svn commit: samba r22714 - in branches: SAMBA_3_0/source/libads
SAMBA_3_0_26/source/libads
jerry at samba.org
jerry at samba.org
Sun May 6 21:06:56 GMT 2007
Author: jerry
Date: 2007-05-06 21:06:55 +0000 (Sun, 06 May 2007)
New Revision: 22714
WebSVN: http://websvn.samba.org/cgi-bin/viewcvs.cgi?view=rev&root=samba&rev=22714
Log:
Prevent DNS lookup storms when the DNS servers are unreachable.
Helps when transitioning from offline to online mode.
Note that this is a quick hack and a better solution
would be to start the DNS server's state between processes
(similar to the namecache entries).
Modified:
branches/SAMBA_3_0/source/libads/dns.c
branches/SAMBA_3_0_26/source/libads/dns.c
Changeset:
Modified: branches/SAMBA_3_0/source/libads/dns.c
===================================================================
--- branches/SAMBA_3_0/source/libads/dns.c 2007-05-06 21:04:30 UTC (rev 22713)
+++ branches/SAMBA_3_0/source/libads/dns.c 2007-05-06 21:06:55 UTC (rev 22714)
@@ -270,45 +270,76 @@
Simple wrapper for a DNS query
*********************************************************************/
+#define DNS_FAILED_WAITTIME 30
+
static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type,
uint8 **buf, int *resp_length )
{
uint8 *buffer = NULL;
size_t buf_len;
int resp_len = NS_PACKETSZ;
-
+ static time_t last_dns_check = 0;
+ static NTSTATUS last_dns_status = NT_STATUS_OK;
+ time_t now = time(NULL);
+
+ /* Try to prevent bursts of DNS lookups if the server is down */
+
+ /* Protect against large clock changes */
+
+ if ( last_dns_check > now )
+ last_dns_check = 0;
+
+ /* IF we had a DNS timeout or a bad server and we are still
+ in the 30 second cache window, just return the previous
+ status and save the network timeout. */
+
+ if ( (NT_STATUS_EQUAL(last_dns_status,NT_STATUS_IO_TIMEOUT) ||
+ NT_STATUS_EQUAL(last_dns_status,NT_STATUS_CONNECTION_REFUSED)) &&
+ (last_dns_check+DNS_FAILED_WAITTIME) > now )
+ {
+ DEBUG(10,("last_dns_check: Returning cached status (%s)\n",
+ nt_errstr(last_dns_status) ));
+ return last_dns_status;
+ }
+
+ /* Send the Query */
do {
if ( buffer )
TALLOC_FREE( buffer );
buf_len = resp_len * sizeof(uint8);
- if (buf_len) {
+ if (buf_len) {
if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
- return NT_STATUS_NO_MEMORY;
+ last_dns_status = NT_STATUS_NO_MEMORY;
+ last_dns_check = time(NULL);
+ return last_dns_status;
}
- } else {
- buffer = NULL;
}
if ( (resp_len = res_query(name, C_IN, q_type, buffer, buf_len)) < 0 ) {
DEBUG(3,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
TALLOC_FREE( buffer );
+ last_dns_status = NT_STATUS_UNSUCCESSFUL;
+
if (errno == ETIMEDOUT) {
- return NT_STATUS_IO_TIMEOUT;
+ last_dns_status = NT_STATUS_IO_TIMEOUT;
}
if (errno == ECONNREFUSED) {
- return NT_STATUS_CONNECTION_REFUSED;
+ last_dns_status = NT_STATUS_CONNECTION_REFUSED;
}
- return NT_STATUS_UNSUCCESSFUL;
+ last_dns_check = time(NULL);
+ return last_dns_status;
}
} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
*buf = buffer;
*resp_length = resp_len;
- return NT_STATUS_OK;
+ last_dns_check = time(NULL);
+ last_dns_status = NT_STATUS_OK;
+ return last_dns_status;
}
/*********************************************************************
Modified: branches/SAMBA_3_0_26/source/libads/dns.c
===================================================================
--- branches/SAMBA_3_0_26/source/libads/dns.c 2007-05-06 21:04:30 UTC (rev 22713)
+++ branches/SAMBA_3_0_26/source/libads/dns.c 2007-05-06 21:06:55 UTC (rev 22714)
@@ -270,45 +270,76 @@
Simple wrapper for a DNS query
*********************************************************************/
+#define DNS_FAILED_WAITTIME 30
+
static NTSTATUS dns_send_req( TALLOC_CTX *ctx, const char *name, int q_type,
uint8 **buf, int *resp_length )
{
uint8 *buffer = NULL;
size_t buf_len;
int resp_len = NS_PACKETSZ;
-
+ static time_t last_dns_check = 0;
+ static NTSTATUS last_dns_status = NT_STATUS_OK;
+ time_t now = time(NULL);
+
+ /* Try to prevent bursts of DNS lookups if the server is down */
+
+ /* Protect against large clock changes */
+
+ if ( last_dns_check > now )
+ last_dns_check = 0;
+
+ /* IF we had a DNS timeout or a bad server and we are still
+ in the 30 second cache window, just return the previous
+ status and save the network timeout. */
+
+ if ( (NT_STATUS_EQUAL(last_dns_status,NT_STATUS_IO_TIMEOUT) ||
+ NT_STATUS_EQUAL(last_dns_status,NT_STATUS_CONNECTION_REFUSED)) &&
+ (last_dns_check+DNS_FAILED_WAITTIME) > now )
+ {
+ DEBUG(10,("last_dns_check: Returning cached status (%s)\n",
+ nt_errstr(last_dns_status) ));
+ return last_dns_status;
+ }
+
+ /* Send the Query */
do {
if ( buffer )
TALLOC_FREE( buffer );
buf_len = resp_len * sizeof(uint8);
- if (buf_len) {
+ if (buf_len) {
if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
- return NT_STATUS_NO_MEMORY;
+ last_dns_status = NT_STATUS_NO_MEMORY;
+ last_dns_check = time(NULL);
+ return last_dns_status;
}
- } else {
- buffer = NULL;
}
if ( (resp_len = res_query(name, C_IN, q_type, buffer, buf_len)) < 0 ) {
DEBUG(3,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
TALLOC_FREE( buffer );
+ last_dns_status = NT_STATUS_UNSUCCESSFUL;
+
if (errno == ETIMEDOUT) {
- return NT_STATUS_IO_TIMEOUT;
+ last_dns_status = NT_STATUS_IO_TIMEOUT;
}
if (errno == ECONNREFUSED) {
- return NT_STATUS_CONNECTION_REFUSED;
+ last_dns_status = NT_STATUS_CONNECTION_REFUSED;
}
- return NT_STATUS_UNSUCCESSFUL;
+ last_dns_check = time(NULL);
+ return last_dns_status;
}
} while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
*buf = buffer;
*resp_length = resp_len;
- return NT_STATUS_OK;
+ last_dns_check = time(NULL);
+ last_dns_status = NT_STATUS_OK;
+ return last_dns_status;
}
/*********************************************************************
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