Add CHANGES and release note for [GL #3958]

Change the tcp-clients configuration value to allow specifying
percents (out of the maximum allowed file descriptors) and set the
default to 50% of that value.

CHANGES

@@ -1,3 +1,7 @@
+6247.	[performance]	Change the "tcp-clients" value to allow specifying
+			percents of the maximum allowed file descriptors and
+			set the default value to 50%. [GL #3958]
+
 6246.	[placeholder]
 
 6245.	[placeholder]
@@ -303,6 +307,8 @@
 			file. [GL #3991]
 
 6160.	[bug]		'delv +ns' could print duplicate output. [GL #4020]
+=======
+>>>>>>> 25abcb8750 (Add CHANGES and release note for [GL #3958])
 
 6159.	[bug]		Fix use-after-free bug in TCP accept connection
 			failure. [GL #4018]

bin/named/config.c

@@ -112,7 +112,7 @@ options {\n\
 	startup-notify-rate 20;\n\
 	statistics-file \"named.stats\";\n\
 	tcp-advertised-timeout 300;\n\
-	tcp-clients 150;\n\
+	tcp-clients 50%;\n\
 	tcp-idle-timeout 300;\n\
 	tcp-initial-timeout 300;\n\
 	tcp-keepalive-timeout 300;\n\

bin/named/include/named/globals.h

@@ -16,6 +16,7 @@
 /*! \file */
 
 #include <stdbool.h>
+#include <sys/resource.h>
 
 #include <isc/log.h>
 #include <isc/loop.h>
@@ -115,6 +116,7 @@ EXTERN bool named_g_foreground	     INIT(false);
 EXTERN bool named_g_logstderr	     INIT(false);
 EXTERN bool named_g_nosyslog	     INIT(false);
 EXTERN const char *named_g_logfile   INIT(NULL);
+EXTERN rlim_t named_g_nofiles	     INIT(0);
 
 EXTERN const char *named_g_defaultsessionkeyfile INIT(NAMED_LOCALSTATEDIR
 						      "/run/named/"

bin/named/include/named/os.h

@@ -17,6 +17,7 @@
 
 #include <pwd.h>
 #include <stdbool.h>
+#include <sys/resource.h>
 
 #include <isc/types.h>
 
@@ -44,7 +45,7 @@ named_os_changeuser(void);
 uid_t
 ns_os_uid(void);
 
-void
+rlim_t
 named_os_adjustnofile(void);
 
 void

bin/named/main.c

@@ -1283,7 +1283,7 @@ setup(void) {
 	 * System resources cannot effectively be tuned on some systems.
 	 * Raise the limit in such cases for safety.
 	 */
-	named_os_adjustnofile();
+	named_g_nofiles = named_os_adjustnofile();
 
 	/*
 	 * If the named configuration filename is relative, prepend the current

bin/named/os.c

@@ -613,7 +613,7 @@ ns_os_uid(void) {
 	return (runas_pw->pw_uid);
 }
 
-void
+rlim_t
 named_os_adjustnofile(void) {
 	int r;
 	struct rlimit rl;
@@ -634,7 +634,7 @@ named_os_adjustnofile(void) {
 			      "maximum allowed value: "
 			      "%" PRIu64,
 			      (uint64_t)rl.rlim_max);
-		return;
+		return (rl.rlim_cur);
 	}
 
 	rl.rlim_cur = rl.rlim_max;
@@ -649,13 +649,13 @@ named_os_adjustnofile(void) {
 		      "%" PRIu64 " to "
 		      "%" PRIu64,
 		      (uint64_t)rlim_old, (uint64_t)rl.rlim_cur);
-	return;
+	return (rl.rlim_cur);
 
 fail:
 	strerror_r(errno, strbuf, sizeof(strbuf));
 	named_main_earlywarning("adjusting limit on open files failed: %s",
 				strbuf);
-	return;
+	return (0);
 }
 
 void

bin/named/server.c

@@ -8459,7 +8459,6 @@ load_configuration(const char *filename, named_server_t *server,
 	 */
 	configure_server_quota(maps, "transfers-out",
 			       &server->sctx->xfroutquota);
-	configure_server_quota(maps, "tcp-clients", &server->sctx->tcpquota);
 	configure_server_quota(maps, "recursive-clients",
 			       &server->sctx->recursionquota);
 	configure_server_quota(maps, "update-quota", &server->sctx->updquota);
@@ -8484,6 +8483,40 @@ load_configuration(const char *filename, named_server_t *server,
 
 	isc_quota_soft(&server->sctx->recursionquota, softquota);
 
