If you have a large number of cups printers, then scanning for print info can cause a client to timeout

(it takes longer than 30 seconds to enumerate them). Make scanning for printers async with a callback
from the main loop. This fixes a bug that was irritating *me* :-).
Jeremy.

source3/include/proto.h

@@ -5995,7 +5995,7 @@ bool dump_a_parameter(int snum, char *parm_name, FILE * f, bool isGlobal);
 struct parm_struct *lp_get_parameter(const char *param_name);
 struct parm_struct *lp_next_parameter(int snum, int *i, int allparameters);
 bool lp_snum_ok(int iService);
-void lp_add_one_printer(char *name, char *comment);
+void lp_add_one_printer(const char *name, const char *comment, void *pdata);
 bool lp_loaded(void);
 void lp_killunused(bool (*snumused) (int));
 void lp_kill_all_services(void);
@@ -6568,11 +6568,15 @@ char* get_server_name( Printer_entry *printer );
 
 /* The following definitions come from printing/pcap.c  */
 
+bool pcap_cache_add_specific(struct pcap_cache **ppcache, const char *name, const char *comment);
+void pcap_cache_destroy_specific(struct pcap_cache **ppcache);
 bool pcap_cache_add(const char *name, const char *comment);
 bool pcap_cache_loaded(void);
+void pcap_cache_replace(const struct pcap_cache *cache);
 void pcap_cache_reload(void);
 bool pcap_printername_ok(const char *printername);
-void pcap_printer_fn(void (*fn)(char *, char *));
+void pcap_printer_fn_specific(const struct pcap_cache *, void (*fn)(const char *, const char *, void *), void *);
+void pcap_printer_fn(void (*fn)(const char *, const char *, void *), void *);
 
 /* The following definitions come from printing/print_aix.c  */
 

source3/include/smb.h

@@ -391,6 +391,7 @@ struct idle_event;
 struct share_mode_entry;
 struct uuid;
 struct named_mutex;
+struct pcap_cache;
 
 struct vfs_fsp_data {
     struct vfs_fsp_data *next;

source3/param/loadparm.c

@@ -7848,7 +7848,7 @@ static void lp_add_auto_services(char *str)
  Auto-load one printer.
 ***************************************************************************/
 
-void lp_add_one_printer(char *name, char *comment)
+void lp_add_one_printer(const char *name, const char *comment, void *pdata)
 {
 	int printers = lp_servicenumber(PRINTERS_NAME);
 	int i;

source3/printing/load.c

@@ -60,5 +60,5 @@ void load_printers(void)
 
 	/* load all printcap printers */
 	if (lp_load_printers() && lp_servicenumber(PRINTERS_NAME) >= 0)
-		pcap_printer_fn(lp_add_one_printer);
+		pcap_printer_fn(lp_add_one_printer, NULL);
 }

source3/printing/pcap.c

@@ -63,41 +63,51 @@
 #include "includes.h"
 
 
-typedef struct pcap_cache {
+struct pcap_cache {
 	char *name;
 	char *comment;
 	struct pcap_cache *next;
-} pcap_cache_t;
+};
 
-static pcap_cache_t *pcap_cache = NULL;
+/* The systemwide printcap cache. */
+static struct pcap_cache *pcap_cache = NULL;
 
-bool pcap_cache_add(const char *name, const char *comment)
+bool pcap_cache_add_specific(struct pcap_cache **ppcache, const char *name, const char *comment)
 {
-	pcap_cache_t *p;
+	struct pcap_cache *p;
 
-	if (name == NULL || ((p = SMB_MALLOC_P(pcap_cache_t)) == NULL))
+	if (name == NULL || ((p = SMB_MALLOC_P(struct pcap_cache)) == NULL))
-		return False;
+		return false;
 
 	p->name = SMB_STRDUP(name);
 	p->comment = (comment && *comment) ? SMB_STRDUP(comment) : NULL;
 
