Subject: Re: [PATCH 1/5 2.6.21-rc4] l2tp: pppol2tp core

From: Patrick McHardy <[email-masked]>
Date: Sat, 24 Mar 2007 15:03:44 +0100

James Chapman wrote:
> [PPPOL2TP]: Add PPP-over-L2TP driver core.
> 
> This driver handles only L2TP data frames; control frames are handled
> by a userspace application. The dfriver implements L2TP using the
> PPPoX socket family. Data is sent or received using regular socket
> sendmsg() / recvmsg() calls. Kernel parameters of the socket can be
> read or modified using ioctl() or [gs]etsockopt() calls.

The interaction with UDP sockets looks pretty horrible IMO. On the
send side I don't see why you can't simply build the UDP header
yourself instead of doing these set_fs + sendmsgs hacks. On the
receive side I it would be nice if you could use the encapsulation
socket stuff thats also used by IPsec.

A couple of random comments:

- your list locking is broken
- list_for_each_entry_safe is only needed if you remove something
  while iterating, its no replacement for locking
- SOCK_2_SESSION/SOCK_2_TUNNEL are terribly ugly and should
  probably be inline functions that use BUG_ON in case of an
  invalid magic
- You should use skb_queue_walk for queue walking
- You should use endian-annotated types
- pppol2tp_fget: why do you want to open sockets for other processes?
  I hope this can go together with the sendmsg hacks