lib: Add lockfile

The pid of the IRMd is stored in a lockfile in shared memory. This
makes checking if the IRMd is running independent of the
configuration, as previously the IRMd pid was stored at the end of the
shm_du_map, which could not be read by an IRMd that would be compiled
with different configuration options.

Also corrects some unnecessary includes

Fixes #21.

4 files changed, 181 insertions, 14 deletions

diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index 9c45269c..a440f7be 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -31,6 +31,7 @@ set(SOURCE_FILES
   ipcp.c
   irm.c
   list.c
+  lockfile.c
   logs.c
   nsm.c
   shm_ap_rbuff.c
diff --git a/src/lib/lockfile.c b/src/lib/lockfile.c
new file mode 100644
index 00000000..a93d5f17
--- /dev/null
+++ b/src/lib/lockfile.c
@@ -0,0 +1,170 @@
+/*
+ * Ouroboros - Copyright (C) 2016
+ *
+ * Lockfile for ouroboros system
+ *
+ *    Dimitri Staessens <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <ouroboros/config.h>
+#include <ouroboros/lockfile.h>
+
+#define OUROBOROS_PREFIX "lockfile"
+
+#include <ouroboros/logs.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#define LF_SIZE (sizeof(pid_t))
+
+struct lockfile {
+        pid_t * api;
+        int fd;
+};
+
+struct lockfile * lockfile_create() {
+        struct lockfile * lf = malloc(sizeof(*lf));
+        if (lf == NULL)
+                return NULL;
+
+        lf->fd = shm_open(LOCKFILE_NAME, O_CREAT | O_EXCL | O_RDWR, 0666);
+        if (lf->fd == -1) {
+                LOG_DBGF("Could not create lock file.");
+                free(lf);
+                return NULL;
+        }
+
+        if (fchmod(lf->fd, 0666)) {
+                LOG_DBGF("Failed to chmod lockfile.");
+                free(lf);
+                return NULL;
+        }
+
+        if (lseek(lf->fd, LF_SIZE - 1, SEEK_SET) < 0) {
+                LOG_DBGF("Failed to extend lockfile.");
+                free(lf);
+                return NULL;
+        }
+
+        if (write(lf->fd, "", 1) != 1) {
+                LOG_DBGF("Failed to finalise lockfile.");
+                free(lf);
+                return NULL;
+        }
+
+        lf->api = mmap(NULL,
+                       LF_SIZE, PROT_READ | PROT_WRITE,
+                       MAP_SHARED,
+                       lf->fd,
+                       0);
+
+        if (lf->api == MAP_FAILED) {
+                LOG_DBGF("Failed to map lockfile.");
+
+                if (shm_unlink(LOCKFILE_NAME) == -1)
+                        LOG_DBGF("Failed to remove invalid lockfile.");
+
+                free(lf);
+                return NULL;
+        }
+
+        *lf->api = getpid();
+
+        return lf;
+}
+
+struct lockfile * lockfile_open() {
+        struct lockfile * lf = malloc(sizeof(*lf));
+        if (lf == NULL)
+                return NULL;
+
+        lf->fd = shm_open(LOCKFILE_NAME, O_RDWR, 0666);
+        if (lf->fd == -1) {
+                LOG_DBGF("Could not open lock file.");
+                free(lf);
+                return NULL;
+        }
+
+        lf->api = mmap(NULL,
+                       LF_SIZE, PROT_READ | PROT_WRITE,
+                       MAP_SHARED,
+                       lf->fd,
+                       0);
+
+        if (lf->api == MAP_FAILED) {
+                LOG_DBGF("Failed to map lockfile.");
+
+                if (shm_unlink(LOCKFILE_NAME) == -1)
+                        LOG_DBGF("Failed to remove invalid lockfile.");
+
+                free(lf);
+                return NULL;
+        }
+
+        return lf;
+}
+
+void lockfile_close(struct lockfile * lf)
+{
+        if (lf == NULL) {
+                LOG_DBGF("Bogus input. Bugging out.");
+                return;
+        }
+
+        if (close(lf->fd) < 0)
+                LOG_DBGF("Couldn't close lockfile.");
+
+        if (munmap(lf->api, LF_SIZE) == -1)
+                LOG_DBGF("Couldn't unmap lockfile.");
+
+        free(lf);
+}
+
+void lockfile_destroy(struct lockfile * lf)
+{
+        if (lf == NULL) {
+                LOG_DBGF("Bogus input. Bugging out.");
+                return;
+        }
+
+        if (getpid() != *lf->api && kill(*lf->api, 0) == 0) {
+                LOG_DBGF("Only IRMd can destroy %s.", LOCKFILE_NAME);
+                return;
+        }
+
+        if (close(lf->fd) < 0)
+                LOG_DBGF("Couldn't close lockfile.");
+
+        if (munmap(lf->api, LF_SIZE) == -1)
+                LOG_DBGF("Couldn't unmap lockfile.");
+
+        if (shm_unlink(LOCKFILE_NAME) == -1)
+                LOG_DBGF("Failed to remove lockfile.");
+
+        free(lf);
+}
+
+pid_t lockfile_owner(struct lockfile * lf)
+{
+        return *lf->api;
+}
diff --git a/src/lib/shm_ap_rbuff.c b/src/lib/shm_ap_rbuff.c
index 4eb91136..cf795601 100644
--- a/src/lib/shm_ap_rbuff.c
+++ b/src/lib/shm_ap_rbuff.c
@@ -26,7 +26,7 @@
 
