libmultipath/uevent.c

   1 /*
   2  * uevent.c - trigger upon netlink uevents from the kernel
   3  *
   4  *      Only kernels from version 2.6.10* on provide the uevent netlink socket.
   5  *      Until the libc-kernel-headers are updated, you need to compile with:
   6  *
   7  *        gcc -I /lib/modules/`uname -r`/build/include -o uevent_listen uevent_listen.c
   8  *
   9  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
  10  *
  11  *      This program is free software; you can redistribute it and/or modify it
  12  *      under the terms of the GNU General Public License as published by the
  13  *      Free Software Foundation version 2 of the License.
  14  *
  15  *      This program is distributed in the hope that it will be useful, but
  16  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  17  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  *      General Public License for more details.
  19  *
  20  *      You should have received a copy of the GNU General Public License along
  21  *      with this program; if not, write to the Free Software Foundation, Inc.,
  22  *      675 Mass Ave, Cambridge, MA 02139, USA.
  23  *
  24  */
  25
  26 #include <unistd.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <stddef.h>
  30 #include <string.h>
  31 #include <fcntl.h>
  32 #include <time.h>
  33 #include <sys/socket.h>
  34 #include <sys/user.h>
  35 #include <sys/un.h>
  36 #include <linux/types.h>
  37 #include <linux/netlink.h>
  38 #include <pthread.h>
  39 #include <sys/mman.h>
  40
  41 #include "memory.h"
  42 #include "debug.h"
  43 #include "uevent.h"
  44
  45 typedef int (uev_trigger)(struct uevent *, void * trigger_data);
  46
  47 pthread_t uevq_thr;
  48 struct uevent *uevqhp, *uevqtp;
  49 pthread_mutex_t uevq_lock, *uevq_lockp = &uevq_lock;
  50 pthread_mutex_t uevc_lock, *uevc_lockp = &uevc_lock;
  51 pthread_cond_t  uev_cond,  *uev_condp  = &uev_cond;
  52 uev_trigger *my_uev_trigger;
  53 void * my_trigger_data;
  54
  55 struct uevent * alloc_uevent (void)
  56 {
  57         return (struct uevent *)MALLOC(sizeof(struct uevent));
  58 }
  59
  60 void
  61 service_uevq(void)
  62 {
  63         int empty;
  64         struct uevent *uev;
  65
  66         do {
  67                 pthread_mutex_lock(uevq_lockp);
  68                 empty = (uevqhp == NULL);
  69                 if (!empty) {
  70                         uev = uevqhp;
  71                         uevqhp = uev->next;
  72                         if (uevqtp == uev)
  73                                 uevqtp = uev->next;
  74                         pthread_mutex_unlock(uevq_lockp);
  75
  76                         if (my_uev_trigger && my_uev_trigger(uev,
  77                                                         my_trigger_data))
  78                                 condlog(0, "uevent trigger error");
  79
  80                         FREE(uev);
  81                 }
  82                 else {
  83                         pthread_mutex_unlock(uevq_lockp);
  84                 }
  85         } while (empty == 0);
  86 }
  87
  88 /*
  89  * Service the uevent queue.
  90  */
  91 static void *
  92 uevq_thread(void * et)
  93 {
  94         mlockall(MCL_CURRENT | MCL_FUTURE);
  95
  96         while (1) {
  97                 pthread_mutex_lock(uevc_lockp);
  98                 pthread_cond_wait(uev_condp, uevc_lockp);
  99                 pthread_mutex_unlock(uevc_lockp);
 100
 101                 service_uevq();
 102         }
 103 }
 104
 105 int uevent_listen(int (*uev_trigger)(struct uevent *, void * trigger_data),
 106                   void * trigger_data)
 107 {
 108         int sock;
 109         struct sockaddr_nl snl;
 110         struct sockaddr_un sun;
 111         socklen_t addrlen;
 112         int retval;
 113         int rcvbufsz = 128*1024;
 114         int rcvsz = 0;
 115         int rcvszsz = sizeof(rcvsz);
 116         unsigned int *prcvszsz = (unsigned int *)&rcvszsz;
 117         pthread_attr_t attr;
 118
 119         my_uev_trigger = uev_trigger;
 120         my_trigger_data = trigger_data;
 121
 122         /*
 123          * Queue uevents for service by dedicated thread so that the uevent
 124          * listening thread does not block on multipathd locks (vecs->lock)
 125          * thereby not getting to empty the socket's receive buffer queue
 126          * often enough.
