Extends multipath support for OSPF. (145368f5) · Commits · 戴 / Bird

doc/bird.sgml

+9 −0

Original line number	Diff line number	Diff line
		@@ -2291,6 +2291,7 @@ protocol ospf <name> {
		stub router <switch>;
		tick <num>;
		ecmp <switch> [limit <num>];
		merge external <switch>;
		area <id> {
		stub;
		nssa;
		@@ -2396,6 +2397,14 @@ protocol ospf <name> {
		nexthops in one route. By default, ECMP is disabled. If enabled,
		default value of the limit is 16.

		<tag>merge external <M>switch</M></tag>
		This option specifies whether OSPF should merge external routes from
		different routers/LSAs for the same destination. When enabled together
		with <cf/ecmp/, equal-cost external routes will be combined to multipath
		routes in the same way as regular routes. When disabled, external routes
		from different LSAs are treated as separate even if they represents the
		same destination. Default value is no.

		<tag>area <M>id</M></tag>
		This defines an OSPF area with given area ID (an integer or an IPv4
		address, similarly to a router ID). The most important area is the

proto/ospf/config.Y

+2 −1

Original line number	Diff line number	Diff line
		@@ -132,7 +132,7 @@ CF_KEYWORDS(ELIGIBLE, POLL, NETWORKS, HIDDEN, VIRTUAL, CHECK, LINK, ONLY, BFD)
		CF_KEYWORDS(RX, BUFFER, LARGE, NORMAL, STUBNET, HIDDEN, SUMMARY, TAG, EXTERNAL)
		CF_KEYWORDS(WAIT, DELAY, LSADB, ECMP, LIMIT, WEIGHT, NSSA, TRANSLATOR, STABILITY)
		CF_KEYWORDS(GLOBAL, LSID, ROUTER, SELF, INSTANCE, REAL, NETMASK, TX, PRIORITY, LENGTH)
		CF_KEYWORDS(SECONDARY)
		CF_KEYWORDS(SECONDARY, MERGE)

		%type <t> opttext
		%type <ld> lsadb_args
		@@ -162,6 +162,7 @@ ospf_proto_item:
		\| STUB ROUTER bool { OSPF_CFG->stub_router = $3; }
		\| ECMP bool { OSPF_CFG->ecmp = $2 ? DEFAULT_ECMP_LIMIT : 0; }
		\| ECMP bool LIMIT expr { OSPF_CFG->ecmp = $2 ? $4 : 0; if ($4 < 0) cf_error("ECMP limit cannot be negative"); }
		\| MERGE EXTERNAL bool { OSPF_CFG->merge_external = $3; }
		\| TICK expr { OSPF_CFG->tick = $2; if($2<=0) cf_error("Tick must be greater than zero"); }
		\| ospf_area
		;

proto/ospf/ospf.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -234,6 +234,7 @@ ospf_start(struct proto *p)
		po->router_id = proto_get_router_id(p->cf);
		po->rfc1583 = c->rfc1583;
		po->stub_router = c->stub_router;
		po->merge_external = c->merge_external;
		po->ebit = 0;
		po->ecmp = c->ecmp;
		po->tick = c->tick;
		@@ -742,6 +743,7 @@ ospf_reconfigure(struct proto p, struct proto_config c)
		return 0;

		po->stub_router = new->stub_router;
		po->merge_external = new->merge_external;
		po->ecmp = new->ecmp;
		po->tick = new->tick;
		po->disp_timer->recurrent = po->tick;

proto/ospf/ospf.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -81,6 +81,7 @@ struct ospf_config
		unsigned tick;
		byte rfc1583;
		byte stub_router;
		byte merge_external;
		byte abr;
		int ecmp;
		list area_list; /* list of struct ospf_area_config */
		@@ -777,6 +778,7 @@ struct proto_ospf
		struct fib rtf; /* Routing table */
		byte rfc1583; /* RFC1583 compatibility */
		byte stub_router; /* Do not forward transit traffic */
		byte merge_external; /* Should i merge external routes? */
		byte ebit; /* Did I originate any ext lsa? */
		byte ecmp; /* Maximal number of nexthops in ECMP route, or 0 */
		struct ospf_area backbone; / If exists */

