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samba-mirror/source3/nmbd/asyncdns.c
Andreas Schneider 2d512b278e debug: Use debuglevel_(get|set) function
Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Thu Nov  8 11:03:11 CET 2018 on sn-devel-144
2018-11-08 11:03:11 +01:00

347 lines
9.2 KiB
C

/*
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"
#include "nmbd/nmbd.h"
#include "lib/util/sys_rw_data.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_set(-1);
while (1) {
NTSTATUS status;
status = read_data_ntstatus(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(struct messaging_context *msg)
{
int fd1[2], fd2[2];
NTSTATUS status;
CatchChild();
if (pipe(fd1) || pipe(fd2)) {
DEBUG(0,("can't create asyncdns pipes\n"));
return;
}
child_pid = 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, sig_term);
status = reinit_after_fork(msg, nmbd_event_context(), true, NULL);
if (!NT_STATUS_IS_OK(status)) {
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(struct messaging_context *msg)
{
struct query_record r;
struct packet_struct *p, *p2;
struct name_record *namerec;
NTSTATUS status;
if (fd_in == -1)
return;
if (!process_exists_by_pid(child_pid)) {
close(fd_in);
close(fd_out);
start_async_dns(msg);
}
status = read_data_ntstatus(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;
return;
}
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;
p2 = p->next;
DLIST_REMOVE(dns_queue, p);
free_packet(p);
p = p2;
} else {
p = p->next;
}
}
if (dns_queue) {
dns_current = dns_queue;
DLIST_REMOVE(dns_queue, dns_queue);
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;
DLIST_ADD(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)));
dns_ip.s_addr = interpret_addr(qname);
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