* Check permissions on incoming network packets. This hook is distinct
* from Netfilter's IP input hooks since it is the first time that the
* incoming sk_buff @skb has been associated with a particular socket, @sk.
+ * Must not sleep inside this hook because some callers hold spinlocks.
* @sk contains the sock (not socket) associated with the incoming sk_buff.
* @skb contains the incoming network data.
* @socket_getpeersec_stream: