diff mbox series

[v4,3/5] batman-adv: mcast: implement multicast packet reception and forwarding

Message ID 20221227193409.13461-4-linus.luessing@c0d3.blue
State Changes Requested
Headers show
Series Implementation of a Stateless Multicast Packet Type | expand

Commit Message

Linus Lüssing Dec. 27, 2022, 7:34 p.m. UTC
Implement functionality to receive and forward a new TVLV capable
multicast packet type.

The new batman-adv multicast packet type allows to contain several
originator destination addresses within a TVLV. Routers on the way will
potentially split the batman-adv multicast packet and adjust its tracker
TVLV contents.

Routing decisions are still based on the selected BATMAN IV or BATMAN V
routing algorithm. So this new batman-adv multicast packet type retains
the same loop-free properties.

Also a new OGM multicast TVLV flag is introduced to signal to other
nodes that we are capable of handling a batman-adv multicast packet and
multicast tracker TVLV. And that all of our hard interfaces have an MTU
of at least 1280 bytes (IPv6 minimum MTU), as a simple solution for now
to avoid MTU issues while forwarding.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
 include/uapi/linux/batadv_packet.h |  48 ++++-
 net/batman-adv/Makefile            |   1 +
 net/batman-adv/main.c              |   2 +
 net/batman-adv/multicast.c         |  48 ++++-
 net/batman-adv/multicast.h         |   5 +
 net/batman-adv/multicast_forw.c    | 274 +++++++++++++++++++++++++++++
 net/batman-adv/originator.c        |   1 +
 net/batman-adv/routing.c           |  68 +++++++
 net/batman-adv/routing.h           |  11 ++
 net/batman-adv/soft-interface.c    |  12 ++
 net/batman-adv/types.h             |  64 +++++++
 11 files changed, 523 insertions(+), 11 deletions(-)
 create mode 100644 net/batman-adv/multicast_forw.c

Comments

Sven Eckelmann Jan. 15, 2023, 5:56 p.m. UTC | #1
On Tuesday, 27 December 2022 20:34:07 CET Linus Lüssing wrote:
> Implement functionality to receive and forward a new TVLV capable
> multicast packet type.
> 
> The new batman-adv multicast packet type allows to contain several
> originator destination addresses within a TVLV. Routers on the way will
> potentially split the batman-adv multicast packet and adjust its tracker
> TVLV contents.
> 
> Routing decisions are still based on the selected BATMAN IV or BATMAN V
> routing algorithm. So this new batman-adv multicast packet type retains
> the same loop-free properties.
> 
> Also a new OGM multicast TVLV flag is introduced to signal to other
> nodes that we are capable of handling a batman-adv multicast packet and
> multicast tracker TVLV. And that all of our hard interfaces have an MTU
> of at least 1280 bytes (IPv6 minimum MTU), as a simple solution for now
> to avoid MTU issues while forwarding.
> 
> Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
>  include/uapi/linux/batadv_packet.h |  48 ++++-
>  net/batman-adv/Makefile            |   1 +
>  net/batman-adv/main.c              |   2 +
>  net/batman-adv/multicast.c         |  48 ++++-
>  net/batman-adv/multicast.h         |   5 +
>  net/batman-adv/multicast_forw.c    | 274 +++++++++++++++++++++++++++++
>  net/batman-adv/originator.c        |   1 +
>  net/batman-adv/routing.c           |  68 +++++++
>  net/batman-adv/routing.h           |  11 ++
>  net/batman-adv/soft-interface.c    |  12 ++
>  net/batman-adv/types.h             |  64 +++++++
>  11 files changed, 523 insertions(+), 11 deletions(-)
>  create mode 100644 net/batman-adv/multicast_forw.c


Acked-by: Sven Eckelmann <sven@narfation.org>

But I want to have at least another maintainer checking the new packet format 
and acking it.

Kind regards,
	Sven

[...]
> +static void
> +batadv_mcast_forw_scrub_dests(struct batadv_priv *bat_priv,
> +			      struct batadv_neigh_node *comp_neigh, u8 *dest,
> +			      u8 *next_dest, u16 num_dests)
> +{
> +	struct batadv_neigh_node *next_neigh;
> +
> +	/* skip first entry, this is what we are comparing with */
> +	eth_zero_addr(dest);
> +	dest += ETH_ALEN;
> +	next_dest += ETH_ALEN;
> +	num_dests--;
> +
> +	batadv_mcast_forw_tracker_for_each_dest(next_dest, num_dests) {
> +		if (is_zero_ether_addr(next_dest))
> +			goto scrub_next;
> +
> +		if (is_multicast_ether_addr(next_dest)) {
> +			eth_zero_addr(dest);
> +			eth_zero_addr(next_dest);
> +			goto scrub_next;
> +		}
> +
> +		next_neigh = batadv_mcast_forw_orig_to_neigh(bat_priv,
> +							     next_dest);
> +		if (!next_neigh) {
> +			eth_zero_addr(next_dest);

Why is the original skb not touched in this case?

