[PATCH 2/2] ppp: implement rtnetlink device handling

[Guillaume Nault <g.nault@alphalink.fr>]

Define PPP device handler for use with rtnetlink.

The only PPP specific attribute is IFLA_PPP_DEV_FD. It is mandatory and
contains the file descriptor of the associated /dev/ppp instance (the
file descriptor which would have been used for ioctl(PPPIOCNEWUNIT) in
the ioctl-based API).

PPP devices created with the rtnetlink API behave like the ones created
with ioctl(PPPIOCNEWUNIT). In particular existing ioctls still apply to
PPP units created with the rtnetlink API.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
---
 drivers/net/ppp/ppp_generic.c | 109 ++++++++++++++++++++++++++++++++++++++++--
 include/uapi/linux/if_link.h  |   8 ++++
 2 files changed, 113 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index bc24537..19476d6 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -46,6 +46,7 @@
 #include <linux/device.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/file.h>
 #include <asm/unaligned.h>
 #include <net/slhc_vj.h>
 #include <linux/atomic.h>
@@ -185,7 +186,9 @@ struct channel {
 
 struct ppp_config {
 	struct file *file;
+	s32 fd;
 	s32 unit;
+	bool ifname_is_set;
 };
 
 /*
@@ -286,6 +289,7 @@ static int unit_get(struct idr *p, void *ptr);
 static int unit_set(struct idr *p, void *ptr, int n);
 static void unit_put(struct idr *p, int n);
 static void *unit_find(struct idr *p, int n);
+static void ppp_setup(struct net_device *dev);
 
 static const struct net_device_ops ppp_netdev_ops;
 
@@ -954,7 +958,7 @@ static struct pernet_operations ppp_net_ops = {
 	.size = sizeof(struct ppp_net),
 };
 
-static int ppp_unit_register(struct ppp *ppp, int unit)
+static int ppp_unit_register(struct ppp *ppp, int unit, bool ifname_is_set)
 {
 	struct ppp_net *pn = ppp_pernet(ppp->ppp_net);
 	int ret;
@@ -984,7 +988,8 @@ static int ppp_unit_register(struct ppp *ppp, int unit)
 
 	ppp->file.index = ret;
 
-	snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ppp->file.index);
+	if (!ifname_is_set)
+		snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ppp->file.index);
 
 	ret = register_netdevice(ppp->dev);
 	if (ret)
@@ -1012,7 +1017,24 @@ static int ppp_dev_configure(struct net *src_net, struct net_device *dev,
 	int indx;
 	int err;
 
-	file = conf->file;
+	if (conf->fd >= 0) {
+		file = fget(conf->fd);
+		if (file) {
+			if (file->f_op != &ppp_device_fops) {
+				fput(file);
+				return -EBADF;
+			}
+
+			/* Don't hold reference on file: ppp_release() is
+			 * responsible for safely freeing the associated
+			 * resources upon release. So file won't go away
+			 * from under us.
+			 */
+			fput(file);
+		}
+	} else {
+		file = conf->file;
+	}
 	if (!file)
 		return -EBADF;
 	if (file->private_data)
@@ -1040,7 +1062,7 @@ static int ppp_dev_configure(struct net *src_net, struct net_device *dev,
 	ppp->mru = PPP_MRU;
 	ppp->ppp_net = src_net;
 
-	err = ppp_unit_register(ppp, conf->unit);
+	err = ppp_unit_register(ppp, conf->unit, conf->ifname_is_set);
 	if (err < 0)
 		return err;
 
@@ -1049,6 +1071,73 @@ static int ppp_dev_configure(struct net *src_net, struct net_device *dev,
 	return 0;
 }
 