+	obj = NULL;
+	result = named_config_get(maps, "tcp-clients", &obj);
+	INSIST(result == ISC_R_SUCCESS);
+
+	uint32_t tcp_clients = 0;
+	if (cfg_obj_isstring(obj)) {
+		const char *str = cfg_obj_asstring(obj);
+		INSIST(strcasecmp(str, "unlimited") == 0);
+		tcp_clients = UINT32_MAX;
+	} else if (cfg_obj_ispercentage(obj)) {
+		INSIST(named_g_nofiles != 0);
+		uint32_t tcp_clients_percent = cfg_obj_aspercentage(obj);
+		tcp_clients = named_g_nofiles * tcp_clients_percent / 100;
+
+		cfg_obj_log(obj, named_g_lctx, ISC_LOG_INFO,
+			    "'tcp-clients %" PRIu32 "%%' - setting to %" PRIu32
+			    " (out of %" PRIu32 " file descriptors)",
+			    tcp_clients_percent, tcp_clients,
+			    (uint32_t)named_g_nofiles);
+	} else {
+		uint64_t value = cfg_obj_asuint64(obj);
+		if (value > UINT32_MAX) {
+			cfg_obj_log(obj, named_g_lctx, ISC_LOG_WARNING,
+				    "'tcp-clients "
+				    "%" PRIu64 "' "
+				    "is too large for this "
+				    "system; reducing to %" PRIu32,
+				    value, UINT32_MAX);
+			value = UINT32_MAX;
+		}
+		tcp_clients = (uint32_t)value;
+	}
+	isc_quota_max(&server->sctx->tcpquota, tcp_clients);
+
 	/*
 	 * Set "blackhole". Only legal at options level; there is
 	 * no default.

doc/arm/reference.rst

@@ -3563,7 +3563,8 @@ system.
    :short: Specifies the maximum number of simultaneous client TCP connections accepted by the server.
 
    This is the maximum number of simultaneous client TCP connections that the
-   server accepts. The default is ``150``.
+   server accepts, in bytes of percentage of maximum allowed file descriptors.
+   The default is ``50%``.
 
 .. namedconf:statement:: clients-per-query
    :tags: server

doc/misc/options

@@ -277,7 +277,7 @@ options {
 	statistics-file <quoted_string>;
 	synth-from-dnssec <boolean>;
 	tcp-advertised-timeout <integer>;
-	tcp-clients <integer>;
+	tcp-clients ( default | unlimited | <sizeval> | <percentage> );
 	tcp-idle-timeout <integer>;
 	tcp-initial-timeout <integer>;
 	tcp-keepalive-timeout <integer>;

doc/notes/notes-current.rst

@@ -44,6 +44,10 @@ Feature Changes
   those versions do not provide the features required by current BIND 9
   releases. :gl:`#4296`
 
+- The ``tcp-clients`` configuration option now also accepts value as percent of
+  maximum allowed file descriptors.  The default has been changed to ``50%``.
+  :gl:`#3958`
+
 Bug Fixes
 ~~~~~~~~~
 

lib/isccfg/namedconf.c

@@ -1313,7 +1313,7 @@ static cfg_clausedef_t options_clauses[] = {
 	{ "statistics-file", &cfg_type_qstring, 0 },
 	{ "statistics-interval", NULL, CFG_CLAUSEFLAG_ANCIENT },
 	{ "tcp-advertised-timeout", &cfg_type_uint32, 0 },
-	{ "tcp-clients", &cfg_type_uint32, 0 },
+	{ "tcp-clients", &cfg_type_sizeorpercent, 0 },
 	{ "tcp-idle-timeout", &cfg_type_uint32, 0 },
 	{ "tcp-initial-timeout", &cfg_type_uint32, 0 },
 	{ "tcp-keepalive-timeout", &cfg_type_uint32, 0 },