It might not be a problem because you are also doing the 
batadv_mcast_forw_orig_to_neigh check in batadv_mcast_forw_packet. But I was 
just wondering about it


Btw. it could happen that you send out a packet with zero destinations in the 
TVLV because the neighbor disappeared between the 
batadv_mcast_forw_orig_to_neigh in batadv_mcast_forw_packet and in 
batadv_mcast_forw_scrub_dests

Kind regards,
	Sven
Linus Lüssing Jan. 16, 2023, 6:31 p.m. UTC | #2
On Sun, Jan 15, 2023 at 06:56:37PM +0100, Sven Eckelmann wrote:
> [...]
> > +static void
> > +batadv_mcast_forw_scrub_dests(struct batadv_priv *bat_priv,
> > +			      struct batadv_neigh_node *comp_neigh, u8 *dest,
> > +			      u8 *next_dest, u16 num_dests)
> > +{
> > +	struct batadv_neigh_node *next_neigh;
> > +
> > +	/* skip first entry, this is what we are comparing with */
> > +	eth_zero_addr(dest);
> > +	dest += ETH_ALEN;
> > +	next_dest += ETH_ALEN;
> > +	num_dests--;
> > +
> > +	batadv_mcast_forw_tracker_for_each_dest(next_dest, num_dests) {
> > +		if (is_zero_ether_addr(next_dest))
> > +			goto scrub_next;
> > +
> > +		if (is_multicast_ether_addr(next_dest)) {
> > +			eth_zero_addr(dest);
> > +			eth_zero_addr(next_dest);
> > +			goto scrub_next;
> > +		}
> > +
> > +		next_neigh = batadv_mcast_forw_orig_to_neigh(bat_priv,
> > +							     next_dest);
> > +		if (!next_neigh) {
> > +			eth_zero_addr(next_dest);
> 
> Why is the original skb not touched in this case?
> 
> It might not be a problem because you are also doing the 
> batadv_mcast_forw_orig_to_neigh check in batadv_mcast_forw_packet. But I was 
> just wondering about it

I actually thought the same at some point, to potentially reduce the
number of neighbor node lookups, and tried it. And then
realized that it can break local reception. The destination
address might be our own one and then the neighbor node lookup
will return NULL, too.

So instead of adding another batadv_is_my_mac() check in yet
another place and branching here in scrub_dests(), I thought I'd keep
it simple.

I could also add these two lines in scrub_dests(), the check and zeroing,
I'm just not quite sure if we would overall gain something with it, as
batadv_is_my_mac() can be a bit expensive at the moment when there are
many interfaces?

> 
> 
> Btw. it could happen that you send out a packet with zero destinations in the 
> TVLV because the neighbor disappeared between the 
> batadv_mcast_forw_orig_to_neigh in batadv_mcast_forw_packet and in 
> batadv_mcast_forw_scrub_dests

Ah good point. Hm, the protocol should be robust enough on
the receiver side to handle it. And it should overall happen very rarely.
I'm indifferent to adding two more lines of code to check that.

> 
> Kind regards,
> 	Sven
Simon Wunderlich Jan. 19, 2023, 12:47 p.m. UTC | #3
On Tuesday, December 27, 2022 8:34:07 PM CET Linus Lüssing wrote:
> +/**
> + * struct batadv_tvlv_mcast_tracker - payload of a multicast tracker tvlv
> + * @num_dests: number of subsequent destination originator MAC addresses
> + * @align: (optional) alignment bytes to make the tracker TVLV 4 bytes
> aligned, + * present if num_dests are even, not present if odd
> + */
> +struct batadv_tvlv_mcast_tracker {
> +       __be16  num_dests;
> +       __u8    align[2];
> +};
> +
The one thing which I really don't like is to have the alignment in the 
beginning, and depending on the number of entries. Normally, such alignments 
should be at the end of the structure so it is straight forward for a parser 
to omit it.

My understanding is that the alignment is due to technical reasons (mac 
address list is assembled by pushing the data to the front), perhaps to save 
another memove/memcpy. However, the data is collected by traversing various 
lists, and if performance would be a concern, then this data should be cached 
and this "technicality" wouldn't be needed either.

So please, skip the alignment in the front and have it in the back.

The rest of the packet format looks good from what I've seen.

Cheers,
      Simon
Linus Lüssing Jan. 21, 2023, 1:15 p.m. UTC | #4
On Thu, Jan 19, 2023 at 01:47:25PM +0100, Simon Wunderlich wrote:
> On Tuesday, December 27, 2022 8:34:07 PM CET Linus Lüssing wrote:
> > +/**
> > + * struct batadv_tvlv_mcast_tracker - payload of a multicast tracker tvlv
> > + * @num_dests: number of subsequent destination originator MAC addresses
> > + * @align: (optional) alignment bytes to make the tracker TVLV 4 bytes
> > aligned, + * present if num_dests are even, not present if odd
> > + */
> > +struct batadv_tvlv_mcast_tracker {
> > +       __be16  num_dests;
> > +       __u8    align[2];
> > +};
> > +
> The one thing which I really don't like is to have the alignment in the 
> beginning, and depending on the number of entries. Normally, such alignments 
> should be at the end of the structure so it is straight forward for a parser 
> to omit it.
> 
> My understanding is that the alignment is due to technical reasons (mac 
> address list is assembled by pushing the data to the front), perhaps to save 
> another memove/memcpy. However, the data is collected by traversing various 
> lists, and if performance would be a concern, then this data should be cached 
> and this "technicality" wouldn't be needed either.

The technical reason was to have the payload data from the IP
header 4 bytes aligned. To allow efficient access in there once the
payload is decapsulated.

