Based on RFC3376 5.1
   If no interface
   state existed for that multicast address before the change (i.e., the
   change consisted of creating a new per-interface record), or if no
   state exists after the change (i.e., the change consisted of deleting
   a per-interface record), then the "non-existent" state is considered
   to have a filter mode of INCLUDE and an empty source list.

Which means a new multicast group should start with state IN().

Function ip_mc_join_group() works correctly for IGMP ASM(Any-Source Multicast)
mode. It adds a group with state EX() and inits crcount to mc_qrv,
so the kernel will send a TO_EX() report message after adding group.

But for IGMPv3 SSM(Source-specific multicast) JOIN_SOURCE_GROUP mode, we
split the group joining into two steps. First we join the group like ASM,
i.e. via ip_mc_join_group(). So the state changes from IN() to EX().

Then we add the source-specific address with INCLUDE mode. So the state
changes from EX() to IN(A).

Before the first step sends a group change record, we finished the second
step. So we will only send the second change record. i.e. TO_IN(A).

Regarding the RFC stands, we should actually send an ALLOW(A) message for
SSM JOIN_SOURCE_GROUP as the state should mimic the 'IN() to IN(A)'
transition.

The issue was exposed by commit a052517a8ff65 ("net/multicast: should not
send source list records when have filter mode change"). Before this change,
we used to send both ALLOW(A) and TO_IN(A). After this change we only send
TO_IN(A).

Fix it by adding a new parameter to init group mode. Also add new wrapper
functions so we don't need to change too much code.

v1 -> v2:
In my first version I only cleared the group change record. But this is not
enough. Because when a new group join, it will init as EXCLUDE and trigger
an filter mode change in ip/ip6_mc_add_src(), which will clear all source
addresses' sf_crcount. This will prevent early joined address sending state
change records if multi source addressed joined at the same time.

In v2 patch, I fixed it by directly initializing the mode to INCLUDE for SSM
JOIN_SOURCE_GROUP. I also split the original patch into two separated patches
for IPv4 and IPv6.

Fixes: a052517a8ff65 ("net/multicast: should not send source list records when have filter mode change")
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This was initially introduced in df2cf4a78e488d26 ("IGMP: Inhibit
reports for local multicast groups") by defining the sysctl in the
ipv4_net_table array, however it was never implemented to be
namespace aware. Fix this by changing the code accordingly.

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch updates ip_check_mc_rcu so that protocol is passed as a u8
instead of a u16.

The motivation is just to avoid any unneeded type transitions since some
systems will require an instruction to zero extend a u8 field to a u16.
Also it makes it a bit more readable as to the fact that protocol is a u8
so there are no byte ordering changes needed to pass it.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The range of addresses between 224.0.0.0 and 224.0.0.255 inclusive, is
reserved for the use of routing protocols and other low-level topology
discovery or maintenance protocols, such as gateway discovery and
group membership reporting.  Multicast routers should not forward any
multicast datagram with destination addresses in this range,
regardless of its TTL.

Currently, IGMP reports are generated for this reserved range of
addresses even though a router will ignore this information since it
has no purpose.  However, the presence of reserved group addresses in
an IGMP membership report uses up network bandwidth and can also
obscure addresses of interest when inspecting membership reports using
packet inspection or debug messages.

Although the RFCs for the various version of IGMP (e.g.RFC 3376 for
v3) do not specify that the reserved addresses be excluded from
membership reports, it should do no harm in doing so.  In particular
there should be no adverse effect in any IGMP snooping functionality
since 224.0.0.x is specifically excluded as per RFC 4541 (IGMP and MLD
Snooping Switches Considerations) section 2.1.2. Data Forwarding
Rules:

    2) Packets with a destination IP (DIP) address in the 224.0.0.X
       range which are not IGMP must be forwarded on all ports.

IGMP reports for local multicast groups can now be optionally
inhibited by means of a system control variable (by setting the value
to zero) e.g.:
    echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports

To retain backwards compatibility the previous behaviour is retained
by default on system boot or reverted by setting the value back to
non-zero e.g.:
    echo 1 >  /proc/sys/net/ipv4/igmp_link_local_mcast_reports

Signed-off-by: Philip Downey <pdowney@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

With this patch, the IGMP and MLD message validation functions are moved
from the bridge code to IPv4/IPv6 multicast files. Some small
refactoring was done to enhance readibility and to iron out some
differences in behaviour between the IGMP and MLD parsing code (e.g. the
skb-cloning of MLD messages is now only done if necessary, just like the
IGMP part always did).

Finally, these IGMP and MLD message validation functions are exported so
that not only the bridge can use it but batman-adv later, too.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>