netdev - Re: [PATCH net] add support of IFF_XMIT_DST

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Date:   Thu, 02 Nov 2017 09:25:05 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Vadim Fedorenko <vfedorenko@...dex-team.ru>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Paweł Staszewski <pstaszewski@...are.pl>
Subject: Re: [PATCH net] add support of IFF_XMIT_DST_RELEASE bit in vlan

On Thu, 2017-11-02 at 17:47 +0300, Vadim Fedorenko wrote:
> On Thu, 2017-11-02 at 07:33 -7000, Eric Dumazet wrote:
> > On Thu, 2017-11-02 at 15:49 +0300, Vadim Fedorenko wrote:
> >> Some time ago Eric Dumazet suggested a "hack the IFF_XMIT_DST_RELEASE
> >> flag on the vlan netdev". But the last comment was "does not support
> >> properly bonding/team.(If the real_dev->privflags IFF_XMIT_DST_RELEASE
> >> bit changes, we want to update all the vlans at the same time )"
> >> 
> >> I've extended that patch to support changes of IFF_XMIT_DST_RELEASE in
> >> bonding/team.
> >> Both bonding and team call netdev_change_features() after recalculation
> >> of features including priv_flags IFF_XMIT_DST_RELEASE bit. So the only
> >> thing needed to support is to recheck this bit in
> >> vlan_transfer_features().
> >> 
> >> Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
> >> Signed-off-by: Vadim Fedorenko <vfedorenko@...dex-team.ru>
> >> ---
> >>  net/8021q/vlan.c         | 3 +++
> >>  net/8021q/vlan_netlink.c | 1 +
> >>  2 files changed, 4 insertions(+)
> >> 
> >> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
> >> index 9649579..510986c 100644
> >> --- a/net/8021q/vlan.c
> >> +++ b/net/8021q/vlan.c
> >> @@ -328,6 +328,9 @@ static void vlan_transfer_features(struct net_device *dev,
> >>  	vlandev->fcoe_ddp_xid = dev->fcoe_ddp_xid;
> >>  #endif
> >>  
> >> +	vlandev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
> >> +	vlandev->priv_flags |= (vlan->real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
> >> +
> >>  	netdev_update_features(vlandev);
> >>  }
> >>  
> >> diff --git a/net/8021q/vlan_netlink.c b/net/8021q/vlan_netlink.c
> >> index 5e831de..9472de8 100644
> >> --- a/net/8021q/vlan_netlink.c
> >> +++ b/net/8021q/vlan_netlink.c
> >> @@ -143,6 +143,7 @@ static int vlan_newlink(struct net *src_net, struct net_device *dev,
> >>  	vlan->vlan_proto = proto;
> >>  	vlan->vlan_id	 = nla_get_u16(data[IFLA_VLAN_ID]);
> >>  	vlan->real_dev	 = real_dev;
> >> +	dev->priv_flags |= (real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
> >>  	vlan->flags	 = VLAN_FLAG_REORDER_HDR;
> >>  
> >>  	err = vlan_check_real_dev(real_dev, vlan->vlan_proto, vlan->vlan_id);
> >
> > What happens if a bonding is composed of two slaves, with different
> > IFF_XMIT_DST_RELEASE settings ?
> 
> According to bond_compute_features() IFF_XMIT_DST_RELEASE flag is cleared from priv_flags
> in such case, so it is cleared in vlan_transfer_features() and vlan device works as before
> the patch.
> The same code exists in team netdev.

I repeat the question.

What happens if a bonding is composed of two slaves A & B,
A has IFF_XMIT_DST_RELEASE set
B has IFF_XMIT_DST_RELEASE cleared.

1) A is added , then B is added.
2) B is added to the bond, then A is added.
3) Before, and after your patches.

Thanks.