* [PATCH net-next] pppoe: optional deactivation of PADT packet handling
@ 2015-12-15 16:06 Guillaume Nault
2015-12-15 16:50 ` Dan Williams
2015-12-15 18:15 ` David Miller
0 siblings, 2 replies; 4+ messages in thread
From: Guillaume Nault @ 2015-12-15 16:06 UTC (permalink / raw)
To: netdev; +Cc: linux-ppp, David Miller
Kernel space shouldn't handle PADT packets since PADT belongs to
PPPoE's control plane.
With "handle_padt" module option, user space can now decide to avoid
kernel interpretation of PADT packets and be responsible for session
disconnection.
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
---
The two open-source PPPoE programs I know of are accel-ppp and pppd
(with the rp-pppoe plugin). Accel-ppp already handles PADT, while
pppd + rp-pppoe doesn't (seems like it doesn't even listen to its
PPPoE Discovery socket once session is established).
drivers/net/ppp/pppoe.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index b8da2ea..1846c3a 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -109,6 +109,18 @@ struct pppoe_net {
rwlock_t hash_lock;
};
+/* PADT packets belong to PPPoE's discovery stage (i.e. control plane)
+ * and should be handled by user space. Unfortunately, some programs
+ * don't listen out for PADT packets and rely on pppoe module for
+ * closing session after reception of PADT.
+ *
+ * This option can be deactivated when PPPoE discovery is handled by
+ * a PADT aware program.
+ */
+static bool handle_padt __read_mostly = true;
+module_param(handle_padt, bool, 0444);
+MODULE_PARM_DESC(handle_padt, "Let kernel interpret incoming PADT");
+
/*
* PPPoE could be in the following stages:
* 1) Discovery stage (to obtain remote MAC and Session ID)
@@ -1173,7 +1185,8 @@ static int __init pppoe_init(void)
goto out_unregister_pppoe_proto;
dev_add_pack(&pppoes_ptype);
- dev_add_pack(&pppoed_ptype);
+ if (handle_padt)
+ dev_add_pack(&pppoed_ptype);
register_netdevice_notifier(&pppoe_notifier);
return 0;
@@ -1189,7 +1202,8 @@ out:
static void __exit pppoe_exit(void)
{
unregister_netdevice_notifier(&pppoe_notifier);
- dev_remove_pack(&pppoed_ptype);
+ if (handle_padt)
+ dev_remove_pack(&pppoed_ptype);
dev_remove_pack(&pppoes_ptype);
unregister_pppox_proto(PX_PROTO_OE);
proto_unregister(&pppoe_sk_proto);
--
2.6.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] pppoe: optional deactivation of PADT packet handling
2015-12-15 16:06 [PATCH net-next] pppoe: optional deactivation of PADT packet handling Guillaume Nault
@ 2015-12-15 16:50 ` Dan Williams
2015-12-16 15:39 ` Guillaume Nault
2015-12-15 18:15 ` David Miller
1 sibling, 1 reply; 4+ messages in thread
From: Dan Williams @ 2015-12-15 16:50 UTC (permalink / raw)
To: Guillaume Nault, netdev; +Cc: linux-ppp, David Miller
On Tue, 2015-12-15 at 17:06 +0100, Guillaume Nault wrote:
> Kernel space shouldn't handle PADT packets since PADT belongs to
> PPPoE's control plane.
> With "handle_padt" module option, user space can now decide to avoid
> kernel interpretation of PADT packets and be responsible for session
> disconnection.
In general, module options like this kinda suck. How about a new PPPoE
ioctl so the option can be toggled for a given socket/session instead?
Then at least you're not locked into a specific PPPoE implementation
for all sessions on the machine.
Dan
> Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
> ---
> The two open-source PPPoE programs I know of are accel-ppp and pppd
> (with the rp-pppoe plugin). Accel-ppp already handles PADT, while
> pppd + rp-pppoe doesn't (seems like it doesn't even listen to its
> PPPoE Discovery socket once session is established).
>
>
> drivers/net/ppp/pppoe.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index b8da2ea..1846c3a 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -109,6 +109,18 @@ struct pppoe_net {
> rwlock_t hash_lock;
> };
>
> +/* PADT packets belong to PPPoE's discovery stage (i.e. control
> plane)
> + * and should be handled by user space. Unfortunately, some programs
> + * don't listen out for PADT packets and rely on pppoe module for
> + * closing session after reception of PADT.
> + *
> + * This option can be deactivated when PPPoE discovery is handled by
> + * a PADT aware program.
