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

[Brodie Greenfield]

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@xxxxxxxxxxxxxxxxxxx>
---
 Documentation/networking/ip-sysctl.txt | 7 +++++++
 include/net/netns/ipv4.h               | 1 +
 include/uapi/linux/sysctl.h            | 1 +
 kernel/sysctl_binary.c                 | 1 +
 net/ipv4/af_inet.c                     | 2 ++
 net/ipv4/ipmr.c                        | 4 +++-
 net/ipv4/sysctl_net_ipv4.c             | 7 +++++++
 7 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 960de8fe3f40..dfc70ef6c42b 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -864,6 +864,13 @@ 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 this causes an O(n) traversal of the same size when
+	the queue is full. 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 e47503b4e4d1..1ca5cabe2d3b 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -184,6 +184,7 @@ struct netns_ipv4 {
 	int sysctl_igmp_max_msf;
 	int sysctl_igmp_llm_reports;
 	int sysctl_igmp_qrv;
+	int sysctl_ip_mr_cache_queue_length;
 
 	struct ping_group_range ping_group_range;
 
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index d71013fffaf6..32e32d4904cd 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -425,6 +425,7 @@ enum
 	NET_TCP_ALLOWED_CONG_CONTROL=123,
 	NET_TCP_MAX_SSTHRESH=124,
 	NET_TCP_FRTO_RESPONSE=125,
+	NET_IPV4_IP_MR_CACHE_QUEUE_LENGTH=126,
 };
 
 enum {
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 07148b497451..8db94e8d97ed 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -367,6 +367,7 @@ static const struct bin_table bin_net_ipv4_table[] = {
 	{ CTL_INT,	NET_IPV4_LOCAL_PORT_RANGE,		"ip_local_port_range" },
 	{ CTL_INT,	NET_IPV4_IGMP_MAX_MEMBERSHIPS,		"igmp_max_memberships" },
 	{ CTL_INT,	NET_IPV4_IGMP_MAX_MSF,			"igmp_max_msf" },
+	{ CTL_INT,	NET_IPV4_IP_MR_CACHE_QUEUE_LENGTH,	"ip_mr_cache_queue_length" },
 	{ CTL_INT,	NET_IPV4_INET_PEER_THRESHOLD,		"inet_peer_threshold" },
 	{ CTL_INT,	NET_IPV4_INET_PEER_MINTTL,		"inet_peer_minttl" },
 	{ CTL_INT,	NET_IPV4_INET_PEER_MAXTTL,		"inet_peer_maxttl" },
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 1fbe2f815474..4b78d12aca36 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1818,6 +1818,8 @@ static __net_init int inet_init_net(struct net *net)
 	net->ipv4.sysctl_igmp_llm_reports = 1;
 	net->ipv4.sysctl_igmp_qrv = 2;
 
+	/* ipmr unresolved queue length max */
+	net->ipv4.sysctl_ip_mr_cache_queue_length = 10;
 	return 0;
 }
 
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 5660adcf7a04..2864f80e2f2a 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1128,6 +1128,7 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 	struct mfc_cache *c;
 	bool found = false;
 	int err;
+	struct net *net = dev_net(dev);
 
 	spin_lock_bh(&mfc_unres_lock);
 	list_for_each_entry(c, &mrt->mfc_unres_queue, _c.list) {
@@ -1140,7 +1141,8 @@ 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 891ed2f91467..b249932ee24e 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -772,6 +772,13 @@ static struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+	{
+		.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
+	},
 #ifdef CONFIG_IP_MULTICAST
 	{
 		.procname	= "igmp_qrv",
-- 
2.19.1