[XFRM]: Add generation count to xfrm_state and xfrm_dst.

Each xfrm_state inserted gets a new generation counter
value.  When a bundle is created, the xfrm_dst objects
get the current generation counter of the xfrm_state
they will attach to at dst->xfrm.

xfrm_bundle_ok() will return false if it sees an
xfrm_dst with a generation count different from the
generation count of the xfrm_state that dst points to.

This provides a facility by which to passively and
cheaply invalidate cached IPSEC routes during SA
database changes.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/xfrm.h

@@ -104,6 +104,8 @@ struct xfrm_state
 	struct xfrm_id		id;
 	struct xfrm_selector	sel;
 
+	u32			genid;
+
 	/* Key manger bits */
 	struct {
 		u8		state;
@@ -590,6 +592,7 @@ struct xfrm_dst
 		struct rt6_info		rt6;
 	} u;
 	struct dst_entry *route;
+	u32 genid;
 	u32 route_mtu_cached;
 	u32 child_mtu_cached;
 	u32 route_cookie;

net/ipv4/xfrm4_policy.c

@@ -93,6 +93,7 @@ __xfrm4_bundle_create(struct xfrm_policy *policy, struct xfrm_state **xfrm, int
 
 		xdst = (struct xfrm_dst *)dst1;
 		xdst->route = &rt->u.dst;
+		xdst->genid = xfrm[i]->genid;
 
 		dst1->next = dst_prev;
 		dst_prev = dst1;

net/ipv6/xfrm6_policy.c

@@ -149,6 +149,7 @@ __xfrm6_bundle_create(struct xfrm_policy *policy, struct xfrm_state **xfrm, int
 
 		xdst = (struct xfrm_dst *)dst1;
 		xdst->route = &rt->u.dst;
+		xdst->genid = xfrm[i]->genid;
 		if (rt->rt6i_node)
 			xdst->route_cookie = rt->rt6i_node->fn_sernum;
 

net/xfrm/xfrm_policy.c

@@ -1536,6 +1536,8 @@ int xfrm_bundle_ok(struct xfrm_dst *first, struct flowi *fl, int family, int str
 			return 0;
 		if (dst->xfrm->km.state != XFRM_STATE_VALID)
 			return 0;
+		if (xdst->genid != dst->xfrm->genid)
+			return 0;
 
 		if (strict && fl && dst->xfrm->props.mode != XFRM_MODE_TUNNEL &&
 		    !xfrm_state_addr_flow_check(dst->xfrm, fl, family))

net/xfrm/xfrm_state.c

@@ -53,6 +53,7 @@ static struct hlist_head *xfrm_state_byspi __read_mostly;
 static unsigned int xfrm_state_hmask __read_mostly;
 static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024;
 static unsigned int xfrm_state_num;
+static unsigned int xfrm_state_genid;
 
 static inline unsigned int __xfrm4_dst_hash(xfrm_address_t *addr, unsigned int hmask)
 {
@@ -745,6 +746,8 @@ static void __xfrm_state_insert(struct xfrm_state *x)
 {
 	unsigned int h = xfrm_dst_hash(&x->id.daddr, x->props.family);
 
+	x->genid = ++xfrm_state_genid;
+
 	hlist_add_head(&x->bydst, xfrm_state_bydst+h);
 	xfrm_state_hold(x);