This patch provides the back end support for equal-cost multi-path

(ECMP) for both IPv4 and IPv6. Previously, multipath route insertion
is disallowed. For example,

	route add -net 192.103.54.0/24 10.9.44.1
	route add -net 192.103.54.0/24 10.9.44.2

The second route insertion will trigger an error message of
"add net 192.103.54.0/24: gateway 10.2.5.2: route already in table"

Multiple default routes can also be inserted. Here is the netstat
output:

default		10.2.5.1	UGS	0	3074	bge0 =>
default		10.2.5.2	UGS	0	0	bge0

When multipath routes exist, the "route delete" command requires
a specific gateway to be specified or else an error message would
be displayed. For example,

	route delete default

would fail and trigger the following error message:

"route: writing to routing socket: No such process"
"delete net default: not in table"

On the other hand,

	route delete default 10.2.5.2

would be successful: "delete net default: gateway 10.2.5.2"

One does not have to specify a gateway if there is only a single
route for a particular destination.

I need to perform more testings on address aliases and multiple
interfaces that have the same IP prefixes. This patch as it
stands today is not yet ready for prime time. Therefore, the ECMP
code fragments are fully guarded by the RADIX_MPATH macro.
Include the "options  RADIX_MPATH" in the kernel configuration
to enable this feature.

Reviewed by:	robert, sam, gnn, julian, kmacy

sys/conf/files

@@ -1670,6 +1670,7 @@ net/ppp_deflate.c		optional ppp_deflate
 net/ppp_tty.c			optional ppp
 net/pfil.c			optional ether | inet
 net/radix.c			standard
+net/radix_mpath.c		standard
 net/raw_cb.c			standard
 net/raw_usrreq.c		standard
 net/route.c			standard

sys/conf/options

@@ -393,6 +393,7 @@ NETATALK		opt_atalk.h
 PPP_BSDCOMP		opt_ppp.h
 PPP_DEFLATE		opt_ppp.h
 PPP_FILTER		opt_ppp.h
+RADIX_MPATH		opt_mpath.h
 SLIP_IFF_OPTS		opt_slip.h
 TCPDEBUG
 TCP_SIGNATURE		opt_inet.h

sys/net/radix.c

@@ -48,6 +48,13 @@
 #include <net/radix.h>
 #endif
 
+#include "opt_mpath.h"
+
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
+
+
 static int	rn_walktree_from(struct radix_node_head *h, void *a, void *m,
 		    walktree_f_t *f, void *w);
 static int rn_walktree(struct radix_node_head *, walktree_f_t *, void *);
@@ -630,6 +637,21 @@ rn_addroute(v_arg, n_arg, head, treenodes)
 	saved_tt = tt = rn_insert(v, head, &keyduplicated, treenodes);
 	if (keyduplicated) {
 		for (t = tt; tt; t = tt, tt = tt->rn_dupedkey) {
+#ifdef RADIX_MPATH
+			/* permit multipath, if enabled for the family */
+			if (rn_mpath_capable(head) && netmask == tt->rn_mask) {
+				/*
+				 * go down to the end of multipaths, so that
+				 * new entry goes into the end of rn_dupedkey
+				 * chain.
+				 */
+				do {
+					t = tt;
+					tt = tt->rn_dupedkey;
+				} while (tt && t->rn_mask == tt->rn_mask);
+				break;
+			}
+#endif
 			if (tt->rn_mask == netmask)
 				return (0);
 			if (netmask == 0 ||

sys/net/radix.h

@@ -130,6 +130,7 @@ struct radix_node_head {
 	void	(*rnh_close)	/* do something when the last ref drops */
 		(struct radix_node *rn, struct radix_node_head *head);
 	struct	radix_node rnh_nodes[3];	/* empty tree for common case */
+	int	rnh_multipath;			/* multipath capable ? */
 #ifdef _KERNEL
 	struct	mtx rnh_mtx;			/* locks entire radix tree */
 #endif

sys/net/route.c

@@ -32,6 +32,7 @@
 
 #include "opt_inet.h"
 #include "opt_mrouting.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -44,6 +45,10 @@
 #include <net/if.h>
 #include <net/route.h>
 
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
+
 #include <netinet/in.h>
 #include <netinet/ip_mroute.h>
 
