[IPSEC]: Add support for Twofish and Serpent.

This patch adds support for the use of twofish and serpent as
ESP algorithms. The ESP index numbers given are in accordance
with RFC2407, draft-ietf-ipsec-ciph-aes-cbc-00 (before Rijndael
was selected), and KAME which assigns 253 to twofishcbc.

Support for using twofish was requested on linux-kernel, and
since I noticed serpent was missing too, included that as well.

include/linux/pfkeyv2.h

@@ -284,7 +284,10 @@ struct sadb_x_nat_t_port {
 #define SADB_X_EALG_BLOWFISHCBC		7
 #define SADB_EALG_NULL			11
 #define SADB_X_EALG_AESCBC		12
-#define SADB_EALG_MAX			12
+#define SADB_EALG_MAX                   253 /* last EALG */
+/* private allocations should use 249-255 (RFC2407) */
+#define SADB_X_EALG_SERPENTCBC  252     /* draft-ietf-ipsec-ciph-aes-cbc-00 */
+#define SADB_X_EALG_TWOFISHCBC  253     /* draft-ietf-ipsec-ciph-aes-cbc-00 */
 
 /* Compression algorithms */
 #define SADB_X_CALG_NONE		0

net/xfrm/xfrm_algo.c

@@ -217,6 +217,40 @@ static struct xfrm_algo_desc ealg_list[] = {
 		.sadb_alg_maxbits = 256
 	}
 },
+{
+        .name = "serpent",
+
+        .uinfo = {
+                .encr = {
+                        .blockbits = 128,
+                        .defkeybits = 128,
+                }
+        },
+
+        .desc = {
+                .sadb_alg_id = SADB_X_EALG_SERPENTCBC,
+                .sadb_alg_ivlen = 8,
+                .sadb_alg_minbits = 128,
+                .sadb_alg_maxbits = 256,
+        }
+},
+{
+        .name = "twofish",
+                 
+        .uinfo = {
+                .encr = {
+                        .blockbits = 128,
+                        .defkeybits = 128,
+                }
+        },
+
+        .desc = {
+                .sadb_alg_id = SADB_X_EALG_TWOFISHCBC,
+                .sadb_alg_ivlen = 8,
+                .sadb_alg_minbits = 128,
+                .sadb_alg_maxbits = 256
+        }
+},
 };
 
 static struct xfrm_algo_desc calg_list[] = {