[lxc-devel] [PATCH] Use container specific domain socket name

[S.Çağlar Onur]

From: "S.Çağlar Onur" <caglar at 10ur.org>

Otherwise trying to start N containers in parallel gives "lxc_container: bind : Address already in use" error.

Found while using Go bindings to create/start/stop large number of containers in parallel so I reproduced the same using Python API to rule out possible Go related problems.

----
import lxc

from queue import Empty
from multiprocessing import Process, Queue

def create(q):
    while True:
        try:
            x = q.get(block=False)
            c = lxc.Container(str(x))
            print("Starting", x)
            c.start()
        except Empty:
            break

if __name__=="__main__":
    work_queue = Queue()
    for i in range(11):
        work_queue.put(i)

    process = [Process(target=create, args=(work_queue,)) for i in range(4)]
    for p in process:
        p.start()

    for p in process:
        p.join()
----

caglar at qgq:~/Project$ sudo python3 cstart.py
Starting 0
Starting 1
lxc_container: bind : Address already in use
Starting 3
Starting 4
Starting 2
lxc_container: lxc_container: bind : Address already in use
bind : Address already in uselxc_container: bind : Address already in use

Starting 5
Starting 6
lxc_container: bind : Address already in use
lxc_container: bind : Address already in use
Starting 7
Starting 8
Starting 9
lxc_container: bind : Address already in use
lxc_container: bind : Address already in use
lxc_container: bind : Address already in use
Starting 10
lxc_container: bind : Address already in use

Signed-off-by: S.Çağlar Onur <caglar at 10ur.org>
---
 src/lxc/lxc.h         |    2 +-
 src/lxc/lxc_monitor.c |    2 +-
 src/lxc/monitor.c     |   10 +++++-----
 src/lxc/state.c       |    2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/lxc/lxc.h b/src/lxc/lxc.h
index db921f0..224d460 100644
--- a/src/lxc/lxc.h
+++ b/src/lxc/lxc.h
@@ -74,7 +74,7 @@ extern int lxc_execute(const char *name, char *const argv[], int quiet,
  * The function will return an fd corresponding to the events
  * Returns a file descriptor on success, < 0 otherwise
  */
-extern int lxc_monitor_open(const char *lxcpath);
+extern int lxc_monitor_open(const char *lxcpath, const char *lxcname);
 
 /*
  * Read the state of the container if this one has changed
diff --git a/src/lxc/lxc_monitor.c b/src/lxc/lxc_monitor.c
index 0530373..4898377 100644
--- a/src/lxc/lxc_monitor.c
+++ b/src/lxc/lxc_monitor.c
@@ -87,7 +87,7 @@ int main(int argc, char *argv[])
 		return -1;
 	}
 
-	fd = lxc_monitor_open(my_args.lxcpath);
+	fd = lxc_monitor_open(my_args.lxcpath, my_args.name);
 	if (fd < 0)
 		return -1;
 
diff --git a/src/lxc/monitor.c b/src/lxc/monitor.c
index afdaf67..2590559 100644
--- a/src/lxc/monitor.c
+++ b/src/lxc/monitor.c
@@ -47,7 +47,7 @@ lxc_log_define(lxc_monitor, lxc);
 #define UNIX_PATH_MAX 108
 #endif
 
-static void lxc_monitor_send(struct lxc_msg *msg, const char *lxcpath)
+static void lxc_monitor_send(struct lxc_msg *msg, const char *lxcpath, const char *lxcname)
 {
 	int fd;
 	struct sockaddr_un addr = { .sun_family = AF_UNIX };
@@ -59,7 +59,7 @@ static void lxc_monitor_send(struct lxc_msg *msg, const char *lxcpath)
 	 * should we take a hash of lxcpath?  a subset of it?
 	 */
 	len = sizeof(addr.sun_path) - 1;
-	ret = snprintf(offset, len, "%s/lxc-monitor", lxcpath);
+	ret = snprintf(offset, len, "%s/%s-monitor", lxcpath, lxcname);
 	if (ret < 0 || ret >= len) {
 		ERROR("lxcpath too long to open monitor");
 		return;
@@ -82,10 +82,10 @@ void lxc_monitor_send_state(const char *name, lxc_state_t state, const char *lxc
 	strncpy(msg.name, name, sizeof(msg.name));
 	msg.name[sizeof(msg.name) - 1] = 0;
 
-	lxc_monitor_send(&msg, lxcpath);
+	lxc_monitor_send(&msg, lxcpath, name);
 }
 
-int lxc_monitor_open(const char *lxcpath)
+int lxc_monitor_open(const char *lxcpath, const char *lxcname)
 {
 	struct sockaddr_un addr = { .sun_family = AF_UNIX };
 	char *offset = &addr.sun_path[1];
@@ -97,7 +97,7 @@ int lxc_monitor_open(const char *lxcpath)
 	 * should we take a hash of lxcpath?  a subset of it?
 	 */
 	len = sizeof(addr.sun_path) - 1;
-	ret = snprintf(offset, len, "%s/lxc-monitor", lxcpath);
+	ret = snprintf(offset, len, "%s/%s-monitor", lxcpath, lxcname);
 	if (ret < 0 || ret >= len) {
 		ERROR("lxcpath too long to open monitor");
 		return -1;
diff --git a/src/lxc/state.c b/src/lxc/state.c
index 3e7e94a..454c02e 100644
--- a/src/lxc/state.c
+++ b/src/lxc/state.c
@@ -201,7 +201,7 @@ extern int lxc_wait(const char *lxcname, const char *states, int timeout, const
 	if (fillwaitedstates(states, s))
 		return -1;
 
-	fd = lxc_monitor_open(lxcpath);
+	fd = lxc_monitor_open(lxcpath, lxcname);
 	if (fd < 0)
 		return -1;
 
-- 
1.7.10.4