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Date: Wed, 14 Aug 2019 19:58:57 +0300
From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To: pruddy@...tta.att-mail.com, Ido Schimmel <idosch@...sch.org>
Cc: netdev@...r.kernel.org, roopa@...ulusnetworks.com,
linus.luessing@...3.blue
Subject: Re: [PATCH net-next] mcast: ensure L-L IPv6 packets are accepted by
bridge
On 8/14/19 7:40 PM, Patrick Ruddy wrote:
> Thanks both for the quick replies, answers inline...
>
> On Wed, 2019-08-14 at 02:55 +0300, Nikolay Aleksandrov wrote:
>> On 8/13/19 10:53 PM, Ido Schimmel wrote:
>>> + Bridge maintainers, Linus
>>>
>>
>> Good catch Ido, thanks!
>> First I'd say the subject needs to reflect that this is a bridge change
>> better, please rearrange it like so - bridge: mcast: ...
>> More below,
>>
>>> On Tue, Aug 13, 2019 at 03:18:04PM +0100, Patrick Ruddy wrote:
>>>> At present only all-nodes IPv6 multicast packets are accepted by
>>>> a bridge interface that is not in multicast router mode. Since
>>>> other protocols can be running in the absense of multicast
>>>> forwarding e.g. OSPFv3 IPv6 ND. Change the test to allow
>>>> all of the FFx2::/16 range to be accepted when not in multicast
>>>> router mode. This aligns the code with IPv4 link-local reception
>>>> and RFC4291
>>>
>>> Can you please quote the relevant part from RFC 4291?
>>>
>>>> Signed-off-by: Patrick Ruddy <pruddy@...tta.att-mail.com>
>>>> ---
>>>> include/net/addrconf.h | 15 +++++++++++++++
>>>> net/bridge/br_multicast.c | 2 +-
>>>> 2 files changed, 16 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/net/addrconf.h b/include/net/addrconf.h
>>>> index becdad576859..05b42867e969 100644
>>>> --- a/include/net/addrconf.h
>>>> +++ b/include/net/addrconf.h
>>>> @@ -434,6 +434,21 @@ static inline void addrconf_addr_solict_mult(const struct in6_addr *addr,
>>>> htonl(0xFF000000) | addr->s6_addr32[3]);
>>>> }
>>>>
>>>> +/*
>>>> + * link local multicast address range ffx2::/16 rfc4291
>>>> + */
>>>> +static inline bool ipv6_addr_is_ll_mcast(const struct in6_addr *addr)
>>>> +{
>>>> +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
>>>> + __be64 *p = (__be64 *)addr;
>>>> + return ((p[0] & cpu_to_be64(0xff0f000000000000UL))
>>>> + ^ cpu_to_be64(0xff02000000000000UL)) == 0UL;
>>>> +#else
>>>> + return ((addr->s6_addr32[0] & htonl(0xff0f0000)) ^
>>>> + htonl(0xff020000)) == 0;
>>>> +#endif
>>>> +}
>>>> +
>>>> static inline bool ipv6_addr_is_ll_all_nodes(const struct in6_addr *addr)
>>>> {
>>>> #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
>>>> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
>>>> index 9b379e110129..ed3957381fa2 100644
>>>> --- a/net/bridge/br_multicast.c
>>>> +++ b/net/bridge/br_multicast.c
>>>> @@ -1664,7 +1664,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
>>>> err = ipv6_mc_check_mld(skb);
>>>>
>>>> if (err == -ENOMSG) {
>>>> - if (!ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
>>>> + if (!ipv6_addr_is_ll_mcast(&ipv6_hdr(skb)->daddr))
>>>> BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
>>>
>>> IIUC, you want IPv6 link-local packets to be locally received, but this
>>> also changes how these packets are flooded. RFC 4541 says that packets
>>
>> Indeed, we'll start flooding them all, not just the all hosts address.
>> If that is at all required it'll definitely have to be optional.
>>
>>> addressed to the all hosts address are a special case and should be
>>> forwarded to all ports:
>>>
>>> "In IPv6, the data forwarding rules are more straight forward because MLD is
>>> mandated for addresses with scope 2 (link-scope) or greater. The only exception
>>> is the address FF02::1 which is the all hosts link-scope address for which MLD
>>> messages are never sent. Packets with the all hosts link-scope address should
>>> be forwarded on all ports."
>>>
>>
>> I wonder what is the problem for the host to join such group on behalf of the bridge ?
>> Then you'll receive the traffic at least locally and the RFC says it itself - MLD is mandated
>> for the other link-local addresses.
