Subject: Re: [PATCH v4 for-next 00/12] Add network namespace support in the RDMA-CM

From: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/[email-masked]>
Date: Wed, 3 Jun 2015 13:03:01 +0300

On 29/05/2015 00:55, Doug Ledford wrote:
> On Thu, 2015-05-28 at 22:05 +0300, Or Gerlitz wrote:
>> So what's your concrete saying here? where should we go from here?
> 
> This excerpt is from the commit log of patch 3/12:
> 
> The IB device and port, together with the P_Key and the IP address should
> be enough to uniquely identify the ULP net device.
> 
> The problem here is that this is wrong.  If we allow more than one
> device per pkey with the same GUID, then DHCP breaks, which is bad in
> and of itself, but it also breaks ipv6 link local addressing.  Which
> means that this hunk in patch 4/12:
> 
> +#if IS_ENABLED(CONFIG_IPV6)
> +       case AF_INET6:
> +               if (ipv6_chk_addr(net, &addr_in6->sin6_addr, dev, 1))
> +                       return true;
> +
> +               break;
> +#endif
> 
> can now be tricked into returning true for incorrect devices.
> 
> Where do we go from here?
> 
> First, I'm inclined to say we should modify the add_child portion of
> IPoIB to refuse to add links to a PKey if that GUID is already present
> on that PKey.  You could then use different PKeys on the default GUID
> for separate namespaces.  If you need separate namespaces on the same
> PKey, then enable alias GUIDs for use on the local adapter and require
> one GUID per namespace on the same PKey.
I don't think blocking the current add_child implementation is needed. I
agree IPv6 SLAAC and DHCP currently don't work well, and adding alias
GUID for child interfaces is important, but the current implementation
can be used with static IPv4 addresses, so I don't think it must be
disabled.

> Then I'm inclined to say that we should map for namespaces using device,
> port, guid/gid, pkey.  And in this situation, since a unique guid/gid on
> any given pkey maps to a unique dhcp identifier and a unique ipv6
> lladdr, this becomes freely interchangeable with device, port, pkey,
> address mappings that this patchset was built around.

What if we change the namespaces patches to map (device, port, GID,
P_Key, IP) to netdev / namespace? That is, to use both the GID and the
IP address. This would allow people to use namespaces with the current
implementation (provided they have a valid configuration with no
conflicting IP addresses), and once alias GUIDs are added, the GUIDs
will be used to uniquely resolve the namespace even with such
misconfigurations.

Regards,
Haggai
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