Netdev List

* Re: [RFC/PATCH] Add a socketoption IPV6_MULTICAST_ALL analogue to the IPV4 version
From: Andre Naujoks @ 2018-08-28  9:36 UTC (permalink / raw)
  To: netdev; +Cc: 吉藤英明, David S. Miller, yoshfuji
In-Reply-To: <CAPA1RqCtkYE8is=kbANNGktgoiqKHZy+0wtE-spUwgq4V-_XTw@mail.gmail.com>

On 5/8/18 1:48 PM, 吉藤英明 wrote:
> Hi,
> 
> 2018-05-08 15:41 GMT+09:00 Andre Naujoks <nautsch2@gmail.com>:
>> On 08.05.2018 08:31, 吉藤英明 wrote:
>>> Hi,
>>>
>>> 2018-05-08 15:03 GMT+09:00 Andre Naujoks <nautsch2@gmail.com>:
>>>> On 11.04.2018 13:02, Andre Naujoks wrote:
>>>>> Hi.
>>>>
>>>> Hi again.
>>>>
>>>> Since it has been a month now, I'd like to send a little "ping" on this subject.
>>>>
>>>> Is anything wrong with this? Or was it just bad timing?

Hi.

Anything new about this? I still think, this is a very useful addition.

If this is not wanted/needed, then I'll stop pinging this topic.

