Re: [PATCH] veth: Be more robust on network device creation when no attributes

[David Miller <davem@davemloft.net>]

From: Serhey Popovych <serhe.popovych@gmail.com>
Date: Fri, 16 Jun 2017 18:05:00 +0300

> There are number of problems with configuration peer
> network device in absence of IFLA_VETH_PEER attributes
> where attributes for main network device shared with
> peer.
> 
> First it is not feasible to configure both network
> devices with same MAC address since this makes
> communication in such configuration problematic.
> 
> This case can be reproduced with following sequence:
> 
>   # ip link add address 02:11:22:33:44:55 type veth
>   # ip li sh
>   ...
>   26: veth0@veth1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc \
>   noop state DOWN mode DEFAULT qlen 1000
>       link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
>   27: veth1@veth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc \
>   noop state DOWN mode DEFAULT qlen 1000
>       link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
> 
> Second it is not possible to register main network device
> with given name and automatically create peer network
> device name. That happens because IFLA_IFNAME used when
> creating main and reused when creating peer.
> 
> This case can be reproduced with following sequence:
> 
>   # ip link add dev veth1a type veth
>   RTNETLINK answers: File exists
> 
> To fix both of the cases check if corresponding netlink
> attributes are taken from peer_tb when valid or
> name based on rtnl ops kind and random address is used.
> 
> Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>

This does not apply cleanly to the 'net' tree, please respin.