 127          */
 128         uevqhp = uevqtp = NULL;
 129
 130         pthread_mutex_init(uevq_lockp, NULL);
 131         pthread_mutex_init(uevc_lockp, NULL);
 132         pthread_cond_init(uev_condp, NULL);
 133
 134         pthread_attr_init(&attr);
 135         pthread_attr_setstacksize(&attr, 64 * 1024);
 136         pthread_create(&uevq_thr, &attr, uevq_thread, NULL);
 137
 138         /*
 139          * First check whether we have a udev socket
 140          */
 141         memset(&sun, 0x00, sizeof(struct sockaddr_un));
 142         sun.sun_family = AF_LOCAL;
 143         strcpy(&sun.sun_path[1], "/org/kernel/dm/multipath_event");
 144         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(sun.sun_path+1) + 1;
 145
 146         sock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 147         if (sock >= 0) {
 148                 const int feature_on = 1;
 149
 150                 condlog(3, "reading events from udev socket.");
 151
 152                 /* the bind takes care of ensuring only one copy running */
 153                 retval = bind(sock, (struct sockaddr *) &sun, addrlen);
 154                 if (retval < 0) {
 155                         condlog(0, "bind failed, exit");
 156                         goto exit;
 157                 }
 158
 159                 /* enable receiving of the sender credentials */
 160                 setsockopt(sock, SOL_SOCKET, SO_PASSCRED,
 161                            &feature_on, sizeof(feature_on));
 162
 163         } else {
 164                 /* Fallback to read kernel netlink events */
 165                 memset(&snl, 0x00, sizeof(struct sockaddr_nl));
 166                 snl.nl_family = AF_NETLINK;
 167                 snl.nl_pid = getpid();
 168                 snl.nl_groups = 0xffffffff;
 169
 170                 sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
 171                 if (sock == -1) {
 172                         condlog(0, "error getting socket, exit");
 173                         return 1;
 174                 }
 175
 176                 condlog(3, "reading events from kernel.");
 177
 178                 /*
 179                  * try to avoid dropping uevents, even so, this is not a guarantee,
 180                  * but it does help to change the netlink uevent socket's
 181                  * receive buffer threshold from the default value of 106,496 to
 182                  * the maximum value of 262,142.
 183                  */
 184                 retval = setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &rcvbufsz,
 185                                     sizeof(rcvbufsz));
 186
 187                 if (retval < 0) {
 188                         condlog(0, "error setting receive buffer size for socket, exit");
 189                         exit(1);
 190                 }
 191                 retval = getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &rcvsz, prcvszsz);
 192                 if (retval < 0) {
 193                         condlog(0, "error setting receive buffer size for socket, exit");
 194                         exit(1);
 195                 }
 196                 condlog(3, "receive buffer size for socket is %u.", rcvsz);
 197
 198                 retval = bind(sock, (struct sockaddr *) &snl,
 199                               sizeof(struct sockaddr_nl));
 200                 if (retval < 0) {
 201                         condlog(0, "bind failed, exit");
 202                         goto exit;
 203                 }
 204         }
 205
 206         while (1) {
 207                 static char buff[HOTPLUG_BUFFER_SIZE + OBJECT_SIZE];
 208                 int i;
 209                 char *pos;
 210                 size_t bufpos;
 211                 ssize_t buflen;
 212                 struct uevent *uev;
 213                 char *buffer;
 214
 215                 buflen = recv(sock, &buff, sizeof(buff), 0);
 216                 if (buflen <  0) {
 217                         condlog(0, "error receiving message");
 218                         continue;
 219                 }
 220
 221                 if ((size_t)buflen > sizeof(buff)-1)
 222                         buflen = sizeof(buff)-1;
 223
 224                 uev = alloc_uevent();
 225
 226                 if (!uev) {
 227                         condlog(1, "lost uevent, oom");
 228                         continue;
 229                 }
 230
 231                 /*
 232                  * Copy the shared receive buffer contents to buffer private
 233                  * to this uevent so we can immediately reuse the shared buffer.
 234                  */
 235                 memcpy(uev->buffer, buff, HOTPLUG_BUFFER_SIZE + OBJECT_SIZE);
 236                 buffer = uev->buffer;
 237                 buffer[buflen] = '\0';
 238
 239                 /* save start of payload */
 240                 bufpos = strlen(buffer) + 1;
 241
 242                 /* action string */
 243                 uev->action = buffer;
 244                 pos = strchr(buffer, '@');
 245                 if (!pos)
 246                         continue;
 247                 pos[0] = '\0';
 248
 249                 /* sysfs path */
 250                 uev->devpath = &pos[1];
 251
 252                 /* hotplug events have the environment attached - reconstruct envp[] */
 253                 for (i = 0; (bufpos < (size_t)buflen) && (i < HOTPLUG_NUM_ENVP-1); i++) {
 254                         int keylen;
 255                         char *key;
 256
 257                         key = &buffer[bufpos];
 258                         keylen = strlen(key);
 259                         uev->envp[i] = key;
 260                         bufpos += keylen + 1;
 261                 }
 262                 uev->envp[i] = NULL;
 263
 264                 condlog(3, "uevent '%s' from '%s'", uev->action, uev->devpath);
 265
 266                 /* print payload environment */
 267                 for (i = 0; uev->envp[i] != NULL; i++)
 268                         condlog(3, "%s", uev->envp[i]);
 269
 270                 /*
 271                  * Queue uevent and poke service pthread.
 272                  */
 273                 pthread_mutex_lock(uevq_lockp);
 274                 if (uevqtp)
 275                         uevqtp->next = uev;
 276                 else
 277                         uevqhp = uev;
 278                 uevqtp = uev;
 279                 uev->next = NULL;
 280                 pthread_mutex_unlock(uevq_lockp);
 281
 282                 pthread_mutex_lock(uevc_lockp);
 283                 pthread_cond_signal(uev_condp);
 284                 pthread_mutex_unlock(uevc_lockp);
 285         }
 286
 287 exit:
 288         close(sock);
 289
 290         pthread_mutex_lock(uevq_lockp);
 291         pthread_cancel(uevq_thr);
 292         pthread_mutex_unlock(uevq_lockp);
 293
 294         pthread_mutex_destroy(uevq_lockp);
 295         pthread_mutex_destroy(uevc_lockp);
 296         pthread_cond_destroy(uev_condp);
 297
 298         return 1;
 299 }