@@ -700,6 +705,67 @@ rtrequest1(int req, struct rt_addrinfo *info, struct rtentry **ret_nrt)
 	}
 	switch (req) {
 	case RTM_DELETE:
+#ifdef RADIX_MPATH
+		/*
+		 * if we got multipath routes, we require users to specify
+		 * a matching RTAX_GATEWAY.
+		 */
+		if (rn_mpath_capable(rnh)) {
+			struct rtentry *rto = NULL;
+
+			rn = rnh->rnh_matchaddr(dst, rnh);
+			if (rn == NULL)
+				senderr(ESRCH);
+ 			rto = rt = RNTORT(rn);
+			rt = rt_mpath_matchgate(rt, gateway);
+			if (!rt)
+				senderr(ESRCH);
+			/*
+			 * this is the first entry in the chain
+			 */
+			if (rto == rt) {
+				rn = rn_mpath_next((struct radix_node *)rt);
+				/*
+				 * there is another entry, now it's active
+				 */
+				if (rn) {
+					rto = RNTORT(rn);
+					RT_LOCK(rto);
+					rto->rt_flags |= RTF_UP;
+					RT_UNLOCK(rto);
+				} else if (rt->rt_flags & RTF_GATEWAY) {
+					/*
+					 * For gateway routes, we need to 
+					 * make sure that we we are deleting
+					 * the correct gateway. 
+					 * rt_mpath_matchgate() does not 
+					 * check the case when there is only
+					 * one route in the chain.  
+					 */
+					if (gateway &&
+					    (rt->rt_gateway->sa_len != gateway->sa_len ||
+					    memcmp(rt->rt_gateway, gateway, gateway->sa_len)))
+						senderr(ESRCH);
+				}
+				/*
+				 * use the normal delete code to remove
+				 * the first entry
+				 */
+				goto normal_rtdel;
+			}
+			/*
+			 * if the entry is 2nd and on up
+			 */
+			if (!rt_mpath_deldup(rto, rt))
+				panic ("rtrequest1: rt_mpath_deldup");
+			RT_LOCK(rt);
+			RT_ADDREF(rt);
+			rt->rt_flags &= ~RTF_UP;
+			goto deldone;  /* done with the RTM_DELETE command */
+		}
+#endif
+
+normal_rtdel:
 		/*
 		 * Remove the item from the tree and return it.
 		 * Complain if it is not there and do no more processing.
@@ -740,6 +806,7 @@ rtrequest1(int req, struct rt_addrinfo *info, struct rtentry **ret_nrt)
 		if ((ifa = rt->rt_ifa) && ifa->ifa_rtrequest)
 			ifa->ifa_rtrequest(RTM_DELETE, rt, info);
 
+deldone:
 		/*
 		 * One more rtentry floating around that is not
 		 * linked to the routing table. rttrash will be decremented
@@ -822,6 +889,22 @@ rtrequest1(int req, struct rt_addrinfo *info, struct rtentry **ret_nrt)
 		rt->rt_ifa = ifa;
 		rt->rt_ifp = ifa->ifa_ifp;
 
+#ifdef RADIX_MPATH
+		/* do not permit exactly the same dst/mask/gw pair */
+		if (rn_mpath_capable(rnh) &&
+			rt_mpath_conflict(rnh, rt, netmask)) {
+			if (rt->rt_gwroute)
+				RTFREE(rt->rt_gwroute);
+			if (rt->rt_ifa) {
+				IFAFREE(rt->rt_ifa);
+			}
+			Free(rt_key(rt));
+			RT_LOCK_DESTROY(rt);
+			uma_zfree(rtzone, rt);
+			senderr(EEXIST);
+		}
+#endif
+
 		/* XXX mtu manipulation will be done in rnh_addaddr -- itojun */
 		rn = rnh->rnh_addaddr(ndst, netmask, rnh, rt->rt_nodes);
 		if (rn == NULL) {
@@ -1166,7 +1249,7 @@ rtinit(struct ifaddr *ifa, int cmd, int flags)
 	struct mbuf *m = NULL;
 	struct rtentry *rt = NULL;
 	struct rt_addrinfo info;
-	int error;
+	int error=0;
 
