[IPSEC]: Add compatibility algorithm name support

This patch adds a compatibility name field for each IPsec algorithm.  This
is needed when parameterised algorithms are used.  For example, "md5" will
become "hmac(md5)", and "aes" will become "cbc(aes)".
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/net/xfrm.h

@@ -854,6 +854,7 @@ struct xfrm_algo_comp_info {
 
 struct xfrm_algo_desc {
 	char *name;
+	char *compat;
 	u8 available:1;
 	union {
 		struct xfrm_algo_auth_info auth;

net/xfrm/xfrm_algo.c

@@ -359,7 +359,8 @@ static struct xfrm_algo_desc *xfrm_get_byname(struct xfrm_algo_desc *list,
 		return NULL;
 
 	for (i = 0; i < entries; i++) {
-		if (strcmp(name, list[i].name))
+		if (strcmp(name, list[i].name) &&
+		    (!list[i].compat || strcmp(name, list[i].compat)))
 			continue;
 
 		if (list[i].available)

net/xfrm/xfrm_user.c

@@ -213,6 +213,7 @@ static int attach_one_algo(struct xfrm_algo **algpp, u8 *props,
 		return -ENOMEM;
 
 	memcpy(p, ualg, len);
+	strcpy(p->alg_name, algo->name);
 	*algpp = p;
 	return 0;
 }