[PATCH 1/2] ipmr: Make cache queue length configurable

[Brodie Greenfield <brodie.greenfield@alliedtelesis.co.nz>]

We want to be able to keep more spaces available in our queue for
processing incoming 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@alliedtelesis.co.nz>
---
 Documentation/networking/ip-sysctl.txt | 8 ++++++++
 include/net/netns/ipv4.h               | 1 +
 net/ipv4/af_inet.c                     | 1 +
 net/ipv4/ipmr.c                        | 4 +++-
 net/ipv4/sysctl_net_ipv4.c             | 7 +++++++
 5 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index acdfb5d2bcaa..02f77e932adf 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -887,6 +887,14 @@ ip_local_reserved_ports - list of comma separated ranges
 
 	Default: Empty
 
+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
+
 ip_unprivileged_port_start - INTEGER
 	This is a per-namespace sysctl.  It defines the first
 	unprivileged port in the network namespace.  Privileged ports
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 104a6669e344..3411d3f18d51 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -187,6 +187,7 @@ struct netns_ipv4 {
 	int sysctl_igmp_max_msf;
 	int sysctl_igmp_llm_reports;
 	int sysctl_igmp_qrv;
+	unsigned int sysctl_ip_mr_cache_queue_length;
 
 	struct ping_group_range ping_group_range;
 
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 0dfb72c46671..8e25538bdb1e 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1827,6 +1827,7 @@ static __net_init int inet_init_net(struct net *net)
 	net->ipv4.sysctl_igmp_llm_reports = 1;
 	net->ipv4.sysctl_igmp_qrv = 2;
 
+	net->ipv4.sysctl_ip_mr_cache_queue_length = 10;
 	return 0;
 }
 
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index ddbf8c9a1abb..c6a6c3e453a9 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1127,6 +1127,7 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 				 struct sk_buff *skb, struct net_device *dev)
 {
 	const struct iphdr *iph = ip_hdr(skb);
+	struct net *net = dev_net(dev);
 	struct mfc_cache *c;
 	bool found = false;
 	int err;
@@ -1142,7 +1143,8 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 
 	if (!found) {
 		/* Create a new entry if allowable */
-		if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
+		if (atomic_read(&mrt->cache_resolve_queue_len) >=
+		    net->ipv4.sysctl_ip_mr_cache_queue_length ||
 		    (c = ipmr_cache_alloc_unres()) == NULL) {
 			spin_unlock_bh(&mfc_unres_lock);
 
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index ba0fc4b18465..78ae86e8c6cb 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -784,6 +784,13 @@ static struct ctl_table ipv4_net_table[] = {
 		.proc_handler	= proc_dointvec
 	},
 #ifdef CONFIG_IP_MULTICAST
+	{
+		.procname	= "ip_mr_cache_queue_length",
+		.data		= &init_net.ipv4.sysctl_ip_mr_cache_queue_length,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
 	{
 		.procname	= "igmp_qrv",
 		.data		= &init_net.ipv4.sysctl_igmp_qrv,
-- 
2.21.0