* RE: [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses
2011-08-19 20:58 ` [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses Stephen Hemminger
@ 2011-08-19 22:18 ` Christian Benvenuti (benve)
2011-08-19 22:24 ` Stephen Hemminger
2011-08-20 15:31 ` Bart De Schuymer
2011-08-22 13:59 ` David Lamparter
2 siblings, 1 reply; 5+ messages in thread
From: Christian Benvenuti (benve) @ 2011-08-19 22:18 UTC (permalink / raw)
To: Stephen Hemminger, David Lamparter
Cc: Nick Carter, Ed Swierk, netdev, bridge, netfilter-devel
The patch description and the code are clearly saying that STP is
an exception, but I am just worried about the users.
Maybe a proper description in the iptables help is sufficient.
Users may otherwise try to use this new hook for STP too
(for example to generate logs or produce statistics/counters
or divert STP traffic to userspace, etc).
Out of curiosity, ... if this gets accepted, shouldn't you provide
NF_BR_LINK_LOCAL_OUT too?
Or maybe you should call it NF_BR_LINK_LOCAL_FWD instead of
NF_BR_LINK_LOCAL_IN?
/Chris
> -----Original Message-----
> From: netfilter-devel-owner@vger.kernel.org [mailto:netfilter-devel-
> owner@vger.kernel.org] On Behalf Of Stephen Hemminger
> Sent: Friday, August 19, 2011 1:58 PM
> To: David Lamparter
> Cc: Nick Carter; Ed Swierk; netdev@vger.kernel.org; bridge@linux-
> foundation.org; netfilter-devel@vger.kernel.org
> Subject: [RFC] bridge: add netfilter hook for forwarding 802.1D group
> addresses
>
> The IEEE standard expects that link local multicast packets will not
> be forwarded by a bridge. But there are cases like 802.1X which may
> require that packets be forwarded. For maximum flexibilty implement
> this via netfilter.
>
> The netfilter chain is slightly different from other chains in that
> if packet is ACCEPTED by the chain, it means it should be forwarded.
> And if the packet verdict result is DROP, the packet is processed
> as a local packet. The default result for this chain is DROP and
> therefore users who do not install any rules will get the same
> result as before; ie. packets are only processed on the local host
> and not forwarded.
>
> Spanning Tree Packets are treated specially and do not
> go through the new chain.
>
> This code is conceptual design concept only. It compiles but
> hasn't been tested.
>
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
>
> ---
> include/linux/netfilter_bridge.h | 5 ++++-
> net/bridge/br_input.c | 15 ++++++++++++---
> net/bridge/netfilter/ebtable_filter.c | 18 ++++++++++++++++--
> 3 files changed, 32 insertions(+), 6 deletions(-)
>
> --- a/include/linux/netfilter_bridge.h 2011-08-19
13:11:51.972125670
> -0700
> +++ b/include/linux/netfilter_bridge.h 2011-08-19
13:13:36.452130443
> -0700
> @@ -22,7 +22,10 @@
> #define NF_BR_POST_ROUTING 4
> /* Not really a hook, but used for the ebtables broute table */
> #define NF_BR_BROUTING 5
> -#define NF_BR_NUMHOOKS 6
> +/* Packets to link local multicast addresses (01-80-C2-00-00-XX) */
> +#define NF_BR_LINK_LOCAL_IN 6
> +
> +#define NF_BR_NUMHOOKS 7
>
> #ifdef __KERNEL__
>
> --- a/net/bridge/br_input.c 2011-08-18 16:12:02.576672548 -0700
> +++ b/net/bridge/br_input.c 2011-08-19 13:28:13.696170518 -0700
> @@ -166,10 +166,19 @@ rx_handler_result_t br_handle_frame(stru
> if (skb->protocol == htons(ETH_P_PAUSE))
> goto drop;
>
> - /* If STP is turned off, then forward */
> - if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
> - goto forward;
> + /* If this is Spanning Tree Protocol packet */
> + if (dest[5] == 0) {
> + /* and STP is turned off, then forward */
> + if (p->br->stp_enabled == BR_NO_STP)
> + goto forward;
> + }
> + /* Hook to allow forwarding other group MAC addresses */
> + else if (p->state == BR_STATE_FORWARDING &&
> + NF_HOOK(NFPROTO_BRIDGE, NF_BR_LINK_LOCAL_IN,
skb,
> skb->dev,
> + NULL, br_handle_frame_finish))
> + return RX_HANDLER_CONSUMED; /* forwarded */
>
> + /* Packet will go only to the local host. */
> if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb,
skb->dev,
> NULL, br_handle_local_finish)) {
> return RX_HANDLER_CONSUMED; /* consumed by
filter */
> --- a/net/bridge/netfilter/ebtable_filter.c 2011-08-19
> 13:14:46.232133631 -0700
> +++ b/net/bridge/netfilter/ebtable_filter.c 2011-08-19
> 13:27:33.436168679 -0700
> @@ -11,8 +11,10 @@
> #include <linux/netfilter_bridge/ebtables.h>
> #include <linux/module.h>
>
> -#define FILTER_VALID_HOOKS ((1 << NF_BR_LOCAL_IN) | (1 <<