> + */
> +static bool handle_padt __read_mostly = true;
> +module_param(handle_padt, bool, 0444);
> +MODULE_PARM_DESC(handle_padt, "Let kernel interpret incoming PADT");
> +
> /*
> * PPPoE could be in the following stages:
> * 1) Discovery stage (to obtain remote MAC and Session ID)
> @@ -1173,7 +1185,8 @@ static int __init pppoe_init(void)
> goto out_unregister_pppoe_proto;
>
> dev_add_pack(&pppoes_ptype);
> - dev_add_pack(&pppoed_ptype);
> + if (handle_padt)
> + dev_add_pack(&pppoed_ptype);
> register_netdevice_notifier(&pppoe_notifier);
>
> return 0;
> @@ -1189,7 +1202,8 @@ out:
> static void __exit pppoe_exit(void)
> {
> unregister_netdevice_notifier(&pppoe_notifier);
> - dev_remove_pack(&pppoed_ptype);
> + if (handle_padt)
> + dev_remove_pack(&pppoed_ptype);
> dev_remove_pack(&pppoes_ptype);
> unregister_pppox_proto(PX_PROTO_OE);
> proto_unregister(&pppoe_sk_proto);
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] pppoe: optional deactivation of PADT packet handling
2015-12-15 16:06 [PATCH net-next] pppoe: optional deactivation of PADT packet handling Guillaume Nault
2015-12-15 16:50 ` Dan Williams
@ 2015-12-15 18:15 ` David Miller
1 sibling, 0 replies; 4+ messages in thread
From: David Miller @ 2015-12-15 18:15 UTC (permalink / raw)
To: g.nault; +Cc: netdev, linux-ppp
From: Guillaume Nault <g.nault@alphalink.fr>
Date: Tue, 15 Dec 2015 17:06:39 +0100
> @@ -109,6 +109,18 @@ struct pppoe_net {
> rwlock_t hash_lock;
> };
>
> +/* PADT packets belong to PPPoE's discovery stage (i.e. control plane)
> + * and should be handled by user space. Unfortunately, some programs
> + * don't listen out for PADT packets and rely on pppoe module for
> + * closing session after reception of PADT.
> + *
> + * This option can be deactivated when PPPoE discovery is handled by
> + * a PADT aware program.
> + */
> +static bool handle_padt __read_mostly = true;
> +module_param(handle_padt, bool, 0444);
> +MODULE_PARM_DESC(handle_padt, "Let kernel interpret incoming PADT");
No module options, please.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net-next] pppoe: optional deactivation of PADT packet handling
2015-12-15 16:50 ` Dan Williams
@ 2015-12-16 15:39 ` Guillaume Nault
0 siblings, 0 replies; 4+ messages in thread
From: Guillaume Nault @ 2015-12-16 15:39 UTC (permalink / raw)
To: Dan Williams; +Cc: netdev, linux-ppp, David Miller
On Tue, Dec 15, 2015 at 10:50:05AM -0600, Dan Williams wrote:
> On Tue, 2015-12-15 at 17:06 +0100, Guillaume Nault wrote:
> > Kernel space shouldn't handle PADT packets since PADT belongs to
> > PPPoE's control plane.
> > With "handle_padt" module option, user space can now decide to avoid
> > kernel interpretation of PADT packets and be responsible for session
> > disconnection.
>
> In general, module options like this kinda suck. How about a new PPPoE
> ioctl so the option can be toggled for a given socket/session instead?
> Then at least you're not locked into a specific PPPoE implementation
> for all sessions on the machine.
>
I've considered this approach too, but by using per session option,
we still have to register pppoed_ptype in pppoe_init() and thus call
pppoe_disc_recv() for any ETH_P_PPP_DISC frame, just in case a session
needs kernel space PADT handling. This makes the approach much less
interesting IMO, hence the original choice for module wide behaviour.
On the other hand, I understand the need for minimising module options.
Thinking a bit more about it, we could drop dev_add_pack() from
pppoe_init() and let pppoe_connect() register ETH_P_PPP_DISC when
necessary. We could even do it per device, as pppoe_connect() knows the
lower device.
The problem is to know when unregistering ETH_P_PPP_DISC. We could
probably use a reference counter, but I'd prefer to avoid complicating
pppoe's connection and disconnection code given that recent history
has shown its relative fragility.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-12-15 16:06 [PATCH net-next] pppoe: optional deactivation of PADT packet handling Guillaume Nault
2015-12-15 16:50 ` Dan Williams
2015-12-16 15:39 ` Guillaume Nault
2015-12-15 18:15 ` David Miller
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