zdtm: add sk-unix-cred test for SCM_CREDENTIALS checkpoint/restore

Test that SCM_CREDENTIALS ancillary messages queued in a unix
socket are correctly saved and restored by CRIU.

Signed-off-by: Ahmed Elaidy <elaidya225@gmail.com>

Author: 3idey

test/zdtm/static/Makefile

@@ -469,6 +469,7 @@ TST_DIR		=				\
 		sk-unix-mntns			\
 		sk-unix01			\
 		sk-unix01-seqpacket		\
+		sk-unix-cred             \
 		sk-unix-dgram-ghost		\
 		unsupported_children_collision  \
 		shared_slave_mount_children	\

test/zdtm/static/sk-unix-cred.c

@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include "zdtmtst.h"
+
+const char *test_doc = "Test SCM_CREDENTIALS checkpoint/restore in unix socket queue\n";
+const char *test_author = "Ahmed Elaidy <elaidya225@gmail.com>";
+char *dirname;
+TEST_OPTION(dirname, string, "directory name", 1);
+int main(int argc, char *argv[])
+{
+	int sk[2];
+	struct msghdr msg = {};
+	struct iovec iov;
+	char buf[64];
+	char cmsg_buf[CMSG_SPACE(sizeof(struct ucred))];
+	struct cmsghdr *cmsg;
+	struct ucred *cred;
+	struct ucred send_cred;
+	int opt = 1;
+
+	test_init(argc, argv);
+
+	if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sk) < 0)
+		return pr_perror("socketpair");
+
+	if (setsockopt(sk[1], SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt)) < 0)
+		return pr_perror("setsockopt SO_PASSCRED");
+
+	/* Send a message with SCM_CREDENTIALS */
+	send_cred.pid = getpid();
+	send_cred.uid = getuid();
+	send_cred.gid = getgid();
+
+	iov.iov_base = buf;
+	iov.iov_len = sizeof(buf);
+
+	memset(cmsg_buf, 0, sizeof(cmsg_buf));
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = cmsg_buf;
+	msg.msg_controllen = sizeof(cmsg_buf);
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_CREDENTIALS;
+	cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
+	memcpy(CMSG_DATA(cmsg), &send_cred, sizeof(struct ucred));
+
+	strcpy(buf, "hello");
+	if (sendmsg(sk[0], &msg, 0) < 0)
+		return pr_perror("sendmsg");
+
+	test_daemon();
+	test_waitsig();
+
+	/* Receive and verify credentials after restore */
+	memset(buf, 0, sizeof(buf));
+	memset(cmsg_buf, 0, sizeof(cmsg_buf));
+	msg.msg_control = cmsg_buf;
+	msg.msg_controllen = sizeof(cmsg_buf);
+	iov.iov_base = buf;
+	iov.iov_len = sizeof(buf);
+
+	if (recvmsg(sk[1], &msg, 0) < 0)
+		return pr_perror("recvmsg");
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	if (!cmsg) {
+		fail("no cmsg after restore");
+		return 1;
+	}
+
+	if (cmsg->cmsg_type != SCM_CREDENTIALS) {
+		fail("wrong cmsg type after restore");
+		return 1;
+	}
+
+	cred = (struct ucred *)CMSG_DATA(cmsg);
+
+	if (cred->uid != send_cred.uid || cred->gid != send_cred.gid) {
+		fail("credentials mismatch after restore: "
+		     "uid %d/%d gid %d/%d",
+		     cred->uid, send_cred.uid,
+		     cred->gid, send_cred.gid);
+		return 1;
+	}
+
+	close(sk[0]);
+	close(sk[1]);
+
+	pass();
+	return 0;
+}