1 files changed, 139 insertions, 0 deletions
diff --git a/test/nsholder.c b/test/nsholder.c
new file mode 100644
index 0000000..aac901b
--- /dev/null
+++ b/test/nsholder.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+/* nsholder - maintain a namespace to be entered by other processes
+ *
+ * Copyright Red Hat
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * Can run in 3 modes:
+ *
+ *   nsholder <path> hold
+ *      Designed to be run inside a namespace, opens a Unix domain
+ *      control socket at <path> and waits until instructed to stop
+ *      with "nsholder <path> stop"
+ *   nsholder <path> pid
+ *      Prints the PID of the nsholder hold process with control
+ *      socket <path>.  This is given in the PID namespace where
+ *      nsholder pid is executed, not the one where nsholder hold is
+ *      running
+ *   nsholder <path> stop
+ *      Instruct the nsholder hold with control socket at <path> to exit.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <linux/un.h>
+
+#define die(...)				\
+	do {					\
+		fprintf(stderr, __VA_ARGS__);	\
+		exit(1);			\
+	} while (0)
+
+static void usage(void)
+{
+	die("Usage: holder <socket path> hold|pid\n");
+}
+
+static void hold(int fd, const struct sockaddr_un *addr)
+{
+	int rc;
+
+	rc = bind(fd, (struct sockaddr *)addr, sizeof(*addr));
+	if (rc < 0)
+		die("bind(): %s\n", strerror(errno));
+
+	rc = listen(fd, 0);
+	if (rc < 0)
+		die("listen(): %s\n", strerror(errno));
+
+	printf("nsholder: local PID=%d  local UID=%d  local GID=%d\n",
+	       getpid(), getuid(), getgid());
+	do {
+		int afd = accept(fd, NULL, NULL);
+		char buf;
+
+		if (afd < 0)
+			die("accept(): %s\n", strerror(errno));
+
+		rc = read(afd, &buf, sizeof(buf));
+		if (rc < 0)
+			die("read(): %s\n", strerror(errno));
+	} while (rc == 0);
+
+	unlink(addr->sun_path);
+}
+
+static void pid(int fd, const struct sockaddr_un *addr)
+{
+	int rc;
+	struct ucred peercred;
+	socklen_t optlen = sizeof(peercred);
+
+	do {
+		rc = connect(fd, (struct sockaddr *)addr, sizeof(*addr));
+		if (rc < 0 && errno != ENOENT && errno != ECONNREFUSED)
+			die("connect(): %s\n", strerror(errno));
+	} while (rc < 0);
+
+	rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
+			&peercred, &optlen);
+	if (rc < 0)
+		die("getsockopet(SO_PEERCRED): %s\n", strerror(errno));
+
+	close(fd);
+
+	printf("%d\n", peercred.pid);
+}
+
+static void stop(int fd, const struct sockaddr_un *addr)
+{
+	int rc;
+	char buf = 'Q';
+
+	rc = connect(fd, (struct sockaddr *)addr, sizeof(*addr));
+	if (rc < 0)
+		die("connect(): %s\n", strerror(errno));
+
+	rc = write(fd, &buf, sizeof(buf));
+	if (rc < 0)
+		die("write(): %s\n",  strerror(errno));
+
+	close(fd);
+}
+
+int main(int argc, char *argv[])
+{
+	int fd;
+	const char *sockname;
+	struct sockaddr_un sockaddr = {
+		.sun_family = AF_UNIX,
+	};
+
+	if (argc != 3)
+		usage();
+
+	sockname = argv[1];
+	strncpy(sockaddr.sun_path, sockname, UNIX_PATH_MAX);
+
+	fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
+	if (fd < 0)
+		die("socket(): %s\n", strerror(errno));
+
+	if (strcmp(argv[2], "hold") == 0)
+		hold(fd, &sockaddr);
+	else if (strcmp(argv[2], "pid") == 0)
+		pid(fd, &sockaddr);
+	else if (strcmp(argv[2], "stop") == 0)
+		stop(fd, &sockaddr);
+	else
+		usage();
+
+	exit(0);
+}