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ospfd: bring back some P2P SPF interface code
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In the case of P2P links it is possible to use IP unnumbered which
yields a strong dependency to the interface data for nexthop
resolution in the SPF calculations. While the SPF code strives to
be as independent of non-LSA data as possible there is no way
around here: one has to resolve the nexthop for such a special case
using the interface data.

For this purpose a new flag 'spf_root_node' is introduced to signal
that interface data can be used for P2P links. For now this flag is
always 'true' since the SPF currently always uses the calculating
node as the root node. This will change with the introduction of
TI-LFA where other nodes can be root nodes.

Signed-off-by: GalaxyGorilla <sascha@netdef.org>
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@GalaxyGorilla
GalaxyGorilla committed Aug 18, 2020
1 parent 3a76b1b commit 6fc9528
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Showing 3 changed files with 58 additions and 22 deletions.
69 changes: 51 additions & 18 deletions ospfd/ospf_spf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -290,7 +290,7 @@ static void ospf_vertex_add_parent(struct vertex *v)
}

static void ospf_spf_init(struct ospf_area *area, struct ospf_lsa *root_lsa,
bool is_dry_run)
bool is_dry_run, bool is_root_node)
{
struct vertex *v;

Expand All @@ -299,6 +299,7 @@ static void ospf_spf_init(struct ospf_area *area, struct ospf_lsa *root_lsa,

area->spf = v;
area->spf_dry_run = is_dry_run;
area->spf_root_node = is_root_node;

/* Reset ABR and ASBR router counts. */
area->abr_count = 0;
Expand Down Expand Up @@ -581,6 +582,7 @@ static unsigned int ospf_nexthop_calculation(struct ospf_area *area,
struct router_lsa_link *l2 = NULL;

if (l->m[0].type == LSA_LINK_TYPE_POINTOPOINT) {

/*
* If the destination is a router which connects
* to the calculating router via a
Expand Down Expand Up @@ -615,20 +617,49 @@ static unsigned int ospf_nexthop_calculation(struct ospf_area *area,
* access links in p2p mode, so we need the IP
* to ARP the nexthop.
*
* Due to these reasons p2p and p2mp
* interfaces are handled the same way here,
* in the style of p2mp as described above.
* If the calculating router is the SPF root
* node and the link is P2P then access the
* interface information directly. This can be
* crucial when e.g. IP unnumbered is used
* where 'correct' nexthop information are not
* available via Router LSAs.
*
* Otherwise handle P2P and P2MP the same way
* as described above using a reverse lookup to
* figure out the nexthop.
*/

struct in_addr nexthop = {.s_addr = 0};
struct ospf_interface *oi = NULL;
struct ospf_neighbor *nbr_w = NULL;

/* Calculating node is root node, link is P2P */
if (area->spf_root_node) {
oi = ospf_if_lookup_by_lsa_pos(area,
lsa_pos);
if (oi->type
== OSPF_IFTYPE_POINTOPOINT) {
nbr_w = ospf_nbr_lookup_by_routerid(
oi->nbrs, &l->link_id);
if (nbr_w) {
added = 1;
nexthop = nbr_w->src;
}
}
}

while ((l2 = ospf_get_next_link(w, v, l2))) {
if (match_stub_prefix(v->lsa,
l->link_data,
l2->link_data)) {
added = 1;
nexthop = l2->link_data;
break;
/* Reverse lookup */
if (!added) {
while ((l2 = ospf_get_next_link(w, v,
l2))) {
if (match_stub_prefix(
v->lsa,
l->link_data,
l2->link_data)) {
added = 1;
nexthop = l2->link_data;
break;
}
}
}