>> It's very late here and maybe I'm missing something.. :)
>>
> The group is being joined by MLD at the L3 level but the packets are
> not being passed up to the l3 interface becasue there is a MLD querier
> on the network
>
That shouldn't matter if the host has joined the group, there is a specific
check for that. If the host has joined the group and we have an mdst then
we'll hit this code:
mdst = br_mdb_get(br, skb, vid);
if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
br_multicast_querier_exists(br, eth_hdr(skb))) {
if ((mdst && mdst->host_joined) ||
br_multicast_is_router(br)) {
local_rcv = true;
br->dev->stats.multicast++;
}
mcast_hit = true;
} else {
local_rcv become true and the packet is passed up, so what is the problem ?
Have you missed to refresh the group and it has expired in the bridge perhaps ?
> snippet from /proc/net/igmp6
> ...
> 40 sw1 ff0200000000000000000001ff008700 1 00000004 0
> 40 sw1 ff020000000000000000000000000002 1 00000004 0
> 40 sw1 ff020000000000000000000000000001 1 0000000C 0
> 40 sw1 ff010000000000000000000000000001 1 00000008 0
> 41 lo1 ff020000000000000000000000000001 1 0000000C 0
> 41 lo1 ff010000000000000000000000000001 1 00000008 0
> 42 sw1.1 ff020000000000000000000000000006 1 00000004 0
> 42 sw1.1 ff020000000000000000000000000005 1 00000004 0
> 42 sw1.1 ff0200000000000000000001ff000000 2 00000004 0
> 42 sw1.1 ff0200000000000000000001ff008700 1 00000004 0
> 42 sw1.1 ff0200000000000000000001ff000099 1 00000004 0
> 42 sw1.1 ff020000000000000000000000000002 1 00000004 0
> 42 sw1.1 ff020000000000000000000000000001 1 0000000C 0
> 42 sw1.1 ff010000000000000000000000000001 1 00000008 0
> ...
>
> the bridge is sw1 and the l3 intervace is sw1.1
>
> Ido is correct about the flooding - I will update the patch with the
> comments and reissue.
>
> Thanks again
>
> -pr
>>
>>> Maybe you want something like:
>>>
>>
>> I think we can do without the new field, either pass local_rcv into br_multicast_rcv() or
>> set it based on return value. The extra test will have to remain unfortunately, but we
>> can reduce the tests by one if carefully done.
>>
>>> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
>>> index 09b1dd8cd853..9f312a73f61c 100644
>>> --- a/net/bridge/br_input.c
>>> +++ b/net/bridge/br_input.c
>>> @@ -132,7 +132,8 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
>>> if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
>>> br_multicast_querier_exists(br, eth_hdr(skb))) {
>>> if ((mdst && mdst->host_joined) ||
>>> - br_multicast_is_router(br)) {
>>> + br_multicast_is_router(br) ||
>>> + BR_INPUT_SKB_CB_LOCAL_RECEIVE(skb)) {
>>> local_rcv = true;
>>> br->dev->stats.multicast++;
>>> }
>>> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
>>> index 9b379e110129..f03cecf6174e 100644
>>> --- a/net/bridge/br_multicast.c
>>> +++ b/net/bridge/br_multicast.c
>>> @@ -1667,6 +1667,9 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
>>> if (!ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
>>> BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
>>>
>>> + if (ipv6_addr_is_ll_mcast(&ipv6_hdr(skb)->daddr))
>>> + BR_INPUT_SKB_CB(skb)->local_receive = 1;
>>> +
>>> if (ipv6_addr_is_all_snoopers(&ipv6_hdr(skb)->daddr)) {
>>> err = br_ip6_multicast_mrd_rcv(br, port, skb);
>>>
>>> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
>>> index b7a4942ff1b3..d76394ca4059 100644
>>> --- a/net/bridge/br_private.h
>>> +++ b/net/bridge/br_private.h
>>> @@ -426,6 +426,7 @@ struct br_input_skb_cb {
>>> #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
>>> u8 igmp;
>>> u8 mrouters_only:1;
>>> + u8 local_receive:1;
>>> #endif
>>> u8 proxyarp_replied:1;
>>> u8 src_port_isolated:1;
>>> @@ -445,8 +446,10 @@ struct br_input_skb_cb {
>>>
>>> #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
>>> # define BR_INPUT_SKB_CB_MROUTERS_ONLY(__skb) (BR_INPUT_SKB_CB(__skb)->mrouters_only)
>>> +# define BR_INPUT_SKB_CB_LOCAL_RECEIVE(__skb) (BR_INPUT_SKB_CB(__skb)->local_receive)
>>> #else
>>> # define BR_INPUT_SKB_CB_MROUTERS_ONLY(__skb) (0)
>>> +# define BR_INPUT_SKB_CB_LOCAL_RECEIVE(__skb) (0)
>>> #endif
>>>
>>> #define br_printk(level, br, format, args...) \
>>>
>
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