5 files changed, 58 insertions, 23 deletions

diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
index 2793d4eac55f..bc0680706870 100644
--- a/Documentation/sysctl/net.txt
+++ b/Documentation/sysctl/net.txt
@@ -291,6 +291,20 @@ user space is responsible for creating them if needed.
 
 Default : 0  (for compatibility reasons)
 
+devconf_inherit_init_net
+----------------------------
+
+Controls if a new network namespace should inherit all current
+settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By
+default, we keep the current behavior: for IPv4 we inherit all current
+settings from init_net and for IPv6 we reset all settings to default.
+
+If set to 1, both IPv4 and IPv6 settings are forced to inherit from
+current ones in init_net. If set to 2, both IPv4 and IPv6 settings are
+forced to reset to their default values.
+
+Default : 0  (for compatibility reasons)
+
 2. /proc/sys/net/unix - Parameters for Unix domain sockets
 -------------------------------------------------------
 
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a57b9a853aab..e675ef97a426 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -630,6 +630,7 @@ struct netdev_queue {
 } ____cacheline_aligned_in_smp;
 
 extern int sysctl_fb_tunnels_only_for_init_net;
+extern int sysctl_devconf_inherit_init_net;
 
 static inline bool net_has_fallback_tunnels(const struct net *net)
 {
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index d67ec17f2cc8..84bf2861f45f 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -36,6 +36,15 @@ static int net_msg_warn;	/* Unused, but still a sysctl */
 int sysctl_fb_tunnels_only_for_init_net __read_mostly = 0;
 EXPORT_SYMBOL(sysctl_fb_tunnels_only_for_init_net);
 
+/* 0 - Keep current behavior:
+ *     IPv4: inherit all current settings from init_net
+ *     IPv6: reset all settings to default
+ * 1 - Both inherit all current settings from init_net
+ * 2 - Both reset all settings to default
+ */
+int sysctl_devconf_inherit_init_net __read_mostly;
+EXPORT_SYMBOL(sysctl_devconf_inherit_init_net);
+
 #ifdef CONFIG_RPS
 static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
 				void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -544,6 +553,15 @@ static struct ctl_table net_core_table[] = {
 		.extra1		= &zero,
 		.extra2		= &one,
 	},
+	{
+		.procname	= "devconf_inherit_init_net",
+		.data		= &sysctl_devconf_inherit_init_net,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &two,
+	},
 	{ }
 };
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index cd027639df2f..cd9033245b98 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2591,32 +2591,32 @@ static __net_init int devinet_init_net(struct net *net)
 	int err;
 	struct ipv4_devconf *all, *dflt;
 #ifdef CONFIG_SYSCTL
-	struct ctl_table *tbl = ctl_forward_entry;
+	struct ctl_table *tbl;
 	struct ctl_table_header *forw_hdr;
 #endif
 
 	err = -ENOMEM;
-	all = &ipv4_devconf;
-	dflt = &ipv4_devconf_dflt;
-
-	if (!net_eq(net, &init_net)) {
-		all = kmemdup(all, sizeof(ipv4_devconf), GFP_KERNEL);
-		if (!all)
-			goto err_alloc_all;
+	all = kmemdup(&ipv4_devconf, sizeof(ipv4_devconf), GFP_KERNEL);
+	if (!all)
+		goto err_alloc_all;
 
-		dflt = kmemdup(dflt, sizeof(ipv4_devconf_dflt), GFP_KERNEL);
-		if (!dflt)
-			goto err_alloc_dflt;
+	dflt = kmemdup(&ipv4_devconf_dflt, sizeof(ipv4_devconf_dflt), GFP_KERNEL);
+	if (!dflt)
+		goto err_alloc_dflt;
 
 #ifdef CONFIG_SYSCTL
-		tbl = kmemdup(tbl, sizeof(ctl_forward_entry), GFP_KERNEL);
-		if (!tbl)
-			goto err_alloc_ctl;
+	tbl = kmemdup(ctl_forward_entry, sizeof(ctl_forward_entry), GFP_KERNEL);
+	if (!tbl)
+		goto err_alloc_ctl;
 
-		tbl[0].data = &all->data[IPV4_DEVCONF_FORWARDING - 1];
-		tbl[0].extra1 = all;
-		tbl[0].extra2 = net;
+	tbl[0].data = &all->data[IPV4_DEVCONF_FORWARDING - 1];
+	tbl[0].extra1 = all;
+	tbl[0].extra2 = net;
 #endif
+
+	if (sysctl_devconf_inherit_init_net != 2 && !net_eq(net, &init_net)) {
+		memcpy(all, init_net.ipv4.devconf_all, sizeof(ipv4_devconf));
+		memcpy(dflt, init_net.ipv4.devconf_dflt, sizeof(ipv4_devconf_dflt));
 	}
 
 #ifdef CONFIG_SYSCTL
@@ -2646,15 +2646,12 @@ err_reg_ctl:
 err_reg_dflt:
 	__devinet_sysctl_unregister(net, all, NETCONFA_IFINDEX_ALL);
 err_reg_all:
-	if (tbl != ctl_forward_entry)
-		kfree(tbl);
+	kfree(tbl);
 err_alloc_ctl:
 #endif
-	if (dflt != &ipv4_devconf_dflt)
-		kfree(dflt);
+	kfree(dflt);
 err_alloc_dflt:
-	if (all != &ipv4_devconf)
-		kfree(all);
+	kfree(all);
 err_alloc_all:
 	return err;
 }
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 57198b3c86da..48cd36311901 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6902,6 +6902,11 @@ static int __net_init addrconf_init_net(struct net *net)
 	if (!dflt)
 		goto err_alloc_dflt;
 
+	if (sysctl_devconf_inherit_init_net == 1 && !net_eq(net, &init_net)) {
+		memcpy(all, init_net.ipv6.devconf_all, sizeof(ipv6_devconf));
+		memcpy(dflt, init_net.ipv6.devconf_dflt, sizeof(ipv6_devconf_dflt));
+	}
+
 	/* these will be inherited by all namespaces */
 	dflt->autoconf = ipv6_defaults.autoconf;
 	dflt->disable_ipv6 = ipv6_defaults.disable_ipv6;