src/lxc/monitor.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  * Dwight Engen <dwight.engen@oracle.com>
   9  *
  10  * This library is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2.1 of the License, or (at your option) any later version.
  14  *
  15  * This library is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with this library; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  23  */
  24
  25 #include <stdio.h>
  26 #include <errno.h>
  27 #include <unistd.h>
  28 #include <string.h>
  29 #include <stdlib.h>
  30 #include <fcntl.h>
  31 #include <sys/types.h>
  32 #include <sys/stat.h>
  33 #include <sys/param.h>
  34 #include <sys/socket.h>
  35 #include <sys/wait.h>
  36 #include <netinet/in.h>
  37 #include <net/if.h>
  38
  39 #include "error.h"
  40 #include "af_unix.h"
  41
  42 #include <lxc/log.h>
  43 #include <lxc/state.h>
  44 #include <lxc/monitor.h>
  45 #include <lxc/utils.h>
  46
  47 lxc_log_define(lxc_monitor, lxc);
  48
  49 /* routines used by monitor publishers (containers) */
  50 static void lxc_monitor_fifo_send(struct lxc_msg *msg, const char *lxcpath)
  51 {
  52         int fd,ret;
  53         char fifo_path[PATH_MAX];
  54
  55         BUILD_BUG_ON(sizeof(*msg) > PIPE_BUF); /* write not guaranteed atomic */
  56         ret = snprintf(fifo_path, sizeof(fifo_path), "%s/monitor-fifo", lxcpath);
  57         if (ret < 0 || ret >= sizeof(fifo_path)) {
  58                 ERROR("lxcpath too long to open monitor fifo");
  59                 return;
  60         }
  61
  62         fd = open(fifo_path, O_WRONLY);
  63         if (fd < 0) {
  64                 /* it is normal for this open to fail when there is no monitor
  65                  * running, so we don't log it
  66                  */
  67                 return;
  68         }
  69
  70         ret = write(fd, msg, sizeof(*msg));
  71         if (ret != sizeof(*msg)) {
  72                 SYSERROR("failed to write monitor fifo %s", fifo_path);
  73                 return;
  74         }
  75
  76         close(fd);
  77 }
  78
  79 void lxc_monitor_send_state(const char *name, lxc_state_t state, const char *lxcpath)
  80 {
  81         struct lxc_msg msg = { .type = lxc_msg_state,
  82                                .value = state };
  83         strncpy(msg.name, name, sizeof(msg.name));
  84         msg.name[sizeof(msg.name) - 1] = 0;
  85
  86         lxc_monitor_fifo_send(&msg, lxcpath);
  87 }
  88
  89
  90 /* routines used by monitor subscribers (lxc-monitor) */
  91 int lxc_monitor_close(int fd)
  92 {
  93         return close(fd);
  94 }
  95
  96 int lxc_monitor_sock_name(const char *lxcpath, struct sockaddr_un *addr) {
  97         size_t len;
  98         int ret;
  99         char *sockname = &addr->sun_path[0]; // 1 for abstract
 100
 101         /* addr.sun_path is only 108 bytes.
 102          * should we take a hash of lxcpath? a subset of it? ftok()? we need
 103          * to make sure it is unique.
