Bug 1252048 - net-snmp snmpd fork() overhead [fix available]

Backported from:

commit f0e87f4918ffc41e03f707e9670ea422cd154a9b

Author: Bart Van Assche <bvanassche@acm.org>

Date:   Sat Jan 31 12:05:24 2015 +0100

    CHANGES: snmpd: BUG: 2596: Reduce fork() overhead

    Avoid that the close() loop that is executed after a fork() delays

    the pass/extend API on systems with a large maximum number of files

    by reducing the number of iterations of this loop on Linux systems.

    See also http://sourceforge.net/p/net-snmp/bugs/2596.

    Reported-by: andymf <andymf@users.sf.net>

diff -up net-snmp-5.7.2/agent/mibgroup/util_funcs.c.test net-snmp-5.7.2/agent/mibgroup/util_funcs.c

--- net-snmp-5.7.2/agent/mibgroup/util_funcs.c.test	2012-10-10 00:28:58.000000000 +0200

+++ net-snmp-5.7.2/agent/mibgroup/util_funcs.c	2015-08-18 10:15:18.888767023 +0200

@@ -480,8 +480,7 @@ get_exec_pipes(char *cmd, int *fdIn, int

         /*

          * close all non-standard open file descriptors 

          */

-        for (cnt = getdtablesize() - 1; cnt >= 2; --cnt)

-            (void) close(cnt);

+        netsnmp_close_fds(1);

         (void) dup(1);          /* stderr */

         for (cnt = 1, cptr1 = cmd, cptr2 = argvs; *cptr1 != 0;

diff -up net-snmp-5.7.2/agent/mibgroup/utilities/execute.c.test net-snmp-5.7.2/agent/mibgroup/utilities/execute.c

--- net-snmp-5.7.2/agent/mibgroup/utilities/execute.c.test	2012-10-10 00:28:58.000000000 +0200

+++ net-snmp-5.7.2/agent/mibgroup/utilities/execute.c	2015-08-18 10:15:18.889767028 +0200

@@ -22,6 +22,9 @@

 #if HAVE_FCNTL_H

 #include <fcntl.h>

 #endif

+#if HAVE_DIRENT_H

+#include <dirent.h>

+#endif

 #if HAVE_SYS_WAIT_H

 #include <sys/wait.h>

 #endif

@@ -207,8 +210,8 @@ run_exec_command( char *command, char *i

         close(opipe[0]);

         close(2);

         dup(1);

-        for (i = getdtablesize()-1; i>2; i--)

-            close(i);

+

+        netsnmp_close_fds(2);

         /*

          * Set up the argv array and execute it

@@ -406,3 +409,30 @@ run_exec_command( char *command, char *i

     return run_shell_command( command, input, output, out_len );

 #endif

 }

+

+/**

+ * Close all file descriptors larger than @fd.

+ */

+void netsnmp_close_fds(int fd)

+{

+#if defined(HAVE_FORK)

+    DIR            *dir;

+    struct dirent  *ent;

+    int             i, largest_fd = -1;

+

+    if ((dir = opendir("/proc/self/fd"))) {

+        while ((ent = readdir(dir))) {

+            if (sscanf(ent->d_name, "%d", &i) == 1) {

+                if (i > largest_fd)

+                    largest_fd = i;

+            }

+        }

+        closedir(dir);

+    } else {

+        largest_fd = getdtablesize() - 1;

+    }

+

+    for (i = largest_fd; i > fd && i > 0; i--)

+        close(i);

+#endif

+}

diff -up net-snmp-5.7.2/agent/mibgroup/utilities/execute.h.test net-snmp-5.7.2/agent/mibgroup/utilities/execute.h

--- net-snmp-5.7.2/agent/mibgroup/utilities/execute.h.test	2012-10-10 00:28:58.000000000 +0200

+++ net-snmp-5.7.2/agent/mibgroup/utilities/execute.h	2015-08-18 10:15:18.889767028 +0200

@@ -3,6 +3,7 @@

 config_belongs_in(agent_module)

+void netsnmp_close_fds(int fd);

 int run_shell_command(char *command, char *input,

                       char *output,  int  *out_len);

 int run_exec_command( char *command, char *input,

diff -up net-snmp-5.7.2/agent/snmpd.c.test net-snmp-5.7.2/agent/snmpd.c

--- net-snmp-5.7.2/agent/snmpd.c.test	2015-08-18 10:15:08.450714809 +0200

+++ net-snmp-5.7.2/agent/snmpd.c	2015-08-18 10:17:31.579430763 +0200

@@ -143,6 +143,7 @@ typedef long    fd_mask;

 #include <net-snmp/agent/agent_module_config.h>

 #include <net-snmp/agent/mib_module_config.h>

+#include "utilities/execute.h" /* netsnmp_close_fds() */

 #include "snmpd.h"

 #include <net-snmp/agent/mib_modules.h>

@@ -451,7 +452,6 @@ main(int argc, char *argv[])

     FILE           *PID;

 #endif

-#ifndef WIN32

 #ifndef NETSNMP_NO_SYSYSTEMD

     /* check if systemd has sockets for us and don't close them */

     prepared_sockets = netsnmp_sd_listen_fds(0);

@@ -462,11 +462,8 @@ main(int argc, char *argv[])

      * inherited from the shell.

      */

     if (!prepared_sockets) {

-        for (i = getdtablesize() - 1; i > 2; --i) {

-            (void) close(i);

-        }

+        netsnmp_close_fds(2);

     }

-#endif /* #WIN32 */

     /*

      * register signals ASAP to prevent default action (usually core)

diff -up net-snmp-5.7.2/apps/snmptrapd.c.test net-snmp-5.7.2/apps/snmptrapd.c

--- net-snmp-5.7.2/apps/snmptrapd.c.test	2015-08-18 10:15:08.450714809 +0200

+++ net-snmp-5.7.2/apps/snmptrapd.c	2015-08-18 10:18:15.454650235 +0200

@@ -97,6 +97,7 @@ SOFTWARE.

 #include <net-snmp/net-snmp-includes.h>

 #include <net-snmp/agent/net-snmp-agent-includes.h>

 #include <net-snmp/library/fd_event_manager.h>

+#include "utilities/execute.h" /* netsnmp_close_fds() */

 #include "snmptrapd_handlers.h"

 #include "snmptrapd_log.h"

 #include "snmptrapd_auth.h"

@@ -662,7 +663,6 @@ main(int argc, char *argv[])

     int             prepared_sockets = 0;

-#ifndef WIN32

 #ifndef NETSNMP_NO_SYSTEMD

     /* check if systemd has sockets for us and don't close them */

     prepared_sockets = netsnmp_sd_listen_fds(0);

@@ -672,11 +672,8 @@ main(int argc, char *argv[])

      * inherited from the shell.

      */

     if (!prepared_sockets) {

-        for (i = getdtablesize() - 1; i > 2; --i) {

-            (void) close(i);

-        }

+        netsnmp_close_fds(2);

     }

-#endif /* #WIN32 */

 #ifdef SIGTERM

     signal(SIGTERM, term_handler);

@@ -1382,18 +1379,6 @@ trapd_update_config(void)

     read_configs();

 }

-

-#if !defined(HAVE_GETDTABLESIZE) && !defined(WIN32)

-#include <sys/resource.h>

-int

-getdtablesize(void)

-{

-    struct rlimit   rl;

-    getrlimit(RLIMIT_NOFILE, &rl);

-    return (rl.rlim_cur);

-}

-#endif

-

 /*

  * Windows Service Related functions 

  */