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SubjectRe: [PATCH] net: bridge: Allow bridge to joing multicast groups
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On 26/07/2019 11:41, Nikolay Aleksandrov wrote:
> On 25/07/2019 17:21, Horatiu Vultur wrote:
>> Hi Nikolay,
>>
>> The 07/25/2019 16:21, Nikolay Aleksandrov wrote:
>>> External E-Mail
>>>
>>>
>>> On 25/07/2019 16:06, Nikolay Aleksandrov wrote:
>>>> On 25/07/2019 14:44, Horatiu Vultur wrote:
>>>>> There is no way to configure the bridge, to receive only specific link
>>>>> layer multicast addresses. From the description of the command 'bridge
>>>>> fdb append' is supposed to do that, but there was no way to notify the
>>>>> network driver that the bridge joined a group, because LLADDR was added
>>>>> to the unicast netdev_hw_addr_list.
>>>>>
>>>>> Therefore update fdb_add_entry to check if the NLM_F_APPEND flag is set
>>>>> and if the source is NULL, which represent the bridge itself. Then add
>>>>> address to multicast netdev_hw_addr_list for each bridge interfaces.
>>>>> And then the .ndo_set_rx_mode function on the driver is called. To notify
>>>>> the driver that the list of multicast mac addresses changed.
>>>>>
>>>>> Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
>>>>> ---
>>>>> net/bridge/br_fdb.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++---
>>>>> 1 file changed, 46 insertions(+), 3 deletions(-)
>>>>>
>>>>
>>>> Hi,
>>>> I'm sorry but this patch is wrong on many levels, some notes below. In general
>>>> NLM_F_APPEND is only used in vxlan, the bridge does not handle that flag at all.
>>>> FDB is only for *unicast*, nothing is joined and no multicast should be used with fdbs.
>>>> MDB is used for multicast handling, but both of these are used for forwarding.
>>>> The reason the static fdbs are added to the filter is for non-promisc ports, so they can
>>>> receive traffic destined for these FDBs for forwarding.
>>>> If you'd like to join any multicast group please use the standard way, if you'd like to join
>>>> it only on a specific port - join it only on that port (or ports) and the bridge and you'll
>>>
>>> And obviously this is for the case where you're not enabling port promisc mode (non-default).
>>> In general you'll only need to join the group on the bridge to receive traffic for it
>>> or add it as an mdb entry to forward it.
>>>
>>>> have the effect that you're describing. What do you mean there's no way ?
>>
>> Thanks for the explanation.
>> There are few things that are not 100% clear to me and maybe you can
>> explain them, not to go totally in the wrong direction. Currently I am
>> writing a network driver on which I added switchdev support. Then I was
>> looking for a way to configure the network driver to copy link layer
>> multicast address to the CPU port.
>>
>> If I am using bridge mdb I can do it only for IP multicast addreses,
>> but how should I do it if I want non IP frames with link layer multicast
>> address to be copy to CPU? For example: all frames with multicast
>> address '01-21-6C-00-00-01' to be copy to CPU. What is the user space
>> command for that?
>>
>
> Check SIOCADDMULTI (ip maddr from iproute2), f.e. add that mac to the port
> which needs to receive it and the bridge will send it up automatically since
> it's unknown mcast (note that if there's a querier, you'll have to make the
> bridge mcast router if it is not the querier itself). It would also flood it to all

Actually you mentioned non-IP traffic, so the querier stuff is not a problem. This
traffic will always be flooded by the bridge (and also a copy will be locally sent up).
Thus only the flooding may need to be controlled.

> other ports so you may want to control that. It really depends on the setup
> and the how the hardware is configured.
>
>>>>
>>>> In addition you're allowing a mix of mcast functions to be called with unicast addresses
>>>> and vice versa, it is not that big of a deal because the kernel will simply return an error
>>>> but still makes no sense.
>>>>
>>>> Nacked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
>>>>
>>>>> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
>>>>> index b1d3248..d93746d 100644
>>>>> --- a/net/bridge/br_fdb.c
>>>>> +++ b/net/bridge/br_fdb.c
>>>>> @@ -175,6 +175,29 @@ static void fdb_add_hw_addr(struct net_bridge *br, const unsigned char *addr)
>>>>> }
>>>>> }
>>>>>
>>>>> +static void fdb_add_hw_maddr(struct net_bridge *br, const unsigned char *addr)
>>>>> +{
>>>>> + int err;
>>>>> + struct net_bridge_port *p;
>>>>> +
>>>>> + ASSERT_RTNL();
>>>>> +
>>>>> + list_for_each_entry(p, &br->port_list, list) {
>>>>> + if (!br_promisc_port(p)) {
>>>>> + err = dev_mc_add(p->dev, addr);
>>>>> + if (err)
>>>>> + goto undo;
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + return;
>>>>> +undo:
>>>>> + list_for_each_entry_continue_reverse(p, &br->port_list, list) {
>>>>> + if (!br_promisc_port(p))
>>>>> + dev_mc_del(p->dev, addr);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> /* When a static FDB entry is deleted, the HW address from that entry is
>>>>> * also removed from the bridge private HW address list and updates all
>>>>> * the ports with needed information.
>>>>> @@ -192,13 +215,27 @@ static void fdb_del_hw_addr(struct net_bridge *br, const unsigned char *addr)
>>>>> }
>>>>> }
>>>>>
>>>>> +static void fdb_del_hw_maddr(struct net_bridge *br, const unsigned char *addr)
>>>>> +{
>>>>> + struct net_bridge_port *p;
>>>>> +
>>>>> + ASSERT_RTNL();
>>>>> +
>>>>> + list_for_each_entry(p, &br->port_list, list) {
>>>>> + if (!br_promisc_port(p))
>>>>> + dev_mc_del(p->dev, addr);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f,
>>>>> bool swdev_notify)
>>>>> {
>>>>> trace_fdb_delete(br, f);
>>>>>
>>>>> - if (f->is_static)
>>>>> + if (f->is_static) {
>>>>> fdb_del_hw_addr(br, f->key.addr.addr);
>>>>> + fdb_del_hw_maddr(br, f->key.addr.addr);
>>>>
>>>> Walking over all ports again for each static delete is a no-go.
>>>>
>>>>> + }
>>>>>
>>>>> hlist_del_init_rcu(&f->fdb_node);
>>>>> rhashtable_remove_fast(&br->fdb_hash_tbl, &f->rhnode,
>>>>> @@ -843,13 +880,19 @@ static int fdb_add_entry(struct net_bridge *br, struct net_bridge_port *source,
>>>>> fdb->is_local = 1;
>>>>> if (!fdb->is_static) {
>>>>> fdb->is_static = 1;
>>>>> - fdb_add_hw_addr(br, addr);
>>>>> + if (flags & NLM_F_APPEND && !source)
>>>>> + fdb_add_hw_maddr(br, addr);
>>>>> + else
>>>>> + fdb_add_hw_addr(br, addr);
>>>>> }
>>>>> } else if (state & NUD_NOARP) {
>>>>> fdb->is_local = 0;
>>>>> if (!fdb->is_static) {
>>>>> fdb->is_static = 1;
>>>>> - fdb_add_hw_addr(br, addr);
>>>>> + if (flags & NLM_F_APPEND && !source)
>>>>> + fdb_add_hw_maddr(br, addr);
>>>>> + else
>>>>> + fdb_add_hw_addr(br, addr);
>>>>> }
>>>>> } else {
>>>>> fdb->is_local = 0;
>>>>>
>>>>
>>>
>>
>

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