/*****************************************************************************\ * slurm_resolv.c - functions for DNS SRV resolution ***************************************************************************** * Copyright (C) 2020 SchedMD LLC. * Written by Tim Wickberg * * This file is part of Slurm, a resource management program. * For details, see . * Please also read the included file: DISCLAIMER. * * Slurm is free software; you can redistribute it and/or modify it under * the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. * * In addition, as a special exception, the copyright holders give permission * to link the code of portions of this program with the OpenSSL library under * certain conditions as described in each individual source file, and * distribute linked combinations including the two. You must obey the GNU * General Public License in all respects for all of the code used other than * OpenSSL. If you modify file(s) with this exception, you may extend this * exception to your version of the file(s), but you are not obligated to do * so. If you do not wish to do so, delete this exception statement from your * version. If you delete this exception statement from all source files in * the program, then also delete it here. * * Slurm is distributed in the hope that it will be useful, but WITHOUT ANY * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License along * with Slurm; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. \*****************************************************************************/ #define _GNU_SOURCE #include #include #include #include #include "src/common/list.h" #include "src/common/slurm_protocol_api.h" #include "src/common/slurm_resolv.h" #include "src/common/xstring.h" #include "src/common/xmalloc.h" #define SRV_RECORD "_slurmctld._tcp" static int _sort_controllers(void *x, void *y) { ctl_entry_t *ctl1 = *(ctl_entry_t **) x; ctl_entry_t *ctl2 = *(ctl_entry_t **) y; return ctl1->priority > ctl2->priority; } extern List resolve_ctls_from_dns_srv(void) { struct __res_state res; ns_msg handle; ns_rr rr; unsigned char answer[512]; int len; List controllers; if (res_ninit(&res)) { error("%s: res_ninit error: %m", __func__); return NULL; } if ((len = res_nsearch(&res, SRV_RECORD, C_IN, T_SRV, answer, sizeof(answer))) < 0) { error("%s: res_nsearch error: %m", __func__); return NULL; } if (ns_initparse(answer, len, &handle) < 0) { error("%s: ns_initparse error: %m", __func__); return NULL; } controllers = list_create(xfree_ptr); for (int i = 0; i < ns_msg_count(handle, ns_s_an); i++) { ctl_entry_t *ctl; if (ns_parserr(&handle, ns_s_an, i, &rr) < 0) { error("%s: ns_parserr", __func__); continue; } if (ns_rr_type(rr) != T_SRV) continue; ctl = xmalloc(sizeof(*ctl)); ctl->priority = ns_get16(ns_rr_rdata(rr)); /* skip the weight field which is currently unused */ ctl->port = ns_get16(ns_rr_rdata(rr) + 2 * NS_INT16SZ); if (dn_expand(ns_msg_base(handle), ns_msg_end(handle), ns_rr_rdata(rr) + 3 * NS_INT16SZ, ctl->hostname, sizeof(ctl->hostname)) < 0) { xfree(ctl); continue; } list_push(controllers, ctl); } if (!list_count(controllers)) { error("%s: no SRV records located", __func__); FREE_NULL_LIST(controllers); } else list_sort(controllers, _sort_controllers); return controllers; }