+static const struct nla_policy ppp_nl_policy[IFLA_PPP_MAX + 1] = {
+	[IFLA_PPP_DEV_FD]	= { .type = NLA_S32 },
+};
+
+static int ppp_nl_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+	if (!data)
+		return -EINVAL;
+
+	if (!data[IFLA_PPP_DEV_FD])
+		return -EINVAL;
+	if (nla_get_s32(data[IFLA_PPP_DEV_FD]) < 0)
+		return -EBADF;
+
+	return 0;
+}
+
+static int ppp_nl_newlink(struct net *src_net, struct net_device *dev,
+			  struct nlattr *tb[], struct nlattr *data[])
+{
+	struct ppp_config conf = {
+		.file = NULL,
+		.unit = -1,
+		.ifname_is_set = true,
+	};
+
+	conf.fd = nla_get_s32(data[IFLA_PPP_DEV_FD]);
+
+	return ppp_dev_configure(src_net, dev, &conf);
+}
+
+static void ppp_nl_dellink(struct net_device *dev, struct list_head *head)
+{
+	unregister_netdevice_queue(dev, head);
+}
+
+static size_t ppp_nl_get_size(const struct net_device *dev)
+{
+	return 0;
+}
+
+static int ppp_nl_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	return 0;
+}
+
+static struct net *ppp_nl_get_link_net(const struct net_device *dev)
+{
+	struct ppp *ppp = netdev_priv(dev);
+
+	return ppp->ppp_net;
+}
+
+static struct rtnl_link_ops ppp_link_ops __read_mostly = {
+	.kind		= "ppp",
+	.maxtype	= IFLA_PPP_MAX,
+	.policy		= ppp_nl_policy,
+	.priv_size	= sizeof(struct ppp),
+	.setup		= ppp_setup,
+	.validate	= ppp_nl_validate,
+	.newlink	= ppp_nl_newlink,
+	.dellink	= ppp_nl_dellink,
+	.get_size	= ppp_nl_get_size,
+	.fill_info	= ppp_nl_fill_info,
+	.get_link_net	= ppp_nl_get_link_net,
+};
+
 #define PPP_MAJOR	108
 
 /* Called at boot time if ppp is compiled into the kernel,
@@ -1077,11 +1166,19 @@ static int __init ppp_init(void)
 		goto out_chrdev;
 	}
 
+	err = rtnl_link_register(&ppp_link_ops);
+	if (err) {
+		pr_err("Failed to register RT netlink PPP handler\n");
+		goto out_class;
+	}
+
 	/* not a big deal if we fail here :-) */
 	device_create(ppp_class, NULL, MKDEV(PPP_MAJOR, 0), NULL, "ppp");
 
 	return 0;
 
+out_class:
+	class_destroy(ppp_class);
 out_chrdev:
 	unregister_chrdev(PPP_MAJOR, "ppp");
 out_net:
@@ -2821,7 +2918,9 @@ static int ppp_create_interface(struct net *net, int *unit, struct file *file)
 {
 	struct ppp_config conf = {
 		.file = file,
+		.fd = -1,
 		.unit = *unit,
+		.ifname_is_set = false,
 	};
 	struct net_device *dev;
 	struct ppp *ppp;
@@ -3038,6 +3137,7 @@ static void __exit ppp_cleanup(void)
 	/* should never happen */
 	if (atomic_read(&ppp_unit_count) || atomic_read(&channel_count))
 		pr_err("PPP: removing module but units remain!\n");
+	rtnl_link_unregister(&ppp_link_ops);
 	unregister_chrdev(PPP_MAJOR, "ppp");
 	device_destroy(ppp_class, MKDEV(PPP_MAJOR, 0));
 	class_destroy(ppp_class);
@@ -3096,4 +3196,5 @@ EXPORT_SYMBOL(ppp_register_compressor);
 EXPORT_SYMBOL(ppp_unregister_compressor);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_CHARDEV(PPP_MAJOR, 0);
+MODULE_ALIAS_RTNL_LINK("ppp");
 MODULE_ALIAS("devname:ppp");
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index a30b780..72b0213 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -470,6 +470,14 @@ enum {
 };
 #define IFLA_GENEVE_MAX	(__IFLA_GENEVE_MAX - 1)
 
+/* PPP section */
+enum {
+	IFLA_PPP_UNSPEC,
+	IFLA_PPP_DEV_FD,
+	__IFLA_PPP_MAX,
+};
+#define IFLA_PPP_MAX (__IFLA_PPP_MAX - 1)
+
 /* Bonding section */
 
 enum {
-- 
2.6.4