> 
> So please, skip the alignment in the front and have it in the back.

The reasons to put the aligment at the front are/were the following
two:

1) We do keep a count of receiving nodes, however it might change
while we are pushing destinations. So it is at the moment easier
to push the padding to the front, when we know exactly how many
destinations we have added to the packet. As discussed offline, I
guess that is what you were refering to above.

2) Alignment changes during routing everytime a router removes an
odd number of destinations from the tracker TVLV. Changing
alignment more to the front would in theory less memory movements.
Example for an ideal case:

[MC-HDR][pad][dest1][dest2]...[dest100][PAYLOAD]
-> dest1 is deleted
[MC-HDR][pad][00000][dest2]...[dest100][PAYLOAD]
-> move only MC-HDR:
[MC-HDR][dest2]...[dest100][PAYLOAD]
 
If the alignment were behind dest100 then everything would need to
be moved.


Even though it's unconventional to have the padding in the front,
I found the idea quite tempting and useful to have the padding in
front, saves quite a bit of code and potential bugs I would hope :D.
And would hopefully (potentially allow to) make the packet routing
a bit faster. So from a "purely technical" point-of-view it seemed
advantageous to me :D.

Another idea would be to have the padding at the end by adding and
keeping a zero-MAC destination entry if the number of destinations
were otherwise even. Disadvantage: Might waste 4 more bytes than
necessary.

> 
> The rest of the packet format looks good from what I've seen.

Thanks for having a look at it!

Regards, Linus
diff mbox series

Patch

diff --git a/include/uapi/linux/batadv_packet.h b/include/uapi/linux/batadv_packet.h
index 9204e4494b25..77021519cd26 100644
--- a/include/uapi/linux/batadv_packet.h
+++ b/include/uapi/linux/batadv_packet.h
@@ -116,6 +116,9 @@  enum batadv_icmp_packettype {
  * 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
+ * @BATADV_MCAST_HAVE_MC_PTYPE_CAPA: we can parse, receive and forward
+ * batman-adv multicast packets with a multicast tracker TVLV. And all our
+ * hard interfaces have an MTU of at least 1280 bytes.
  */
 enum batadv_mcast_flags {
 	BATADV_MCAST_WANT_ALL_UNSNOOPABLES	= 1UL << 0,
@@ -123,6 +126,7 @@  enum batadv_mcast_flags {
 	BATADV_MCAST_WANT_ALL_IPV6		= 1UL << 2,
 	BATADV_MCAST_WANT_NO_RTR4		= 1UL << 3,
 	BATADV_MCAST_WANT_NO_RTR6		= 1UL << 4,
+	BATADV_MCAST_HAVE_MC_PTYPE_CAPA		= 1UL << 5,
 };
 
 /* tt data subtypes */
@@ -174,14 +178,16 @@  enum batadv_bla_claimframe {
  * @BATADV_TVLV_TT: translation table tvlv
  * @BATADV_TVLV_ROAM: roaming advertisement tvlv
  * @BATADV_TVLV_MCAST: multicast capability tvlv
+ * @BATADV_TVLV_MCAST_TRACKER: multicast tracker tvlv
  */
 enum batadv_tvlv_type {
-	BATADV_TVLV_GW		= 0x01,
-	BATADV_TVLV_DAT		= 0x02,
-	BATADV_TVLV_NC		= 0x03,
-	BATADV_TVLV_TT		= 0x04,
-	BATADV_TVLV_ROAM	= 0x05,
-	BATADV_TVLV_MCAST	= 0x06,
+	BATADV_TVLV_GW			= 0x01,
+	BATADV_TVLV_DAT			= 0x02,
+	BATADV_TVLV_NC			= 0x03,
+	BATADV_TVLV_TT			= 0x04,
+	BATADV_TVLV_ROAM		= 0x05,
+	BATADV_TVLV_MCAST		= 0x06,
+	BATADV_TVLV_MCAST_TRACKER	= 0x07,
 };
 
 #pragma pack(2)
@@ -487,6 +493,25 @@  struct batadv_bcast_packet {
 	 */
 };
 
+/**
+ * struct batadv_mcast_packet - multicast packet for network payload
+ * @packet_type: batman-adv packet type, part of the general header
+ * @version: batman-adv protocol version, part of the general header
+ * @ttl: time to live for this packet, part of the general header
+ * @reserved: reserved byte for alignment
+ * @tvlv_len: length of the appended tvlv buffer (in bytes)
+ */
+struct batadv_mcast_packet {
+	__u8 packet_type;
+	__u8 version;
+	__u8 ttl;
+	__u8 reserved;
+	__be16 tvlv_len;
+	/* "4 bytes boundary + 2 bytes" long to make the payload after the
+	 * following ethernet header again 4 bytes boundary aligned
+	 */
+};
+
 /**
  * struct batadv_coded_packet - network coded packet
  * @packet_type: batman-adv packet type, part of the general header
@@ -628,6 +653,17 @@  struct batadv_tvlv_mcast_data {
 	__u8 reserved[3];
 };
 
+/**
+ * struct batadv_tvlv_mcast_tracker - payload of a multicast tracker tvlv
+ * @num_dests: number of subsequent destination originator MAC addresses
+ * @align: (optional) alignment bytes to make the tracker TVLV 4 bytes aligned,
+ * present if num_dests are even, not present if odd
+ */
+struct batadv_tvlv_mcast_tracker {
+	__be16	num_dests;
+	__u8	align[2];
+};
+
 #pragma pack()
 
