nstool: Detect what namespaces target is in

Give nstool the ability to detect what namespaces the target process is in,
relative to where it's called.  That is, those namespace types for which
the target is not in the same namespace as the caller.  For now, just
print this information with "info", which can be useful for debugging.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 143 insertions, 14 deletions

diff --git a/test/nstool.c b/test/nstool.c
index 345b908..2682c6b 100644
--- a/test/nstool.c
+++ b/test/nstool.c
@@ -15,8 +15,13 @@
 #include <errno.h>
 #include <unistd.h>
 #include <getopt.h>
+#include <stdarg.h>
+#include <limits.h>
 #include <sys/socket.h>
 #include <linux/un.h>
+#include <sched.h>
+
+#define	ARRAY_SIZE(a)	((int)(sizeof(a) / sizeof((a)[0])))
 
 #define die(...)				\
 	do {					\
@@ -24,6 +29,28 @@
 		exit(1);			\
 	} while (0)
 
+struct ns_type {
+	int flag;
+	const char *name;
+};
+
+const struct ns_type nstypes[] = {
+	{ CLONE_NEWCGROUP, "cgroup" },
+	{ CLONE_NEWIPC, "ipc" },
+	{ CLONE_NEWNET, "net" },
+	{ CLONE_NEWNS, "mnt" },
+	{ CLONE_NEWPID, "pid" },
+	{ CLONE_NEWTIME, "time" },
+	{ CLONE_NEWUSER, "user" },
+	{ CLONE_NEWUTS, "uts" },
+};
+
+struct holder_info {
+	pid_t pid;
+	uid_t uid;
+	gid_t gid;
+};
+
 static void usage(void)
 {
 	die("Usage:\n"
@@ -41,12 +68,16 @@ static void usage(void)
 	    "    terminate.\n");
 }
 
-static int connect_ctl(const char * sockpath, bool wait)
+static int connect_ctl(const char *sockpath, bool wait,
+		       struct holder_info *info,
+		       struct ucred *peercred)
 {
 	int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
 	struct sockaddr_un addr = {
 		.sun_family = AF_UNIX,
 	};
+	struct holder_info discard;
+	ssize_t len;
 	int rc;
 
 	if (fd < 0)
@@ -61,6 +92,28 @@ static int connect_ctl(const char * sockpath, bool wait)
 			die("connect() to %s: %s\n", sockpath, strerror(errno));
 	} while (rc < 0);
 
+	if (!info)
+		info = &discard;
+
+	/* Always read the info structure, even if we don't need it,
+	 * so that the holder doesn't get a broken pipe error
+	 */
+	len = read(fd, info, sizeof(*info));
+	if (len < 0)
+		die("read() on control socket %s: %s\n", sockpath, strerror(errno));
+	if ((size_t)len < sizeof(*info))
+		die("short read() on control socket %s\n", sockpath);
+
+	if (peercred) {
+		socklen_t optlen = sizeof(*peercred);
+
+		rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
+				peercred, &optlen);
+		if (rc < 0)
+			die("getsockopet(SO_PEERCRED) %s: %s\n",
+			    sockpath, strerror(errno));
+	}
+
 	return fd;
 }
 
@@ -71,6 +124,7 @@ static void cmd_hold(int argc, char *argv[])
 		.sun_family = AF_UNIX,
 	};
 	const char *sockpath = argv[1];
+	struct holder_info info;
 	int rc;
 
 	if (argc != 2)
@@ -89,8 +143,10 @@ static void cmd_hold(int argc, char *argv[])
 	if (rc < 0)
 		die("listen() on %s: %s\n", sockpath, strerror(errno));
 
-	printf("nstool hold: local PID=%d  local UID=%u  local GID=%u\n",
-	       getpid(), getuid(), getgid());
+	info.pid = getpid();
+	info.uid = getuid();
+	info.gid = getgid();
+
 	do {
 		int afd = accept(fd, NULL, NULL);
 		char buf;
@@ -98,6 +154,12 @@ static void cmd_hold(int argc, char *argv[])
 		if (afd < 0)
 			die("accept(): %s\n", strerror(errno));
 
+		rc = write(afd, &info, sizeof(info));
+		if (rc < 0)
+			die("write(): %s\n", strerror(errno));
+		if ((size_t)rc < sizeof(info))
+			die("short write() on control socket\n");
+
 		rc = read(afd, &buf, sizeof(buf));
 		if (rc < 0)
 			die("read(): %s\n", strerror(errno));
@@ -106,6 +168,68 @@ static void cmd_hold(int argc, char *argv[])
 	unlink(sockpath);
 }
 
