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[ospfd] Bug #330: SPF must consider that nexthop-calc may fail

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2007-01-24 Paul Jakma <paul.jakma@sun.com>

	* ospf_spf.c: Bug #330: Nexthop calculation sometimes may fail,
	  and it needs to indicate this result to SPF.
	  (ospf_spf_add_parent) Flush of parent list needs to be done here,
	  for simplicity.
	  (ospf_nexthop_calculation) Caller needs to know whether
	  nexthop calculation succeeded. Every return statement must
	  correctly indicate such.
	  (ospf_spf_next) Queueing/prioritisation of vertices in SPF
	  must take into account whether nexthop_calculation succeeded,
	  or SPF may fail to find best paths.
This commit is contained in:
Paul Jakma 2007-01-24 14:51:51 +00:00
parent fb6724a6b9
commit bc20c1a463
2 changed files with 81 additions and 59 deletions
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13
ospfd/ChangeLog
View File

@ -1,3 +1,16 @@
2007-01-24 Paul Jakma <paul.jakma@sun.com>
* ospf_spf.c: Bug #330: Nexthop calculation sometimes may fail,
and it needs to indicate this result to SPF.
(ospf_spf_add_parent) Flush of parent list needs to be done here,
for simplicity.
(ospf_nexthop_calculation) Caller needs to know whether
nexthop calculation succeeded. Every return statement must
correctly indicate such.
(ospf_spf_next) Queueing/prioritisation of vertices in SPF
must take into account whether nexthop_calculation succeeded,
or SPF may fail to find best paths.
2006-12-12 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
* ospf_interface.c: (ospf_if_is_configured, ospf_if_lookup_by_prefix,

