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batman-adv: mcast: detect, distribute and maintain multicast router presence

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To be able to apply our group aware multicast optimizations to packets
with a scope greater than link-local we need to not only keep track of
multicast listeners but also multicast routers.

With this patch a node detects the presence of multicast routers on
its segment by checking if
/proc/sys/net/ipv{4,6}/conf/<bat0|br0(bat)>/mc_forwarding is set for one
thing. This option is enabled by multicast routing daemons and needed
for the kernel's multicast routing tables to receive and route packets.

For another thing if a bridge is configured on top of bat0 then the
presence of an IPv6 multicast router behind this bridge is currently
detected by checking for an IPv6 multicast "All Routers Address"
(ff02::2). This should later be replaced by querying the bridge, which
performs proper, RFC4286 compliant Multicast Router Discovery (our
simplified approach includes more hosts than necessary, most notably
not just multicast routers but also unicast ones and is not applicable
for IPv4).

If no multicast router is detected then this is signalized via the new
BATADV_MCAST_WANT_NO_RTR4 and BATADV_MCAST_WANT_NO_RTR6
multicast tvlv flags.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
This commit is contained in:
Linus Lüssing
2019-06-11 22:58:40 +02:00
committed by Simon Wunderlich
parent 3bcacd1e06
commit 61caf3d109
4 changed files with 399 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/uapi/linux/batadv_packet.h
View File

@@ -107,12 +107,20 @@ enum batadv_icmp_packettype {
* @BATADV_MCAST_WANT_ALL_UNSNOOPABLES: we want all packets destined for
* 224.0.0.0/24 or ff02::1
* @BATADV_MCAST_WANT_ALL_IPV4: we want all IPv4 multicast packets
* (both link-local and routable ones)
* @BATADV_MCAST_WANT_ALL_IPV6: we want all IPv6 multicast packets
* (both link-local and routable ones)
* @BATADV_MCAST_WANT_NO_RTR4: we have no IPv4 multicast router and therefore
* only need routable IPv4 multicast packets we signed up for explicitly
* @BATADV_MCAST_WANT_NO_RTR6: we have no IPv6 multicast router and therefore
* only need routable IPv6 multicast packets we signed up for explicitly
*/
enum batadv_mcast_flags {
BATADV_MCAST_WANT_ALL_UNSNOOPABLES = 1UL << 0,
BATADV_MCAST_WANT_ALL_IPV4 = 1UL << 1,
BATADV_MCAST_WANT_ALL_IPV6 = 1UL << 2,
BATADV_MCAST_WANT_NO_RTR4 = 1UL << 3,
BATADV_MCAST_WANT_NO_RTR6 = 1UL << 4,
};
/* tt data subtypes */