libxl: Add libxl__prepare_sockaddr_un() helper

There is going to be a few more users that want to use UNIX socket, this
helper is to prepare the `struct sockaddr_un` and check that the path
isn't too long.

Also start to use it in libxl_qmp.c.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxl/libxl_internal.h

@@ -47,6 +47,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/socket.h>
+#include <sys/un.h>
 #include <sys/file.h>
 #include <sys/ioctl.h>
 
@@ -4420,6 +4421,9 @@ static inline bool libxl__string_is_default(char **s)
 {
     return *s == NULL;
 }
+
+_hidden int libxl__prepare_sockaddr_un(libxl__gc *gc, struct sockaddr_un *un,
+                                       const char *path, const char *what);
 #endif
 
 /*

tools/libxl/libxl_qmp.c

@@ -428,6 +428,7 @@ static libxl__qmp_handler *qmp_init_handler(libxl__gc *gc, uint32_t domid)
 static int qmp_open(libxl__qmp_handler *qmp, const char *qmp_socket_path,
                     int timeout)
 {
+    GC_INIT(qmp->ctx);
     int ret = -1;
     int i = 0;
     struct sockaddr_un addr;
@@ -447,13 +448,9 @@ static int qmp_open(libxl__qmp_handler *qmp, const char *qmp_socket_path,
         goto out;
     }
 
-    if (sizeof(addr.sun_path) <= strlen(qmp_socket_path)) {
-        ret = -1;
+    ret = libxl__prepare_sockaddr_un(gc, &addr, qmp_socket_path, "QMP socket");
+    if (ret)
         goto out;
-    }
-    memset(&addr, 0, sizeof(addr));
-    addr.sun_family = AF_UNIX;
-    strncpy(addr.sun_path, qmp_socket_path, sizeof(addr.sun_path));
 
     do {
         ret = connect(qmp->qmp_fd, (struct sockaddr *) &addr, sizeof(addr));
@@ -471,6 +468,7 @@ static int qmp_open(libxl__qmp_handler *qmp, const char *qmp_socket_path,
 out:
     if (ret == -1 && qmp->qmp_fd > -1) close(qmp->qmp_fd);
 
+    GC_FREE;
     return ret;
 }
 

tools/libxl/libxl_utils.c

@@ -1234,6 +1234,21 @@ int libxl__random_bytes(libxl__gc *gc, uint8_t *buf, size_t len)
     return ret;
 }
 
+int libxl__prepare_sockaddr_un(libxl__gc *gc,
+                               struct sockaddr_un *un, const char *path,
+                               const char *what)
+{
+    if (sizeof(un->sun_path) <= strlen(path)) {
+        LOG(ERROR, "UNIX socket path '%s' is too long for %s", path, what);
+        LOG(DEBUG, "Path must be less than %zu bytes", sizeof(un->sun_path));
+        return ERROR_INVAL;
+    }
+    memset(un, 0, sizeof(struct sockaddr_un));
+    un->sun_family = AF_UNIX;
+    strncpy(un->sun_path, path, sizeof(un->sun_path));
+    return 0;
+}
+
 /*
  * Local variables:
  * mode: C