[PATCH 4.14 25/34] bonding: fix PACKET_ORIGDEV regression

Greg Kroah-Hartman
2019-03-18T09:35:17Z

From: Michal Soltys <soltys@ziu.info>

[ Upstream commit 3c963a3306eada999be5ebf4f293dfa3d3945487 ]

This patch fixes a subtle PACKET_ORIGDEV regression which was a side
effect of fixes introduced by:

6a9e461f6fe4 bonding: pass link-local packets to bonding master also.

... to:

b89f04c61efe bonding: deliver link-local packets with skb->dev set to link that packets arrived on

While 6a9e461f6fe4 restored pre-b89f04c61efe presence of link-local
packets on bonding masters (which is required e.g. by linux bridges
participating in spanning tree or needed for lab-like setups created
with group_fwd_mask) it also caused the originating device
information to be lost due to cloning.

Maciej Żenczykowski proposed another solution that doesn't require
packet cloning and retains original device information - instead of
returning RX_HANDLER_PASS for all link-local packets it's now limited
only to packets from inactive slaves.

At the same time, packets passed to bonding masters retain correct
information about the originating device and PACKET_ORIGDEV can be used
to determine it.

This elegantly solves all issues so far:

- link-local packets that were removed from bonding masters
- LLDP daemons being forced to explicitly bind to slave interfaces
- PACKET_ORIGDEV having no effect on bond interfaces

Fixes: 6a9e461f6fe4 (bonding: pass link-local packets to bonding master also.)
Reported-by: Vincent Bernat <vincent@bernat.ch>
Signed-off-by: Michal Soltys <soltys@ziu.info>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/bonding/bond_main.c | 35 ++++++++++++++---------------------
1 file changed, 14 insertions(+), 21 deletions(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1177,29 +1177,22 @@ static rx_handler_result_t bond_handle_f
}
}

- /* Link-local multicast packets should be passed to the
- * stack on the link they arrive as well as pass them to the
- * bond-master device. These packets are mostly usable when
- * stack receives it with the link on which they arrive
- * (e.g. LLDP) they also must be available on master. Some of
- * the use cases include (but are not limited to): LLDP agents
- * that must be able to operate both on enslaved interfaces as
- * well as on bonds themselves; linux bridges that must be able
- * to process/pass BPDUs from attached bonds when any kind of
- * STP version is enabled on the network.
+ /*
+ * For packets determined by bond_should_deliver_exact_match() call to
+ * be suppressed we want to make an exception for link-local packets.
+ * This is necessary for e.g. LLDP daemons to be able to monitor
+ * inactive slave links without being forced to bind to them
+ * explicitly.
+ *
+ * At the same time, packets that are passed to the bonding master
+ * (including link-local ones) can have their originating interface
+ * determined via PACKET_ORIGDEV socket option.
*/
- if (is_link_local_ether_addr(eth_hdr(skb)->h_dest)) {
- struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
-
- if (nskb) {
- nskb->dev = bond->dev;
- nskb->queue_mapping = 0;
- netif_rx(nskb);
- }
- return RX_HANDLER_PASS;
- }
- if (bond_should_deliver_exact_match(skb, slave, bond))
+ if (bond_should_deliver_exact_match(skb, slave, bond)) {
+ if (is_link_local_ether_addr(eth_hdr(skb)->h_dest))
+ return RX_HANDLER_PASS;
return RX_HANDLER_EXACT;
+ }

skb->dev = bond->dev;