proto/ospf/rt.c

+351 −192

Original line number	Diff line number	Diff line
		@@ -37,9 +37,15 @@ ospf_rt_initort(struct fib_node *fn)
		}

		static inline int
		unresolved_vlink(struct mpnh *nhs)
		nh_is_vlink(struct mpnh *nhs)
		{
		return nhs && !nhs->iface;
		return !nhs->iface;
		}

		static inline int
		unresolved_vlink(ort *ort)
		{
		return ort->n.nhs && nh_is_vlink(ort->n.nhs);
		}

		static inline struct mpnh *
		@@ -54,7 +60,7 @@ new_nexthop(struct proto_ospf po, ip_addr gw, struct iface iface, unsigned cha
		}

		static inline struct mpnh *
		copy_nexthop(struct proto_ospf po, struct mpnh src)
		copy_nexthop(struct proto_ospf po, const struct mpnh src)
		{
		struct mpnh *nh = lp_alloc(po->nhpool, sizeof(struct mpnh));
		nh->gw = src->gw;
		@@ -64,72 +70,138 @@ copy_nexthop(struct proto_ospf po, struct mpnh src)
		return nh;
		}


		/* If new is better return 1 */
		/* Compare nexthops during merge.
		We need to maintain nhs sorted to eliminate duplicities */
		static int
		ri_better(struct proto_ospf po, orta new, orta *old)
		cmp_nhs(struct mpnh s1, struct mpnh s2)
		{
		if (old->type == RTS_DUMMY)
		return 1;
		int r;

		if (new->type < old->type)
		if (!s1)
		return 1;

		if (new->type > old->type)
		return 0;
		if (!s2)
		return -1;

		if (new->metric1 < old->metric1)
		return 1;
		r = ((int) s2->weight) - ((int) s1->weight);
		if (r)
		return r;

		if (new->metric1 > old->metric1)
		return 0;
		r = ipa_compare(s1->gw, s2->gw);
		if (r)
		return r;

		return 0;
		return ((int) s1->iface->index) - ((int) s2->iface->index);
		}

		static struct mpnh *
		merge_nexthops(struct proto_ospf po, struct mpnh s1, struct mpnh *s2, int r1, int r2)
		{
		struct mpnh *root = NULL;
		struct mpnh **n = &root;
		int count = po->ecmp;

		/* Whether the ASBR or the forward address destination is preferred
		in AS external route selection according to 16.4.1. */
		static inline int
		epath_preferred(orta *ep)
		/*
		* r1, r2 signalize whether we can reuse nexthops from s1, s2.
		* New nexthops (s2, new) can be reused if they are not inherited
		* from the parent (i.e. it is allocated in calc_next_hop()).
		* Current nexthops (s1, en->nhs) can be reused if they weren't
		* inherited in previous steps (that is stored in nhs_reuse,
		* i.e. created by merging or allocalted in calc_next_hop()).
		*
		* Generally, a node first inherits shared nexthops from its
		* parent and later possibly gets reusable copy during merging.
		*/

		while ((s1 \|\| s2) && count--)
		{
		return (ep->type == RTS_OSPF) && (ep->oa->areaid != 0);
		int cmp = cmp_nhs(s1, s2);
		if (cmp < 0)
		{
		*n = r1 ? s1 : copy_nexthop(po, s1);
		s1 = s1->next;
		}
		else if (cmp > 0)
		{
		*n = r2 ? s2 : copy_nexthop(po, s2);
		s2 = s2->next;
		}
		else
		{
		*n = r1 ? s1 : (r2 ? s2 : copy_nexthop(po, s1));
		s1 = s1->next;
		s2 = s2->next;
		}
		n = &((*n)->next);
		}
		*n = NULL;

		/* 16.4. (3), return 1 if new is better */
		static int
		ri_better_asbr(struct proto_ospf po, orta new, orta *old)
		return root;
		}

