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When multiple multicast routers are present in a broadcast domain then
only one of them will be detectable via IGMP/MLD query snooping. The
multicast router with the lowest IP address will become the selected and
active querier while all other multicast routers will then refrain from
sending queries.
To detect such rather silent multicast routers, too, RFC4286
("Multicast Router Discovery") provides a standardized protocol to
detect multicast routers for multicast snooping switches.
This patch implements the necessary MRD Advertisement message parsing
and after successful processing adds such routers to the internal
multicast router list.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>
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With this patch the internal use of the skb_trimmed is reduced to
the ICMPv6/IGMP checksum verification. And for the length checks
the newly introduced helper functions are used instead of calculating
and checking with skb->len directly.
These changes should hopefully make it easier to verify that length
checks are performed properly.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This patch refactors ip_mc_check_igmp(), ipv6_mc_check_mld() and
their callers (more precisely, the Linux bridge) to not rely on
the skb_trimmed parameter anymore.
An skb with its tail trimmed to the IP packet length was initially
introduced for the following three reasons:
1) To be able to verify the ICMPv6 checksum.
2) To be able to distinguish the version of an IGMP or MLD query.
They are distinguishable only by their size.
3) To avoid parsing data for an IGMPv3 or MLDv2 report that is
beyond the IP packet but still within the skb.
The first case still uses a cloned and potentially trimmed skb to
verfiy. However, there is no need to propagate it to the caller.
For the second and third case explicit IP packet length checks were
added.
This hopefully makes ip_mc_check_igmp() and ipv6_mc_check_mld() easier
to read and verfiy, as well as easier to use.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The recent refactoring of the IGMP and MLD parsing code into
ipv6_mc_check_mld() / ip_mc_check_igmp() introduced a potential crash /
BUG() invocation for bridges:
I wrongly assumed that skb_get() could be used as a simple reference
counter for an skb which is not the case. skb_get() bears additional
semantics, a user count. This leads to a BUG() invocation in
pskb_expand_head() / kernel panic if pskb_may_pull() is called on an skb
with a user count greater than one - unfortunately the refactoring did
just that.
Fixing this by removing the skb_get() call and changing the API: The
caller of ipv6_mc_check_mld() / ip_mc_check_igmp() now needs to
additionally check whether the returned skb_trimmed is a clone.
Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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> net/core/skbuff.c:4108:13: sparse: incorrect type in assignment (different base types)
> net/ipv6/mcast_snoop.c:63 ipv6_mc_check_exthdrs() warn: unsigned 'offset' is never less than zero.
Introduced by 9afd85c9e4552b276e2f4cfefd622bdeeffbbf26
("net: Export IGMP/MLD message validation code")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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