zdtm: Add simple test with descriptor in unix socket

https://travis-ci.org/criupatchwork/criu/builds/177945936
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/static/Makefile

@@ -135,6 +135,7 @@ TST_NOFILE	:=				\
 		dumpable02			\
 		remap_dead_pid			\
 		remap_dead_pid_root			\
+		scm00				\
 		aio00				\
 		aio01				\
 		fd				\

test/zdtm/static/scm00.c

@@ -0,0 +1,128 @@
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that SCM_RIGHTS are preserved";
+const char *test_author	= "Pavel Emelyanov <xemul@virtuozzo.com>";
+
+static int send_fd(int via, int fd)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	struct iovec iov;
+	char buf[CMSG_SPACE(sizeof(int))], c = '\0';
+	int *fdp;
+
+	h.msg_control = buf;
+	h.msg_controllen = sizeof(buf);
+	ch = CMSG_FIRSTHDR(&h);
+	ch->cmsg_level = SOL_SOCKET;
+	ch->cmsg_type = SCM_RIGHTS;
+	ch->cmsg_len = CMSG_LEN(sizeof(int));
+	fdp = (int *)CMSG_DATA(ch);
+	*fdp = fd;
+	h.msg_iov = &iov;
+	h.msg_iovlen = 1;
+	iov.iov_base = &c;
+	iov.iov_len = sizeof(c);
+
+	if (sendmsg(via, &h, 0) <= 0)
+		return -1;
+
+	return 0;
+}
+
+static int recv_fd(int via)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	struct iovec iov;
+	char buf[CMSG_SPACE(sizeof(int))], c;
+	int *fdp;
+
+	h.msg_control = buf;
+	h.msg_controllen = sizeof(buf);
+	h.msg_iov = &iov;
+	h.msg_iovlen = 1;
+	iov.iov_base = &c;
+	iov.iov_len = sizeof(c);
+
+	if (recvmsg(via, &h, 0) <= 0)
+		return -1;
+
+	ch = CMSG_FIRSTHDR(&h);
+	if (h.msg_flags & MSG_TRUNC)
+		return -2;
+	if (ch == NULL)
+		return -3;
+	if (ch->cmsg_type != SCM_RIGHTS)
+		return -4;
+
+	fdp = (int *)CMSG_DATA(ch);
+	return *fdp;
+}
+
+int main(int argc, char **argv)
+{
+	int sk[2], p[2];
+#define MSG "HELLO"
+	char buf[8]; /* bigger than the MSG to check boundaries */
+
+	test_init(argc, argv);
+
+	if (socketpair(PF_UNIX, SOCK_DGRAM, 0, sk) < 0) {
+		pr_perror("Can't make unix pair");
+		exit(1);
+	}
+
+	if (pipe(p) < 0) {
+		pr_perror("Can't make pipe");
+		exit(1);
+	}
+
+	if (send_fd(sk[0], p[0]) < 0) {
+		pr_perror("Can't send descriptor");
+		exit(1);
+	}
+
+	close(p[0]);
+
+	/* Swap pipe ends to make scm recv put pipe into different place */
+	dup2(p[1], p[0]);
+	close(p[1]);
+	p[1] = p[0];
+	p[0] = -1;
+
+	test_daemon();
+	test_waitsig();
+
+	p[0] = recv_fd(sk[1]);
+	if (p[0] < 0) {
+		fail("Can't recv pipe back (%d)", p[0]);
+		goto out;
+	}
+
+	if (write(p[1], MSG, sizeof(MSG)) != sizeof(MSG)) {
+		fail("Pipe write-broken");
+		goto out;
+	}
+
+	if (read(p[0], buf, sizeof(buf)) != sizeof(MSG)) {
+		fail("Pipe read-broken");
+		goto out;
+	}
+
+	if (strcmp(buf, MSG)) {
+		buf[sizeof(buf) - 1] = '\0';
+		fail("Pipe read-broken (%s)", buf);
+		goto out;
+	}
+
+	pass();
+out:
+	return 0;
+}

test/zdtm/static/scm00.desc

@@ -0,0 +1 @@
+{'flags': 'crfail'}