check: Add some basic checks

* /proc/<pid>/map_files
* sock diag
* ns_last_pid sysctl
* SO_PEEK_OFF sockoptions
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-check.c

+#include <unistd.h>
+#include <sys/socket.h>
+#include "sockets.h"
 #include "crtools.h"
 #include "log.h"
+#include "util-net.h"
+
+static int check_map_files(void)
+{
+	int ret;
+
+	ret = access("/proc/self/map_files", R_OK);
+	if (!ret)
+		return 0;
+
+	pr_msg("/proc/<pid>/map_files directory is missing.\n");
+	return -1;
+}
+
+static int check_sock_diag(void)
+{
+	int ret;
+
+	ret = collect_sockets();
+	if (!ret)
+		return 0;
+
+	pr_msg("sock diag infrastructure is incomplete.\n");
+	return -1;
+}
+
+static int check_ns_last_pid(void)
+{
+	int ret;
+
+	ret = access(LAST_PID_PATH, W_OK);
+	if (!ret)
+		return 0;
+
+	pr_msg("%s sysctl is missing.\n", LAST_PID_PATH);
+	return -1;
+}
+
+static int check_sock_peek_off(void)
+{
+	int sk;
+	int ret, off, sz;
+
+	sk = socket(PF_UNIX, SOCK_DGRAM, 0);
+	if (sk < 0) {
+		pr_perror("Can't create unix socket for check");
+		return -1;
+	}
+
+	ret = getsockopt(sk, SOL_SOCKET, SO_PEEK_OFF, &off, (socklen_t *)&sz);
+	close(sk);
+
+	if ((ret == 0) && (off == -1) && (sz == sizeof(int)))
+		return 0;
+
+	pr_msg("SO_PEEK_OFF sockoption doesn't work.\n");
+	return -1;
+}
 
 int cr_check(void)
 {
-	return 0;
+	int ret = 0;
+
+	ret |= check_map_files();
+	ret |= check_sock_diag();
+	ret |= check_ns_last_pid();
+	ret |= check_sock_peek_off();
+
+	if (!ret)
+		pr_msg("Looks good.\n");
+
+	return ret;
 }

include/util-net.h

@@ -4,6 +4,10 @@
 #define UNIX_PATH_MAX (sizeof(struct sockaddr_un) - \
 			(size_t)((struct sockaddr_un *) 0)->sun_path)
 
+#ifndef SO_PEEK_OFF
+#define SO_PEEK_OFF            42
+#endif
+
 extern int send_fd(int sock, struct sockaddr_un *saddr, int len, int fd);
 extern int recv_fd(int sock);
 #endif

parasite.c

@@ -11,10 +11,6 @@
 
 #ifdef CONFIG_X86_64
 
-#ifndef SO_PEEK_OFF
-#define SO_PEEK_OFF            42
-#endif
-
 static void *brk_start, *brk_end, *brk_tail;
 
 static struct page_entry page;