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OSPF: Fix next hop calculation for PtP links in IPv4 OSPFv3-AF

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In such case, next hop has to be taken from Link-LSA like in broadcast
case, not from neighbor source address like in other PtP cases.

Also add some checks, comments and code cleanup.
This commit is contained in:
Ondrej Zajicek (work) 2017-10-09 20:36:14 +02:00
parent d3f4f92b0e
commit f097f7659c
1 changed files with 82 additions and 33 deletions
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109
proto/ospf/rt.c
View File

@ -10,9 +10,7 @@
#include "ospf.h"
static void add_cand(list * l, struct top_hash_entry *en,
struct top_hash_entry *par, u32 dist,
struct ospf_area *oa, int i);
static void add_cand(struct ospf_area *oa, struct top_hash_entry *en, struct top_hash_entry *par, u32 dist, int i, uint lif, uint nif);
static void rt_sync(struct ospf_proto *p);
@ -509,7 +507,7 @@ spfa_process_rt(struct ospf_proto *p, struct ospf_area *oa, struct top_hash_entr
break;
}
add_cand(&oa->cand, tmp, act, act->dist + rtl.metric, oa, i);
add_cand(oa, tmp, act, act->dist + rtl.metric, i, rtl.lif, rtl.nif);
}
}
@ -532,7 +530,7 @@ spfa_process_net(struct ospf_proto *p, struct ospf_area *oa, struct top_hash_ent
for (i = 0; i < cnt; i++)
{
tmp = ospf_hash_find_rt(p->gr, oa->areaid, ln->routers[i]);
add_cand(&oa->cand, tmp, act, act->dist, oa, -1);
add_cand(oa, tmp, act, act->dist, -1, 0, 0);
}
}
@ -651,7 +649,8 @@ ospf_rt_spfa(struct ospf_area *oa)
}
static int
link_back(struct ospf_area *oa, struct top_hash_entry *en, struct top_hash_entry *par)
link_back(struct ospf_area *oa, struct top_hash_entry *en,
struct top_hash_entry *par, uint lif, uint nif)
{
struct ospf_proto *p = oa->po;
struct ospf_lsa_rt_walk rtl;
@ -689,6 +688,10 @@ link_back(struct ospf_area *oa, struct top_hash_entry *en, struct top_hash_entry
tmp = ospf_hash_find_net(p->gr, oa->areaid, rtl.id, rtl.nif);
if (tmp == par)
{
/*
* Note that there may be multiple matching Rt-fields if router 'en'
* have multiple interfaces to net 'par'. Perhaps we should do ECMP.
*/
if (ospf_is_v2(p))
en->lb = ipa_from_u32(rtl.data);
else
@ -700,7 +703,13 @@ link_back(struct ospf_area *oa, struct top_hash_entry *en, struct top_hash_entry
case LSART_VLNK:
case LSART_PTP:
/* Not necessary the same link, see RFC 2328 [23] */
/*
* For OSPFv2, not necessary the same link, see RFC 2328 [23].
* For OSPFv3, we verify that by comparing nif and lif fields.
*/
if (ospf_is_v3(p) && ((rtl.lif != nif) || (rtl.nif != lif)))
break;
tmp = ospf_hash_find_rt(p->gr, oa->areaid, rtl.id);
if (tmp == par)
return 1;
@ -1679,13 +1688,27 @@ inherit_nexthops(struct nexthop *pn)
return pn && (ipa_nonzero(pn->gw) || !pn->iface);
}
static inline ip_addr
link_lsa_lladdr(struct ospf_proto *p, struct top_hash_entry *en)
{
struct ospf_lsa_link *link_lsa = en->lsa_body;
ip6_addr ll = link_lsa->lladdr;
if (ip6_zero(ll))
return IPA_NONE;
return ospf_is_ip4(p) ? ipa_from_ip4(ospf3_6to4(ll)) : ipa_from_ip6(ll);
}
static struct nexthop *
calc_next_hop(struct ospf_area *oa, struct top_hash_entry *en,
struct top_hash_entry *par, int pos)
struct top_hash_entry *par, int pos, uint lif, uint nif)
{
struct ospf_proto *p = oa->po;
struct nexthop *pn = par->nhs;
struct ospf_iface *ifa;
struct top_hash_entry *link = NULL;
struct ospf_iface *ifa = NULL;
ip_addr nh = IPA_NONE;
u32 rid = en->lsa.rt;
/* 16.1.1. The next hop calculation */
@ -1710,6 +1733,9 @@ calc_next_hop(struct ospf_area *oa, struct top_hash_entry *en,
if (!ifa)
return NULL;
if (ospf_is_v3(p) && (ifa->iface_id != lif))
