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

[Brodie Greenfield]

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@xxxxxxxxxxxxxxxxxxx>
---
 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
+	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
+	},
 	{ }
 };
 
-- 
2.21.0