From d90a4fc57b00b4a1f6c196bcb96025251b555dd9 Mon Sep 17 00:00:00 2001
From: zdohnal <zdohnal@redhat.com>
Date: Fri, 18 Jun 2021 12:27:53 +0200
Subject: [PATCH] cups-browsed.c: Make NotifLeaseDuration configurable and
 renew after half the lease duration not 60 sec before end

1) NotifLeaseDuration directive for cups-browsed.conf - it will make
   lease duration for notifications configurable by users. IMO it is not
   useful for regular users, but it is helpful during sanity testing
   (for verifying that we actually renew the subscription when time
   comes). The current hardcoded 1 day is unusuable for that :( .
   I implemented the lowest threshold to 300s to prevent a possible DoS.
2) Subscription renewal is set to happen in the middle of NotifLeaseDuration,
   not one minute before lease expiration. This was a problem on busy servers,
   where cups-browsed was busy and wasn't able to renew the subscription
   before cupsd removed it. Then if some jobs had come before the subscription
   was created again, the queue got disabled. The proposed approach is based
   on behavior of DHCP.
---
 utils/cups-browsed.c       | 17 +++++++++++++----
 utils/cups-browsed.conf.5  | 11 +++++++++++
 utils/cups-browsed.conf.in |  8 ++++++++
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/utils/cups-browsed.c b/utils/cups-browsed.c
index 61d6c551..2d367c59 100644
--- a/utils/cups-browsed.c
+++ b/utils/cups-browsed.c
@@ -142,7 +142,6 @@ static int  ldap_rebind_proc(LDAP *RebindLDAPHandle,
 #define TIMEOUT_REMOVE      -1
 #define TIMEOUT_CHECK_LIST   2
 
-#define NOTIFY_LEASE_DURATION (24 * 60 * 60)
 #define CUPS_DBUS_NAME "org.cups.cupsd.Notifier"
 #define CUPS_DBUS_PATH "/org/cups/cupsd/Notifier"
 #define CUPS_DBUS_INTERFACE "org.cups.cupsd.Notifier"
@@ -508,6 +507,7 @@ static int autoshutdown_timeout = 30;
 static autoshutdown_inactivity_type_t autoshutdown_on = NO_QUEUES;
 static guint autoshutdown_exec_id = 0;
 static const char *default_printer = NULL;
+static unsigned int notify_lease_duration = 86400;
 
 static int debug_stderr = 0;
 static int debug_logfile = 0;
@@ -5017,7 +5017,7 @@ create_subscription ()
   ippAddString (req, IPP_TAG_SUBSCRIPTION, IPP_TAG_URI,
 		"notify-recipient-uri", NULL, "dbus://");
   ippAddInteger (req, IPP_TAG_SUBSCRIPTION, IPP_TAG_INTEGER,
-		 "notify-lease-duration", NOTIFY_LEASE_DURATION);
+		 "notify-lease-duration", notify_lease_duration);
 
   resp = cupsDoRequest (conn, req, "/");
   if (!resp || cupsLastError() != IPP_STATUS_OK) {
@@ -5060,7 +5060,7 @@ renew_subscription (int id)
   ippAddString (req, IPP_TAG_SUBSCRIPTION, IPP_TAG_URI,
 		"notify-recipient-uri", NULL, "dbus://");
   ippAddInteger (req, IPP_TAG_SUBSCRIPTION, IPP_TAG_INTEGER,
-		 "notify-lease-duration", NOTIFY_LEASE_DURATION);
+		 "notify-lease-duration", notify_lease_duration);
 
   resp = cupsDoRequest (conn, req, "/");
   if (!resp || cupsLastError() != IPP_STATUS_OK) {
@@ -11857,6 +11857,15 @@ read_configuration (const char *filename)
       } else
 	debug_printf("Invalid %s value: %d\n",
 		     line, t);
+    } else if (!strcasecmp(line, "NotifLeaseDuration") && value) {
+      int t = atoi(value);
+      if (t >= 300) {
+	  notify_lease_duration = t;
+	debug_printf("Set %s to %d sec.\n",
+		     line, t);
+      } else
+	debug_printf("Invalid %s value: %d\n",
+		     line, t);
     } else if (!strcasecmp(line, "HttpMaxRetries") && value) {
       int t = atoi(value);
       if (t > 0) {
@@ -12728,7 +12737,7 @@ int main(int argc, char*argv[]) {
   /* Subscribe to CUPS' D-Bus notifications and create a proxy to receive
      the notifications */
   subscription_id = create_subscription ();
-  g_timeout_add_seconds (NOTIFY_LEASE_DURATION - 60,
+  g_timeout_add_seconds (notify_lease_duration / 2,
 			 renew_subscription_timeout,
 			 &subscription_id);
   cups_notifier = cups_notifier_proxy_new_for_bus_sync (G_BUS_TYPE_SYSTEM,
diff --git a/utils/cups-browsed.conf.5 b/utils/cups-browsed.conf.5
index c47f8e8d..263f0843 100644
--- a/utils/cups-browsed.conf.5
+++ b/utils/cups-browsed.conf.5
@@ -966,6 +966,17 @@ shutdown.
 
 .fam T
 .fi
+NotifLeaseDuration defines how long the D-BUS subscription created by cups-browsed
+in cupsd will last before cupsd cancels it. The default value is 1 day
+in seconds - 86400. The subscription renewal is set to happen after half of
+NotifLeaseDuration passed. The D-BUS notifications are used for watching over queues
+and doing specific actions when a D-BUS notification comes.
+.PP
+.nf
+.fam C
+        NotifLeaseDuration 86400
+.fam T
+.fi
 .SH SEE ALSO
 
 \fBcups-browsed\fP(8)
diff --git a/utils/cups-browsed.conf.in b/utils/cups-browsed.conf.in
index 3cc4ebb1..ffdf83d6 100644
--- a/utils/cups-browsed.conf.in
+++ b/utils/cups-browsed.conf.in
@@ -741,3 +741,11 @@ BrowseRemoteProtocols @BROWSEREMOTEPROTOCOLS@
 # on the size of the file.
 
 # DebugLogFileSize 300
+
+# NotifLeaseDuration defines how long the D-BUS subscription created by cups-browsed
+# in cupsd will last before cupsd cancels it. The default value is 1 day
+# in seconds - 86400. The subscription renewal is set to happen after half of
+# NotifLeaseDuration passed. The D-BUS notifications are used for watching over queues
+# and doing specific actions when a D-BUS notification comes.
+
+# NotifLeaseDuration 86400
-- 
2.31.1