 #endif /* _UAPI_LINUX_BATADV_PACKET_H_ */
diff --git a/net/batman-adv/Makefile b/net/batman-adv/Makefile
index 3bd0760c76a2..b51d8b071b56 100644
--- a/net/batman-adv/Makefile
+++ b/net/batman-adv/Makefile
@@ -20,6 +20,7 @@  batman-adv-y += hash.o
 batman-adv-$(CONFIG_BATMAN_ADV_DEBUG) += log.o
 batman-adv-y += main.o
 batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += multicast.o
+batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += multicast_forw.o
 batman-adv-y += netlink.o
 batman-adv-$(CONFIG_BATMAN_ADV_NC) += network-coding.o
 batman-adv-y += originator.o
diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index e8a449915566..50b2bf2b748c 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -532,6 +532,8 @@  static void batadv_recv_handler_init(void)
 
 	/* broadcast packet */
 	batadv_rx_handler[BATADV_BCAST] = batadv_recv_bcast_packet;
+	/* multicast packet */
+	batadv_rx_handler[BATADV_MCAST] = batadv_recv_mcast_packet;
 
 	/* unicast packets ... */
 	/* unicast with 4 addresses packet */
diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 27511a063311..f2b1e523fd85 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -243,6 +243,37 @@  static u8 batadv_mcast_mla_rtr_flags_get(struct batadv_priv *bat_priv,
 	return flags;
 }
 
+/**
+ * batadv_mcast_mla_forw_flags_get() - get multicast forwarding flags
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Checks if all active hard interfaces have an MTU larger or equal to 1280
+ * bytes (IPv6 minimum MTU).
+ *
+ * Return: BATADV_MCAST_HAVE_MC_PTYPE_CAPA if yes, BATADV_NO_FLAGS otherwise.
+ */
+static u8 batadv_mcast_mla_forw_flags_get(struct batadv_priv *bat_priv)
+{
+	const struct batadv_hard_iface *hard_iface;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
+		if (hard_iface->if_status != BATADV_IF_ACTIVE)
+			continue;
+
+		if (hard_iface->soft_iface != bat_priv->soft_iface)
+			continue;
+
+		if (hard_iface->net_dev->mtu < IPV6_MIN_MTU) {
+			rcu_read_unlock();
+			return BATADV_NO_FLAGS;
+		}
+	}
+	rcu_read_unlock();
+
+	return BATADV_MCAST_HAVE_MC_PTYPE_CAPA;
+}
+
 /**
  * batadv_mcast_mla_flags_get() - get the new multicast flags
  * @bat_priv: the bat priv with all the soft interface information
@@ -264,6 +295,7 @@  batadv_mcast_mla_flags_get(struct batadv_priv *bat_priv)
 	mla_flags.enabled = 1;
 	mla_flags.tvlv_flags |= batadv_mcast_mla_rtr_flags_get(bat_priv,
 							       bridge);
+	mla_flags.tvlv_flags |= batadv_mcast_mla_forw_flags_get(bat_priv);
 
 	if (!bridge)
 		return mla_flags;
@@ -814,23 +846,25 @@  static void batadv_mcast_flags_log(struct batadv_priv *bat_priv, u8 flags)
 {
 	bool old_enabled = bat_priv->mcast.mla_flags.enabled;
 	u8 old_flags = bat_priv->mcast.mla_flags.tvlv_flags;
-	char str_old_flags[] = "[.... . ]";
+	char str_old_flags[] = "[.... . .]";
 
-	sprintf(str_old_flags, "[%c%c%c%s%s]",
+	sprintf(str_old_flags, "[%c%c%c%s%s%c]",
 		(old_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) ? 'U' : '.',
 		(old_flags & BATADV_MCAST_WANT_ALL_IPV4) ? '4' : '.',
 		(old_flags & BATADV_MCAST_WANT_ALL_IPV6) ? '6' : '.',
 		!(old_flags & BATADV_MCAST_WANT_NO_RTR4) ? "R4" : ". ",
-		!(old_flags & BATADV_MCAST_WANT_NO_RTR6) ? "R6" : ". ");
+		!(old_flags & BATADV_MCAST_WANT_NO_RTR6) ? "R6" : ". ",
+		!(old_flags & BATADV_MCAST_HAVE_MC_PTYPE_CAPA) ? 'P' : '.');
 
 	batadv_dbg(BATADV_DBG_MCAST, bat_priv,
-		   "Changing multicast flags from '%s' to '[%c%c%c%s%s]'\n",
+		   "Changing multicast flags from '%s' to '[%c%c%c%s%s%c]'\n",
 		   old_enabled ? str_old_flags : "<undefined>",
 		   (flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) ? 'U' : '.',
 		   (flags & BATADV_MCAST_WANT_ALL_IPV4) ? '4' : '.',
 		   (flags & BATADV_MCAST_WANT_ALL_IPV6) ? '6' : '.',
 		   !(flags & BATADV_MCAST_WANT_NO_RTR4) ? "R4" : ". ",
-		   !(flags & BATADV_MCAST_WANT_NO_RTR6) ? "R6" : ". ");
+		   !(flags & BATADV_MCAST_WANT_NO_RTR6) ? "R6" : ". ",
+		   !(flags & BATADV_MCAST_HAVE_MC_PTYPE_CAPA) ? 'P' : '.');
 }
 