		/* Returns true if there are device nexthops in n */
		static inline int
		has_device_nexthops(const struct mpnh *n)
		{
		if (old->type == RTS_DUMMY)
		for (; n; n = n->next)
		if (ipa_zero(n->gw))
		return 1;

		if (!po->rfc1583)
		return 0;
		}

		/* Replace device nexthops with nexthops to gw */
		static struct mpnh *
		fix_device_nexthops(struct proto_ospf po, const struct mpnh n, ip_addr gw)
		{
		int new_pref = epath_preferred(new);
		int old_pref = epath_preferred(old);
		struct mpnh *root1 = NULL;
		struct mpnh *root2 = NULL;
		struct mpnh **nn1 = &root1;
		struct mpnh **nn2 = &root2;

		if (new_pref > old_pref)
		return 1;
		/* This is a bit tricky. We cannot just copy the list and update n->gw,
		because the list should stay sorted, so we create two lists, one with new
		gateways and one with old ones, and then merge them. */

		if (new_pref < old_pref)
		return 0;
		for (; n; n = n->next)
		{
		struct mpnh *nn = new_nexthop(po, ipa_zero(n->gw) ? gw : n->gw, n->iface, n->weight);

		if (ipa_zero(n->gw))
		{
		*nn1 = nn;
		nn1 = &(nn->next);
		}
		else
		{
		*nn2 = nn;
		nn2 = &(nn->next);
		}
		}

		if (new->metric1 < old->metric1)
		return 1;
		return merge_nexthops(po, root1, root2, 1, 1);
		}

		if (new->metric1 > old->metric1)
		return 0;

		/* Larger area ID is preferred */
		if (new->oa->areaid > old->oa->areaid)
		return 1;
		/* Whether the ASBR or the forward address destination is preferred
		in AS external route selection according to 16.4.1. */
		static inline int
		epath_preferred(const orta *ep)
		{
		return (ep->type == RTS_OSPF) && (ep->oa->areaid != 0);
		}

		return 0;
		/* Whether the ext route has ASBR/next_hop marked as preferred. */
		static inline int
		orta_pref(const orta *nf)
		{
		return !!(nf->options & ORTA_PREF);
		}

		/* Classify orta entries according to RFC 3101 2.5 (6e) priorities:
		Type-7 LSA with P-bit, Type-5 LSA, Type-7 LSA without P-bit */
		static int
		orta_prio(orta *nf)
		orta_prio(const orta *nf)
		{
		/* RFC 3103 2.5 (6e) priorities */
		u32 opts = nf->options & (ORTA_NSSA \| ORTA_PROP);
		@@ -145,98 +217,246 @@ orta_prio(orta *nf)
		return 0;
		}

		/* 16.4. (6), return 1 if new is better */
		/* Whether the route is better according to RFC 3101 2.5 (6e):
		Prioritize Type-7 LSA with P-bit, then Type-5 LSA, then higher router ID */
		static int
		orta_prefer_lsa(const orta new, const orta old)
		{
		int pn = orta_prio(new);
		int po = orta_prio(old);

		return (pn > po) \|\| ((pn == po) && (new->en->lsa.rt > old->en->lsa.rt));
		}

		/*
		* Compare an existing routing table entry with a new one. Applicable for
		* intra-area routes, inter-area routes and router entries. Returns integer
		* <, = or > than 0 if the new orta is less, equal or more preferred than
		* the old orta.
		*/
		static int
		ri_better_ext(struct proto_ospf po, orta new, orta *old)
		orta_compare(const struct proto_ospf po, const orta new, const orta *old)
		{
		int r;

		if (old->type == RTS_DUMMY)
		return 1;

		/* 16.4. (6a) */
		if (new->type < old->type)
		/* Prefer intra-area to inter-area to externals */
		r = ((int) old->type) - ((int) new->type);
		if (r) return r;

		/* Prefer lowest type 1 metric */
		r = ((int) old->metric1) - ((int) new->metric1);
		if (r) return r;


		/* Rest is BIRD-specific */

		/* Area-wide routes should not mix next-hops from different areas.
		This generally should not happen unless there is some misconfiguration. */
		if (new->oa->areaid != old->oa->areaid)
		return (new->oa->areaid > old->oa->areaid) ? 1 : -1;

