cmd/zed/zed_log.c

   1 /*
   2  * This file is part of the ZFS Event Daemon (ZED)
   3  * for ZFS on Linux (ZoL) <http://zfsonlinux.org/>.
   4  * Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
   5  * Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
   6  * Refer to the ZoL git commit log for authoritative copyright attribution.
   7  *
   8  * The contents of this file are subject to the terms of the
   9  * Common Development and Distribution License Version 1.0 (CDDL-1.0).
  10  * You can obtain a copy of the license from the top-level file
  11  * "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
  12  * You may not use this file except in compliance with the license.
  13  */
  14
  15 #include <assert.h>
  16 #include <errno.h>
  17 #include <stdarg.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <sys/types.h>
  22 #include <syslog.h>
  23 #include <unistd.h>
  24 #include "zed_log.h"
  25
  26 #define ZED_LOG_MAX_LOG_LEN     1024
  27
  28 static struct {
  29         unsigned do_stderr:1;
  30         unsigned do_syslog:1;
  31         const char *identity;
  32         int priority;
  33         int pipe_fd[2];
  34 } _ctx;
  35
  36 /*
  37  * Initialize the logging subsystem.
  38  */
  39 void
  40 zed_log_init(const char *identity)
  41 {
  42         if (identity) {
  43                 const char *p = strrchr(identity, '/');
  44                 _ctx.identity = (p != NULL) ? p + 1 : identity;
  45         } else {
  46                 _ctx.identity = NULL;
  47         }
  48         _ctx.pipe_fd[0] = -1;
  49         _ctx.pipe_fd[1] = -1;
  50 }
  51
  52 /*
  53  * Shutdown the logging subsystem.
  54  */
  55 void
  56 zed_log_fini(void)
  57 {
  58         zed_log_stderr_close();
  59         zed_log_syslog_close();
  60 }
  61
  62 /*
  63  * Create pipe for communicating daemonization status between the parent and
  64  * child processes across the double-fork().
  65  */
  66 void
  67 zed_log_pipe_open(void)
  68 {
  69         if ((_ctx.pipe_fd[0] != -1) || (_ctx.pipe_fd[1] != -1))
  70                 zed_log_die("Invalid use of zed_log_pipe_open in PID %d",
  71                     (int)getpid());
  72
  73         if (pipe(_ctx.pipe_fd) < 0)
  74                 zed_log_die("Failed to create daemonize pipe in PID %d: %s",
  75                     (int)getpid(), strerror(errno));
  76 }
  77
  78 /*
  79  * Close the read-half of the daemonize pipe.
  80  *
  81  * This should be called by the child after fork()ing from the parent since
  82  * the child will never read from this pipe.
  83  */
  84 void
  85 zed_log_pipe_close_reads(void)
  86 {
  87         if (_ctx.pipe_fd[0] < 0)
  88                 zed_log_die(
  89                     "Invalid use of zed_log_pipe_close_reads in PID %d",
  90                     (int)getpid());
  91
  92         if (close(_ctx.pipe_fd[0]) < 0)
  93                 zed_log_die(
  94                     "Failed to close reads on daemonize pipe in PID %d: %s",
  95                     (int)getpid(), strerror(errno));
  96
  97         _ctx.pipe_fd[0] = -1;
  98 }
  99
 100 /*
 101  * Close the write-half of the daemonize pipe.
 102  *
 103  * This should be called by the parent after fork()ing its child since the
 104  * parent will never write to this pipe.
 105  *
 106  * This should also be called by the child once initialization is complete
 107  * in order to signal the parent that it can safely exit.
 108  */
 109 void
 110 zed_log_pipe_close_writes(void)
 111 {
 112         if (_ctx.pipe_fd[1] < 0)
 113                 zed_log_die(
 114                     "Invalid use of zed_log_pipe_close_writes in PID %d",
 115                     (int)getpid());
 116
 117         if (close(_ctx.pipe_fd[1]) < 0)
 118                 zed_log_die(
 119                     "Failed to close writes on daemonize pipe in PID %d: %s",
 120                     (int)getpid(), strerror(errno));
 121
 122         _ctx.pipe_fd[1] = -1;
 123 }
 124
 125 /*
 126  * Block on reading from the daemonize pipe until signaled by the child
 127  * (via zed_log_pipe_close_writes()) that initialization is complete.
