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/* $OpenBSD: ntp_dns.c,v 1.26 2020/04/12 14:20:56 otto Exp $ */
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/*
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* Copyright (c) 2003-2008 Henning Brauer <henning@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#include <sys/resource.h>
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#include <sys/time.h>
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#include <resolv.h>
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#include <netinet/in.h>
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#include <err.h>
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#include <errno.h>
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#include <poll.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <string.h>
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#include <syslog.h>
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#include <resolv.h>
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#include <unistd.h>
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#include "ntpd.h"
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volatile sig_atomic_t quit_dns = 0;
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static struct imsgbuf *ibuf_dns;
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extern int non_numeric;
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void sighdlr_dns(int);
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int dns_dispatch_imsg(struct ntpd_conf *);
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int probe_root_ns(void);
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void probe_root(void);
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void
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sighdlr_dns(int sig)
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{
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switch (sig) {
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case SIGTERM:
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case SIGINT:
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quit_dns = 1;
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break;
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}
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}
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void
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ntp_dns(struct ntpd_conf *nconf, struct passwd *pw)
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{
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struct pollfd pfd[1];
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int nfds, nullfd;
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res_init();
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if (setpriority(PRIO_PROCESS, 0, 0) == -1)
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log_warn("could not set priority");
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log_init(nconf->debug ? LOG_TO_STDERR : LOG_TO_SYSLOG, nconf->verbose,
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LOG_DAEMON);
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if (!nconf->debug && setsid() == -1)
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fatal("setsid");
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log_procinit("dns");
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if ((nullfd = open("/dev/null", O_RDWR, 0)) == -1)
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fatal(NULL);
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if (!nconf->debug) {
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dup2(nullfd, STDIN_FILENO);
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dup2(nullfd, STDOUT_FILENO);
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dup2(nullfd, STDERR_FILENO);
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}
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close(nullfd);
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setproctitle("dns engine");
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if (setgroups(1, &pw->pw_gid) ||
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setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
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setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
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fatal("can't drop privileges");
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signal(SIGTERM, sighdlr_dns);
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signal(SIGINT, sighdlr_dns);
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signal(SIGHUP, SIG_IGN);
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if ((ibuf_dns = malloc(sizeof(struct imsgbuf))) == NULL)
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fatal(NULL);
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imsg_init(ibuf_dns, PARENT_SOCK_FILENO);
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if (pledge("stdio dns", NULL) == -1)
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err(1, "pledge");
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if (non_numeric)
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probe_root();
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else
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log_debug("all addresses numeric, no dns probe");
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while (quit_dns == 0) {
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pfd[0].fd = ibuf_dns->fd;
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pfd[0].events = POLLIN;
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if (ibuf_dns->w.queued)
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pfd[0].events |= POLLOUT;
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if ((nfds = poll(pfd, 1, INFTIM)) == -1)
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if (errno != EINTR) {
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log_warn("poll error");
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quit_dns = 1;
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}
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if (nfds > 0 && (pfd[0].revents & POLLOUT))
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if (msgbuf_write(&ibuf_dns->w) <= 0 &&
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errno != EAGAIN) {
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log_warn("pipe write error (to ntp engine)");
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quit_dns = 1;
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}
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if (nfds > 0 && pfd[0].revents & POLLIN) {
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nfds--;
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if (dns_dispatch_imsg(nconf) == -1)
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quit_dns = 1;
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}
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}
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msgbuf_clear(&ibuf_dns->w);
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free(ibuf_dns);
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exit(0);
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}
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int
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dns_dispatch_imsg(struct ntpd_conf *nconf)
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{
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struct imsg imsg;
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int n, cnt;
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char *name;
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struct ntp_addr *h, *hn;
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struct ibuf *buf;
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const char *str;
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size_t len;
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if (((n = imsg_read(ibuf_dns)) == -1 && errno != EAGAIN) || n == 0)
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return (-1);
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for (;;) {
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if ((n = imsg_get(ibuf_dns, &imsg)) == -1)
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return (-1);
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if (n == 0)
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break;
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switch (imsg.hdr.type) {
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case IMSG_HOST_DNS:
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case IMSG_CONSTRAINT_DNS:
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if (imsg.hdr.type == IMSG_HOST_DNS)
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str = "IMSG_HOST_DNS";
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else
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str = "IMSG_CONSTRAINT_DNS";
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name = imsg.data;
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if (imsg.hdr.len < 1 + IMSG_HEADER_SIZE)
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fatalx("invalid %s received", str);
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len = imsg.hdr.len - 1 - IMSG_HEADER_SIZE;
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if (name[len] != '\0' ||
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strlen(name) != len)
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fatalx("invalid %s received", str);
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if ((cnt = host_dns(name, nconf->status.synced,
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&hn)) == -1)
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break;
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buf = imsg_create(ibuf_dns, imsg.hdr.type,
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imsg.hdr.peerid, 0,
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cnt * (sizeof(struct sockaddr_storage) + sizeof(int)));
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if (cnt > 0) {
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if (buf) {
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for (h = hn; h != NULL; h = h->next) {
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if (imsg_add(buf, &h->ss,
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sizeof(h->ss)) == -1) {
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buf = NULL;
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break;
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}
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if (imsg_add(buf, &h->notauth,
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sizeof(int)) == -1) {
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buf = NULL;
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break;
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}
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}
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}
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host_dns_free(hn);
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hn = NULL;
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}
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if (buf)
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imsg_close(ibuf_dns, buf);
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break;
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case IMSG_SYNCED:
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nconf->status.synced = 1;
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break;
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case IMSG_UNSYNCED:
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nconf->status.synced = 0;
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break;
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default:
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break;
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}
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imsg_free(&imsg);
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}
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return (0);
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}
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int
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probe_root_ns(void)
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{
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int ret;
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int old_retrans, old_retry, old_options;
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unsigned char buf[4096];
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old_retrans = _res.retrans;
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old_retry = _res.retry;
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old_options = _res.options;
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_res.retrans = 1;
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_res.retry = 1;
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_res.options |= RES_USE_CD;
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ret = res_query(".", C_IN, T_NS, buf, sizeof(buf));
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_res.retrans = old_retrans;
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_res.retry = old_retry;
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_res.options = old_options;
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return ret;
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}
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void
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probe_root(void)
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{
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int n;
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n = probe_root_ns();
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if (n < 0) {
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/* give programs like unwind a second chance */
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sleep(1);
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n = probe_root_ns();
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}
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if (imsg_compose(ibuf_dns, IMSG_PROBE_ROOT, 0, 0, -1, &n,
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sizeof(int)) == -1)
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fatalx("probe_root");
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}
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