+static ssize_t getlink(char *buf, size_t bufsiz, const char *fmt, ...)
+{
+	char linkpath[PATH_MAX];
+	ssize_t linklen;
+	va_list ap;
+
+	va_start(ap, fmt);
+	if (vsnprintf(linkpath, sizeof(linkpath), fmt, ap) >= PATH_MAX)
+		die("Truncated path \"%s\"\n", linkpath);
+	va_end(ap);
+
+	linklen = readlink(linkpath, buf, bufsiz);
+	if (linklen < 0)
+		die("readlink() on %s: %s\n", linkpath, strerror(errno));
+	if ((size_t)linklen >= bufsiz)
+		die("Target of symbolic link %s is too long\n", linkpath);
+
+	return linklen;
+}
+
+static int detect_namespaces(pid_t pid)
+{
+	int i;
+	int flags = 0;
+
+	for (i = 0; i < ARRAY_SIZE(nstypes); i++) {
+		const struct ns_type *nst = &nstypes[i];
+		char selflink[PATH_MAX], pidlink[PATH_MAX];
+		ssize_t selflen, pidlen;
+
+		selflen = getlink(selflink, sizeof(selflink),
+				  "/proc/self/ns/%s", nst->name);
+		pidlen = getlink(pidlink, sizeof(pidlink),
+				 "/proc/%d/ns/%s", pid, nst->name);
+
+		if ((selflen != pidlen) || memcmp(selflink, pidlink, selflen))
+			flags |= nst->flag;
+	}
+
+	return flags;
+}
+
+static void print_nstypes(int flags)
+{
+	bool first = true;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(nstypes); i++) {
+		const struct ns_type *nst = &nstypes[i];
+
+		if (!(flags & nst->flag))
+			continue;
+
+		printf("%s%s", first ? "" : ", " , nst->name);
+		first = false;
+		flags &= ~nst->flag;
+	}
+
+	if (flags)
+		printf("%s0x%x", first ? "" : ", ", flags);
+}
+
 static void cmd_info(int argc, char *argv[])
 {
 	const struct option options[] = {
@@ -114,11 +238,11 @@ static void cmd_info(int argc, char *argv[])
 		{ 0 },
 	};
 	bool pidonly = false, waitforsock = false;
-	struct ucred peercred;
-	socklen_t optlen = sizeof(peercred);
 	const char *optstring = "pw";
+	struct holder_info info;
+	struct ucred peercred;
 	const char *sockpath;
-	int fd, rc, opt;
+	int fd, opt;
 
 	do {
 		opt = getopt_long(argc, argv, optstring, options, NULL);
@@ -144,23 +268,28 @@ static void cmd_info(int argc, char *argv[])
 
 	sockpath = argv[optind];
 
-	fd = connect_ctl(sockpath, waitforsock);
-
-	rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
-			&peercred, &optlen);
-	if (rc < 0)
-		die("getsockopet(SO_PEERCRED) %s: %s\n",
-		    sockpath, strerror(errno));
+	fd = connect_ctl(sockpath, waitforsock, &info, &peercred);
 
 	close(fd);
 
 	if (pidonly) {
 		printf("%d\n", peercred.pid);
 	} else {
+		int flags = detect_namespaces(peercred.pid);
+
+		printf("Namespaces: ");
+		print_nstypes(flags);
+		printf("\n");
+
 		printf("As seen from calling context:\n");
 		printf("\tPID:\t%d\n", peercred.pid);
 		printf("\tUID:\t%u\n", peercred.uid);
 		printf("\tGID:\t%u\n", peercred.gid);
+
+		printf("As seen from holding context:\n");
+		printf("\tPID:\t%d\n", info.pid);
+		printf("\tUID:\t%u\n", info.uid);
+		printf("\tGID:\t%u\n", info.gid);
 	}
 }
 
@@ -173,7 +302,7 @@ static void cmd_stop(int argc, char *argv[])
 	if (argc != 2)
 		usage();
 
-	fd = connect_ctl(sockpath, false);
+	fd = connect_ctl(sockpath, false, NULL, NULL);
 
 	rc = write(fd, &buf, sizeof(buf));
 	if (rc < 0)