[IPSEC]: Add xfrm_state_afinfo->init_flags

This patch adds the xfrm_state_afinfo->init_flags hook which allows
each address family to perform any common initialisation that does
not require a corresponding destructor call.

It will be used subsequently to set the XFRM_STATE_NOPMTUDISC flag
in IPv4.

It also fixes up the error codes returned by xfrm_init_state.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: James Morris <jmorris@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 1845b73..9d206c2 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1058,10 +1058,26 @@
 
 int xfrm_init_state(struct xfrm_state *x)
 {
+	struct xfrm_state_afinfo *afinfo;
+	int family = x->props.family;
 	int err;
 
-	err = -ENOENT;
-	x->type = xfrm_get_type(x->id.proto, x->props.family);
+	err = -EAFNOSUPPORT;
+	afinfo = xfrm_state_get_afinfo(family);
+	if (!afinfo)
+		goto error;
+
+	err = 0;
+	if (afinfo->init_flags)
+		err = afinfo->init_flags(x);
+
+	xfrm_state_put_afinfo(afinfo);
+
+	if (err)
+		goto error;
+
+	err = -EPROTONOSUPPORT;
+	x->type = xfrm_get_type(x->id.proto, family);
 	if (x->type == NULL)
 		goto error;