log(L_WARN "%s: Inconsistent interface ID %u/%u", p->p.name, ifa->iface_id, lif);
return new_nexthop(p, IPA_NONE, ifa->iface, ifa->ecmp_weight);
}
@ -1720,14 +1746,44 @@ calc_next_hop(struct ospf_area *oa, struct top_hash_entry *en,
if (!ifa)
return NULL;
if (ospf_is_v3(p) && (ifa->iface_id != lif))
log(L_WARN "%s: Inconsistent interface ID %u/%u", p->p.name, ifa->iface_id, lif);
if (ifa->type == OSPF_IT_VLINK)
return new_nexthop(p, IPA_NONE, NULL, 0);
/* FIXME: On physical PtP links we may skip next-hop altogether */
if (ospf_is_v2(p) || ospf_is_ip6(p))
{
/*
* In this case, next-hop is a source address from neighbor's packets.
* That is necessary for OSPFv2 and practical for OSPFv3 (as it works even
* if neighbor uses LinkLSASuppression), but does not work with OSPFv3-AF
* on IPv4 topology, where src is IPv6 but next-hop should be IPv4.
*/
struct ospf_neighbor *m = find_neigh(ifa, rid);
if (!m || (m->state != NEIGHBOR_FULL))
return NULL;
return new_nexthop(p, m->ip, ifa->iface, ifa->ecmp_weight);
nh = m->ip;
}
else
{
/*
* Next-hop is taken from lladdr field of Link-LSA, based on Neighbor
* Iface ID (nif) field in our Router-LSA, which is just nbr->iface_id.
*/
link = ospf_hash_find(p->gr, ifa->iface_id, nif, rid, LSA_T_LINK);
if (!link)
return NULL;
nh = link_lsa_lladdr(p, link);
if (ipa_zero(nh))
return NULL;
}
return new_nexthop(p, nh, ifa->iface, ifa->ecmp_weight);
}
/* The third case - bcast or nbma neighbor */
@ -1754,21 +1810,14 @@ calc_next_hop(struct ospf_area *oa, struct top_hash_entry *en,
* Next-hop is taken from lladdr field of Link-LSA, en->lb_id
* is computed in link_back().
*/
struct top_hash_entry *lhe;
lhe = ospf_hash_find(p->gr, pn->iface->index, en->lb_id, rid, LSA_T_LINK);
if (!lhe)
link = ospf_hash_find(p->gr, pn->iface->index, en->lb_id, rid, LSA_T_LINK);
if (!link)
return NULL;
struct ospf_lsa_link *llsa = lhe->lsa_body;
if (ip6_zero(llsa->lladdr))
nh = link_lsa_lladdr(p, link);
if (ipa_zero(nh))
return NULL;
ip_addr nh = ospf_is_ip4(p) ?
ipa_from_ip4(ospf3_6to4(llsa->lladdr)) :
ipa_from_ip6(llsa->lladdr);
return new_nexthop(p, nh, pn->iface, pn->weight);
}
}
@ -1782,8 +1831,8 @@ calc_next_hop(struct ospf_area *oa, struct top_hash_entry *en,
/* Add LSA into list of candidates in Dijkstra's algorithm */
static void
add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
u32 dist, struct ospf_area *oa, int pos)
add_cand(struct ospf_area *oa, struct top_hash_entry *en, struct top_hash_entry *par,
u32 dist, int pos, uint lif, uint nif)
{
struct ospf_proto *p = oa->po;
node *prev, *n;
@ -1813,10 +1862,10 @@ add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
return;
/* We should check whether there is a reverse link from en to par, */
if (!link_back(oa, en, par))
if (!link_back(oa, en, par, lif, nif))
return;
struct nexthop *nhs = calc_next_hop(oa, en, par, pos);
struct nexthop *nhs = calc_next_hop(oa, en, par, pos, lif, nif);
if (!nhs)
{
log(L_WARN "%s: Cannot find next hop for LSA (Type: %04x, Id: %R, Rt: %R)",
@ -1873,20 +1922,20 @@ add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
prev = NULL;
if (EMPTY_LIST(*l))
if (EMPTY_LIST(oa->cand))
{
add_head(l, &en->cn);
add_head(&oa->cand, &en->cn);
}
else
{
WALK_LIST(n, *l)
WALK_LIST(n, oa->cand)
{
act = SKIP_BACK(struct top_hash_entry, cn, n);
if ((act->dist > dist) ||
((act->dist == dist) && (act->lsa_type == LSA_T_RT)))
{
if (prev == NULL)
add_head(l, &en->cn);
add_head(&oa->cand, &en->cn);
else
insert_node(&en->cn, prev);
added = 1;
@ -1897,7 +1946,7 @@ add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
if (!added)
{
add_tail(l, &en->cn);
add_tail(&oa->cand, &en->cn);
}
}
}