-	p->next = pcap_cache;
+	DEBUG(11,("pcap_cache_add_specific: Adding name %s info %s\n",
-	pcap_cache = p;
+		p->name, p->comment ? p->comment : ""));
 
-	return True;
+	p->next = *ppcache;
+	*ppcache = p;
+
+	return true;
 }
 
-static void pcap_cache_destroy(pcap_cache_t *cache)
+void pcap_cache_destroy_specific(struct pcap_cache **pp_cache)
 {
-	pcap_cache_t *p, *next;
+	struct pcap_cache *p, *next;
 
-	for (p = cache; p != NULL; p = next) {
+	for (p = *pp_cache; p != NULL; p = next) {
 		next = p->next;
 
 		SAFE_FREE(p->name);
 		SAFE_FREE(p->comment);
 		SAFE_FREE(p);
 	}
+	*pp_cache = NULL;
+}
+
+bool pcap_cache_add(const char *name, const char *comment)
+{
+	return pcap_cache_add_specific(&pcap_cache, name, comment);
 }
 
 bool pcap_cache_loaded(void)
@@ -105,11 +115,21 @@ bool pcap_cache_loaded(void)
 	return (pcap_cache != NULL);
 }
 
+void pcap_cache_replace(const struct pcap_cache *pcache)
+{
+	const struct pcap_cache *p;
+
+	pcap_cache_destroy_specific(&pcap_cache);
+	for (p = pcache; p; p = p->next) {
+		pcap_cache_add(p->name, p->comment);
+	}
+}
+
 void pcap_cache_reload(void)
 {
 	const char *pcap_name = lp_printcapname();
 	bool pcap_reloaded = False;
-	pcap_cache_t *tmp_cache = NULL;
+	struct pcap_cache *tmp_cache = NULL;
 	XFILE *pcap_file;
 	char *pcap_line;
 
@@ -223,9 +243,9 @@ done:
 	DEBUG(3, ("reload status: %s\n", (pcap_reloaded) ? "ok" : "error"));
 
 	if (pcap_reloaded)
-		pcap_cache_destroy(tmp_cache);
+		pcap_cache_destroy_specific(&tmp_cache);
 	else {
-		pcap_cache_destroy(pcap_cache);
+		pcap_cache_destroy_specific(&pcap_cache);
 		pcap_cache = tmp_cache;
 	}
 
@@ -235,7 +255,7 @@ done:
 
 bool pcap_printername_ok(const char *printername)
 {
-	pcap_cache_t *p;
+	struct pcap_cache *p;
 
 	for (p = pcap_cache; p != NULL; p = p->next)
 		if (strequal(p->name, printername))
@@ -245,19 +265,22 @@ bool pcap_printername_ok(const char *printername)
 }
 
 /***************************************************************************
-run a function on each printer name in the printcap file. The function is 
+run a function on each printer name in the printcap file.
-passed the primary name and the comment (if possible). Note the fn() takes
-strings in DOS codepage. This means the xxx_printer_fn() calls must be fixed
-to return DOS codepage. FIXME !! JRA.
-
-XXX: I'm not sure if this comment still applies.. Anyone?  -Rob
 ***************************************************************************/
-void pcap_printer_fn(void (*fn)(char *, char *))
-{
-	pcap_cache_t *p;
 
-	for (p = pcap_cache; p != NULL; p = p->next)
+void pcap_printer_fn_specific(const struct pcap_cache *pc,
-		fn(p->name, p->comment);
+			void (*fn)(const char *, const char *, void *),
+			void *pdata)
+{
+	const struct pcap_cache *p;
+
+	for (p = pc; p != NULL; p = p->next)
+		fn(p->name, p->comment, pdata);
 
 	return;
 }
+
+void pcap_printer_fn(void (*fn)(const char *, const char *, void *), void *pdata)
+{
+	return pcap_printer_fn_specific(pcap_cache, fn, pdata);
+}

source3/printing/print_cups.c

@@ -106,9 +106,46 @@ static http_t *cups_connect(TALLOC_CTX *frame)
 	return http;
 }
 
