Combine route_cache() and rtalloc_mpath() in new route_mpath().

Fill and check the cache and call rtalloc_mpath() together.  Then
the caller of route_mpath() does not have to care about the uint32_t
*src pointer and just pass struct in_addr.  All the conversions are
done inside the functions.

A previous version of this diff was backed out.  There was an
additional rtisvalid() in rtalloc_mpath() that prevented packet
output via interfaces that were not up.  Now the route in the cache
has to be valid, but after new lookup, rtalloc_mpath() may return
invalid routes.  This generates less errors in userland an preserves
existing behavior.

OK sashan@

2 files changed, 38 insertions, 2 deletions

diff --git a/sys/net/route.c b/sys/net/route.c
index 9dadb5aa5eb..028199bd4c0 100644
--- a/sys/net/route.c
+++ b/sys/net/route.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: route.c,v 1.435 2024/02/29 12:01:59 naddy Exp $	*/
+/*	$OpenBSD: route.c,v 1.436 2024/03/31 15:53:12 bluhm Exp $	*/
 /*	$NetBSD: route.c,v 1.14 1996/02/13 22:00:46 christos Exp $	*/
 
 /*
@@ -239,6 +239,24 @@ route_cache(struct route *ro, const struct in_addr *dst,
 	return (ESRCH);
 }
 
+/*
+ * Check cache for route, else allocate a new one, potentially using multipath
+ * to select the peer.  Update cache and return valid route or NULL.
+ */
+struct rtentry *
+route_mpath(struct route *ro, const struct in_addr *dst,
+    const struct in_addr *src, u_int rtableid)
+{
+	if (route_cache(ro, dst, src, rtableid)) {
+		uint32_t *s = NULL;
+
+		if (ro->ro_srcin.s_addr != INADDR_ANY)
+			s = &ro->ro_srcin.s_addr;
+		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa, s, ro->ro_tableid);
+	}
+	return (ro->ro_rt);
+}
+
 #ifdef INET6
 int
 route6_cache(struct route *ro, const struct in6_addr *dst,
@@ -277,6 +295,20 @@ route6_cache(struct route *ro, const struct in6_addr *dst,
 
 	return (ESRCH);
 }
+
+struct rtentry *
+route6_mpath(struct route *ro, const struct in6_addr *dst,
+    const struct in6_addr *src, u_int rtableid)
+{
+	if (route6_cache(ro, dst, src, rtableid)) {
+		uint32_t *s = NULL;
+
+		if (!IN6_IS_ADDR_UNSPECIFIED(&ro->ro_srcin6))
+			s = &ro->ro_srcin6.s6_addr32[0];
+		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa, s, ro->ro_tableid);
+	}
+	return (ro->ro_rt);
+}
 #endif
 
 /*
diff --git a/sys/net/route.h b/sys/net/route.h
index c05a70d0636..a301193e79a 100644
--- a/sys/net/route.h
+++ b/sys/net/route.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: route.h,v 1.209 2024/02/29 12:01:59 naddy Exp $	*/
+/*	$OpenBSD: route.h,v 1.210 2024/03/31 15:53:12 bluhm Exp $	*/
 /*	$NetBSD: route.h,v 1.9 1996/02/13 22:00:49 christos Exp $	*/
 
 /*
@@ -465,8 +465,12 @@ struct bfd_config;
 void	 route_init(void);
 int	 route_cache(struct route *, const struct in_addr *,
 	    const struct in_addr *, u_int);
+struct rtentry *route_mpath(struct route *, const struct in_addr *,
+	    const struct in_addr *, u_int);
 int	 route6_cache(struct route *, const struct in6_addr *,
 	    const struct in6_addr *, u_int);
+struct rtentry *route6_mpath(struct route *, const struct in6_addr *,
+	    const struct in6_addr *, u_int);
 void	 rtm_ifchg(struct ifnet *);
 void	 rtm_ifannounce(struct ifnet *, int);
 void	 rtm_bfd(struct bfd_config *);