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Unix SMB/CIFS implementation.
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Copyright (C) Andrew Tridgell 1997-1998
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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/***************************************************************************
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Add a DNS result to the name cache.
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****************************************************************************/
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static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
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int name_type = question->name_type;
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pull_ascii_nstring(qname, sizeof(qname), question->name);
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/* add the fail to WINS cache of names. give it 1 hour in the cache */
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DEBUG(3,("add_dns_result: Negative DNS answer for %s\n", qname));
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add_name_to_subnet( wins_server_subnet, qname, name_type,
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NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
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/* add it to our WINS cache of names. give it 2 hours in the cache */
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DEBUG(3,("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));
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add_name_to_subnet( wins_server_subnet, qname, name_type,
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NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
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return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
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static int fd_in = -1, fd_out = -1;
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static pid_t child_pid = -1;
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/* this is the structure that is passed between the parent and child */
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struct in_addr result;
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/* a queue of pending requests waiting to be sent to the DNS child */
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static struct packet_struct *dns_queue;
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/* the packet currently being processed by the dns child */
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static struct packet_struct *dns_current;
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/***************************************************************************
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return the fd used to gather async dns replies. This is added to the select
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****************************************************************************/
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/***************************************************************************
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handle DNS queries arriving from the parent
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****************************************************************************/
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static void asyncdns_process(void)
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struct query_record r;
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status = read_data(fd_in, (char *)&r, sizeof(r));
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if (!NT_STATUS_IS_OK(status)) {
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pull_ascii_nstring( qname, sizeof(qname), r.name.name);
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r.result.s_addr = interpret_addr(qname);
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if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
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/**************************************************************************** **
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catch a sigterm (in the child process - the parent has a different handler
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see nmbd.c for details).
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We need a separate term handler here so we don't release any
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names that our parent is going to release, or overwrite a
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WINS db that our parent is going to write.
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**************************************************************************** */
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static void sig_term(int sig)
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/***************************************************************************
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Called by the parent process when it receives a SIGTERM - also kills the
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child so we don't get child async dns processes lying around, causing trouble.
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****************************************************************************/
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void kill_async_dns_child(void)
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kill(child_pid, SIGTERM);
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/***************************************************************************
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create a child process to handle DNS lookups
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****************************************************************************/
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void start_async_dns(void)
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if (pipe(fd1) || pipe(fd2)) {
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DEBUG(0,("can't create asyncdns pipes\n"));
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child_pid = sys_fork();
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DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
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CatchSignal(SIGUSR2, SIG_IGN);
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CatchSignal(SIGUSR1, SIG_IGN);
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CatchSignal(SIGHUP, SIG_IGN);
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CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
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if (!NT_STATUS_IS_OK(reinit_after_fork(nmbd_messaging_context(),
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nmbd_event_context(), true))) {
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DEBUG(0,("reinit_after_fork() failed\n"));
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smb_panic("reinit_after_fork() failed");
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/***************************************************************************
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check if a particular name is already being queried
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****************************************************************************/
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static bool query_current(struct query_record *r)
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return dns_current &&
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nmb_name_equal(&r->name,
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&dns_current->packet.nmb.question.question_name);
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/***************************************************************************
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write a query to the child process
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****************************************************************************/
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static bool write_child(struct packet_struct *p)
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struct query_record r;
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r.name = p->packet.nmb.question.question_name;
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return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
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/***************************************************************************
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****************************************************************************/
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void run_dns_queue(void)
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struct query_record r;
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struct packet_struct *p, *p2;
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struct name_record *namerec;
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if (!process_exists_by_pid(child_pid)) {
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status = read_data(fd_in, (char *)&r, sizeof(r));
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if (!NT_STATUS_IS_OK(status)) {
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DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
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namerec = add_dns_result(&r.name, r.result);
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if (query_current(&r)) {
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DEBUG(3,("DNS calling send_wins_name_query_response\n"));
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send_wins_name_query_response(NAM_ERR, dns_current, NULL);
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send_wins_name_query_response(0,dns_current,namerec);
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dns_current->locked = False;
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free_packet(dns_current);
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/* loop over the whole dns queue looking for entries that
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match the result we just got */
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for (p = dns_queue; p;) {
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struct nmb_packet *nmb = &p->packet.nmb;
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struct nmb_name *question = &nmb->question.question_name;
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if (nmb_name_equal(question, &r.name)) {
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DEBUG(3,("DNS calling send_wins_name_query_response\n"));
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send_wins_name_query_response(NAM_ERR, p, NULL);
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send_wins_name_query_response(0,p,namerec);
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p->prev->next = p->next;
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p->next->prev = p->prev;
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dns_current = dns_queue;
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dns_queue = dns_queue->next;
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dns_queue->prev = NULL;
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dns_current->next = NULL;
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if (!write_child(dns_current)) {
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DEBUG(3,("failed to send DNS query to child!\n"));
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/***************************************************************************
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****************************************************************************/
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bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
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if (in_dns || fd_in == -1)
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if (!write_child(p)) {
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DEBUG(3,("failed to send DNS query to child!\n"));
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DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
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/***************************************************************************
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we use this when we can't do async DNS lookups
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****************************************************************************/
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bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
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struct name_record *namerec = NULL;
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struct in_addr dns_ip;
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pull_ascii_nstring(qname, sizeof(qname), question->name);
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DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
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dns_ip.s_addr = interpret_addr(qname);
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namerec = add_dns_result(question, dns_ip);
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if(namerec == NULL) {
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send_wins_name_query_response(NAM_ERR, p, NULL);
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send_wins_name_query_response(0, p, namerec);
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/***************************************************************************
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With sync dns there is no child to kill on SIGTERM.
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****************************************************************************/
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void kill_async_dns_child(void)