127
ospfd/ospf_spf.c
View File

@ -405,37 +405,6 @@ ospf_get_next_link (struct vertex *v, struct vertex *w,
return NULL;
}
/*
* Consider supplied next-hop for inclusion to the supplied list of
* equal-cost next-hops, adjust list as neccessary.
*
* (Discussed on GNU Zebra list 27 May 2003, [zebra 19184])
*
* Note that below is a bit of a hack, and limits ECMP to paths that go to
* same nexthop. Where as paths via inequal output_cost interfaces could
* still quite easily be ECMP due to remote cost differences.
*
* TODO: It really should be done by way of recording currently valid
* backlinks and determining the appropriate nexthops from the list of
* backlinks, or even simpler, just flushing nexthop list if we find a lower
* cost path to a candidate vertex in SPF, maybe.
*/
static void
ospf_spf_add_parent (struct vertex *v, struct vertex *w,
struct vertex_nexthop *newhop)
{
struct vertex_parent *vp;
/* we must have a newhop.. */
assert (v && w && newhop);
/* new parent is <= existing parents, add it */
vp = vertex_parent_new (v, ospf_lsa_has_link (w->lsa, v->lsa), newhop);
listnode_add (w->parents, vp);
return;
}
static void
ospf_spf_flush_parents (struct vertex *w)
{
@ -450,13 +419,49 @@ ospf_spf_flush_parents (struct vertex *w)
}
}
/*
* Consider supplied next-hop for inclusion to the supplied list of
* equal-cost next-hops, adjust list as neccessary.
*/
static void
ospf_spf_add_parent (struct vertex *v, struct vertex *w,
struct vertex_nexthop *newhop,
struct router_lsa_link *l)
{
struct vertex_parent *vp;
unsigned int new_distance;
/* we must have a newhop.. */
assert (v && w && l && newhop);
new_distance = v->distance + ntohs (l->m[0].metric);
/* We shouldn't get here unless callers have determined V(l)->W is
* shortest / equal-shortest path.
*/
assert (new_distance <= w->distance);
/* Adding parent for a new, better path: flush existing parents from W. */
if (new_distance < w->distance)
{
ospf_spf_flush_parents (w);
w->distance = new_distance;
}
/* new parent is <= existing parents, add it to parent list */
vp = vertex_parent_new (v, ospf_lsa_has_link (w->lsa, v->lsa), newhop);
listnode_add (w->parents, vp);
return;
}
/* 16.1.1. Calculate nexthop from root through V (parent) to
* vertex W (destination).
*
* The link must be supplied if V is the root vertex. In all other cases
* it may be NULL.
*/
static void
static unsigned int
ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
struct vertex *w, struct router_lsa_link *l)
{
@ -464,6 +469,7 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
struct vertex_nexthop *nh;
struct vertex_parent *vp;
struct ospf_interface *oi = NULL;
unsigned int added = 0;
if (IS_DEBUG_OSPF_EVENT)
{
@ -571,7 +577,8 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
nh = vertex_nexthop_new ();
nh->oi = oi;
nh->router = l2->link_data;
ospf_spf_add_parent (v, w, nh);
ospf_spf_add_parent (v, w, nh, l);
return 1;
}
else
zlog_info("ospf_nexthop_calculation(): "
@ -596,13 +603,14 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
nh = vertex_nexthop_new ();
nh->oi = vl_data->nexthop.oi;
nh->router = vl_data->nexthop.router;
ospf_spf_add_parent (v, w, nh);
ospf_spf_add_parent (v, w, nh, l);
return 1;
}
else
zlog_info("ospf_nexthop_calculation(): "
"vl_data for VL link not found");
zlog_info("ospf_nexthop_calculation(): "
"vl_data for VL link not found");
} /* end virtual-link from V to W */
return;
return 0;
} /* end W is a Router vertex */
else
{
@ -613,13 +621,13 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
nh = vertex_nexthop_new ();
nh->oi = oi;
nh->router.s_addr = 0;
ospf_spf_add_parent (v, w, nh);
return;
ospf_spf_add_parent (v, w, nh, l);
return 1;
}
}
zlog_info("ospf_nexthop_calculation(): "
"Unknown attached link");
return;
return 0;
} /* end V is the root */
/* Check if W's parent is a network connected to root. */
else if (v->type == OSPF_VERTEX_NETWORK)
@ -647,11 +655,12 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
nh = vertex_nexthop_new ();
nh->oi = vp->nexthop->oi;
nh->router = l->link_data;
ospf_spf_add_parent (v, w, nh);
added = 1;
ospf_spf_add_parent (v, w, nh, l);
}
return;
}
}
return added;
}
/* 16.1.1 para 4. If there is at least one intervening router in the
@ -660,9 +669,12 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
* parent.
*/
for (ALL_LIST_ELEMENTS (v->parents, node, nnode, vp))
ospf_spf_add_parent (v, w, vp->nexthop);
{
added = 1;
ospf_spf_add_parent (v, w, vp->nexthop, l);
}
return;
return added;
}
/* RFC2328 Section 16.1 (2).
@ -801,12 +813,11 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
{
/* prepare vertex W. */
w = ospf_vertex_new (w_lsa);
w->distance = distance;
/* Calculate nexthop to W. */
w->distance = distance;
ospf_nexthop_calculation (area, v, w, l);
pqueue_enqueue (w, candidate);
if (ospf_nexthop_calculation (area, v, w, l))
pqueue_enqueue (w, candidate);
}
else if (w_lsa->stat >= 0)
{
@ -828,17 +839,15 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
/* less than. */
else
{
/* Found a lower-cost path to W. */
w->distance = distance;
/* Flush existing parent list from W */
ospf_spf_flush_parents (w);
/* Calculate new nexthop(s) to W. */
ospf_nexthop_calculation (area, v, w, l);
/* Decrease the key of the node in the heap, re-sort the heap. */
trickle_down (w_lsa->stat, candidate);
/* Found a lower-cost path to W.
* nexthop_calculation is conditional, if it finds
* valid nexthop it will call spf_add_parents, which
* will flush the old parents
*/
if (ospf_nexthop_calculation (area, v, w, l))
/* Decrease the key of the node in the heap,
* re-sort the heap. */
trickle_down (w_lsa->stat, candidate);
}
} /* end W is already on the candidate list */
} /* end loop over the links in V's LSA */