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-rw-r--r--source3/nmbd/asyncdns.c365
1 files changed, 365 insertions, 0 deletions
diff --git a/source3/nmbd/asyncdns.c b/source3/nmbd/asyncdns.c
new file mode 100644
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--- /dev/null
+++ b/source3/nmbd/asyncdns.c
@@ -0,0 +1,365 @@
+/*
+ Unix SMB/CIFS implementation.
+ a async DNS handler
+ Copyright (C) Andrew Tridgell 1997-1998
+
+ This program 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 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "includes.h"
+
+/***************************************************************************
+ Add a DNS result to the name cache.
+****************************************************************************/
+
+static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
+{
+ int name_type = question->name_type;
+ unstring qname;
+
+ pull_ascii_nstring(qname, sizeof(qname), question->name);
+
+ if (!addr.s_addr) {
+ /* add the fail to WINS cache of names. give it 1 hour in the cache */
+ DEBUG(3,("add_dns_result: Negative DNS answer for %s\n", qname));
+ add_name_to_subnet( wins_server_subnet, qname, name_type,
+ NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
+ return NULL;
+ }
+
+ /* add it to our WINS cache of names. give it 2 hours in the cache */
+ DEBUG(3,("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));
+
+ add_name_to_subnet( wins_server_subnet, qname, name_type,
+ NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
+
+ return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
+}
+
+#ifndef SYNC_DNS
+
+static int fd_in = -1, fd_out = -1;
+static pid_t child_pid = -1;
+static int in_dns;
+
+/* this is the structure that is passed between the parent and child */
+struct query_record {
+ struct nmb_name name;
+ struct in_addr result;
+};
+
+/* a queue of pending requests waiting to be sent to the DNS child */
+static struct packet_struct *dns_queue;
+
+/* the packet currently being processed by the dns child */
+static struct packet_struct *dns_current;
+
+
+/***************************************************************************
+ return the fd used to gather async dns replies. This is added to the select
+ loop
+ ****************************************************************************/
+
+int asyncdns_fd(void)
+{
+ return fd_in;
+}
+
+/***************************************************************************
+ handle DNS queries arriving from the parent
+ ****************************************************************************/
+static void asyncdns_process(void)
+{
+ struct query_record r;
+ unstring qname;
+
+ DEBUGLEVEL = -1;
+
+ while (1) {
+ NTSTATUS status;
+
+ status = read_data(fd_in, (char *)&r, sizeof(r));
+
+ if (!NT_STATUS_IS_OK(status)) {
+ break;
+ }
+
+ pull_ascii_nstring( qname, sizeof(qname), r.name.name);
+ r.result.s_addr = interpret_addr(qname);
+
+ if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
+ break;
+ }
+
+ _exit(0);
+}
+
+/**************************************************************************** **
+ catch a sigterm (in the child process - the parent has a different handler
+ see nmbd.c for details).
+ We need a separate term handler here so we don't release any
+ names that our parent is going to release, or overwrite a
+ WINS db that our parent is going to write.
+ **************************************************************************** */
+
+static void sig_term(int sig)
+{
+ _exit(0);
+}
+
+/***************************************************************************
+ Called by the parent process when it receives a SIGTERM - also kills the
+ child so we don't get child async dns processes lying around, causing trouble.
+ ****************************************************************************/
+
+void kill_async_dns_child(void)
+{
+ if (child_pid > 0) {
+ kill(child_pid, SIGTERM);
+ child_pid = -1;
+ }
+}
+
+/***************************************************************************
+ create a child process to handle DNS lookups
+ ****************************************************************************/
+void start_async_dns(void)
+{
+ int fd1[2], fd2[2];
+
+ CatchChild();
+
+ if (pipe(fd1) || pipe(fd2)) {
+ DEBUG(0,("can't create asyncdns pipes\n"));
+ return;
+ }
+
+ child_pid = sys_fork();
+
+ if (child_pid) {
+ fd_in = fd1[0];
+ fd_out = fd2[1];
+ close(fd1[1]);
+ close(fd2[0]);
+ DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
+ return;
+ }
+
+ fd_in = fd2[0];
+ fd_out = fd1[1];
+
+ CatchSignal(SIGUSR2, SIG_IGN);
+ CatchSignal(SIGUSR1, SIG_IGN);
+ CatchSignal(SIGHUP, SIG_IGN);
+ CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
+
+ if (!reinit_after_fork(nmbd_messaging_context(), true)) {
+ DEBUG(0,("reinit_after_fork() failed\n"));
+ smb_panic("reinit_after_fork() failed");