		/* Prefer routes for configured stubnets (!nhs) to regular routes to dummy
		vlink nexthops. We intentionally return -1 if both are stubnets or vlinks. */
		if (!old->nhs)
		return -1;
		if (!new->nhs)
		return 1;
		if (nh_is_vlink(new->nhs))
		return -1;
		if (nh_is_vlink(old->nhs))
		return 1;

		if (new->type > old->type)

		if (po->ecmp)
		return 0;

		/* 16.4. (6b), same type */
		if (new->type == RTS_OSPF_EXT2)
		{
		if (new->metric2 < old->metric2)
		/* Prefer routes with higher Router ID, just to be more deterministic */
		if (new->rid > old->rid)
		return 1;

		if (new->metric2 > old->metric2)
		return 0;
		return -1;
		}

		/* 16.4. (6c) */
		if (!po->rfc1583)
		/*
		* Compare ASBR routing table entry with a new one, used for precompute ASBRs
		* for AS external route selection (RFC 2328 16.4 (3)), Returns integer < or >
		* than 0 if the new ASBR is less or more preferred than the old ASBR.
		*/
		static int
		orta_compare_asbr(const struct proto_ospf po, const orta new, const orta *old)
		{
		u32 new_pref = new->options & ORTA_PREF;
		u32 old_pref = old->options & ORTA_PREF;
		int r;

		if (new_pref > old_pref)
		if (old->type == RTS_DUMMY)
		return 1;

		if (new_pref < old_pref)
		return 0;
		if (!po->rfc1583)
		{
		r = epath_preferred(new) - epath_preferred(old);
		if (r) return r;
		}

		/* 16.4. (6d) */
		if (new->metric1 < old->metric1)
		r = ((int) old->metric1) - ((int) new->metric1);
		if (r) return r;

		/* Larger area ID is preferred */
		if (new->oa->areaid > old->oa->areaid)
		return 1;

		if (new->metric1 > old->metric1)
		return 0;
		/* There is just one ASBR of that RID per area, so tie is not possible */
		return -1;
		}

		/* RFC 3103, 2.5. (6e) */
		int new_prio = orta_prio(new);
		int old_prio = orta_prio(old);
		/*
		* Compare a routing table entry with a new one, for AS external routes
		* (RFC 2328 16.4) and NSSA routes (RFC 3103 2.5), Returns integer <, = or >
		* than 0 if the new orta is less, equal or more preferred than the old orta.
		*/
		static int
		orta_compare_ext(const struct proto_ospf po, const orta new, const orta *old)
		{
		int r;

		if (new_prio > old_prio)
		if (old->type == RTS_DUMMY)
		return 1;

		if (old_prio > new_prio)
		/* 16.4 (6a) - prefer routes with lower type */
		r = ((int) old->type) - ((int) new->type);
		if (r) return r;

		/* 16.4 (6b) - prefer routes with lower type 2 metric */
		if (new->type == RTS_OSPF_EXT2)
		{
		r = ((int) old->metric2) - ((int) new->metric2);
		if (r) return r;
		}

		/* 16.4 (6c) - if not RFC1583, prefer routes with preferred ASBR/next_hop */
		if (!po->rfc1583)
		{
		r = orta_pref(new) - orta_pref(old);
		if (r) return r;
		}

		/* 16.4 (6d) - prefer routes with lower type 1 metric */
		r = ((int) old->metric1) - ((int) new->metric1);
		if (r) return r;


		if (po->ecmp && po->merge_external)
		return 0;