 	if (flags & RTF_HOST) {
 		dst = ifa->ifa_dstaddr;
@@ -1208,10 +1291,32 @@ rtinit(struct ifaddr *ifa, int cmd, int flags)
 		if ((rnh = rt_tables[dst->sa_family]) == NULL)
 			goto bad;
 		RADIX_NODE_HEAD_LOCK(rnh);
+#ifdef RADIX_MPATH
+		if (rn_mpath_capable(rnh)) {
+
+			rn = rnh->rnh_matchaddr(dst, rnh);
+			if (rn == NULL) 
+				error = ESRCH;
+			else {
+				rt = RNTORT(rn);
+				/*
+				 * for interface route the rt->rt_gateway is
+				 * sockaddr_intf for cloning ARP entries, so
+				 * rt_mpath_matchgate must use the interface
+				 * address
+				 */
+				rt = rt_mpath_matchgate(rt, ifa->ifa_addr);
+				if (!rt) 
+					error = ESRCH;
+			}
+		}
+		else
+#endif
 		error = ((rn = rnh->rnh_lookup(dst, netmask, rnh)) == NULL ||
 		    (rn->rn_flags & RNF_ROOT) ||
 		    RNTORT(rn)->rt_ifa != ifa ||
 		    !sa_equal((struct sockaddr *)rn->rn_key, dst));
+
 		RADIX_NODE_HEAD_UNLOCK(rnh);
 		if (error) {
 bad:
@@ -1235,6 +1340,21 @@ rtinit(struct ifaddr *ifa, int cmd, int flags)
 		 * notify any listening routing agents of the change
 		 */
 		RT_LOCK(rt);
+#ifdef RADIX_MPATH
+		/*
+		 * in case address alias finds the first address
+		 * e.g. ifconfig bge0 192.103.54.246/24
+		 * e.g. ifconfig bge0 192.103.54.247/24
+		 * the address set in the route is 192.103.54.246
+		 * so we need to replace it with 192.103.54.247
+		 */
+		if (memcmp(rt->rt_ifa->ifa_addr, ifa->ifa_addr, ifa->ifa_addr->sa_len)) {
+			IFAFREE(rt->rt_ifa);
+			IFAREF(ifa);
+			rt->rt_ifp = ifa->ifa_ifp;
+			rt->rt_ifa = ifa;
+		}
+#endif
 		rt_newaddrmsg(cmd, ifa, error, rt);
 		if (cmd == RTM_DELETE) {
 			/*

sys/net/route.h

@@ -97,6 +97,9 @@ struct mbuf;
  */
 #ifndef RNF_NORMAL
 #include <net/radix.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 #endif
 struct rtentry {
 	struct	radix_node rt_nodes[2];	/* tree glue, and other values */

sys/net/rtsock.c

@@ -30,6 +30,8 @@
  * $FreeBSD$
  */
 #include "opt_sctp.h"
+#include "opt_mpath.h"
+
 #include <sys/param.h>
 #include <sys/domain.h>
 #include <sys/kernel.h>
@@ -420,6 +422,24 @@ route_output(struct mbuf *m, struct socket *so)
 			RADIX_NODE_HEAD_UNLOCK(rnh);
 			senderr(ESRCH);
 		}
+#ifdef RADIX_MPATH
+		/*
+		 * for RTM_CHANGE/LOCK, if we got multipath routes,
+		 * we require users to specify a matching RTAX_GATEWAY.
+		 *
+		 * for RTM_GET, gate is optional even with multipath.
+		 * if gate == NULL the first match is returned.
+		 * (no need to call rt_mpath_matchgate if gate == NULL)
+		 */
+		if (rn_mpath_capable(rnh) &&
+		    (rtm->rtm_type != RTM_GET || info.rti_info[RTAX_GATEWAY])) {
+			rt = rt_mpath_matchgate(rt, info.rti_info[RTAX_GATEWAY]);
+			if (!rt) {
+				RADIX_NODE_HEAD_UNLOCK(rnh);
+				senderr(ESRCH);
+			}
+		}
+#endif
 		RT_LOCK(rt);
 		RT_ADDREF(rt);
 		RADIX_NODE_HEAD_UNLOCK(rnh);

sys/netinet/in_proto.c

@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_pf.h"
 #include "opt_carp.h"
 #include "opt_sctp.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -51,6 +52,9 @@ __FBSDID("$FreeBSD$");
 