 /**
@@ -1828,6 +1862,10 @@  void batadv_mcast_init(struct batadv_priv *bat_priv)
 	batadv_tvlv_handler_register(bat_priv, batadv_mcast_tvlv_ogm_handler,
 				     NULL, NULL, BATADV_TVLV_MCAST, 2,
 				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
+	batadv_tvlv_handler_register(bat_priv, NULL, NULL,
+				     batadv_mcast_forw_tracker_tvlv_handler,
+				     BATADV_TVLV_MCAST_TRACKER, 1,
+				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
 
 	INIT_DELAYED_WORK(&bat_priv->mcast.work, batadv_mcast_mla_update);
 	batadv_mcast_start_timer(bat_priv);
diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
index a9770d8d6d36..a5c0f384bb9a 100644
--- a/net/batman-adv/multicast.h
+++ b/net/batman-adv/multicast.h
@@ -52,6 +52,11 @@  void batadv_mcast_free(struct batadv_priv *bat_priv);
 
 void batadv_mcast_purge_orig(struct batadv_orig_node *orig_node);
 
+/* multicast_forw.c */
+
+int batadv_mcast_forw_tracker_tvlv_handler(struct batadv_priv *bat_priv,
+					   struct sk_buff *skb);
+
 #else
 
 static inline enum batadv_forw_mode
diff --git a/net/batman-adv/multicast_forw.c b/net/batman-adv/multicast_forw.c
new file mode 100644
index 000000000000..4a6e0def0987
--- /dev/null
+++ b/net/batman-adv/multicast_forw.c
@@ -0,0 +1,274 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) B.A.T.M.A.N. contributors:
+ *
+ * Linus Lüssing
+ */
+
+#include "multicast.h"
+#include "main.h"
+
+#include <linux/byteorder/generic.h>
+#include <linux/errno.h>
+#include <linux/etherdevice.h>
+#include <linux/gfp.h>
+#include <linux/if_ether.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+#include <uapi/linux/batadv_packet.h>
+
+#include "originator.h"
+#include "routing.h"
+#include "send.h"
+
+#define batadv_mcast_forw_tracker_for_each_dest(dest, num_dests) \
+	for (; num_dests; num_dests--, (dest) += ETH_ALEN)
+
+/**
+ * batadv_mcast_forw_tracker_hdrlen() - calculate tracker TVLV header length
+ * @num_dests: the number of destination addresses to taken into account
+ *
+ * Return: The size of the multicast tracker TVLV structure if the number of
+ * destinations is even or that size minus the 2 alignment bytes otherwise.
+ */
+static int batadv_mcast_forw_tracker_hdrlen(unsigned int num_dests)
+{
+	struct batadv_tvlv_mcast_tracker *mcast_tracker;
+	unsigned int len = sizeof(*mcast_tracker);
+
+	/* new #dests even: with 2 byte padding to TVLV */
+	if (!(num_dests % 2))
+		return len;
+	/* new #dests odd: without 2 byte padding to TVLV */
+	else
+		return len - sizeof(mcast_tracker->align);
+}
+
+/**
+ * batadv_mcast_forw_orig_to_neigh() - get next hop neighbor to an orig address
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig_addr: the originator MAC address to search the best next hop router for
+ *
+ * Return: A neighbor node which is the best router towards the given originator
+ * address.
+ */
+static struct batadv_neigh_node *
+batadv_mcast_forw_orig_to_neigh(struct batadv_priv *bat_priv, u8 *orig_addr)
+{
+	struct batadv_neigh_node *neigh_node;
+	struct batadv_orig_node *orig_node;
+
+	orig_node = batadv_orig_hash_find(bat_priv, orig_addr);
+	if (!orig_node)
+		return NULL;
+
+	neigh_node = batadv_find_router(bat_priv, orig_node, NULL);
+	batadv_orig_node_put(orig_node);
+
+	return neigh_node;
+}
+
+/**
+ * batadv_mcast_forw_scrub_dests() - scrub destinations in a tracker TVLV
+ * @bat_priv: the bat priv with all the soft interface information
+ * @comp_neigh: next hop neighbor to scrub+collect destinations for
+ * @dest: start MAC entry in original skb's tracker TVLV
+ * @next_dest: start MAC entry in to be sent skb's tracker TVLV
+ * @num_dests: number of remaining destination MAC entries to iterate over
+ *
+ * This sorts destination entries into either the original batman-adv
+ * multicast packet or the skb (copy) that is going to be sent to comp_neigh
+ * next.
+ *
+ * In preparation for the next, to be (unicast) transmitted batman-adv multicast
+ * packet skb to be sent to the given neighbor node, tries to collect all
+ * originator MAC addresses that have the given neighbor node as their next hop
+ * in the to be transmitted skb (copy), which next_dest points into. That is we
+ * zero all destination entries in next_dest which do not have comp_neigh as
+ * their next hop. And zero all destination entries in the original skb that
+ * would have comp_neigh as their next hop (to avoid redundant transmissions and
+ * duplicated payload later).
+ */
+static void
+batadv_mcast_forw_scrub_dests(struct batadv_priv *bat_priv,
+			      struct batadv_neigh_node *comp_neigh, u8 *dest,
+			      u8 *next_dest, u16 num_dests)
+{
+	struct batadv_neigh_node *next_neigh;
+
+	/* skip first entry, this is what we are comparing with */
+	eth_zero_addr(dest);
+	dest += ETH_ALEN;
+	next_dest += ETH_ALEN;
+	num_dests--;
+
+	batadv_mcast_forw_tracker_for_each_dest(next_dest, num_dests) {