> NF_BR_FORWARD) | \
> - (1 << NF_BR_LOCAL_OUT))
> +#define FILTER_VALID_HOOKS ((1 << NF_BR_LOCAL_IN) | \
> + (1 << NF_BR_FORWARD) | \
> + (1 << NF_BR_LOCAL_OUT) | \
> + (1 << NF_BR_LINK_LOCAL_IN))
>
> static struct ebt_entries initial_chains[] =
> {
> @@ -28,6 +30,10 @@ static struct ebt_entries initial_chains
> .name = "OUTPUT",
> .policy = EBT_ACCEPT,
> },
> + {
> + .name = "LINKLOCAL",
> + .policy = EBT_DROP,
> + },
> };
>
> static struct ebt_replace_kernel initial_table =
> @@ -39,6 +45,7 @@ static struct ebt_replace_kernel initial
> [NF_BR_LOCAL_IN] = &initial_chains[0],
> [NF_BR_FORWARD] = &initial_chains[1],
> [NF_BR_LOCAL_OUT] = &initial_chains[2],
> + [NF_BR_LINK_LOCAL_IN] = &initial_chains[3],
> },
> .entries = (char *)initial_chains,
> };
> @@ -95,6 +102,13 @@ static struct nf_hook_ops ebt_ops_filter
> .hooknum = NF_BR_LOCAL_OUT,
> .priority = NF_BR_PRI_FILTER_OTHER,
> },
> + {
> + .hook = ebt_in_hook,
> + .owner = THIS_MODULE,
> + .pf = NFPROTO_BRIDGE,
> + .hooknum = NF_BR_LINK_LOCAL_IN,
> + .priority = NF_BR_PRI_FILTER_BRIDGED,
> + },
> };
>
> static int __net_init frame_filter_net_init(struct net *net)
> --
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses
2011-08-19 20:58 ` [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses Stephen Hemminger
2011-08-19 22:18 ` Christian Benvenuti (benve)
@ 2011-08-20 15:31 ` Bart De Schuymer
2011-08-22 13:59 ` David Lamparter
2 siblings, 0 replies; 5+ messages in thread
From: Bart De Schuymer @ 2011-08-20 15:31 UTC (permalink / raw)
To: Stephen Hemminger
Cc: David Lamparter, Nick Carter, Ed Swierk, netdev, bridge,
netfilter-devel
Op 19/08/2011 22:58, Stephen Hemminger schreef:
> Signed-off-by: Stephen Hemminger<shemminger@vyatta.com>
>
> ---
> include/linux/netfilter_bridge.h | 5 ++++-
> net/bridge/br_input.c | 15 ++++++++++++---
> net/bridge/netfilter/ebtable_filter.c | 18 ++++++++++++++++--
> 3 files changed, 32 insertions(+), 6 deletions(-)
>
> --- a/include/linux/netfilter_bridge.h 2011-08-19 13:11:51.972125670 -0700
> +++ b/include/linux/netfilter_bridge.h 2011-08-19 13:13:36.452130443 -0700
> @@ -22,7 +22,10 @@
> #define NF_BR_POST_ROUTING 4
> /* Not really a hook, but used for the ebtables broute table */
> #define NF_BR_BROUTING 5
> -#define NF_BR_NUMHOOKS 6
> +/* Packets to link local multicast addresses (01-80-C2-00-00-XX) */
> +#define NF_BR_LINK_LOCAL_IN 6
> +
> +#define NF_BR_NUMHOOKS 7
>
You will need to make sure you don't break backwards compatibility with
the ebtables userspace tool. ebtables.h::struct ebt_replace is a
structure used for communication between userspace and the kernel. It
has the member hook_entry defined like this:
struct ebt_entries __user *hook_entry[NF_BR_NUMHOOKS];
cheers,
Bart
--
Bart De Schuymer
www.artinalgorithms.be
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses
2011-08-19 20:58 ` [RFC] bridge: add netfilter hook for forwarding 802.1D group addresses Stephen Hemminger
2011-08-19 22:18 ` Christian Benvenuti (benve)
2011-08-20 15:31 ` Bart De Schuymer
@ 2011-08-22 13:59 ` David Lamparter
2 siblings, 0 replies; 5+ messages in thread
From: David Lamparter @ 2011-08-22 13:59 UTC (permalink / raw)
To: Stephen Hemminger
Cc: David Lamparter, Nick Carter, Ed Swierk, netdev, bridge,
netfilter-devel, David Miller
On Fri, Aug 19, 2011 at 01:58:10PM -0700, Stephen Hemminger wrote:
> The IEEE standard expects that link local multicast packets will not
> be forwarded by a bridge. But there are cases like 802.1X which may
> require that packets be forwarded. For maximum flexibilty implement
> this via netfilter.
>
> The netfilter chain is slightly different from other chains in that
> if packet is ACCEPTED by the chain, it means it should be forwarded.
> And if the packet verdict result is DROP, the packet is processed
> as a local packet.
Exactly this functionality already exists by way of the BROUTING chain
in the broute table. Currently, link-local packets are hardcodedly
treated as local before they even reach that chain. Nick's patch, in
conjunction with BROUTING, provides exactly what you're trying to do.
Now, without bridge netfilter, your patch becomes rather useless while
Nick's patch still allows per-group (and therefore per-protocol)
control.
Further, Nick's patch is considerably less intrusive.
I would therefore ask for Nick's patch to be merged.
-David
P.S.: this whole issue is starting to get rather annoying
^ permalink raw reply [flat|nested] 5+ messages in thread