zdtm: Add scm05 test

Create socketpair and epoll. Add one end of the socketpair
to epoll and then twice send it over another end.

After restore check, that epoll can be received
via socket, and that it contains event.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm/static/Makefile

@@ -170,6 +170,7 @@ TST_NOFILE	:=				\
 		scm02				\
 		scm03				\
 		scm04				\
+		scm05				\
 		aio00				\
 		aio01				\
 		fd				\

test/zdtm/static/scm05.c

+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/epoll.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that SCM_RIGHTS are preserved";
+const char *test_author	= "Kirill Tkhai <ktkhai@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))];
+	char c = '\0';
+	int *fdp;
+
+	memset(buf, 0, sizeof(buf));
+	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[0] = 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, int *fd)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	struct iovec iov;
+	char buf[CMSG_SPACE(sizeof(int))];
+	char 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;
+
+	if (h.msg_flags & MSG_CTRUNC) {
+		test_msg("CTR\n");
+		return -2;
+	}
+
+	/* No 2 SCM-s here, kernel merges them upon send */
+	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);
+	*fd = fdp[0];
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct epoll_event event = {
+		.events = EPOLLIN,
+        };
+	int sk[2], ep, ret;
+
+	test_init(argc, argv);
+
+	if (socketpair(PF_UNIX, SOCK_DGRAM, 0, sk) < 0) {
+		pr_perror("Can't make unix pair");
+		exit(1);
+	}
+
+	ep = epoll_create(1);
+	if (ep < 0) {
+		perror("Can't create epoll");
+		exit(1);
+	}
+
+	event.data.fd = sk[1];
+	if (epoll_ctl(ep, EPOLL_CTL_ADD, sk[1], &event) < 0) {
+		perror("Can't add fd");
+		exit(1);
+	}
+
+	if (send_fd(sk[0], ep) < 0) {
+		pr_perror("Can't send epoll");
+		exit(1);
+	}
+	if (send_fd(sk[0], ep) < 0) {
+		pr_perror("Can't send epoll");
+		exit(1);
+	}
+
+	close(ep);
+	memset(&event, 0, sizeof(event));
+
+	test_daemon();
+	test_waitsig();
+
+	if (recv_fd(sk[1], &ep) < 0) {
+		fail("Can't recv epoll back");
+		ret = -1;
+		goto out;
+	}
+
+	ret = epoll_wait(ep, &event, 1, 0);
+	if (ret != 1) {
+		fail("Can't get epoll event");
+		ret = -1;
+		goto out;
+	}
+
+	pass();
+	ret = 0;
+out:
+	return ret;
+}