		/* make it more deterministic */
		if (new->rid > old->rid)
		/*
		* RFC 3101 2.5 (6e) - prioritize Type-7 LSA with P-bit, then Type-5 LSA, then
		* LSA with higher router ID. Although this should apply just to functionally
		* equivalent LSAs (i.e. ones with the same non-zero forwarding address), we
		* use it also to disambiguate otherwise equally preferred nexthops.
		*/
		if (orta_prefer_lsa(new, old))
		return 1;

		return 0;
		return -1;
		}


		static inline void
		ri_install_net(struct proto_ospf po, ip_addr prefix, int pxlen, orta new)
		ort_replace(ort o, const orta new)
		{
		memcpy(&o->n, new, sizeof(orta));
		}

		static void
		ort_merge(struct proto_ospf po, ort o, const orta *new)
		{
		orta *old = &o->n;

		if (old->nhs != new->nhs)
		{
		old->nhs = merge_nexthops(po, old->nhs, new->nhs, old->nhs_reuse, new->nhs_reuse);
		old->nhs_reuse = 1;
		}

		if (old->rid < new->rid)
		old->rid = new->rid;
		}

		static void
		ort_merge_ext(struct proto_ospf po, ort o, const orta *new)
		{
		orta *old = &o->n;

		if (old->nhs != new->nhs)
		{
		old->nhs = merge_nexthops(po, old->nhs, new->nhs, old->nhs_reuse, new->nhs_reuse);
		old->nhs_reuse = 1;
		}

		if (old->tag != new->tag)
		old->tag = 0;

		/*
		* Even with multipath, we store only one LSA in orta.en for the purpose of
		* NSSA/ext translation. Therefore, we apply procedures from RFC 3101 2.5 (6e)
		* to all chosen LSAs for given network, not just to functionally equivalent
		* ones (i.e. ones with the same non-zero forwarding address).
		*/
		if (orta_prefer_lsa(new, old))
		{
		old->options = new->options;
		old->rid = new->rid;
		old->oa = new->oa;
		old->en = new->en;
		}
		}



		static inline void
		ri_install_net(struct proto_ospf po, ip_addr prefix, int pxlen, const orta new)
		{
		ort old = (ort ) fib_get(&po->rtf, &prefix, pxlen);
		if (ri_better(po, new, &old->n))
		memcpy(&old->n, new, sizeof(orta));
		int cmp = orta_compare(po, new, &old->n);

		if (cmp > 0)
		ort_replace(old, new);
		else if (cmp == 0)
		ort_merge(po, old, new);
		}

		static inline void
		ri_install_rt(struct ospf_area oa, u32 rid, orta new)
		ri_install_rt(struct ospf_area oa, u32 rid, const orta new)
		{
		ip_addr addr = ipa_from_rid(rid);
		ort old = (ort ) fib_get(&oa->rtr, &addr, MAX_PREFIX_LENGTH);
		if (ri_better(oa->po, new, &old->n))
		memcpy(&old->n, new, sizeof(orta));
		int cmp = orta_compare(oa->po, new, &old->n);

		if (cmp > 0)
		ort_replace(old, new);
		else if (cmp == 0)
		ort_merge(oa->po, old, new);
		}

		static inline void
		ri_install_asbr(struct proto_ospf po, ip_addr addr, orta *new)
		ri_install_asbr(struct proto_ospf po, ip_addr addr, const orta *new)
		{
		ort old = (ort ) fib_get(&po->backbone->rtr, addr, MAX_PREFIX_LENGTH);
		if (ri_better_asbr(po, new, &old->n))
		memcpy(&old->n, new, sizeof(orta));
		if (orta_compare_asbr(po, new, &old->n) > 0)
		ort_replace(old, new);
		}

		static inline void
		ri_install_ext(struct proto_ospf po, ip_addr prefix, int pxlen, orta new)
		ri_install_ext(struct proto_ospf po, ip_addr prefix, int pxlen, const orta new)
		{
		ort old = (ort ) fib_get(&po->rtf, &prefix, pxlen);
		if (ri_better_ext(po, new, &old->n))
		memcpy(&old->n, new, sizeof(orta));
		int cmp = orta_compare_ext(po, new, &old->n);

		if (cmp > 0)
		ort_replace(old, new);
		else if (cmp == 0)
		ort_merge_ext(po, old, new);
		}

		static inline struct ospf_iface *
		@@ -842,7 +1062,7 @@ ospf_rt_sum_tr(struct ospf_area *oa)

