netdev - Re: [PATCH net-next v2 2/2] ipoib: show VF broadcast address

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Message-ID: <CAOJe8K1OycscWUKfYKP73bK_eJdmG3=-_yK6ajSUpXpfGEEgwQ@mail.gmail.com>
Date:   Fri, 14 Jun 2019 16:37:02 +0300
From:   Denis Kirjanov <kda@...ux-powerpc.org>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     davem@...emloft.net, dledford@...hat.com, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/2] ipoib: show VF broadcast address

On 6/13/19, Michal Kubecek <mkubecek@...e.cz> wrote:
> On Thu, Jun 13, 2019 at 04:20:03PM +0200, Denis Kirjanov wrote:
>> in IPoIB case we can't see a VF broadcast address for but
>> can see for PF
>>
>> Before:
>> 11: ib1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 2044 qdisc pfifo_fast
>> state UP mode DEFAULT group default qlen 256
>>     link/infiniband
>> 80:00:00:66:fe:80:00:00:00:00:00:00:24:8a:07:03:00:a4:3e:7c brd
>> 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
>>     vf 0 MAC 14:80:00:00:66:fe, spoof checking off, link-state disable,
>> trust off, query_rss off
>> ...
>>
>> After:
>> 11: ib1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 2044 qdisc pfifo_fast
>> state UP mode DEFAULT group default qlen 256
>>     link/infiniband
>> 80:00:00:66:fe:80:00:00:00:00:00:00:24:8a:07:03:00:a4:3e:7c brd
>> 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
>>     vf 0     link/infiniband
>> 80:00:00:66:fe:80:00:00:00:00:00:00:24:8a:07:03:00:a4:3e:7c brd
>> 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff, spoof
>> checking off, link-state disable, trust off, query_rss off
>>
>> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
>> ---
>>  include/uapi/linux/if_link.h | 5 +++++
>>  net/core/rtnetlink.c         | 6 ++++++
>>  2 files changed, 11 insertions(+)
>>
>> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
>> index 5b225ff63b48..1f36dd3a45d6 100644
>> --- a/include/uapi/linux/if_link.h
>> +++ b/include/uapi/linux/if_link.h
>> @@ -681,6 +681,7 @@ enum {
>>  enum {
>>  	IFLA_VF_UNSPEC,
>>  	IFLA_VF_MAC,		/* Hardware queue specific attributes */
>> +	IFLA_VF_BROADCAST,
>>  	IFLA_VF_VLAN,		/* VLAN ID and QoS */
>>  	IFLA_VF_TX_RATE,	/* Max TX Bandwidth Allocation */
>>  	IFLA_VF_SPOOFCHK,	/* Spoof Checking on/off switch */
>
> Oops, I forgot to mention one important point when reviewing v1: the new
> attribute type must be added at the end (just before __IFLA_VF_MAX) so
> that you do not change value of existing IFLA_VF_* constants (this would
> break compatibility).

Right, I've also missed that that the change breaks KABI.

>
>> @@ -704,6 +705,10 @@ struct ifla_vf_mac {
>>  	__u8 mac[32]; /* MAX_ADDR_LEN */
>>  };
>>
>> +struct ifla_vf_broadcast {
>> +	__u8 broadcast[32];
>> +};
>> +
>>  struct ifla_vf_vlan {
>>  	__u32 vf;
>>  	__u32 vlan; /* 0 - 4095, 0 disables VLAN filter */
>
> My first idea was that to question the need of a wrapping structure as
> we couldn't modify that structure in the future anyway so that there
> does not seem to be any gain against simply passing the address as a
> binary with attribute length equal to address length (like we do with
> IFLA_ADDRESS and IFLA_BROADCAST).
>
> But then I checked other IFLA_VF_* attributes and I'm confused. The
> structure seems to be
>
>     IFLA_VF_INFO_LIST
>         IFLA_VF_INFO
>             IFLA_VF_MAC
>             IFLA_VF_VLAN
>             ...
>         IFLA_VF_INFO
>             IFLA_VF_MAC
>             IFLA_VF_VLAN
>             ...
>         ...
>
> Each IFLA_VF_INFO corresponds to one virtual function but its number is
> not determined by an attribute within this nest. Instead, each of the
> neste IFLA_VF_* attributes is a structure containing "__u32 vf" and it's
> only matter of convention that within one IFLA_VF_INFO nest, all data
> belongs to the same VF, neither do_setlink() nor do_setvfinfo() check
> it.
>
> I guess you should either follow this weird pattern or introduce proper
> IFLA_VF_ID to be used for IFLA_VF_BROADCAST and all future IFLA_VF_*
> attributes. However, each new attribute makes IFLA_VF_INFO bigger and
> lowers the number of VFs that can be stored in an IFLA_VF_INFO_LIST nest
> without exceeding the hard limit of 65535 bytes so that we cannot afford
> to add too many.

I've just put it as other attrs for now.

>
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index cec60583931f..88304212f127 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
> ...
>> @@ -1753,6 +1758,7 @@ static const struct nla_policy
>> ifla_info_policy[IFLA_INFO_MAX+1] = {
>>
>>  static const struct nla_policy ifla_vf_policy[IFLA_VF_MAX+1] = {
>>  	[IFLA_VF_MAC]		= { .len = sizeof(struct ifla_vf_mac) },
>> +	[IFLA_VF_BROADCAST]	= {. len = sizeof(struct ifla_vf_broadcast) },
>>  	[IFLA_VF_VLAN]		= { .len = sizeof(struct ifla_vf_vlan) },
>>  	[IFLA_VF_VLAN_LIST]     = { .type = NLA_NESTED },
>>  	[IFLA_VF_TX_RATE]	= { .len = sizeof(struct ifla_vf_tx_rate) },
>
> As you do not implement setting the broadcast address (is that possible
> at all?),

According to rfc4391 it's formed from the components like p_key,
q_key, mtu and other.

 NLA_REJECT would be more appropriate so that the request isn't
> silently ignored.

Anyway, I've sent v3.

Thanks!

>
> Michal
>