 128  *
 129  * This should only be called by the parent while waiting to exit after
 130  * fork()ing the child.
 131  */
 132 void
 133 zed_log_pipe_wait(void)
 134 {
 135         ssize_t n;
 136         char c;
 137
 138         if (_ctx.pipe_fd[0] < 0)
 139                 zed_log_die("Invalid use of zed_log_pipe_wait in PID %d",
 140                     (int)getpid());
 141
 142         for (;;) {
 143                 n = read(_ctx.pipe_fd[0], &c, sizeof (c));
 144                 if (n < 0) {
 145                         if (errno == EINTR)
 146                                 continue;
 147                         zed_log_die(
 148                             "Failed to read from daemonize pipe in PID %d: %s",
 149                             (int)getpid(), strerror(errno));
 150                 }
 151                 if (n == 0) {
 152                         break;
 153                 }
 154         }
 155 }
 156
 157 /*
 158  * Start logging messages at the syslog [priority] level or higher to stderr.
 159  * Refer to syslog(3) for valid priority values.
 160  */
 161 void
 162 zed_log_stderr_open(int priority)
 163 {
 164         _ctx.do_stderr = 1;
 165         _ctx.priority = priority;
 166 }
 167
 168 /*
 169  * Stop logging messages to stderr.
 170  */
 171 void
 172 zed_log_stderr_close(void)
 173 {
 174         if (_ctx.do_stderr)
 175                 _ctx.do_stderr = 0;
 176 }
 177
 178 /*
 179  * Start logging messages to syslog.
 180  * Refer to syslog(3) for valid option/facility values.
 181  */
 182 void
 183 zed_log_syslog_open(int facility)
 184 {
 185         _ctx.do_syslog = 1;
 186         openlog(_ctx.identity, LOG_NDELAY | LOG_PID, facility);
 187 }
 188
 189 /*
 190  * Stop logging messages to syslog.
 191  */
 192 void
 193 zed_log_syslog_close(void)
 194 {
 195         if (_ctx.do_syslog) {
 196                 _ctx.do_syslog = 0;
 197                 closelog();
 198         }
 199 }
 200
 201 /*
 202  * Auxiliary function to log a message to syslog and/or stderr.
 203  */
 204 static void
 205 _zed_log_aux(int priority, const char *fmt, va_list vargs)
 206 {
 207         char buf[ZED_LOG_MAX_LOG_LEN];
 208         int n;
 209
 210         if (!fmt)
 211                 return;
 212
 213         n = vsnprintf(buf, sizeof (buf), fmt, vargs);
 214         if ((n < 0) || (n >= sizeof (buf))) {
 215                 buf[sizeof (buf) - 2] = '+';
 216                 buf[sizeof (buf) - 1] = '\0';
 217         }
 218
 219         if (_ctx.do_syslog)
 220                 syslog(priority, "%s", buf);
 221
 222         if (_ctx.do_stderr && (priority <= _ctx.priority))
 223                 fprintf(stderr, "%s\n", buf);
 224 }
 225
 226 /*
 227  * Log a message at the given [priority] level specified by the printf-style
 228  * format string [fmt].
 229  */
 230 void
 231 zed_log_msg(int priority, const char *fmt, ...)
 232 {
 233         va_list vargs;
 234
 235         if (fmt) {
 236                 va_start(vargs, fmt);
 237                 _zed_log_aux(priority, fmt, vargs);
 238                 va_end(vargs);
 239         }
 240 }
 241
 242 /*
 243  * Log a fatal error message specified by the printf-style format string [fmt].
 244  */
 245 void
 246 zed_log_die(const char *fmt, ...)
 247 {
 248         va_list vargs;
 249
 250         if (fmt) {
 251                 va_start(vargs, fmt);
 252                 _zed_log_aux(LOG_ERR, fmt, vargs);
 253                 va_end(vargs);
 254         }
 255         exit(EXIT_FAILURE);
 256 }