		/* 16.3. (5) */
		if ((metric < re->n.metric1) \|\|
		((metric == re->n.metric1) && unresolved_vlink(re->n.nhs)))
		((metric == re->n.metric1) && unresolved_vlink(re)))
		{
		/* We want to replace the next-hop even if the metric is equal
		to replace a virtual next-hop through vlink with a real one.
		@@ -1129,13 +1349,24 @@ ospf_rt_abr1(struct proto_ospf *po)
		struct area_net *anet;
		ort nf, default_nf;

		/* RFC 2328 G.3 - incomplete resolution of virtual next hops - routers */
		FIB_WALK(&po->backbone->rtr, nftmp)
		{
		nf = (ort *) nftmp;

		if (nf->n.type && unresolved_vlink(nf))
		reset_ri(nf);
		}
		FIB_WALK_END;


		FIB_WALK(&po->rtf, nftmp)
		{
		nf = (ort *) nftmp;


		/* RFC 2328 G.3 - incomplete resolution of virtual next hops */
		if (nf->n.type && unresolved_vlink(nf->n.nhs))
		/* RFC 2328 G.3 - incomplete resolution of virtual next hops - networks */
		if (nf->n.type && unresolved_vlink(nf))
		reset_ri(nf);


		@@ -1361,7 +1592,7 @@ static void
		ospf_ext_spf(struct proto_ospf *po)
		{
		ort nf1, nf2;
		orta nfa;
		orta nfa = {};
		struct top_hash_entry *en;
		struct proto *p = &po->proto;
		struct ospf_lsa_ext *le;
		@@ -1369,7 +1600,6 @@ ospf_ext_spf(struct proto_ospf *po)
		ip_addr ip, rtid, rt_fwaddr;
		u32 br_metric, rt_metric, rt_tag;
		struct ospf_area *atmp;
		struct mpnh* nhs = NULL;

		OSPF_TRACE(D_EVENTS, "Starting routing table calculation for ext routes");

		@@ -1465,7 +1695,7 @@ ospf_ext_spf(struct proto_ospf *po)
		if (!rt_fwaddr_valid)
		{
		nf2 = nf1;
		nhs = nf1->n.nhs;
		nfa.nhs = nf1->n.nhs;
		br_metric = nf1->n.metric1;
		}
		else
		@@ -1491,11 +1721,15 @@ ospf_ext_spf(struct proto_ospf *po)
		if (!nf2->n.nhs)
		continue;

		nhs = nf2->n.nhs;
		/* If gw is zero, it is a device route */
		if (ipa_zero(nhs->gw))
		nhs = new_nexthop(po, rt_fwaddr, nhs->iface, nhs->weight);
		nfa.nhs = nf2->n.nhs;
		br_metric = nf2->n.metric1;

		/* Replace device nexthops with nexthops to forwarding address from LSA */
		if (has_device_nexthops(nfa.nhs))
		{
		nfa.nhs = fix_device_nexthops(po, nfa.nhs, rt_fwaddr);
		nfa.nhs_reuse = 1;
		}
		}

		if (ebit)
		@@ -1526,8 +1760,6 @@ ospf_ext_spf(struct proto_ospf *po)
		nfa.tag = rt_tag;
		nfa.rid = en->lsa.rt;
		nfa.oa = atmp; /* undefined in RFC 2328 */
		nfa.voa = NULL;
		nfa.nhs = nhs;
		nfa.en = en; /* store LSA for later (NSSA processing) */

		ri_install_ext(po, ip, pxlen, &nfa);
		@@ -1745,81 +1977,6 @@ calc_next_hop(struct ospf_area oa, struct top_hash_entry en,
		return NULL;
		}

