-/* $OpenBSD: rde_decide.c,v 1.80 2021/01/14 08:29:26 claudio Exp $ */
+/* $OpenBSD: rde_decide.c,v 1.81 2021/02/02 15:24:43 claudio Exp $ */
/*
* Copyright (c) 2003, 2004 Claudio Jeker <claudio@openbsd.org>
#include "rde.h"
#include "log.h"
-int prefix_cmp(struct prefix *, struct prefix *);
+int prefix_cmp(struct prefix *, struct prefix *, int *);
+void prefix_insert(struct prefix *, struct prefix *, struct rib_entry *);
+void prefix_remove(struct prefix *, struct rib_entry *);
/*
* Decision Engine RFC implementation:
* Phase 1:
* already added prefix.
*/
int
-prefix_cmp(struct prefix *p1, struct prefix *p2)
+prefix_cmp(struct prefix *p1, struct prefix *p2, int *testall)
{
struct rde_aspath *asp1, *asp2;
struct rde_peer *peer1, *peer2;
u_int32_t p1id, p2id;
int p1cnt, p2cnt, i;
+ /*
+ * If a match happens before the MED check then the list is
+ * correctly sorted. If a match happens after MED then further
+ * elements may need to be checked to ensure that all paths
+ * which could affect this path were considered. This only
+ * matters for strict MED evaluation and in that case testall
+ * is set to 1. If the check happens to be on the MED check
+ * itself testall is set to 2.
+ */
+ *testall = 0;
+
if (p1 == NULL)
return -1;
if (p2 == NULL)
/*
* 5. MED decision
* Only comparable between the same neighboring AS or if
- * 'rde med compare always' is set.
+ * 'rde med compare always' is set. In the first case
+ * set the testall flag since further elements need to be
+ * evaluated as well.
*/
if ((rde_decisionflags() & BGPD_FLAG_DECISION_MED_ALWAYS) ||
aspath_neighbor(asp1->aspath) == aspath_neighbor(asp2->aspath)) {
+ if (!(rde_decisionflags() & BGPD_FLAG_DECISION_MED_ALWAYS))
+ *testall = 2;
/* lowest value wins */
if (asp1->med < asp2->med)
return 1;
return -1;
}
+ if (!(rde_decisionflags() & BGPD_FLAG_DECISION_MED_ALWAYS))
+ *testall = 1;
+
/*
* 6. EBGP is cooler than IBGP
* It is absolutely important that the ebgp value in peer_config.ebgp
fatalx("Uh, oh a politician in the decision process");
}
+void
+prefix_insert(struct prefix *new, struct prefix *ep, struct rib_entry *re)
+{
+ struct prefix_list redo = LIST_HEAD_INITIALIZER(redo);
+ struct prefix *xp, *np, *rp, *ip = ep;
+ int testall, selected = 0;
+
+ /* start scan at the entry point (ep) or if the head if ep == NULL */
+ if (ep == NULL)
+ ep = LIST_FIRST(&re->prefix_h);
+
+ for (xp = ep; xp != NULL; xp = np) {
+ np = LIST_NEXT(xp, entry.list.rib);
+
+ if (prefix_cmp(new, xp, &testall) > 0) {
+ /* new is preferred over xp */
+ if (testall == 0)
+ break; /* we're done */
+ else if (testall == 2) {
+ /*
+ * MED inversion, take out prefix and
+ * put it onto redo queue.
+ */
+ LIST_REMOVE(xp, entry.list.rib);
+ if (LIST_EMPTY(&redo))
+ LIST_INSERT_HEAD(&redo, xp,
+ entry.list.rib);
+ else
+ LIST_INSERT_AFTER(rp, xp,
+ entry.list.rib);
+ rp = xp;
+ } else {
+ /*
+ * lock insertion point and
+ * continue on with scan
+ */
+ selected = 1;
+ continue;
+ }
+ } else {
+ /*
+ * p is less preferred, remember insertion point
+ * If p got selected during a testall traverse
+ * do not alter the insertion point unless this
+ * happened on an actual MED check.
+ */
+ if (testall == 2)
+ selected = 0;
+ if (!selected)
+ ip = xp;
+ }
+ }
+
+ if (ip == NULL)
+ LIST_INSERT_HEAD(&re->prefix_h, new, entry.list.rib);
+ else
+ LIST_INSERT_AFTER(ip, new, entry.list.rib);
+
+ /* Fixup MED order again. All elements are < new */
+ while (!LIST_EMPTY(&redo)) {
+ xp = LIST_FIRST(&redo);
+ LIST_REMOVE(xp, entry.list.rib);
+
+ prefix_insert(xp, new, re);
+ }
+}
+
+void
+prefix_remove(struct prefix *old, struct rib_entry *re)
+{
+ struct prefix_list redo = LIST_HEAD_INITIALIZER(redo);
+ struct prefix *xp, *np, *rp;
+ int testall;
+
+ xp = LIST_NEXT(old, entry.list.rib);
+ LIST_REMOVE(old, entry.list.rib);
+ /* check if a MED inversion could be possible */
+ prefix_cmp(old, xp, &testall);
+ if (testall > 0) {
+ /* maybe MED route, scan tail for other possible routes */
+ for (; xp != NULL; xp = np) {
+ np = LIST_NEXT(xp, entry.list.rib);
+
+ /* only interested in the testall result */
+ prefix_cmp(old, xp, &testall);
+ if (testall == 0)
+ break; /* we're done */
+ else if (testall == 2) {
+ /*
+ * possible MED inversion, take out prefix and
+ * put it onto redo queue.
+ */
+ LIST_REMOVE(xp, entry.list.rib);
+ if (LIST_EMPTY(&redo))
+ LIST_INSERT_HEAD(&redo, xp,
+ entry.list.rib);
+ else
+ LIST_INSERT_AFTER(rp, xp,
+ entry.list.rib);
+ rp = xp;
+ }
+ }
+ }
+
+ /* Fixup MED order again, reinsert prefixes from the start */
+ while (!LIST_EMPTY(&redo)) {
+ xp = LIST_FIRST(&redo);
+ LIST_REMOVE(xp, entry.list.rib);
+
+ prefix_insert(xp, NULL, re);
+ }
+}
+
/*
* Find the correct place to insert the prefix in the prefix list.
* If the active prefix has changed we need to send an update.
}
if (old != NULL)
- LIST_REMOVE(old, entry.list.rib);
-
- if (new != NULL) {
- if (LIST_EMPTY(&re->prefix_h))
- LIST_INSERT_HEAD(&re->prefix_h, new, entry.list.rib);
- else {
- LIST_FOREACH(xp, &re->prefix_h, entry.list.rib) {
- if (prefix_cmp(new, xp) > 0) {
- LIST_INSERT_BEFORE(xp, new,
- entry.list.rib);
- break;
- } else if (LIST_NEXT(xp, entry.list.rib) ==
- NULL) {
- /* if xp last element ... */
- LIST_INSERT_AFTER(xp, new,
- entry.list.rib);
- break;
- }
- }
- }
- }
+ prefix_remove(old, re);
+
+ if (new != NULL)
+ prefix_insert(new, NULL, re);
xp = LIST_FIRST(&re->prefix_h);
if (xp != NULL) {
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