net: netlink: virtual tap device management

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index f78b430f4af5..86fde81ac2e6 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -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 */