		/* Compare nexthops during merge.
		We need to maintain nhs sorted to eliminate duplicities */
		static int
		cmp_nhs(struct mpnh s1, struct mpnh s2)
		{
		int r;

		if (!s1)
		return 1;

		if (!s2)
		return -1;

		r = ((int) s2->weight) - ((int) s1->weight);
		if (r)
		return r;

		r = ipa_compare(s1->gw, s2->gw);
		if (r)
		return r;

		return ((int) s1->iface->index) - ((int) s2->iface->index);
		}

		static void
		merge_nexthops(struct proto_ospf po, struct top_hash_entry en,
		struct top_hash_entry par, struct mpnh new)
		{
		if (en->nhs == new)
		return;

		int r1 = en->nhs_reuse;
		int r2 = (par->nhs != new);
		int count = po->ecmp;
		struct mpnh *s1 = en->nhs;
		struct mpnh *s2 = new;
		struct mpnh **n = &(en->nhs);

		/*
		* r1, r2 signalize whether we can reuse nexthops from s1, s2.
		* New nexthops (s2, new) can be reused if they are not inherited
		* from the parent (i.e. it is allocated in calc_next_hop()).
		* Current nexthops (s1, en->nhs) can be reused if they weren't
		* inherited in previous steps (that is stored in nhs_reuse,
		* i.e. created by merging or allocalted in calc_next_hop()).
		*
		* Generally, a node first inherits shared nexthops from its
		* parent and later possibly gets reusable copy during merging.
		*/

		while ((s1 \|\| s2) && count--)
		{
		int cmp = cmp_nhs(s1, s2);
		if (cmp < 0)
		{
		*n = r1 ? s1 : copy_nexthop(po, s1);
		s1 = s1->next;
		}
		else if (cmp > 0)
		{
		*n = r2 ? s2 : copy_nexthop(po, s2);
		s2 = s2->next;
		}
		else
		{
		*n = r1 ? s1 : (r2 ? s2 : copy_nexthop(po, s1));
		s1 = s1->next;
		s2 = s2->next;
		}
		n = &((*n)->next);
		}
		*n = NULL;

		en->nhs_reuse=1;
		}

		/* Add LSA into list of candidates in Dijkstra's algorithm */
		static void
		@@ -1866,33 +2023,35 @@ add_cand(list * l, struct top_hash_entry en, struct top_hash_entry par,
		return;
		}

		if (dist == en->dist)
		/* We know that en->color == CANDIDATE and en->nhs is defined. */

		if ((dist == en->dist) && !nh_is_vlink(en->nhs))
		{
		/*
		* For multipath, we should merge nexthops. We do not mix dummy
		* vlink nexthops, device nexthops and gateway nexthops. We merge
		* gateway nexthops only. We prefer device nexthops over gateway
		* nexthops and gateway nexthops over vlink nexthops. We either
		* keep old nexthops, merge old and new, or replace old with new.
		* For multipath, we should merge nexthops. We merge regular nexthops only.
		* Dummy vlink nexthops are less preferred and handled as a special case.
		*
		* During merging, new nexthops (nhs) can be reused if they are not
		* inherited from the parent (i.e. they are allocated in calc_next_hop()).
		* Current nexthops (en->nhs) can be reused if they weren't inherited in
		* previous steps (that is stored in nhs_reuse, i.e. created by merging or
		* allocated in calc_next_hop()).
		*
		* We know that en->color == CANDIDATE and en->nhs is defined.
		* Generally, a node first inherits shared nexthops from its parent and
		* later possibly gets reusable copy during merging.
		*/
		struct mpnh *onhs = en->nhs;

		/* Keep old ones */
		if (!po->ecmp \|\| !nhs->iface \|\| (onhs->iface && ipa_zero(onhs->gw)))
		if (!po->ecmp \|\| nh_is_vlink(nhs) \|\| (nhs == en->nhs))
		return;

		/* Merge old and new */
		if (ipa_nonzero(nhs->gw) && ipa_nonzero(onhs->gw))
		{
		merge_nexthops(po, en, par, nhs);
		int new_reuse = (par->nhs != nhs);
		en->nhs = merge_nexthops(po, en->nhs, nhs, en->nhs_reuse, new_reuse);
		en->nhs_reuse = 1;
		return;
		}

		/* Fallback to replace old ones */
		}

		DBG(" Adding candidate: rt: %R, id: %R, type: %u\n",
		en->lsa.rt, en->lsa.id, en->lsa.type);

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