 104          */
 105         memset(addr, 0, sizeof(*addr));
 106         addr->sun_family = AF_UNIX;
 107         len = sizeof(addr->sun_path) - 1;
 108         ret = snprintf(sockname, len, "%s/monitor-sock", lxcpath);
 109         if (ret < 0 || ret >= len) {
 110                 ERROR("lxcpath too long for unix socket");
 111                 return -1;
 112         }
 113         return 0;
 114 }
 115
 116 int lxc_monitor_open(const char *lxcpath)
 117 {
 118         struct sockaddr_un addr;
 119         int fd,ret;
 120         int retry,backoff_ms[] = {10, 50, 100};
 121
 122         if (lxc_monitor_sock_name(lxcpath, &addr) < 0)
 123                 return -1;
 124
 125         fd = socket(PF_UNIX, SOCK_STREAM, 0);
 126         if (fd < 0) {
 127                 ERROR("socket : %s", strerror(errno));
 128                 return -1;
 129         }
 130
 131         for (retry = 0; retry < sizeof(backoff_ms)/sizeof(backoff_ms[0]); retry++) {
 132                 ret = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
 133                 if (ret == 0 || errno != ECONNREFUSED)
 134                         break;
 135                 ERROR("connect : backing off %d", backoff_ms[retry]);
 136                 usleep(backoff_ms[retry] * 1000);
 137         }
 138
 139         if (ret < 0) {
 140                 ERROR("connect : %s", strerror(errno));
 141                 goto err1;
 142         }
 143         return fd;
 144 err1:
 145         close(fd);
 146         return ret;
 147 }
 148
 149 int lxc_monitor_read_timeout(int fd, struct lxc_msg *msglxc, int timeout)
 150 {
 151         fd_set rfds;
 152         struct timeval tv;
 153         int ret;
 154
 155         if (timeout != -1) {
 156                 FD_ZERO(&rfds);
 157                 FD_SET(fd, &rfds);
 158
 159                 tv.tv_sec = timeout;
 160                 tv.tv_usec = 0;
 161
 162                 ret = select(fd+1, &rfds, NULL, NULL, &tv);
 163                 if (ret == -1)
 164                         return -1;
 165                 else if (!ret)
 166                         return -2;  // timed out
 167         }
 168
 169         ret = recv(fd, msglxc, sizeof(*msglxc), 0);
 170         if (ret <= 0) {
 171                 SYSERROR("client failed to recv (monitord died?) %s",
 172                          strerror(errno));
 173                 return -1;
 174         }
 175         return ret;
 176 }
 177
 178 int lxc_monitor_read(int fd, struct lxc_msg *msg)
 179 {
 180         return lxc_monitor_read_timeout(fd, msg, -1);
 181 }
 182
 183
 184
 185 /* used to spawn a monitord either on startup of a daemon container, or when
 186  * lxc-monitor starts
 187  */
 188 int lxc_monitord_spawn(const char *lxcpath)
 189 {
 190         pid_t pid1,pid2;
 191         int pipefd[2];
 192         char pipefd_str[11];
 193
 194         char * const args[] = {
 195                 "/usr/bin/lxc-monitord",
 196                 (char *)lxcpath,
 197                 pipefd_str,
 198                 NULL,
 199         };
 200
 201         /* double fork to avoid zombies when monitord exits */
 202         pid1 = fork();
 203         if (pid1 < 0) {
 204                 SYSERROR("failed to fork");
 205                 return -1;
 206         }
 207
 208         if (pid1) {
 209                 waitpid(pid1, NULL, 0);
 210                 return 0;
 211         }
 212
 213         if (pipe(pipefd) < 0) {
 214                 SYSERROR("failed to create pipe");
 215                 exit(EXIT_FAILURE);
 216         }
 217
 218         pid2 = fork();
 219         if (pid2 < 0) {
 220                 SYSERROR("failed to fork");
 221                 exit(EXIT_FAILURE);
 222         }
 223         if (pid2) {
 224                 char c;
 225                 /* wait for daemon to create socket */
 226                 close(pipefd[1]);
 227                 /* sync with child, we're ignoring the return from read
 228                  * because regardless if it works or not, either way we've
 229                  * synced with the child process. the if-empty-statement
 230                  * construct is to quiet the warn-unused-result warning.
 231                  */
 232                 if (read(pipefd[0], &c, 1)) ;
 233                 close(pipefd[0]);
 234                 exit(EXIT_SUCCESS);
 235         }
 236
 237         umask(0);
 238         if (setsid() < 0) {
 239                 SYSERROR("failed to setsid");
 240                 exit(EXIT_FAILURE);
 241         }
 242         close(0);
 243         close(1);
 244         close(2);
 245         open("/dev/null", O_RDONLY);
 246         open("/dev/null", O_RDWR);
 247         open("/dev/null", O_RDWR);
 248         close(pipefd[0]);
 249         sprintf(pipefd_str, "%d", pipefd[1]);
 250         execvp(args[0], args);
 251         exit(EXIT_FAILURE);
 252 }