Doing overlapping regions is hard... At application.c:1341 we currently assign region->ar_oid to oid. However, with overlapping regions this can cause a recursion, because region might be the parent of the previous region that would cause the oid to traverse back and cause a loop.
This can easily be fixed by changing this line to vb->av_oid, but I also found that the code doesn't produce the cleanest searchrange end, adjacent regions might not be taken into account on a single run because of the else statement on line 1363. With the following registration it will result in: blocklist: Registering 1.3.6.1.4.1.30155.1.9.129 context() priority(1) timeout(1.50s) AgentX(556403008/718113859): Registering 1.3.6.1.4.1.30155.1 context() priority(1) timeout(5.00s) AgentX(556403008/718113859): Registering 1.3.6.1.4.1.30155.2 context() priority(1) timeout(5.00s) AgentX(556403008/718113859): Registering 1.3.6.1.4.1.30155.5 context() priority(1) timeout(5.00s) AgentX(556403008/718113859): Registering 1.3.6.1.4.1.30155.6 context() priority(1) timeout(5.00s) ... GetNextRequest{333882979, 0, 0, {{1.3.6.1.4.1.30155.1.9.128.1.24.3:null}}} AgentX(556403008/718113859): GetNextRequest{1517163039, 0, 0, {{1.3.6.1.4.1.30155.1.9.128.1.24.3-1.3.6.1.4.1.30155.1.9.129:null}}} AgentX(556403008/718113859): Response{1517163039, 0, 0, {{1.3.6.1.4.1.30155.1.9.128.1.24.3:endOfMibView}}} blocklist: GetNextRequest{1339241491, 0, 0, {{1.3.6.1.4.1.30155.1.9.129(incl)-1.3.6.1.4.1.30155.1.9.130:null}}} blocklist: Response{1339241491, 0, 0, {{1.3.6.1.4.1.30155.1.9.129:endOfMibView}}} AgentX(556403008/718113859): GetNextRequest{1545296030, 0, 0, {{1.3.6.1.4.1.30155.1.9.130(incl)-1.3.6.1.4.1.30155.2:null}}} AgentX(556403008/718113859): Response{1545296030, 0, 0, {{1.3.6.1.4.1.30155.1.10.1.0:2}}} to ... GetNextRequest{2078129483, 0, 0, {{1.3.6.1.4.1.30155.1.9.129.1.1.1.192.168.153.0.24:null}}} blocklist: GetNextRequest{-1870096078, 0, 0, {{1.3.6.1.4.1.30155.1.9.129.1.1.1.192.168.153.0.24-1.3.6.1.4.1.30155.1.9.130:null}}} blocklist: Response{-1870096078, 0, 0, {{1.3.6.1.4.1.30155.1.9.129.1.1.1.192.168.153.0.24:endOfMibView}}} AgentX(3175611302/2074212055): GetNextRequest{-867062125, 0, 0, {{1.3.6.1.4.1.30155.1.9.130(incl)-1.3.6.1.4.1.30155.3:null}}} AgentX(3175611302/2074212055): Response{-867062125, 0, 0, {{1.3.6.1.4.1.30155.1.10.1.0:2}}} OK? martijn@ Index: application.c =================================================================== RCS file: /cvs/src/usr.sbin/snmpd/application.c,v retrieving revision 1.12 diff -u -p -r1.12 application.c --- application.c 29 Aug 2022 18:05:08 -0000 1.12 +++ application.c 30 Aug 2022 14:29:50 -0000 @@ -1287,7 +1287,7 @@ appl_varbind_backend(struct appl_varbind 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 || @@ -1338,33 +1338,41 @@ appl_varbind_backend(struct appl_varbind } 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;