[stgt] [PATCH v2] handle SEM Key clash between multiple tgt instances

[Or Gerlitz]

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 management socket file using ftok(3). Renamed the variable name for
the array that holds the management socket path on both mgmt.c & tgtadm.c

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

---

changes from v1:
	removed "extern char mgmt_path[]" from ipc_init in mgmt.c
	made a comment on the path to mgmt_path var name change at the changelog

 usr/log.c    |   15 +++++++++++++--
 usr/mgmt.c   |    8 ++++----
 usr/tgtadm.c |    6 +++---
 3 files changed, 20 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..b1c118e 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 +568,6 @@ int ipc_init(void)
 	extern short control_port;
 	int fd, err;
 	struct sockaddr_un addr;
-	char path[256];

 	fd = socket(AF_LOCAL, SOCK_STREAM, 0);
 	if (fd < 0) {
@@ -575,11 +575,11 @@ 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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