Re: [PATCH net-next 1/2] socket: Allow external sockets to use socket syscalls

From: Alex Gartrell
Date: Fri Dec 26 2014 - 14:26:52 EST

Hello Jason,

Thanks again for your comments.

On 12/26/14 4:45 AM, Jason Wang wrote:
@@ -388,6 +388,7 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
sock->file = file;
file->f_flags = O_RDWR | (flags & O_NONBLOCK);
file->private_data = sock;
+ file->private_data_is_socket = true;

This is only safe if all user of sock_alloc_file() have full support for
each method in proto_ops.

This doesn't change anything in the invocation of the syscalls, as every file allocated through this path already passes the "is_socket" test due to the (sadly missing here)
file = alloc_file(..., &socket_file_ops)
above, so this makes things no less safe than they were.

Of course we also need to implement these proto_ops for the tun device in the subsequent patch to make it work.

return file;
@@ -411,7 +412,7 @@ static int sock_map_fd(struct socket *sock, int flags)

struct socket *sock_from_file(struct file *file, int *err)
- if (file->f_op == &socket_file_ops)
+ if (file->private_data_is_socket)
return file->private_data; /* set in sock_map_fd */

*err = -ENOTSOCK;

Not sure it's the best method, how about a dedicated f_op to do this?

So like a get_socket operation? That would simplify this a lot, certainly (we wouldn't need to move private_data around in the tun driver).

Alex Gartrell <agartrell@xxxxxx>

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