• Jason Wang's avatar
    net: core: explicitly select a txq before doing l2 forwarding · f663dd9a
    Jason Wang authored
    
    
    Currently, the tx queue were selected implicitly in ndo_dfwd_start_xmit(). The
    will cause several issues:
    
    - NETIF_F_LLTX were removed for macvlan, so txq lock were done for macvlan
      instead of lower device which misses the necessary txq synchronization for
      lower device such as txq stopping or frozen required by dev watchdog or
      control path.
    - dev_hard_start_xmit() was called with NULL txq which bypasses the net device
      watchdog.
    - dev_hard_start_xmit() does not check txq everywhere which will lead a crash
      when tso is disabled for lower device.
    
    Fix this by explicitly introducing a new param for .ndo_select_queue() for just
    selecting queues in the case of l2 forwarding offload. netdev_pick_tx() was also
    extended to accept this parameter and dev_queue_xmit_accel() was used to do l2
    forwarding transmission.
    
    With this fixes, NETIF_F_LLTX could be preserved for macvlan and there's no need
    to check txq against NULL in dev_hard_start_xmit(). Also there's no need to keep
    a dedicated ndo_dfwd_start_xmit() and we can just reuse the code of
    dev_queue_xmit() to do the transmission.
    
    In the future, it was also required for macvtap l2 forwarding support since it
    provides a necessary synchronization method.
    
    Cc: John Fastabend <john.r.fastabend@intel.com>
    Cc: Neil Horman <nhorman@tuxdriver.com>
    Cc: e1000-devel@lists.sourceforge.net
    Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
    Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
    Acked-by: default avatarJohn Fastabend <john.r.fastabend@intel.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    f663dd9a