *dev;
+ struct module *module;
+ struct list_head list;
+};
+
+extern int netlink_add_tap(struct netlink_tap *nt);
+extern int __netlink_remove_tap(struct netlink_tap *nt);
+extern int netlink_remove_tap(struct netlink_tap *nt);
+
#endif /* __LINUX_NETLINK_H */
@@ -57,6 +57,7 @@
#include <linux/audit.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
+#include <linux/if_arp.h>
#include <asm/cacheflush.h>
#include <net/net_namespace.h>
@@ -101,6 +102,9 @@ static atomic_t nl_table_users = ATOMIC_INIT(0);
static ATOMIC_NOTIFIER_HEAD(netlink_chain);
+static DEFINE_SPINLOCK(netlink_tap_lock);
+static struct list_head netlink_tap_all __read_mostly;
+
static inline u32 netlink_group_mask(u32 group)
{
return group ? 1 << (group - 1) : 0;
@@ -111,6 +115,100 @@ static inline struct hlist_head *nl_portid_hashfn(struct nl_portid_hash *hash, u
return &hash->table[jhash_1word(portid, hash->rnd) & hash->mask];
}
+int netlink_add_tap(struct netlink_tap *nt)
+{
+ if (unlikely(nt->dev->type != ARPHRD_NETLINK))
+ return -EINVAL;
+
+ spin_lock(&netlink_tap_lock);
+ list_add_rcu(&nt->list, &netlink_tap_all);
+ spin_unlock(&netlink_tap_lock);
+
+ if (nt->module)
+ __module_get(nt->module);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(netlink_add_tap);
+
+int __netlink_remove_tap(struct netlink_tap *nt)
+{
+ bool found = false;
+ struct netlink_tap *tmp;
+
+ spin_lock(&netlink_tap_lock);
+
+ list_for_each_entry(tmp, &netlink_tap_all, list) {
+ if (nt == tmp) {
+ list_del_rcu(&nt->list);
+ found = true;
+ goto out;
+ }
+ }
+
+ pr_warn("__netlink_remove_tap: %p not found\n", nt);
+out:
+ spin_unlock(&netlink_tap_lock);
+
+ if (found && nt->module)
+ module_put(nt->module);
+
+ return found ? 0 : -ENODEV;
+}
+EXPORT_SYMBOL_GPL(__netlink_remove_tap);
+
+int netlink_remove_tap(struct netlink_tap *nt)
+{
+ int ret;
+
+ ret = __netlink_remove_tap(nt);
+ synchronize_net();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(netlink_remove_tap);
+
+static int __netlink_deliver_tap_skb(struct sk_buff *skb,
+ struct net_device *dev)
+{
+ struct sk_buff *nskb;
+ int ret = -ENOMEM;
+
+ dev_hold(dev);
+ nskb = skb_clone(skb, GFP_ATOMIC);
+ if (nskb) {
+ nskb->dev = dev;
+ ret = dev_queue_xmit(nskb);
+ if (unlikely(ret > 0))
+ ret = net_xmit_errno(ret);
+ }
+
+ dev_put(dev);
+ return ret;
+}
+
+static void __netlink_deliver_tap(struct sk_buff *skb)
+{
+ int ret;
+ struct netlink_tap *tmp;
+
+ list_for_each_entry_rcu(tmp, &netlink_tap_all, list) {
+ ret = __netlink_deliver_tap_skb(skb, tmp->dev);
+ if (unlikely(ret))
+ break;
+ }
+}
+
+static void netlink_deliver_tap(struct sk_buff *skb)
+{
+ rcu_read_lock();
+
+ if (unlikely(!list_empty(&netlink_tap_all)))
+ __netlink_deliver_tap(skb);
+
+ rcu_read_unlock();
+}
+
static void netlink_overrun(struct sock *sk)
{
struct netlink_sock *nlk = nlk_sk(sk);
@@ -1518,6 +1616,8 @@ static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
{
int len = skb->len;
+ netlink_deliver_tap(skb);
+
#ifdef CONFIG_NETLINK_MMAP
if (netlink_skb_is_mmaped(skb))
netlink_queue_mmaped_skb(sk, skb);
@@ -1578,6 +1678,11 @@ static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb,
ret = -ECONNREFUSED;
if (nlk->netlink_rcv != NULL) {
+ /* We could do a netlink_deliver_tap(skb) here as well
+ * but since this is intended for the kernel only, we
+ * should rather let it stay under the hood.
+ */
+
ret = skb->len;
netlink_skb_set_owner_r(skb, sk);
NETLINK_CB(skb).sk = ssk;
@@ -2975,6 +3080,8 @@ static int __init netlink_proto_init(void)
nl_table[i].compare = netlink_compare;
}
+ INIT_LIST_HEAD(&netlink_tap_all);
+
netlink_add_usersock_entry();
sock_register(&netlink_family_ops);
Similarly to the networking receive path with ptype_all taps, we add the possibility to register netdevices that are for ARPHRD_NETLINK to the netlink subsystem, so that those can be used for netlink analyzers resp. debuggers. We do not offer a direct callback function as out-of-tree modules could do crap with it. Instead, a netdevice must be registered properly and only receives a clone, managed by the netlink layer. Symbols are exported as GPL-only. Signed-off-by: Daniel Borkmann <dborkman@redhat.com> --- include/linux/netlink.h | 10 +++++ net/netlink/af_netlink.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 117 insertions(+)