Subject: Re: [RFC PATCH net-next] ppp: Allow ppp device connected to an l2tp session to change of namespace

From: James Chapman <[email-masked]>
Date: Thu, 24 Oct 2013 11:55:45 +0100

On 24/10/13 11:30, François Cachereul wrote:
> Remove NETIF_F_NETNS_LOCAL flag from ppp device in ppp_connect_channel()
> if the device is connected to a l2tp session socket.
> Restore the flag in ppp_disconnect_channel().

What about pppd's network namespace? Also, L2TP's tunnel socket (UDP or
L2TP/IP) will be in a different namespace if the ppp interface is moved.

> 
> Signed-off-by: François CACHEREUL <[email-masked]>
> ---
> I'm trying to get rid of this flag for ppp device connected to l2tp
> session, it's seem to be safe to do it for as l2tp_ppp module hasn't any
> reference to the ppp device except to the device name. We can probably
> do it for others modules but pppoe and pptp will require more work.
> 
> I remove the flag for l2tp in ppp_generic.c because I couldn't find a
> place like a callback to do it in l2tp_ppp.c. The best will be to 
> remove the flag for all ppp devices.
> 
> François
> 
>  drivers/net/ppp/ppp_generic.c |   11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
> index 72ff14b..7ccf2ae 100644
> --- a/drivers/net/ppp/ppp_generic.c
> +++ b/drivers/net/ppp/ppp_generic.c
> @@ -54,6 +54,8 @@
>  #include <net/net_namespace.h>
>  #include <net/netns/generic.h>
>  
> +#include <linux/if_pppox.h>
> +
>  #define PPP_VERSION	"2.4.2"
>  
>  /*
> @@ -2861,6 +2863,7 @@ ppp_connect_channel(struct channel *pch, int unit)
>  	struct ppp_net *pn;
>  	int ret = -ENXIO;
>  	int hdrlen;
> +	struct sock *sk;
>  
>  	pn = ppp_pernet(pch->chan_net);
>  
> @@ -2883,6 +2886,13 @@ ppp_connect_channel(struct channel *pch, int unit)
>  	++ppp->n_channels;
>  	pch->ppp = ppp;
>  	atomic_inc(&ppp->file.refcnt);
> +
> +	/* allow ppp net device to be moved in another network namespace
> +	 * if it's connected to an l2tp session */
> +	sk = (struct sock *)pch->chan->private;
> +	if (sk && sk->sk_protocol == PX_PROTO_OL2TP)
> +		ppp->dev->features &= ~NETIF_F_NETNS_LOCAL;
> +
>  	ppp_unlock(ppp);
>  	ret = 0;
>  
> @@ -2912,6 +2922,7 @@ ppp_disconnect_channel(struct channel *pch)
>  		list_del(&pch->clist);
>  		if (--ppp->n_channels == 0)
>  			wake_up_interruptible(&ppp->file.rwait);
> +		ppp->dev->features |= NETIF_F_NETNS_LOCAL;
>  		ppp_unlock(ppp);
>  		if (atomic_dec_and_test(&ppp->file.refcnt))
>  			ppp_destroy_interface(ppp);
> 

-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
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