[PATCH net-next] net: Export net->ipv6.sysctl.ip_nonlocal_bind to /proc

[Kirill Tkhai <ktkhai@virtuozzo.com>]

Currenly, this parameter can be configured via sysctl
only. But sysctl is considered as depricated interface
(man 2 sysctl), and it only can applied to current's net
namespace (this requires to do setns() to change it in
not current's net ns).

So, let's export the parameter to /proc in standard way,
and this allows to access another process namespace
via /proc/[pid]/net/ip6_nonlocal_bind.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 net/ipv6/proc.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index 6e57028d2e91..2d0aa59c2d0d 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -312,6 +312,47 @@ int snmp6_unregister_dev(struct inet6_dev *idev)
 	return 0;
 }
 
+static int nonlocal_bind_show(struct seq_file *seq, void *v)
+{
+	struct net *net = seq->private;
+
+	seq_printf(seq, "%d\n", !!net->ipv6.sysctl.ip_nonlocal_bind);
+	return 0;
+}
+
+static int open_nonlocal_bind(struct inode *inode, struct file *file)
+{
+	return single_open_net(inode, file, nonlocal_bind_show);
+}
+
+static ssize_t write_nonlocal_bind(struct file *file, const char __user *ubuf,
+				   size_t count, loff_t *ppos)
+{
+	struct net *net = ((struct seq_file *)file->private_data)->private;
+	char buf[3];
+
+	if (*ppos || count <= 0 || count > sizeof(buf))
+		return -EINVAL;
+
+	if (copy_from_user(buf, ubuf, count))
+		return -EFAULT;
+	buf[0] -= '0';
+	if ((count == 3 && buf[2] != '\0') ||
+	    (count >= 2 && buf[1] != '\n') ||
+	    (buf[0] != 0 && buf[0] != 1))
+		return -EINVAL;
+
+	net->ipv6.sysctl.ip_nonlocal_bind = buf[0];
+	return count;
+}
+
+static const struct file_operations nonlocal_bind_ops = {
+	.open	= open_nonlocal_bind,
+	.read	= seq_read,
+	.write	= write_nonlocal_bind,
+	.release = single_release_net,
+};
+
 static int __net_init ipv6_proc_init_net(struct net *net)
 {
 	if (!proc_create("sockstat6", 0444, net->proc_net,
@@ -321,12 +362,18 @@ static int __net_init ipv6_proc_init_net(struct net *net)
 	if (!proc_create("snmp6", 0444, net->proc_net, &snmp6_seq_fops))
 		goto proc_snmp6_fail;
 
+        if (!proc_create_data("ip6_nonlocal_bind", 0644,
+			       net->proc_net, &nonlocal_bind_ops, net))
+		goto proc_bind_fail;
+
 	net->mib.proc_net_devsnmp6 = proc_mkdir("dev_snmp6", net->proc_net);
 	if (!net->mib.proc_net_devsnmp6)
 		goto proc_dev_snmp6_fail;
 	return 0;
 
 proc_dev_snmp6_fail:
+	remove_proc_entry("ip6_nonlocal_bind", net->proc_net);
+proc_bind_fail:
 	remove_proc_entry("snmp6", net->proc_net);
 proc_snmp6_fail:
 	remove_proc_entry("sockstat6", net->proc_net);
@@ -337,6 +384,7 @@ static void __net_exit ipv6_proc_exit_net(struct net *net)
 {
 	remove_proc_entry("sockstat6", net->proc_net);
 	remove_proc_entry("dev_snmp6", net->proc_net);
+	remove_proc_entry("ip6_nonlocal_bind", net->proc_net);
 	remove_proc_entry("snmp6", net->proc_net);
 }