netdev - Re: [PATCH net] ipvlan: do not add hardware address of master to its unicast filter list

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Message-Id: <20200306.223625.760484008125865765.davem@davemloft.net>
Date:   Fri, 06 Mar 2020 22:36:25 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     jwiesner@...e.com
Cc:     netdev@...r.kernel.org, maheshb@...gle.com,
        Andreas.Taschner@...e.com, mkubecek@...e.cz
Subject: Re: [PATCH net] ipvlan: do not add hardware address of master to
 its unicast filter list

From: Jiri Wiesner <jwiesner@...e.com>
Date: Thu, 5 Mar 2020 20:31:01 +0100

> There is a problem when ipvlan slaves are created on a master device that
> is a vmxnet3 device (ipvlan in VMware guests). The vmxnet3 driver does not
> support unicast address filtering. When an ipvlan device is brought up in
> ipvlan_open(), the ipvlan driver calls dev_uc_add() to add the hardware
> address of the vmxnet3 master device to the unicast address list of the
> master device, phy_dev->uc. This inevitably leads to the vmxnet3 master
> device being forced into promiscuous mode by __dev_set_rx_mode().
> 
> Promiscuous mode is switched on the master despite the fact that there is
> still only one hardware address that the master device should use for
> filtering in order for the ipvlan device to be able to receive packets.
> The comment above struct net_device describes the uc_promisc member as a
> "counter, that indicates, that promiscuous mode has been enabled due to
> the need to listen to additional unicast addresses in a device that does
> not implement ndo_set_rx_mode()". Moreover, the design of ipvlan
> guarantees that only the hardware address of a master device,
> phy_dev->dev_addr, will be used to transmit and receive all packets from
> its ipvlan slaves. Thus, the unicast address list of the master device
> should not be modified by ipvlan_open() and ipvlan_stop() in order to make
> ipvlan a workable option on masters that do not support unicast address
> filtering.
> 
> Fixes: 2ad7bf3638411 ("ipvlan: Initial check-in of the IPVLAN driver")
> Reported-by: Per Sundstrom <per.sundstrom@...qube.se>
> Signed-off-by: Jiri Wiesner <jwiesner@...e.com>

Please fix this warning and resubmit, thank you:

  CC [M]  drivers/net/ipvlan/ipvlan_main.o
drivers/net/ipvlan/ipvlan_main.c: In function ‘ipvlan_open’:
drivers/net/ipvlan/ipvlan_main.c:167:21: warning: unused variable ‘phy_dev’ [-Wunused-variable]
  167 |  struct net_device *phy_dev = ipvlan->phy_dev;
      |                     ^~~~~~~