Re: [PATCH net-next 1/1] veth: tweak creation of veth device

From: Roman Mashak <redacted>
Date: Tue, 10 Oct 2017 16:08:44 -0400

When creating veth pair, at first rtnl_new_link() creates veth_dev, i.e.
one end of the veth pipe, but not registers it; then veth_newlink() gets
invoked, where peer dev is created _and_ registered, followed by veth_dev
registration, which may fail if peer information, that is VETH_INFO_PEER
attribute, has not been provided and the kernel will allocate unique veth
name.

So, we should ask the kernel to allocate unique name for veth_dev only
when peer info is not available.

Example:

% ip link dev veth0 type veth
RTNETLINK answers: File exists

After fix:
% ip link dev veth0 type veth
% ip link show dev veth0
5: veth0@veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether f6:ef:8b:96:f4:ec brd ff:ff:ff:ff:ff:ff
%

Signed-off-by: Roman Mashak <redacted>

I'm not so sure about this.

If we specify an explicit tb[IFLA_NAME], we shouldn't completely ignore that
request from the user just because they didn't give any peer information.

I see what happens in this case, the peer gets 'veth0' and then since
the user asked for 'veth0' for the non-peer it conflicts.

Well, too bad.  The user must work to orchestrate things such that
this doesn't happen.  That means either providing the IFLA_NAME for
both the peer and the non-peer, or specifying neither.

I'm not applying this, sorry.