-bool cups_cache_reload(void)
+static void send_pcap_info(const char *name, const char *info, void *pd)
+{
+	int fd = *(int *)pd;
+	size_t namelen = name ? strlen(name)+1 : 0;
+	size_t infolen = info ? strlen(info)+1 : 0;
+
+	DEBUG(11,("send_pcap_info: writing namelen %u\n", (unsigned int)namelen));
+	if (sys_write(fd, &namelen, sizeof(namelen)) != sizeof(namelen)) {
+		DEBUG(10,("send_pcap_info: namelen write failed %s\n",
+			strerror(errno)));
+		return;
+	}
+	DEBUG(11,("send_pcap_info: writing infolen %u\n", (unsigned int)infolen));
+	if (sys_write(fd, &infolen, sizeof(infolen)) != sizeof(infolen)) {
+		DEBUG(10,("send_pcap_info: infolen write failed %s\n",
+			strerror(errno)));
+		return;
+	}
+	if (namelen) {
+		DEBUG(11,("send_pcap_info: writing name %s\n", name));
+		if (sys_write(fd, name, namelen) != namelen) {
+			DEBUG(10,("send_pcap_info: name write failed %s\n",
+				strerror(errno)));
+			return;
+		}
+	}
+	if (infolen) {
+		DEBUG(11,("send_pcap_info: writing info %s\n", info));
+		if (sys_write(fd, info, infolen) != infolen) {
+			DEBUG(10,("send_pcap_info: info write failed %s\n",
+				strerror(errno)));
+			return;
+		}
+	}
+}
+
+static bool cups_cache_reload_async(int fd)
 {
 	TALLOC_CTX *frame = talloc_stackframe();
+	struct pcap_cache *tmp_pcap_cache = NULL;
 	http_t		*http = NULL;		/* HTTP connection to server */
 	ipp_t		*request = NULL,	/* IPP Request */
 			*response = NULL;	/* IPP Response */
@@ -226,7 +263,7 @@ bool cups_cache_reload(void)
 		if (name == NULL)
 			break;
 
-		if (!pcap_cache_add(name, info)) {
+		if (!pcap_cache_add_specific(&tmp_pcap_cache, name, info)) {
 			goto out;
 		}
 	}
@@ -318,7 +355,7 @@ bool cups_cache_reload(void)
 		if (name == NULL)
 			break;
 
-		if (!pcap_cache_add(name, info)) {
+		if (!pcap_cache_add_specific(&tmp_pcap_cache, name, info)) {
 			goto out;
 		}
 	}
@@ -335,10 +372,178 @@ bool cups_cache_reload(void)
 	if (http)
 		httpClose(http);
 
+	/* Send all the entries up the pipe. */
+	if (tmp_pcap_cache) {
+		pcap_printer_fn_specific(tmp_pcap_cache,
+				send_pcap_info,
+				(void *)&fd);
+
+		pcap_cache_destroy_specific(&tmp_pcap_cache);
+	}
 	TALLOC_FREE(frame);
 	return ret;
 }
 