 #include <ouroboros/logs.h>
 #include <ouroboros/shm_ap_rbuff.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/lockfile.h>
 
 #include <pthread.h>
 #include <sys/mman.h>
@@ -215,7 +215,7 @@ void shm_ap_rbuff_close(struct shm_ap_rbuff * rb)
 void shm_ap_rbuff_destroy(struct shm_ap_rbuff * rb)
 {
         char fn[25];
-        struct shm_du_map * dum = NULL;
+        struct lockfile * lf = NULL;
 
         if (rb == NULL) {
                 LOG_DBGF("Bogus input. Bugging out.");
@@ -223,15 +223,17 @@ void shm_ap_rbuff_destroy(struct shm_ap_rbuff * rb)
         }
 
         if (rb->api != getpid()) {
-                dum = shm_du_map_open();
-                if (shm_du_map_owner(dum) == getpid()) {
+                lf = lockfile_open();
+                if (lf == NULL)
+                        return;
+                if (lockfile_owner(lf) == getpid()) {
                         LOG_DBGF("Ringbuffer %d destroyed by IRMd %d.",
                                  rb->api, getpid());
-                        shm_du_map_close(dum);
+                        lockfile_close(lf);
                 } else {
                         LOG_ERR("AP-I %d tried to destroy rbuff owned by %d.",
                                 getpid(), rb->api);
-                        shm_du_map_close(dum);
+                        lockfile_close(lf);
                         return;
                 }
         }
diff --git a/src/lib/shm_du_map.c b/src/lib/shm_du_map.c
index 53959676..01d1e23d 100644
--- a/src/lib/shm_du_map.c
+++ b/src/lib/shm_du_map.c
@@ -29,9 +29,11 @@
 #include <pthread.h>
 #include <sys/mman.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <stdlib.h>
 #include <string.h>
 #include <signal.h>
+#include <errno.h>
 #include <sys/stat.h>
 
 #define OUROBOROS_PREFIX "shm_du_map"
@@ -270,14 +272,6 @@ struct shm_du_map * shm_du_map_open()
         return dum;
 }
 
-pid_t shm_du_map_owner(struct shm_du_map * dum)
-{
-        if (dum == NULL)
-                return -1;
-
-        return *dum->api;
-}
-
 void * shm_du_map_sanitize(void * o)
 {
         struct shm_du_map * dum = (struct shm_du_map *) o;