[maint,v2,4/4] batman-adv: mcast: fix duplicate mcast packets from BLA backbone to mesh
Commit Message
Scenario:
* Multicast frame send from BLA backbone gateways (multiple nodes
with their bat0 bridged together, with BLA enabled) sharing the same
LAN to nodes in the mesh
Issue:
* Nodes receive the frame multiple times on bat0 from the mesh,
once from each foreign BLA backbone gateway which shares the same LAN
with another
For multicast frames via batman-adv broadcast packets coming from the
same BLA backbone but from different backbone gateways duplicates are
currently detected via a CRC history of previously received packets.
However this CRC so far was not performed for multicast frames received
via batman-adv unicast packets. Fixing this by appyling the same check
for such packets, too.
Room for improvements in the future: Ideally we would introduce the
possibility to not only claim a client, but a complete originator, too.
This would allow us to only send a multicast-in-unicast packet from a BLA
backbone gateway claiming the node and by that avoid potential redundant
transmissions in the first place.
Fixes: e5cf86d30a9b ("batman-adv: add broadcast duplicate check")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
---
net/batman-adv/bridge_loop_avoidance.c | 86 +++++++++++++++++++++-----
1 file changed, 70 insertions(+), 16 deletions(-)
Comments
On Friday, September 4, 2020 8:28:03 PM CEST Linus Lüssing wrote:
> @@ -1626,7 +1626,8 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv
> *bat_priv, if (entry->crc != crc)
> continue;
>
> - if (batadv_compare_eth(entry->orig, bcast_packet->orig))
> + if (!is_zero_ether_addr(entry->orig) &&
> + batadv_compare_eth(entry->orig, orig))
> continue;
>
> /* this entry seems to match: same crc, not too old,
Shouldn't this check also be skipped if the orig parameter is a zero mac
address? i.e.:
if (!is_zero_ether_addr(orig)) {
if (!is_zero_ether_addr(entry->orig) && batadv_compare_eth(entry->orig,
orig))
continue;
}
Whether orig is zero can probably be checked once before the loop and the
result cached in a bool variable.
A little comment may also be nice to explain this part a bit better.
The rest looks good.
Cheers,
Simon
On Wed, Sep 09, 2020 at 02:15:51PM +0200, Simon Wunderlich wrote:
> On Friday, September 4, 2020 8:28:03 PM CEST Linus Lüssing wrote:
> > @@ -1626,7 +1626,8 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv
> > *bat_priv, if (entry->crc != crc)
> > continue;
> >
> > - if (batadv_compare_eth(entry->orig, bcast_packet->orig))
> > + if (!is_zero_ether_addr(entry->orig) &&
> > + batadv_compare_eth(entry->orig, orig))
> > continue;
> >
> > /* this entry seems to match: same crc, not too old,
>
> Shouldn't this check also be skipped if the orig parameter is a zero mac
> address? i.e.:
>
> if (!is_zero_ether_addr(orig)) {
> if (!is_zero_ether_addr(entry->orig) && batadv_compare_eth(entry->orig,
> orig))
> continue;
> }
Would be redundant. If entry->orig is non-zero and
the compare_eth() says they are equal, then orig must also be
non-zero.
I initially wanted to leave the code as unchanged as possible for
net / maint. Should I do the restructuring to enhance readability, with
the bool in this patch or in additional patch for net-next?
On Wednesday, September 9, 2020 5:27:56 PM CEST Linus Lüssing wrote:
> On Wed, Sep 09, 2020 at 02:15:51PM +0200, Simon Wunderlich wrote:
> > On Friday, September 4, 2020 8:28:03 PM CEST Linus Lüssing wrote:
> > > @@ -1626,7 +1626,8 @@ bool batadv_bla_check_bcast_duplist(struct
> > > batadv_priv *bat_priv, if (entry->crc != crc)
> > >
> > > continue;
> > >
> > > - if (batadv_compare_eth(entry->orig, bcast_packet->orig))
> > > + if (!is_zero_ether_addr(entry->orig) &&
> > > + batadv_compare_eth(entry->orig, orig))
> > >
> > > continue;
> > >
> > > /* this entry seems to match: same crc, not too old,
> >
> > Shouldn't this check also be skipped if the orig parameter is a zero mac
> > address? i.e.:
> >
> > if (!is_zero_ether_addr(orig)) {
> >
> > if (!is_zero_ether_addr(entry->orig) && batadv_compare_eth(entry->orig,
> >
> > orig))
> >
> > continue;
> >
> > }
>
> Would be redundant. If entry->orig is non-zero and
> the compare_eth() says they are equal, then orig must also be
> non-zero.
OK good point, that's not really obvious (at least to me).
>
> I initially wanted to leave the code as unchanged as possible for
> net / maint. Should I do the restructuring to enhance readability, with
> the bool in this patch or in additional patch for net-next?