+		if (is_zero_ether_addr(next_dest))
+			goto scrub_next;
+
+		if (is_multicast_ether_addr(next_dest)) {
+			eth_zero_addr(dest);
+			eth_zero_addr(next_dest);
+			goto scrub_next;
+		}
+
+		next_neigh = batadv_mcast_forw_orig_to_neigh(bat_priv,
+							     next_dest);
+		if (!next_neigh) {
+			eth_zero_addr(next_dest);
+			goto scrub_next;
+		}
+
+		/* Is this for our next packet to transmit? */
+		if (batadv_compare_eth(next_neigh->addr, comp_neigh->addr))
+			eth_zero_addr(dest);
+		else
+			eth_zero_addr(next_dest);
+
+		batadv_neigh_node_put(next_neigh);
+scrub_next:
+		dest += ETH_ALEN;
+	}
+}
+
+/**
+ * batadv_mcast_forw_packet() - forward a batman-adv multicast packet
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the received or locally generated batman-adv multicast packet
+ * @local_xmit: indicates that the packet was locally generated and not received
+ *
+ * Parses the tracker TVLV of a batman-adv multicast packet and forwards the
+ * packet as indicated in this TVLV.
+ *
+ * Caller needs to set the skb network header to the start of the multicast
+ * tracker TVLV (excluding the generic TVLV header) and the skb transport header
+ * to the next byte after this multicast tracker TVLV.
+ *
+ * Caller needs to free the skb.
+ *
+ * Return: NET_RX_SUCCESS or NET_RX_DROP on success or a negative error
+ * code on failure. NET_RX_SUCCESS if the received packet is supposed to be
+ * decapsulated and forwarded to the own soft interface, NET_RX_DROP otherwise.
+ */
+static int batadv_mcast_forw_packet(struct batadv_priv *bat_priv,
+				    struct sk_buff *skb, bool local_xmit)
+{
+	struct batadv_tvlv_mcast_tracker *mcast_tracker;
+	unsigned int tvlv_len, tracker_hdrlen;
+	struct batadv_neigh_node *neigh_node;
+	unsigned long offset, num_dests_off;
+	struct sk_buff *nexthop_skb;
+	unsigned char *skb_net_hdr;
+	bool local_recv = false;
+	bool xmitted = false;
+	u8 *dest, *next_dest;
+	u16 num_dests;
+	int ret;
+
+	/* check if num_dests is within skb length */
+	num_dests_off = offsetof(struct batadv_tvlv_mcast_tracker, num_dests);
+	if (num_dests_off > skb_network_header_len(skb))
+		return -EINVAL;
+
+	skb_net_hdr = skb_network_header(skb);
+	mcast_tracker = (struct batadv_tvlv_mcast_tracker *)skb_net_hdr;
+	num_dests = ntohs(mcast_tracker->num_dests);
+
+	tracker_hdrlen = batadv_mcast_forw_tracker_hdrlen(num_dests);
+	dest = (u8 *)mcast_tracker + tracker_hdrlen;
+
+	/* check if full tracker tvlv is within skb length */
+	tvlv_len = tracker_hdrlen + ETH_ALEN * num_dests;
+	if (tvlv_len > skb_network_header_len(skb))
+		return -EINVAL;
+
+	batadv_mcast_forw_tracker_for_each_dest(dest, num_dests) {
+		if (is_zero_ether_addr(dest))
+			continue;
+
+		/* only unicast originator addresses supported */
+		if (is_multicast_ether_addr(dest)) {
+			eth_zero_addr(dest);
+			continue;
+		}
+
+		if (batadv_is_my_mac(bat_priv, dest)) {
+			eth_zero_addr(dest);
+			local_recv = true;
+			continue;
+		}
+
+		neigh_node = batadv_mcast_forw_orig_to_neigh(bat_priv, dest);
+		if (!neigh_node) {
+			eth_zero_addr(dest);
+			continue;
+		}
+
+		nexthop_skb = skb_copy(skb, GFP_ATOMIC);
+		if (!nexthop_skb) {
+			batadv_neigh_node_put(neigh_node);
+			return -ENOMEM;
+		}
+
+		offset = dest - skb->data;
+		next_dest = nexthop_skb->data + offset;
+
+		batadv_mcast_forw_scrub_dests(bat_priv, neigh_node, dest,
+					      next_dest, num_dests);
+
+		batadv_inc_counter(bat_priv, BATADV_CNT_MCAST_TX);
+		batadv_add_counter(bat_priv, BATADV_CNT_MCAST_TX_BYTES,
+				   nexthop_skb->len + ETH_HLEN);
+		xmitted = true;
+		ret = batadv_send_unicast_skb(nexthop_skb, neigh_node);
+
+		batadv_neigh_node_put(neigh_node);
+
+		if (ret < 0)
+			return ret;
+	}
+
+	if (xmitted) {
+		if (local_xmit) {
+			batadv_inc_counter(bat_priv, BATADV_CNT_MCAST_TX_LOCAL);
+			batadv_add_counter(bat_priv,
+					   BATADV_CNT_MCAST_TX_LOCAL_BYTES,
+					   skb->len -
+					   skb_transport_offset(skb));
+		} else {
+			batadv_inc_counter(bat_priv, BATADV_CNT_MCAST_FWD);
+			batadv_add_counter(bat_priv, BATADV_CNT_MCAST_FWD_BYTES,
+					   skb->len + ETH_HLEN);
+		}
+	}
+
+	if (local_recv)
+		return NET_RX_SUCCESS;
+	else
+		return NET_RX_DROP;
+}
+
+/**
+ * batadv_mcast_forw_tracker_tvlv_handler() - handle an mcast tracker tvlv
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the received batman-adv multicast packet
+ *
+ * Parses the tracker TVLV of an incoming batman-adv multicast packet and
+ * forwards the packet as indicated in this TVLV.
+ *
+ * Caller needs to set the skb network header to the start of the multicast
+ * tracker TVLV (excluding the generic TVLV header) and the skb transport header
+ * to the next byte after this multicast tracker TVLV.
+ *
+ * Caller needs to free the skb.
+ *
+ * Return: NET_RX_SUCCESS or NET_RX_DROP on success or a negative error
