Rewrite the searchrange end calculation routine.

The old one had a bug which allowed it to move backwards on overlapping
regions and also didn't always returned the optimal end position.

OK tb@

diff --git a/usr.sbin/snmpd/application.c b/usr.sbin/snmpd/application.c
index 06065c6..479f44e 100644 (file)
--- a/usr.sbin/snmpd/application.c
+++ b/usr.sbin/snmpd/application.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: application.c,v 1.14 2022/08/30 17:37:03 martijn Exp $        */
+/*     $OpenBSD: application.c,v 1.15 2022/08/31 09:19:22 martijn Exp $        */
 
 /*
  * Copyright (c) 2021 Martijn van Duren <martijn@openbsd.org>
@@ -1279,7 +1279,7 @@ appl_varbind_backend(struct appl_varbind_internal *ivb)
        struct appl_request_upstream *ureq = ivb->avi_request_upstream;
        struct appl_region search, *region, *pregion;
        struct appl_varbind *vb = &(ivb->avi_varbind);
-       struct ber_oid oid;
+       struct ber_oid oid, nextsibling;
        int next, cmp;
 
        next = ureq->aru_pdu->be_type == SNMP_C_GETNEXTREQ ||
@@ -1330,33 +1330,41 @@ appl_varbind_backend(struct appl_varbind_internal *ivb)
        }
        ivb->avi_region = region;
        if (next) {
-               oid = region->ar_oid;
+               oid = vb->av_oid;
+               /*
+                * For the searchrange end we only want contiguous regions.
+                * This means directly connecting, or overlapping with the same
+                * backend.
+                */
                do {
                        pregion = region;
                        region = appl_region_next(ureq->aru_ctx, &oid, pregion);
-                       if (region != NULL &&
-                           appl_region_cmp(region, pregion) > 0)
-                               oid = region->ar_oid;
-                       else
+                       if (region == NULL) {
+                               oid = pregion->ar_oid;
                                ober_oid_nextsibling(&oid);
-               } while (region != NULL &&
-                   region->ar_backend == pregion->ar_backend);
-               if (region == NULL) {
-                       vb->av_oid_end = pregion->ar_oid;
-                       if (pregion->ar_instance &&
-                           vb->av_oid_end.bo_n < BER_MAX_OID_LEN)
-                               vb->av_oid_end.bo_id[vb->av_oid_end.bo_n++] = 0;
-                       else
-                               ober_oid_nextsibling(&(vb->av_oid_end));
-               } else {
-                       if (ober_oid_cmp(&(region->ar_oid),
-                           &(ivb->avi_region->ar_oid)) == 2)
-                               vb->av_oid_end = region->ar_oid;
-                       else {
-                               vb->av_oid_end = ivb->avi_region->ar_oid;
-                               ober_oid_nextsibling(&(vb->av_oid_end));
+                               break;
                        }
-               }
+                       cmp = ober_oid_cmp(&(region->ar_oid), &oid);
+                       if (cmp == 2)
+                               oid = region->ar_oid;
+                       else if (cmp == 1) {
+                               /* Break out if we find a gap */
+                               nextsibling = pregion->ar_oid;
+                               ober_oid_nextsibling(&nextsibling);
+                               if (ober_oid_cmp(&(region->ar_oid),
+                                   &nextsibling) != 0) {
+                                       oid = pregion->ar_oid;
+                                       ober_oid_nextsibling(&oid);
+                                       break;
+                               }
+                               oid = region->ar_oid;
+                       } else if (cmp == -2) {
+                               oid = pregion->ar_oid;
+                               ober_oid_nextsibling(&oid);
+                       } else
+                               fatalx("We can't stop/move back on getnext");
+               } while (region->ar_backend == pregion->ar_backend);
+               vb->av_oid_end = oid;
        }
        return 0;