tipc: introduce TIPC encryption & authentication

This commit offers an option to encrypt and authenticate all messaging,
including the neighbor discovery messages. The currently most advanced
algorithm supported is the AEAD AES-GCM (like IPSec or TLS). All
encryption/decryption is done at the bearer layer, just before leaving
or after entering TIPC.

Supported features:
- Encryption & authentication of all TIPC messages (header + data);
- Two symmetric-key modes: Cluster and Per-node;
- Automatic key switching;
- Key-expired revoking (sequence number wrapped);
- Lock-free encryption/decryption (RCU);
- Asynchronous crypto, Intel AES-NI supported;
- Multiple cipher transforms;
- Logs & statistics;

Two key modes:
- Cluster key mode: One single key is used for both TX & RX in all
nodes in the cluster.
- Per-node key mode: Each nodes in the cluster has one specific TX key.
For RX, a node requires its peers' TX key to be able to decrypt the
messages from those peers.

Key setting from user-space is performed via netlink by a user program
(e.g. the iproute2 'tipc' tool).

Internal key state machine:

                                 Attach    Align(RX)
                                     +-+   +-+
                                     | V   | V
        +---------+      Attach     +---------+
        |  IDLE   |---------------->| PENDING |(user = 0)
        +---------+                 +---------+
           A   A                   Switch|  A
           |   |                         |  |
           |   | Free(switch/revoked)    |  |
     (Free)|   +----------------------+  |  |Timeout
           |              (TX)        |  |  |(RX)
           |                          |  |  |
           |                          |  v  |
        +---------+      Switch     +---------+
        | PASSIVE |<----------------| ACTIVE  |
        +---------+       (RX)      +---------+
        (user = 1)                  (user >= 1)

The number of TFMs is 10 by default and can be changed via the procfs
'net/tipc/max_tfms'. At this moment, as for simplicity, this file is
also used to print the crypto statistics at runtime:

echo 0xfff1 > /proc/sys/net/tipc/max_tfms

The patch defines a new TIPC version (v7) for the encryption message (-
backward compatibility as well). The message is basically encapsulated
as follows:

   +----------------------------------------------------------+
   | TIPCv7 encryption  | Original TIPCv2    | Authentication |
   | header             | packet (encrypted) | Tag            |
   +----------------------------------------------------------+

The throughput is about ~40% for small messages (compared with non-
encryption) and ~9% for large messages. With the support from hardware
crypto i.e. the Intel AES-NI CPU instructions, the throughput increases
upto ~85% for small messages and ~55% for large messages.

By default, the new feature is inactive (i.e. no encryption) until user
sets a key for TIPC. There is however also a new option - "TIPC_CRYPTO"
in the kernel configuration to enable/disable the new code when needed.

MAINTAINERS | add two new files 'crypto.h' & 'crypto.c' in tipc

Acked-by: Ying Xue <ying.xue@windreiver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/msg.h

@@ -102,16 +102,42 @@ struct plist;
 #define TIPC_MEDIA_INFO_OFFSET	5
 
 struct tipc_skb_cb {
-	struct sk_buff *tail;
-	unsigned long nxt_retr;
-	unsigned long retr_stamp;
-	u32 bytes_read;
-	u32 orig_member;
-	u16 chain_imp;
-	u16 ackers;
-	u16 retr_cnt;
-	bool validated;
-};
+	union {
+		struct {
+			struct sk_buff *tail;
+			unsigned long nxt_retr;
+			unsigned long retr_stamp;
+			u32 bytes_read;
+			u32 orig_member;
+			u16 chain_imp;
+			u16 ackers;
+			u16 retr_cnt;
+		} __packed;
+#ifdef CONFIG_TIPC_CRYPTO
+		struct {
+			struct tipc_crypto *rx;
+			struct tipc_aead *last;
+			u8 recurs;
+		} tx_clone_ctx __packed;
+#endif
+	} __packed;
+	union {
+		struct {
+			u8 validated:1;
+#ifdef CONFIG_TIPC_CRYPTO
+			u8 encrypted:1;
+			u8 decrypted:1;
+			u8 probe:1;
+			u8 tx_clone_deferred:1;
+#endif
+		};
+		u8 flags;
+	};
+	u8 reserved;
+#ifdef CONFIG_TIPC_CRYPTO
+	void *crypto_ctx;
+#endif
+} __packed;
 
 #define TIPC_SKB_CB(__skb) ((struct tipc_skb_cb *)&((__skb)->cb[0]))