+ * code on failure. NET_RX_SUCCESS if the received packet is supposed to be
+ * decapsulated and forwarded to the own soft interface, NET_RX_DROP otherwise.
+ */
+int batadv_mcast_forw_tracker_tvlv_handler(struct batadv_priv *bat_priv,
+					   struct sk_buff *skb)
+{
+	return batadv_mcast_forw_packet(bat_priv, skb, false);
+}
diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 34903df4fe93..e46ce83c516a 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -942,6 +942,7 @@  struct batadv_orig_node *batadv_orig_node_new(struct batadv_priv *bat_priv,
 #ifdef CONFIG_BATMAN_ADV_MCAST
 	orig_node->mcast_flags = BATADV_MCAST_WANT_NO_RTR4;
 	orig_node->mcast_flags |= BATADV_MCAST_WANT_NO_RTR6;
+	orig_node->mcast_flags |= BATADV_MCAST_HAVE_MC_PTYPE_CAPA;
 	INIT_HLIST_NODE(&orig_node->mcast_want_all_unsnoopables_node);
 	INIT_HLIST_NODE(&orig_node->mcast_want_all_ipv4_node);
 	INIT_HLIST_NODE(&orig_node->mcast_want_all_ipv6_node);
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 163cd43c4821..432184548849 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -1270,3 +1270,71 @@  int batadv_recv_bcast_packet(struct sk_buff *skb,
 	batadv_orig_node_put(orig_node);
 	return ret;
 }
+
+#ifdef CONFIG_BATMAN_ADV_MCAST
+/**
+ * batadv_recv_mcast_packet() - process received batman-adv multicast packet
+ * @skb: the received batman-adv multicast packet
+ * @recv_if: interface that the skb is received on
+ *
+ * Parses the given, received batman-adv multicast packet. Depending on the
+ * contents of its TVLV forwards it and/or decapsulates it to hand it to the
+ * soft interface.
+ *
+ * Return: NET_RX_DROP if the skb is not consumed, NET_RX_SUCCESS otherwise.
+ */
+int batadv_recv_mcast_packet(struct sk_buff *skb,
+			     struct batadv_hard_iface *recv_if)
+{
+	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
+	struct batadv_mcast_packet *mcast_packet;
+	int hdr_size = sizeof(*mcast_packet);
+	unsigned char *tvlv_buff;
+	int ret = NET_RX_DROP;
+	u16 tvlv_buff_len;
+
+	if (batadv_check_unicast_packet(bat_priv, skb, hdr_size) < 0)
+		goto free_skb;
+
+	/* create a copy of the skb, if needed, to modify it. */
+	if (skb_cow(skb, ETH_HLEN) < 0)
+		goto free_skb;
+
+	/* packet needs to be linearized to access the tvlv content */
+	if (skb_linearize(skb) < 0)
+		goto free_skb;
+
+	mcast_packet = (struct batadv_mcast_packet *)skb->data;
+
+	tvlv_buff = (unsigned char *)(skb->data + hdr_size);
+	tvlv_buff_len = ntohs(mcast_packet->tvlv_len);
+
+	if (tvlv_buff_len > skb->len - hdr_size)
+		goto free_skb;
+
+	ret = batadv_tvlv_containers_process(bat_priv, BATADV_MCAST, NULL, skb,
+					     tvlv_buff, tvlv_buff_len);
+	if (ret >= 0) {
+		batadv_inc_counter(bat_priv, BATADV_CNT_MCAST_RX);
+		batadv_add_counter(bat_priv, BATADV_CNT_MCAST_RX_BYTES,
+				   skb->len + ETH_HLEN);
+	}
+
+	hdr_size += tvlv_buff_len;
+
+	if (ret == NET_RX_SUCCESS && (skb->len - hdr_size >= ETH_HLEN)) {
+		batadv_inc_counter(bat_priv, BATADV_CNT_MCAST_RX_LOCAL);
+		batadv_add_counter(bat_priv, BATADV_CNT_MCAST_RX_LOCAL_BYTES,
+				   skb->len - hdr_size);
+
+		batadv_interface_rx(bat_priv->soft_iface, skb, hdr_size, NULL);
+		/* skb was consumed */
+		skb = NULL;
+	}
+
+free_skb:
+	kfree_skb(skb);
+
+	return ret;
+}
+#endif /* CONFIG_BATMAN_ADV_MCAST */
diff --git a/net/batman-adv/routing.h b/net/batman-adv/routing.h
index 5f387786e9a7..d8293a83fb82 100644
--- a/net/batman-adv/routing.h
+++ b/net/batman-adv/routing.h
@@ -27,6 +27,17 @@  int batadv_recv_frag_packet(struct sk_buff *skb,
 			    struct batadv_hard_iface *iface);
 int batadv_recv_bcast_packet(struct sk_buff *skb,
 			     struct batadv_hard_iface *recv_if);
+#ifdef CONFIG_BATMAN_ADV_MCAST
+int batadv_recv_mcast_packet(struct sk_buff *skb,
+			     struct batadv_hard_iface *recv_if);
+#else
+static inline int batadv_recv_mcast_packet(struct sk_buff *skb,
+					   struct batadv_hard_iface *recv_if)
+{
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+#endif
 int batadv_recv_tt_query(struct sk_buff *skb,
 			 struct batadv_hard_iface *recv_if);
 int batadv_recv_roam_adv(struct sk_buff *skb,
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 125f4628687c..97f4d7abe54e 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -922,6 +922,18 @@  static const struct {
 	{ "tt_response_rx" },
 	{ "tt_roam_adv_tx" },
 	{ "tt_roam_adv_rx" },
+#ifdef CONFIG_BATMAN_ADV_MCAST
+	{ "mcast_tx" },
+	{ "mcast_tx_bytes" },
+	{ "mcast_tx_local" },
+	{ "mcast_tx_local_bytes" },
+	{ "mcast_rx" },
+	{ "mcast_rx_bytes" },
+	{ "mcast_rx_local" },
+	{ "mcast_rx_local_bytes" },
+	{ "mcast_fwd" },
+	{ "mcast_fwd_bytes" },
+#endif
 #ifdef CONFIG_BATMAN_ADV_DAT
 	{ "dat_get_tx" },
 	{ "dat_get_rx" },
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index ca9449ec9836..a2fee3325b29 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -862,6 +862,70 @@  enum batadv_counters {
 	 */
 	BATADV_CNT_TT_ROAM_ADV_RX,
 