+ }
+
+ asyncdns_process();
+}
+
+
+/***************************************************************************
+check if a particular name is already being queried
+ ****************************************************************************/
+static bool query_current(struct query_record *r)
+{
+ return dns_current &&
+ nmb_name_equal(&r->name,
+ &dns_current->packet.nmb.question.question_name);
+}
+
+
+/***************************************************************************
+ write a query to the child process
+ ****************************************************************************/
+static bool write_child(struct packet_struct *p)
+{
+ struct query_record r;
+
+ r.name = p->packet.nmb.question.question_name;
+
+ return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
+}
+
+/***************************************************************************
+ check the DNS queue
+ ****************************************************************************/
+void run_dns_queue(void)
+{
+ struct query_record r;
+ struct packet_struct *p, *p2;
+ struct name_record *namerec;
+ NTSTATUS status;
+
+ if (fd_in == -1)
+ return;
+
+ /* Allow SIGTERM to kill us. */
+ BlockSignals(False, SIGTERM);
+
+ if (!process_exists_by_pid(child_pid)) {
+ close(fd_in);
+ close(fd_out);
+ start_async_dns();
+ }
+
+ status = read_data(fd_in, (char *)&r, sizeof(r));
+
+ if (!NT_STATUS_IS_OK(status)) {
+ DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
+ fd_in = -1;
+ BlockSignals(True, SIGTERM);
+ return;
+ }
+
+ BlockSignals(True, SIGTERM);
+
+ namerec = add_dns_result(&r.name, r.result);
+
+ if (dns_current) {
+ if (query_current(&r)) {
+ DEBUG(3,("DNS calling send_wins_name_query_response\n"));
+ in_dns = 1;
+ if(namerec == NULL)
+ send_wins_name_query_response(NAM_ERR, dns_current, NULL);
+ else
+ send_wins_name_query_response(0,dns_current,namerec);
+ in_dns = 0;
+ }
+
+ dns_current->locked = False;
+ free_packet(dns_current);
+ dns_current = NULL;
+ }
+
+ /* loop over the whole dns queue looking for entries that
+ match the result we just got */
+ for (p = dns_queue; p;) {
+ struct nmb_packet *nmb = &p->packet.nmb;
+ struct nmb_name *question = &nmb->question.question_name;
+
+ if (nmb_name_equal(question, &r.name)) {
+ DEBUG(3,("DNS calling send_wins_name_query_response\n"));
+ in_dns = 1;
+ if(namerec == NULL)
+ send_wins_name_query_response(NAM_ERR, p, NULL);
+ else
+ send_wins_name_query_response(0,p,namerec);
+ in_dns = 0;
+ p->locked = False;
+
+ if (p->prev)
+ p->prev->next = p->next;
+ else
+ dns_queue = p->next;
+ if (p->next)
+ p->next->prev = p->prev;
+ p2 = p->next;
+ free_packet(p);
+ p = p2;
+ } else {
+ p = p->next;
+ }
+ }
+
+ if (dns_queue) {
+ dns_current = dns_queue;
+ dns_queue = dns_queue->next;
+ if (dns_queue)
+ dns_queue->prev = NULL;
+ dns_current->next = NULL;
+
+ if (!write_child(dns_current)) {
+ DEBUG(3,("failed to send DNS query to child!\n"));
+ return;
+ }
+ }
+}
+
+/***************************************************************************
+queue a DNS query
+ ****************************************************************************/
+
+bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
+{
+ if (in_dns || fd_in == -1)
+ return False;
+
+ if (!dns_current) {
+ if (!write_child(p)) {
+ DEBUG(3,("failed to send DNS query to child!\n"));
+ return False;
+ }
+ dns_current = p;
+ p->locked = True;
+ } else {
+ p->locked = True;
+ p->next = dns_queue;
+ p->prev = NULL;
+ if (p->next)
+ p->next->prev = p;
+ dns_queue = p;
+ }
+
+ DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
+ return True;
+}
+
+#else
+
+
+/***************************************************************************
+ we use this when we can't do async DNS lookups
+ ****************************************************************************/
+
+bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
+{
+ struct name_record *namerec = NULL;
+ struct in_addr dns_ip;
+ unstring qname;
+
+ pull_ascii_nstring(qname, sizeof(qname), question->name);
+
+ DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
+
+ /* Unblock TERM signal so we can be killed in DNS lookup. */
+ BlockSignals(False, SIGTERM);
+
+ dns_ip.s_addr = interpret_addr(qname);
+
+ /* Re-block TERM signal. */
+ BlockSignals(True, SIGTERM);
+
+ namerec = add_dns_result(question, dns_ip);
+ if(namerec == NULL) {
+ send_wins_name_query_response(NAM_ERR, p, NULL);
+ } else {
+ send_wins_name_query_response(0, p, namerec);
+ }
+ return False;
+}
+
+/***************************************************************************
+ With sync dns there is no child to kill on SIGTERM.
+ ****************************************************************************/
+
+void kill_async_dns_child(void)
+{
+ return;
+}
+#endif
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