netlink: add real_num_[tr]x_queues to ifinfo

This patch adds the number of active tx/rx queues to ifinfo message.

Now there are two ways of determining the number of active queues:
1) by counting entries in /sys/class/net/eth[0-9]+/queues/
2) by ioctl syscall if a driver implements ethtool_ops->get_channels()

Default mq qdisc sets up pfifo_fast only for active queues. So, if we want
to reproduce this behavior with custom leaf qdiscs, we should use one
of these methods which are foreign for the code where netlink was used.

Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru>
---
 include/uapi/linux/if_link.h | 2 ++
 net/core/rtnetlink.c         | 6 ++++++
 2 files changed, 8 insertions(+)

On Thu, Jan 30, 2020 at 08:57:49PM +0300, Dmitry Yakunin wrote:
> This patch adds the number of active tx/rx queues to ifinfo message.
> 
> Now there are two ways of determining the number of active queues:
> 1) by counting entries in /sys/class/net/eth[0-9]+/queues/
> 2) by ioctl syscall if a driver implements ethtool_ops->get_channels()
> 
> Default mq qdisc sets up pfifo_fast only for active queues. So, if we want
> to reproduce this behavior with custom leaf qdiscs, we should use one
> of these methods which are foreign for the code where netlink was used.

Netlink interface for get_channels() and set_channels() ethtool_ops is
one of the first I plan to submit when net-next is open again after the
merge window.

Michal

> 
> Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru>
> ---
>  include/uapi/linux/if_link.h | 2 ++
>  net/core/rtnetlink.c         | 6 ++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 8aec876..6566b63 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -169,6 +169,8 @@ enum {
>  	IFLA_MAX_MTU,
>  	IFLA_PROP_LIST,
>  	IFLA_ALT_IFNAME, /* Alternative ifname */
> +	IFLA_REAL_NUM_TX_QUEUES,
> +	IFLA_REAL_NUM_RX_QUEUES,
>  	__IFLA_MAX
>  };
>  
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index d9001b5..3ebae18 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1013,7 +1013,9 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
>  	       + nla_total_size(1) /* IFLA_CARRIER */
>  	       + nla_total_size(4) /* IFLA_PROMISCUITY */
>  	       + nla_total_size(4) /* IFLA_NUM_TX_QUEUES */
> +	       + nla_total_size(4) /* IFLA_REAL_NUM_TX_QUEUES */
>  	       + nla_total_size(4) /* IFLA_NUM_RX_QUEUES */
> +	       + nla_total_size(4) /* IFLA_REAL_NUM_RX_QUEUES */
>  	       + nla_total_size(4) /* IFLA_GSO_MAX_SEGS */
>  	       + nla_total_size(4) /* IFLA_GSO_MAX_SIZE */
>  	       + nla_total_size(1) /* IFLA_OPERSTATE */
> @@ -1687,10 +1689,12 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
>  	    nla_put_u32(skb, IFLA_GROUP, dev->group) ||
>  	    nla_put_u32(skb, IFLA_PROMISCUITY, dev->promiscuity) ||
>  	    nla_put_u32(skb, IFLA_NUM_TX_QUEUES, dev->num_tx_queues) ||
> +	    nla_put_u32(skb, IFLA_REAL_NUM_TX_QUEUES, dev->real_num_tx_queues) ||
>  	    nla_put_u32(skb, IFLA_GSO_MAX_SEGS, dev->gso_max_segs) ||
>  	    nla_put_u32(skb, IFLA_GSO_MAX_SIZE, dev->gso_max_size) ||
>  #ifdef CONFIG_RPS
>  	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES, dev->num_rx_queues) ||
> +	    nla_put_u32(skb, IFLA_REAL_NUM_RX_QUEUES, dev->real_num_rx_queues) ||
>  #endif
>  	    put_master_ifindex(skb, dev) ||
>  	    nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||
> @@ -1803,7 +1807,9 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
>  	[IFLA_EXT_MASK]		= { .type = NLA_U32 },
>  	[IFLA_PROMISCUITY]	= { .type = NLA_U32 },
>  	[IFLA_NUM_TX_QUEUES]	= { .type = NLA_U32 },
> +	[IFLA_REAL_NUM_TX_QUEUES] = { .type = NLA_U32 },
>  	[IFLA_NUM_RX_QUEUES]	= { .type = NLA_U32 },
> +	[IFLA_REAL_NUM_RX_QUEUES] = { .type = NLA_U32 },
>  	[IFLA_GSO_MAX_SEGS]	= { .type = NLA_U32 },
>  	[IFLA_GSO_MAX_SIZE]	= { .type = NLA_U32 },
>  	[IFLA_PHYS_PORT_ID]	= { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
> -- 
> 2.7.4
>