files: Send/receive fds with pointers on their struct fdinfo_list_entry in receiver

For moving to a single transport socket scheme, we need to be able to differ
fds in receive queue from each other. Add a fle pointer as identifier for that.

v2: Rebase on compel
travis-ci: success for Rework file opening scheme to make it asynchronous (rev5)
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/files.c

@@ -957,6 +957,23 @@ err:
 	return -1;
 }
 
+int recv_fd_from_peer(struct fdinfo_list_entry *fle)
+{
+	struct fdinfo_list_entry *tmp;
+	int fd, ret;
+
+	ret = recv_fds(fle->fe->fd, &fd, 1, (void *)&tmp, sizeof(struct fdinfo_list_entry *));
+	if (ret)
+		return -1;
+
+	if (tmp != fle) {
+		pr_err("Received wrong fle\n");
+		return -1;
+	}
+
+	return fd;
+}
+
 int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock)
 {
 	struct sockaddr_un saddr;
@@ -967,7 +984,7 @@ int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock)
 	transport_name_gen(&saddr, &len,
 			futex_get(&fle->real_pid), fle->fe->fd);
 	pr_info("\t\tSend fd %d to %s\n", fd, saddr.sun_path + 1);
-	return send_fd(sock, &saddr, len, fd);
+	return send_fds(sock, &saddr, len, &fd, 1, (void *)&fle, sizeof(struct fdinfo_list_entry *));
 }
 
 static int send_fd_to_self(int fd, struct fdinfo_list_entry *fle, int sock)
@@ -1077,7 +1094,7 @@ static int receive_fd(int pid, struct fdinfo_list_entry *fle)
 
 	pr_info("\tReceive fd for %d\n", fle->fe->fd);
 
-	tmp = recv_fd(fle->fe->fd);
+	tmp = recv_fd_from_peer(fle);
 	if (tmp < 0) {
 		pr_err("Can't get fd %d\n", tmp);
 		return -1;

criu/include/files.h

@@ -148,6 +148,7 @@ extern int file_desc_add(struct file_desc *d, u32 id, struct file_desc_ops *ops)
 extern struct fdinfo_list_entry *file_master(struct file_desc *d);
 extern struct file_desc *find_file_desc_raw(int type, u32 id);
 
+extern int recv_fd_from_peer(struct fdinfo_list_entry *fle);
 extern int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock);
 extern int restore_fown(int fd, FownEntry *fown);
 extern int rst_file_params(int fd, FownEntry *fown, int flags);

criu/pipes.c

@@ -237,7 +237,7 @@ static int recv_pipe_fd(struct pipe_info *pi)
 
 	pr_info("\tWaiting fd for %d\n", fd);
 
-	tmp = recv_fd(fd);
+	tmp = recv_fd_from_peer(fle);
 	if (tmp < 0) {
 		pr_err("Can't get fd %d\n", tmp);
 		return -1;

criu/sk-unix.c

@@ -1097,7 +1097,7 @@ static int open_unixsk_pair_slave(struct unix_sk_info *ui)
 	pr_info("Opening pair slave (id %#x ino %#x peer %#x) on %d\n",
 			ui->ue->id, ui->ue->ino, ui->ue->peer, fle->fe->fd);
 
-	sk = recv_fd(fle->fe->fd);
+	sk = recv_fd_from_peer(fle);
 	if (sk < 0) {
 		pr_err("Can't recv pair slave\n");
 		return -1;

criu/tty.c

@@ -923,7 +923,7 @@ static int receive_tty(struct tty_info *info)
 	fle = file_master(&info->d);
 	pr_info("\tWaiting tty fd %d (pid %d)\n", fle->fe->fd, fle->pid);
 
-	fd = recv_fd(fle->fe->fd);
+	fd = recv_fd_from_peer(fle);
 	close(fle->fe->fd);
 	if (fd < 0) {
 		pr_err("Can't get fd %d\n", fd);