Expand Down Expand Up @@ -1180,7 +1211,8 @@ ospf_rtrs_print (struct route_table *rtrs)
/* Calculating the shortest-path tree for an area, see RFC2328 16.1. */
void ospf_spf_calculate(struct ospf_area *area, struct ospf_lsa *root_lsa,
struct route_table *new_table,
struct route_table *new_rtrs, bool is_dry_run)
struct route_table *new_rtrs, bool is_dry_run,
bool is_root_node)
{
struct vertex_pqueue_head candidate;
struct vertex *v;
Expand Down Expand Up @@ -1219,7 +1251,7 @@ void ospf_spf_calculate(struct ospf_area *area, struct ospf_lsa *root_lsa,
* Initialize the shortest-path tree to only the root (which is usually
* the router doing the calculation).
*/
ospf_spf_init(area, root_lsa, is_dry_run);
ospf_spf_init(area, root_lsa, is_dry_run, is_root_node);

/* Set Area A's TransitCapability to false. */
area->transit = OSPF_TRANSIT_FALSE;
Expand Down Expand Up @@ -1296,7 +1328,8 @@ void ospf_spf_calculate(struct ospf_area *area, struct ospf_lsa *root_lsa,
}

int ospf_spf_calculate_areas(struct ospf *ospf, struct route_table *new_table,
struct route_table *new_rtrs, bool is_dry_run)
struct route_table *new_rtrs, bool is_dry_run,
bool is_root_node)
{
struct ospf_area *area;
struct listnode *node, *nnode;
Expand All @@ -1310,15 +1343,15 @@ int ospf_spf_calculate_areas(struct ospf *ospf, struct route_table *new_table,
continue;

ospf_spf_calculate(area, area->router_lsa_self, new_table,
new_rtrs, is_dry_run);
new_rtrs, is_dry_run, is_root_node);
areas_processed++;
}

/* SPF for backbone, if required */
if (ospf->backbone) {
area = ospf->backbone;
ospf_spf_calculate(area, area->router_lsa_self, new_table,
new_rtrs, is_dry_run);
new_rtrs, is_dry_run, is_root_node);
areas_processed++;
}

Expand Down Expand Up @@ -1347,8 +1380,8 @@ static int ospf_spf_calculate_schedule_worker(struct thread *thread)
monotime(&spf_start_time);
new_table = route_table_init(); /* routing table */
new_rtrs = route_table_init(); /* ABR/ASBR routing table */
areas_processed =
ospf_spf_calculate_areas(ospf, new_table, new_rtrs, false);
areas_processed = ospf_spf_calculate_areas(ospf, new_table, new_rtrs,
false, true);
spf_time = monotime_since(&spf_start_time, NULL);

ospf_vl_shut_unapproved(ospf);
Expand Down
5 changes: 3 additions & 2 deletions ospfd/ospf_spf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -75,11 +75,12 @@ extern void ospf_spf_calculate_schedule(struct ospf *, ospf_spf_reason_t);
extern void ospf_spf_calculate(struct ospf_area *area,
struct ospf_lsa *root_lsa,
struct route_table *new_table,
struct route_table *new_rtrs, bool is_dry_run);
struct route_table *new_rtrs, bool is_dry_run,
bool is_root_node);
extern int ospf_spf_calculate_areas(struct ospf *ospf,
struct route_table *new_table,
struct route_table *new_rtrs,
bool is_dry_run);
bool is_dry_run, bool is_root_node);
extern void ospf_rtrs_free(struct route_table *);

extern void ospf_spf_print(struct vty *vty, struct vertex *v, int i);
Expand Down
6 changes: 4 additions & 2 deletions ospfd/ospfd.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -410,8 +410,10 @@ struct ospf_area {

/* Shortest Path Tree. */
struct vertex *spf;
bool spf_dry_run; /* flag for checking if the SPF calculation is
intended for the local RIB */
bool spf_dry_run; /* flag for checking if the SPF calculation is
intended for the local RIB */
bool spf_root_node; /* flag for checking if the calculating node is the
root node of the SPF tree */

/* Threads. */
struct thread *t_stub_router; /* Stub-router timer */
Expand Down

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