[stgt] [PATCH] handle SEM Key clash between multiple tgt instances

[Or Gerlitz]

From: Roland Friedwagner <roland.friedwagner at wu.ac.at>

commit e2f95b537 "semaphore key clash with Open-iSCSI initiator" didn't
address a further clash introduced when multiple tgt instances are
running. Address that by creating the IPC semaphore keyid based on
the managment socket file using ftok(3).

Signed-off-by: Roland Friedwagner <roland.friedwagner at wu.ac.at>
Signed-off-by: Or Gerlitz <ogerlitz at mellanox.com>

---
 usr/log.c    |   15 +++++++++++++--
 usr/mgmt.c   |    9 +++++----
 usr/tgtadm.c |    6 +++---
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/usr/log.c b/usr/log.c
index 06cd8bf..2f0c4d4 100644
--- a/usr/log.c
+++ b/usr/log.c
@@ -33,7 +33,6 @@

 #include "log.h"

-#define SEMKEY	0x54475444L /* TGTD */
 #define LOGDBG 0

 #if LOGDBG
@@ -50,6 +49,8 @@ static pid_t pid;
 static int logarea_init (int size)
 {
 	int shmid;
+	extern char mgmt_path[];
+	key_t semkey;

 	logdbg(stderr,"enter logarea_init\n");

@@ -109,13 +110,23 @@ static int logarea_init (int size)

 	shmctl(shmid, IPC_RMID, NULL);

-	if ((la->semid = semget(SEMKEY, 1, 0666 | IPC_CREAT)) < 0) {
+	if ((semkey = ftok(mgmt_path, 'a')) < 0) {
+		syslog(LOG_ERR, "semkey failed %d", errno);
+		return 1;
+	}
+
+        if ((semget(semkey, 0, IPC_EXCL)) > 0) {
+		/* Semkey may exists after SIGKILL tgtd */
+		syslog(LOG_WARNING, "semkey 0x%x already exists", semkey);
+	}
+	if ((la->semid = semget(semkey, 1, 0666 | IPC_CREAT)) < 0) {
 		syslog(LOG_ERR, "semget failed %d", errno);
 		shmdt(la->buff);
 		shmdt(la->start);
 		shmdt(la);
 		return 1;
 	}
+	syslog(LOG_INFO, "semkey 0x%x", semkey);

 	la->semarg.val=1;
 	if (semctl(la->semid, 0, SETVAL, la->semarg) < 0) {
diff --git a/usr/mgmt.c b/usr/mgmt.c
index 5a6a03b..fb703a6 100644
--- a/usr/mgmt.c
+++ b/usr/mgmt.c
@@ -59,6 +59,7 @@ struct mgmt_task {
 };

 static int ipc_fd;
+char mgmt_path[256];

 static void set_show_results(struct tgtadm_rsp *rsp, int *err)
 {
@@ -567,7 +568,7 @@ int ipc_init(void)
 	extern short control_port;
 	int fd, err;
 	struct sockaddr_un addr;
-	char path[256];
+	extern char mgmt_path[];

 	fd = socket(AF_LOCAL, SOCK_STREAM, 0);
 	if (fd < 0) {
@@ -575,11 +576,11 @@ int ipc_init(void)
 		return -1;
 	}

-	sprintf(path, "%s.%d", TGT_IPC_NAMESPACE, control_port);
-	unlink(path);
+	sprintf(mgmt_path, "%s.%d", TGT_IPC_NAMESPACE, control_port);
+	unlink(mgmt_path);
 	memset(&addr, 0, sizeof(addr));
 	addr.sun_family = AF_LOCAL;
-	strncpy(addr.sun_path, path, sizeof(addr.sun_path));
+	strncpy(addr.sun_path, mgmt_path, sizeof(addr.sun_path));

 	err = bind(fd, (struct sockaddr *) &addr, sizeof(addr));
 	if (err) {
diff --git a/usr/tgtadm.c b/usr/tgtadm.c
index e81a419..9821917 100644
--- a/usr/tgtadm.c
+++ b/usr/tgtadm.c
@@ -190,7 +190,7 @@ static int ipc_mgmt_connect(int *fd)
 {
 	int err;
 	struct sockaddr_un addr;
-	char path[256];
+	char mgmt_path[256];

 	*fd = socket(AF_LOCAL, SOCK_STREAM, 0);
 	if (*fd < 0) {
@@ -200,8 +200,8 @@ static int ipc_mgmt_connect(int *fd)

 	memset(&addr, 0, sizeof(addr));
 	addr.sun_family = AF_LOCAL;
-	sprintf(path, "%s.%d", TGT_IPC_NAMESPACE, control_port);
-	strncpy(addr.sun_path, path, sizeof(addr.sun_path));
+	sprintf(mgmt_path, "%s.%d", TGT_IPC_NAMESPACE, control_port);
+	strncpy(addr.sun_path, mgmt_path, sizeof(addr.sun_path));

 	err = connect(*fd, (struct sockaddr *) &addr, sizeof(addr));
 	if (err < 0)
--
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