+#ifdef CONFIG_BATMAN_ADV_MCAST
+	/**
+	 * @BATADV_CNT_MCAST_TX: transmitted batman-adv multicast packets
+	 *  counter
+	 */
+	BATADV_CNT_MCAST_TX,
+
+	/**
+	 * @BATADV_CNT_MCAST_TX_BYTES: transmitted batman-adv multicast packets
+	 *  bytes counter
+	 */
+	BATADV_CNT_MCAST_TX_BYTES,
+
+	/**
+	 * @BATADV_CNT_MCAST_TX_LOCAL: counter for multicast packets which
+	 *  were locally encapsulated and transmitted as batman-adv multicast
+	 *  packets
+	 */
+	BATADV_CNT_MCAST_TX_LOCAL,
+
+	/**
+	 * @BATADV_CNT_MCAST_TX_LOCAL_BYTES: bytes counter for multicast packets
+	 *  which were locally encapsulated and transmitted as batman-adv
+	 *  multicast packets
+	 */
+	BATADV_CNT_MCAST_TX_LOCAL_BYTES,
+
+	/**
+	 * @BATADV_CNT_MCAST_RX: received batman-adv multicast packet counter
+	 */
+	BATADV_CNT_MCAST_RX,
+
+	/**
+	 * @BATADV_CNT_MCAST_RX_BYTES: received batman-adv multicast packet
+	 *  bytes counter
+	 */
+	BATADV_CNT_MCAST_RX_BYTES,
+
+	/**
+	 * @BATADV_CNT_MCAST_RX_LOCAL: counter for received batman-adv multicast
+	 *  packets which were forwarded to the local soft interface
+	 */
+	BATADV_CNT_MCAST_RX_LOCAL,
+
+	/**
+	 * @BATADV_CNT_MCAST_RX_LOCAL_BYTES: bytes counter for received
+	 *  batman-adv multicast packets which were forwarded to the local soft
+	 *  interface
+	 */
+	BATADV_CNT_MCAST_RX_LOCAL_BYTES,
+
+	/**
+	 * @BATADV_CNT_MCAST_FWD: counter for received batman-adv multicast
+	 *  packets which were forwarded to other, neighboring nodes
+	 */
+	BATADV_CNT_MCAST_FWD,
+
+	/**
+	 * @BATADV_CNT_MCAST_FWD_BYTES: bytes counter for received batman-adv
+	 *  multicast packets which were forwarded to other, neighboring nodes
+	 */
+	BATADV_CNT_MCAST_FWD_BYTES,
+#endif
+
 #ifdef CONFIG_BATMAN_ADV_DAT
 	/**
 	 * @BATADV_CNT_DAT_GET_TX: transmitted dht GET traffic packet counter