netns: Introduce a routine that runs ip tool for dump/restore

The thing is that the ip utililty is very likely to have support
for ifaddrs and routes dumping and restore (rtnl messages are
symmetrical wrt dump/restore and this can be easily dump in there).

Thus, the best we can do it just use this tool for that and carry
the "raw" images with ifaddrs and routes dump.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

net.c

@@ -170,6 +170,63 @@ static int restore_links(int pid)
 	return ret;
 }
 
+int run_ip_tool(char *arg1, char *arg2, int fdin, int fdout)
+{
+	int pid, ret, status;
+
+	pr_debug("\tRunning ip %s %s\n", arg1, arg2);
+
+	pid = fork();
+	if (pid < 0) {
+		pr_perror("Can't forn IP tool");
+		return -1;
+	}
+
+	if (!pid) {
+		char *ip_tool_cmd;
+
+		ip_tool_cmd = getenv("CR_IP_TOOL");
+		if (!ip_tool_cmd)
+			ip_tool_cmd = "ip";
+
+		if (fdin < 0)
+			close(0);
+		else if (fdin != 0) {
+			dup2(fdin, 0);
+			close(fdin);
+		}
+
+		if (fdout < 0)
+			close(1);
+		else if (fdout != 1) {
+			dup2(fdout, 1);
+			close(fdout);
+		}
+
+		if (log_get_fd() != 2) {
+			dup2(log_get_fd(), 2);
+			close(log_get_fd());
+		}
+
+		execlp(ip_tool_cmd, "ip", arg1, arg2, NULL);
+		exit(-1);
+	}
+
+	ret = waitpid(pid, &status, 0);
+	if (ret < 0) {
+		pr_perror("Can't wait IP tool");
+		return -1;
+	}
+
+	if (!(WIFEXITED(status) && !WEXITSTATUS(status))) {
+		pr_err("IP tool failed on %s %s with %d (%d)\n", arg1, arg2,
+				status, WEXITSTATUS(status));
+		return -1;
+	}
+
+	return 0;
+}
+
 int dump_net_ns(int pid, struct cr_fdset *fds)
 {
 	int ret;