FreeBSD previously provided route caching for TCP (and UDP). Re-add

route caching for TCP, with some improvements. In particular, invalidate
the route cache if a new route is added, which might be a better match.
The cache is automatically invalidated if the old route is deleted.

Submitted by:	Mike Karels
Reviewed by:	gnn
Differential Revision:	https://reviews.freebsd.org/D4306

3 files changed, 35 insertions, 1 deletions

diff --git a/sys/net/route.c b/sys/net/route.c
index 45f479c..77c775d 100644
--- a/sys/net/route.c
+++ b/sys/net/route.c
@@ -201,6 +201,16 @@ rt_tables_get_rnh(int table, int fam)
 	return (*rt_tables_get_rnh_ptr(table, fam));
 }
 
+rt_gen_t
+rt_tables_get_gen(int table, int fam)
+{
+	struct rib_head *rnh;
+
+	rnh = *rt_tables_get_rnh_ptr(table, fam);
+	return (rnh->rnh_gen);
+}
+
+
 /*
  * route initialization must occur before ip6_init2(), which happenas at
  * SI_ORDER_MIDDLE.
@@ -1754,6 +1764,7 @@ rtrequest1_fib(int req, struct rt_addrinfo *info, struct rtentry **ret_nrt,
 			*ret_nrt = rt;
 			RT_ADDREF(rt);
 		}
+		rnh->rnh_gen++;		/* Routing table updated */
 		RT_UNLOCK(rt);
 		break;
 	case RTM_CHANGE:
diff --git a/sys/net/route.h b/sys/net/route.h
index 6cc1e1c..596214e 100644
--- a/sys/net/route.h
+++ b/sys/net/route.h
@@ -98,6 +98,14 @@ struct rt_metrics {
 /* lle state is exported in rmx_state rt_metrics field */
 #define	rmx_state	rmx_weight
 
+/*
+ * Keep a generation count of routing table, incremented on route addition,
+ * so we can invalidate caches.  This is accessed without a lock, as precision
+ * is not required.
+ */
+typedef volatile u_int rt_gen_t;	/* tree generation (for adds) */
+#define RT_GEN(fibnum, af)	rt_tables_get_gen(fibnum, af)
+
 #define	RT_DEFAULT_FIB	0	/* Explicitly mark fib=0 restricted cases */
 #define	RT_ALL_FIBS	-1	/* Announce event for every fib */
 #ifdef _KERNEL
@@ -398,6 +406,20 @@ struct rt_addrinfo {
 	}							\
 } while (0)
 
+/*
+ * Validate a cached route based on a supplied cookie.  If there is an
+ * out-of-date cache, simply free it.  Update the generation number
+ * for the new allocation
+ */
+#define RT_VALIDATE(ro, cookiep, fibnum) do {				\
+	rt_gen_t cookie = RT_GEN(fibnum, (ro)->ro_dst.sa_family);	\
+	if (*(cookiep) != cookie && (ro)->ro_rt != NULL) {		\
+		RTFREE((ro)->ro_rt);					\
+		(ro)->ro_rt = NULL;					\
+		*(cookiep) = cookie;					\
+	}								\
+} while (0)
+
 struct ifmultiaddr;
 struct rib_head;
 
@@ -415,6 +437,7 @@ int	 rt_setgate(struct rtentry *, struct sockaddr *, struct sockaddr *);
 void 	 rt_maskedcopy(struct sockaddr *, struct sockaddr *, struct sockaddr *);
 struct rib_head *rt_table_init(int);
 void	rt_table_destroy(struct rib_head *);
+rt_gen_t rt_tables_get_gen(int table, int fam);
 
 int	rtsock_addrmsg(int, struct ifaddr *, int);
 int	rtsock_routemsg(int, struct ifnet *ifp, int, struct rtentry *, int);
diff --git a/sys/net/route_var.h b/sys/net/route_var.h
index 86fc8a9..a8ef56a 100644
--- a/sys/net/route_var.h
+++ b/sys/net/route_var.h
@@ -41,7 +41,7 @@ struct rib_head {
 	rn_walktree_t		*rnh_walktree;	/* traverse tree */
 	rn_walktree_from_t	*rnh_walktree_from; /* traverse tree below a */
 	rn_close_t		*rnh_close;	/*do something when the last ref drops*/
-	u_int			rnh_gen;	/* generation counter */
+	rt_gen_t		rnh_gen;	/* generation counter */
 	int			rnh_multipath;	/* multipath capable ? */
 	struct radix_node	rnh_nodes[3];	/* empty tree for common case */
 	struct rwlock		rib_lock;	/* config/data path lock */