 #include <net/if.h>
 #include <net/route.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
@@ -352,7 +356,11 @@ struct domain inetdomain = {
 	.dom_name =		"internet",
 	.dom_protosw =		inetsw,
 	.dom_protoswNPROTOSW =	&inetsw[sizeof(inetsw)/sizeof(inetsw[0])],
+#ifdef RADIX_MPATH
+	.dom_rtattach =		rn4_mpath_inithead,
+#else
 	.dom_rtattach =		in_inithead,
+#endif
 	.dom_rtoffset =		32,
 	.dom_maxrtkey =		sizeof(struct sockaddr_in)
 };

sys/netinet/ip_output.c

@@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_ipsec.h"
 #include "opt_mac.h"
 #include "opt_mbuf_stress_test.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -54,6 +55,9 @@ __FBSDID("$FreeBSD$");
 #include <net/netisr.h>
 #include <net/pfil.h>
 #include <net/route.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
@@ -225,7 +229,12 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 		 * operation (as it is for ARP).
 		 */
 		if (ro->ro_rt == NULL)
+#ifdef RADIX_MPATH
+			rtalloc_mpath(ro,
+			    ntohl(ip->ip_src.s_addr ^ ip->ip_dst.s_addr));
+#else
 			rtalloc_ign(ro, 0);
+#endif
 		if (ro->ro_rt == NULL) {
 			ipstat.ips_noroute++;
 			error = EHOSTUNREACH;

sys/netinet6/in6_proto.c

@@ -69,6 +69,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_ipstealth.h"
 #include "opt_carp.h"
 #include "opt_sctp.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/socket.h>
@@ -83,6 +84,9 @@ __FBSDID("$FreeBSD$");
 #include <net/if.h>
 #include <net/radix.h>
 #include <net/route.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
@@ -347,7 +351,11 @@ struct domain inet6domain = {
 	.dom_protosw =		(struct protosw *)inet6sw,
 	.dom_protoswNPROTOSW =	(struct protosw *)
 				&inet6sw[sizeof(inet6sw)/sizeof(inet6sw[0])],
+#ifdef RADIX_MPATH
+	.dom_rtattach =		rn6_mpath_inithead,
+#else
 	.dom_rtattach =		in6_inithead,
+#endif
 	.dom_rtoffset =		offsetof(struct sockaddr_in6, sin6_addr) << 3,
 	.dom_maxrtkey =		sizeof(struct sockaddr_in6),
 	.dom_ifattach =		in6_domifattach,

sys/netinet6/in6_src.c

@@ -65,6 +65,7 @@ __FBSDID("$FreeBSD$");
 
 #include "opt_inet.h"
 #include "opt_inet6.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -84,6 +85,9 @@ __FBSDID("$FreeBSD$");
 
 #include <net/if.h>
 #include <net/route.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 
 #include <netinet/in.h>
 #include <netinet/in_var.h>
@@ -568,7 +572,12 @@ selectroute(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 			sa6->sin6_scope_id = 0;
 
 			if (clone) {
+#ifdef RADIX_MPATH
+				rtalloc_mpath((struct route *)ro,
+				    ntohl(sa6->sin6_addr.s6_addr32[3]));
+#else
 				rtalloc((struct route *)ro);
+#endif
 			} else {
 				ro->ro_rt = rtalloc1(&((struct route *)ro)
 						     ->ro_dst, 0, 0UL);

sys/netinet6/nd6_nbr.c

@@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_inet6.h"
 #include "opt_ipsec.h"
 #include "opt_carp.h"
+#include "opt_mpath.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -55,6 +56,9 @@ __FBSDID("$FreeBSD$");
 #include <net/if_dl.h>
 #include <net/if_var.h>
 #include <net/route.h>
+#ifdef RADIX_MPATH
+#include <net/radix_mpath.h>
+#endif
 
 #include <netinet/in.h>
 #include <netinet/in_var.h>
@@ -208,13 +212,23 @@ nd6_ns_input(struct mbuf *m, int off, int icmp6len)
 		struct rtentry *rt;
 		struct sockaddr_in6 tsin6;
 		int need_proxy;
+#ifdef RADIX_MPATH
+		struct route_in6 ro;
+#endif
 
 		bzero(&tsin6, sizeof tsin6);
 		tsin6.sin6_len = sizeof(struct sockaddr_in6);
 		tsin6.sin6_family = AF_INET6;
 		tsin6.sin6_addr = taddr6;
 
+#ifdef RADIX_MPATH
+		bzero(&ro, sizeof(ro));
+		ro.ro_dst = tsin6;
+		rtalloc_mpath((struct route *)&ro, RTF_ANNOUNCE);
+		rt = ro.ro_rt;
+#else
 		rt = rtalloc1((struct sockaddr *)&tsin6, 0, 0);
+#endif
 		need_proxy = (rt && (rt->rt_flags & RTF_ANNOUNCE) != 0 &&
 		    rt->rt_gateway->sa_family == AF_LINK);
 		if (rt)