Personally, I would prefer having a bit more readability or verbose comments
in front of those kind of logic if statements. Or avoid those logic
connections and have multiple "ifs" in a row where possible to enhance
readbility.
This patch is pretty heavy already as is, adding a bool doesn't make a big
difference IMHO.
Cheers,
Simon
@@ -1580,14 +1580,16 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
}
/**
- * batadv_bla_check_bcast_duplist() - Check if a frame is in the broadcast dup.
+ * batadv_bla_check_duplist() - Check if a frame is in the broadcast dup.
* @bat_priv: the bat priv with all the soft interface information
- * @skb: contains the bcast_packet to be checked
- *
- * check if it is on our broadcast list. Another gateway might
- * have sent the same packet because it is connected to the same backbone,
- * so we have to remove this duplicate.
+ * @skb: contains the multicast packet to be checked
+ * @payload_ptr: pointer to position inside the head buffer of the skb
+ * marking the start of the data to be CRC'ed
*
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
+
* This is performed by checking the CRC, which will tell us
* with a good chance that it is the same packet. If it is furthermore
* sent by another host, drop it. We allow equal packets from
@@ -1595,19 +1597,17 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
*
* Return: true if a packet is in the duplicate list, false otherwise.
*/
-bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
- struct sk_buff *skb)
+static bool batadv_bla_check_duplist(struct batadv_priv *bat_priv,
+ struct sk_buff *skb, u8 *payload_ptr,
+ const u8 *orig)
{
+ struct batadv_bcast_duplist_entry *entry;
+ bool ret = false;
int i, curr;
__be32 crc;
- struct batadv_bcast_packet *bcast_packet;
- struct batadv_bcast_duplist_entry *entry;
- bool ret = false;
-
- bcast_packet = (struct batadv_bcast_packet *)skb->data;
/* calculate the crc ... */
- crc = batadv_skb_crc32(skb, (u8 *)(bcast_packet + 1));
+ crc = batadv_skb_crc32(skb, payload_ptr);
spin_lock_bh(&bat_priv->bla.bcast_duplist_lock);
@@ -1626,7 +1626,8 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
if (entry->crc != crc)
continue;
- if (batadv_compare_eth(entry->orig, bcast_packet->orig))
+ if (!is_zero_ether_addr(entry->orig) &&
+ batadv_compare_eth(entry->orig, orig))
continue;
/* this entry seems to match: same crc, not too old,
@@ -1643,7 +1644,7 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
entry = &bat_priv->bla.bcast_duplist[curr];
entry->crc = crc;
entry->entrytime = jiffies;
- ether_addr_copy(entry->orig, bcast_packet->orig);
+ ether_addr_copy(entry->orig, orig);
bat_priv->bla.bcast_duplist_curr = curr;
out:
@@ -1652,6 +1653,52 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
return ret;
}
+/**
+ * batadv_bla_check_ucast_duplist() - Check if a frame is in the broadcast dup.
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: contains the multicast packet to be checked, decapsulated from a
+ * unicast_packet
+ *
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
+ *
+ * Return: true if a packet is in the duplicate list, false otherwise.
+ */
+static bool batadv_bla_check_ucast_duplist(struct batadv_priv *bat_priv,
+ struct sk_buff *skb)
+{
+ u8 orig[ETH_ALEN];
+
+ eth_zero_addr(orig);
+
+ return batadv_bla_check_duplist(bat_priv, skb, (u8 *)skb->data, orig);
+}
+
+/**
+ * batadv_bla_check_bcast_duplist() - Check if a frame is in the broadcast dup.
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: contains the bcast_packet to be checked
+ *
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
+ *
+ * Return: true if a packet is in the duplicate list, false otherwise.
+ */
+bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
+ struct sk_buff *skb)
+{
+ struct batadv_bcast_packet *bcast_packet;
+ u8 *payload_ptr;
+
+ bcast_packet = (struct batadv_bcast_packet *)skb->data;
+ payload_ptr = (u8 *)(bcast_packet + 1);
+
+ return batadv_bla_check_duplist(bat_priv, skb, payload_ptr,
+ bcast_packet->orig);
+}
+
/**
* batadv_bla_is_backbone_gw_orig() - Check if the originator is a gateway for
* the VLAN identified by vid.
@@ -1852,6 +1899,13 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb,
(!is_broadcast_ether_addr(ethhdr->h_dest) || is_bcast))
goto handled;
+ /* potential duplicates from foreign BLA backbone gateways via
+ * multicast-in-unicast packets
+ */
+ if (is_multicast_ether_addr(ethhdr->h_dest) && !is_bcast &&
+ batadv_bla_check_ucast_duplist(bat_priv, skb))
+ goto handled;
+
ether_addr_copy(search_claim.addr, ethhdr->h_source);
search_claim.vid = vid;
claim = batadv_claim_hash_find(bat_priv, &search_claim);