Regards
  Andre

>>>
>>> I'm just curious... What kind of behaviour do you expect?
>>>
>>> Unless you explicitly join the group, you cannot get traffic for the group
>>> because of multicast filtering at device level (multicast fitlering) or at the
>>> switch level (MLD).
>>>
>>> If an application is interested in (several) multicast groups, it should
>>> explicitly join the group.  So I cannot find valid (or meaningful) use-case.
>>
>> I expect only to receive the multicast traffic of groups I explicitly joined on that
>> socket. This is was the IPv4 version of this socket option already does. The problem
>> only exists if multiple groups are joined and the socket therefore has to be bound
>> to the "any"-address. Then we get traffic from all multicast groups joined by any(!)
>> process on the system (plus anything else on that IP-port).
> 
> Okay I agree that we should be able NOT to get such traffic.
> 
> Acked-By: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
> 
> --yoshfuji
> 
>>
>> Regards
>>   Andre
>>
>>>
>>> --yoshfuji
>>>
>>>>
>>>> Regards
>>>>   Andre
>>>>
>>>>>
>>>>> I was running into a problem, when trying to join multiple multicast groups
>>>>> on a single socket and thus binding to the any-address on said socket. I
>>>>> received traffic from multicast groups, I did not join on that socket and
>>>>> was at first surprised by that. After reading some old e-mails/threads,
>>>>> which came to the conclusion "It is, as it is."
>>>>> (e.g https://marc.info/?l=linux-kernel&m=115815686626791&w=2), I discovered
>>>>> the IPv4 socketoption IP_MULTICAST_ALL, which, when disabled, does exactly
>>>>> what I would expect from a socket by default.
>>>>>
>>>>> I propose a socket option for IPv6, which does the same and has the same
>>>>> default as the IPv4 version. My first thought was, to just apply
>>>>> IP_MULTICAST_ALL to a ipv6 socket, but that would change the behavior of
>>>>> current applications and would probably be a big no-no.
>>>>>
>>>>> Regards
>>>>>   Andre
>>>>>
>>>>>
>>>>> From 473653086c05a3de839c3504885053f6254c7bc5 Mon Sep 17 00:00:00 2001
>>>>> From: Andre Naujoks <nautsch2@gmail.com>
>>>>> Date: Wed, 11 Apr 2018 12:38:28 +0200
>>>>> Subject: [PATCH] Add a socketoption IPV6_MULTICAST_ALL analogue to the IPV4
>>>>>  version
>>>>>
>>>>> The socket option will be enabled by default to ensure current behaviour
>>>>> is not changed. This is the same for the IPv4 version.
>>>>>
>>>>> A socket bound to in6addr_any and a specific port will receive all traffic
>>>>> on that port. Analogue to IP_MULTICAST_ALL, disable this behaviour, if
>>>>> one or more multicast groups were joined (using said socket) and only
>>>>> pass on multicast traffic from groups, which were explicitly joined via
>>>>> this socket.
>>>>>
>>>>> Without this option disabled a socket (system even) joined to multiple
>>>>> multicast groups is very hard to get right. Filtering by destination
>>>>> address has to take place in user space to avoid receiving multicast
>>>>> traffic from other multicast groups, which might have traffic on the same
>>>>> port.
>>>>>
>>>>> The extension of the IP_MULTICAST_ALL socketoption to just apply to ipv6,
>>>>> too, is not done to avoid changing the behaviour of current applications.
>>>>>
>>>>> Signed-off-by: Andre Naujoks <nautsch2@gmail.com>
>>>>> ---
>>>>>  include/linux/ipv6.h     |  3 ++-
>>>>>  include/uapi/linux/in6.h |  1 +
>>>>>  net/ipv6/af_inet6.c      |  1 +
>>>>>  net/ipv6/ipv6_sockglue.c | 11 +++++++++++
>>>>>  net/ipv6/mcast.c         |  2 +-
>>>>>  5 files changed, 16 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
>>>>> index 8415bf1a9776..495e834c1367 100644
>>>>> --- a/include/linux/ipv6.h
>>>>> +++ b/include/linux/ipv6.h
>>>>> @@ -274,7 +274,8 @@ struct ipv6_pinfo {
>>>>>                                                */
>>>>>                               dontfrag:1,
>>>>>                               autoflowlabel:1,
>>>>> -                             autoflowlabel_set:1;
>>>>> +                             autoflowlabel_set:1,
>>>>> +                             mc_all:1;
>>>>>       __u8                    min_hopcount;
>>>>>       __u8                    tclass;
>>>>>       __be32                  rcv_flowinfo;
>>>>> diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
>>>>> index ed291e55f024..71d82fe15b03 100644
>>>>> --- a/include/uapi/linux/in6.h
>>>>> +++ b/include/uapi/linux/in6.h
>>>>> @@ -177,6 +177,7 @@ struct in6_flowlabel_req {
>>>>>  #define IPV6_V6ONLY          26
>>>>>  #define IPV6_JOIN_ANYCAST    27
>>>>>  #define IPV6_LEAVE_ANYCAST   28
>>>>> +#define IPV6_MULTICAST_ALL   29
>>>>>
>>>>>  /* IPV6_MTU_DISCOVER values */
>>>>>  #define IPV6_PMTUDISC_DONT           0
>>>>> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
>>>>> index 8da0b513f188..7844cd9d2f10 100644
>>>>> --- a/net/ipv6/af_inet6.c
>>>>> +++ b/net/ipv6/af_inet6.c
>>>>> @@ -209,6 +209,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
>>>>>       np->hop_limit   = -1;
>>>>>       np->mcast_hops  = IPV6_DEFAULT_MCASTHOPS;
>>>>>       np->mc_loop     = 1;
>>>>> +     np->mc_all      = 1;
>>>>>       np->pmtudisc    = IPV6_PMTUDISC_WANT;
>>>>>       np->repflow     = net->ipv6.sysctl.flowlabel_reflect;
>>>>>       sk->sk_ipv6only = net->ipv6.sysctl.bindv6only;
>>>>> diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
>>>>> index 4d780c7f0130..b2bc1942a2ee 100644
>>>>> --- a/net/ipv6/ipv6_sockglue.c
>>>>> +++ b/net/ipv6/ipv6_sockglue.c
>>>>> @@ -664,6 +664,13 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
>>>>>                       retv = ipv6_sock_ac_drop(sk, mreq.ipv6mr_ifindex, &mreq.ipv6mr_acaddr);
>>>>>               break;
>>>>>       }
>>>>> +     case IPV6_MULTICAST_ALL:
>>>>> +             if (optlen < sizeof(int))
>>>>> +                     goto e_inval;
>>>>> +             np->mc_all = valbool;
>>>>> +             retv = 0;
>>>>> +             break;
>>>>> +
>>>>>       case MCAST_JOIN_GROUP:
>>>>>       case MCAST_LEAVE_GROUP:
>>>>>       {
>>>>> @@ -1255,6 +1262,10 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
>>>>>               val = np->mcast_oif;
>>>>>               break;
>>>>>
>>>>> +     case IPV6_MULTICAST_ALL:
>>>>> +             val = np->mc_all;
>>>>> +             break;
>>>>> +
>>>>>       case IPV6_UNICAST_IF:
>>>>>               val = (__force int)htonl((__u32) np->ucast_oif);
>>>>>               break;
>>>>> diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
>>>>> index 793159d77d8a..623ad00eb3c2 100644
>>>>> --- a/net/ipv6/mcast.c
>>>>> +++ b/net/ipv6/mcast.c
>>>>> @@ -622,7 +622,7 @@ bool inet6_mc_check(struct sock *sk, const struct in6_addr *mc_addr,
>>>>>       }
>>>>>       if (!mc) {
>>>>>               rcu_read_unlock();
>>>>> -             return true;
>>>>> +             return np->mc_all;
>>>>>       }
>>>>>       read_lock(&mc->sflock);
>>>>>       psl = mc->sflist;
>>>>>
>>>>
>>

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