netdev - Re: [PATCH 2/2] ip6mr: Make cache queue length configurable

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Date:   Wed, 6 Mar 2019 20:25:02 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Brodie Greenfield <Brodie.Greenfield@...iedtelesis.co.nz>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
        "yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Luuk Paulussen" <Luuk.Paulussen@...iedtelesis.co.nz>
Subject: Re: [PATCH 2/2] ip6mr: Make cache queue length configurable

On 7/03/19 9:20 AM, Brodie Greenfield wrote:
> We want to be able to keep more spaces available in our queue for
> processing incoming IPv6 multicast traffic (adding (S,G) entries) - this
> lets us learn more groups faster, rather than dropping them at this stage.
> 
> Signed-off-by: Brodie Greenfield <brodie.greenfield@...iedtelesis.co.nz>
> ---
>   Documentation/networking/ip-sysctl.txt | 8 ++++++++
>   include/net/netns/ipv6.h               | 1 +
>   net/ipv6/af_inet6.c                    | 1 +
>   net/ipv6/ip6mr.c                       | 4 +++-
>   net/ipv6/sysctl_net_ipv6.c             | 7 +++++++
>   5 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index 02f77e932adf..68eada3ca915 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1481,6 +1481,14 @@ skip_notify_on_dev_down - BOOLEAN
>   	on userspace caches to track link events and evict routes.
>   	Default: false (generate message)
>   
> +ip_mr_cache_queue_length - INTEGER

Should be "ip6_mr_cache_queue_length" for this patch.

> +	Limit the number of multicast packets we can have in the queue to be
> +	resolved.
> +	Bear in mind that when an unresolved multicast packet is received,
> +	there is an O(n) traversal of the queue. This should be considered
> +	if increasing.
> +	Default: 10
> +
>   IPv6 Fragmentation:
>   
>   ip6frag_high_thresh - INTEGER
> diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
> index ef1ed529f33c..84b58424c799 100644
> --- a/include/net/netns/ipv6.h
> +++ b/include/net/netns/ipv6.h
> @@ -46,6 +46,7 @@ struct netns_sysctl_ipv6 {
>   	int max_hbh_opts_len;
>   	int seg6_flowlabel;
>   	bool skip_notify_on_dev_down;
> +	unsigned int ip6_mr_cache_queue_length;
>   };
>   
>   struct netns_ipv6 {
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index d99753b5e39b..6551bb63e5a2 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -856,6 +856,7 @@ static int __net_init inet6_net_init(struct net *net)
>   	net->ipv6.sysctl.max_hbh_opts_cnt = IP6_DEFAULT_MAX_HBH_OPTS_CNT;
>   	net->ipv6.sysctl.max_dst_opts_len = IP6_DEFAULT_MAX_DST_OPTS_LEN;
>   	net->ipv6.sysctl.max_hbh_opts_len = IP6_DEFAULT_MAX_HBH_OPTS_LEN;
> +	net->ipv6.sysctl.ip6_mr_cache_queue_length = 10;
>   	atomic_set(&net->ipv6.fib6_sernum, 1);
>   
>   	err = ipv6_init_mibs(net);
> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
> index cc01aa3f2b5e..bb445871437e 100644
> --- a/net/ipv6/ip6mr.c
> +++ b/net/ipv6/ip6mr.c
> @@ -1135,6 +1135,7 @@ static int ip6mr_cache_report(struct mr_table *mrt, struct sk_buff *pkt,
>   static int ip6mr_cache_unresolved(struct mr_table *mrt, mifi_t mifi,
>   				  struct sk_buff *skb, struct net_device *dev)
>   {
> +	struct net *net = dev_net(dev);
>   	struct mfc6_cache *c;
>   	bool found = false;
>   	int err;
> @@ -1153,7 +1154,8 @@ static int ip6mr_cache_unresolved(struct mr_table *mrt, mifi_t mifi,
>   		 *	Create a new entry if allowable
>   		 */
>   
> -		if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
> +		if (atomic_read(&mrt->cache_resolve_queue_len) >=
> +		    net->ipv6.sysctl.ip6_mr_cache_queue_length ||
>   		    (c = ip6mr_cache_alloc_unres()) == NULL) {
>   			spin_unlock_bh(&mfc_unres_lock);
>   
> diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
> index e15cd37024fd..a27299d4cc34 100644
> --- a/net/ipv6/sysctl_net_ipv6.c
> +++ b/net/ipv6/sysctl_net_ipv6.c
> @@ -159,6 +159,13 @@ static struct ctl_table ipv6_table_template[] = {
>   		.mode		= 0644,
>   		.proc_handler	= proc_dointvec
>   	},
> +	{
> +		.procname	= "ip6_mr_cache_queue_length",
> +		.data		= &init_net.ipv6.sysctl.ip6_mr_cache_queue_length,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec
> +	},
>   	{ }
>   };
>   
>