+static struct pcap_cache *local_pcap_copy;
+struct fd_event *cache_fd_event;
+
+static bool cups_pcap_load_async(int *pfd)
+{
+	int fds[2];
+	pid_t pid;
+
+	if (cache_fd_event) {
+		DEBUG(3,("cups_pcap_load_async: already waiting for "
+			"a refresh event\n" ));
+		return false;
+	}
+
+	DEBUG(5,("cups_pcap_load_async: asynchronously loading cups printers\n"));
+
+	if (pipe(fds) == -1) {
+		return false;
+	}
+
+	pid = sys_fork();
+	if (pid == (pid_t)-1) {
+		DEBUG(10,("cups_pcap_load_async: fork failed %s\n",
+			strerror(errno) ));
+		close(fds[0]);
+		close(fds[1]);
+		return false;
+	}
+
+	if (pid) {
+		DEBUG(10,("cups_pcap_load_async: child pid = %u\n",
+			(unsigned int)pid ));
+		/* Parent. */
+		close(fds[1]);
+		*pfd = fds[0];
+		return true;
+	}
+
+	/* Child. */
+	close(fds[0]);
+	cups_cache_reload_async(fds[1]);
+	close(fds[1]);
+	_exit(0);
+}
+
+static void cups_async_callback(struct event_context *event_ctx,
+				struct fd_event *event,
+				uint16 flags,
+				void *p)
+{
+	TALLOC_CTX *frame = talloc_stackframe();
+	int fd = *(int *)p;
+	struct pcap_cache *tmp_pcap_cache = NULL;
+
+	DEBUG(5,("cups_async_callback: callback received for printer data. "
+		"fd = %d\n", fd));
+
+	TALLOC_FREE(cache_fd_event);
+
+	while (1) {
+		char *name = NULL, *info = NULL;
+		size_t namelen = 0, infolen = 0;
+
+		if (sys_read(fd, &namelen, sizeof(namelen)) !=
+				sizeof(namelen)) {
+			DEBUG(10,("cups_async_callback: namelen read failed %d %s\n",
+				errno, strerror(errno)));
+			break;
+		}
+		if (sys_read(fd, &infolen, sizeof(infolen)) !=
+				sizeof(infolen)) {
+			DEBUG(10,("cups_async_callback: infolen read failed %s\n",
+				strerror(errno)));
+			break;
+		}
+		if (namelen) {
+			name = TALLOC_ARRAY(frame, char, namelen);
+			if (!name) {
+				break;
+			}
+			if (sys_read(fd, name, namelen) != namelen) {
+				DEBUG(10,("cups_async_callback: name read failed %s\n",
+					strerror(errno)));
+				break;
+			}
+		} else {
+			name = NULL;
+		}
+		if (infolen) {
+			info = TALLOC_ARRAY(frame, char, infolen);
+			if (!info) {
+				break;
+			}
+			if (sys_read(fd, info, infolen) != infolen) {
+				DEBUG(10,("cups_async_callback: info read failed %s\n",
+					strerror(errno)));
+				break;
+			}
+		} else {
+			info = NULL;
+		}
+
+		/* Add to our local pcap cache. */
+		pcap_cache_add_specific(&tmp_pcap_cache, name, info);
+		TALLOC_FREE(name);
+		TALLOC_FREE(info);
+	}
+
+	TALLOC_FREE(frame);
+	if (tmp_pcap_cache) {
+		/* We got a namelist, replace our local cache. */
+		pcap_cache_destroy_specific(&local_pcap_copy);
+		local_pcap_copy = tmp_pcap_cache;
+
+		/* And the systemwide pcap cache. */
+		pcap_cache_replace(local_pcap_copy);
+	} else {
+		DEBUG(2,("cups_async_callback: failed to read a new "
+			"printer list\n"));
+	}
+	close(fd);
+}
+
+bool cups_cache_reload(void)
+{
+	int fd = -1;
+
+	/* Set up an async refresh. */
+	if (!cups_pcap_load_async(&fd)) {
+		return false;
+	}
+	if (!local_pcap_copy) {
+		/* We have no local cache, wait directly for
+		 * async refresh to complete.
+		 */
+		cups_async_callback(smbd_event_context(),
+					NULL,
+					EVENT_FD_READ,
+					(void *)&fd);
+		if (!local_pcap_copy) {
+			return false;
+		}
+	} else {
+		/* Replace the system cache with our
+		 * local copy. */
+		pcap_cache_replace(local_pcap_copy);
+
+		/* Trigger an event when the pipe can be read. */
+		cache_fd_event = event_add_fd(smbd_event_context(),
+					NULL, fd,
+					EVENT_FD_READ,
+					cups_async_callback,
+					(void *)&fd);
+		if (!cache_fd_event) {
+			close(fd);
+			return false;
+		}
+	}
+	return true;
+}
 
 /*
  * 'cups_job_delete()' - Delete a job.