[B.A.T.M.A.N.] [PATCH v2 04/12] batman-adv: add generic netlink query API to replace debugfs files

[Andrew Lunn <andrew@lunn.ch>]

From: Matthias Schiffer <mschiffer@universe-factory.net>

debugfs is currently severely broken virtually everywhere in the kernel
where files are dynamically added and removed (see
http://lkml.iu.edu/hypermail/linux/kernel/1506.1/02196.html for some
details). In addition to that, debugfs is not namespace-aware.

Also, the debugfs interface will try to fix the whole list of originators/
TT entries into a single buffer. The situation has improved in recent
kernels,as the seq_file infrastructure will fall back to vmalloc now when
kmalloc fails. Still, converting all information to text and potentially
retrying multiple times until the buffer is big enough is very inefficient.

This commit adds generic infrastructur for the netlink interface to
batman-adv and implements the following command:

* BATADV_CMD_GET_ROUTING_ALGOS: will return the list of supported routing
  algorithms
* BATADV_CMD_GET_MESH_INFO: will return basic information about a
  batman-adv softif (name, index and MAC address for both the softif and
  the primary hardif; routing algorithm; batman-adv version)
* BATADV_CMD_GET_HARDIFS: will return the list of hardifs (including
  index, name and MAC address) of all hardifs for a given softif

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
v2: Added missing includes and forward declarations of structures.
---
 Makefile                        |   1 +
 include/uapi/linux/batman_adv.h |  49 ++++++++
 net/batman-adv/Makefile         |   1 +
 net/batman-adv/main.c           |  51 ++++++++
 net/batman-adv/main.h           |   2 +
 net/batman-adv/netlink.c        | 260 ++++++++++++++++++++++++++++++++++++++++
 net/batman-adv/netlink.h        |  41 +++++++
 7 files changed, 405 insertions(+)
 create mode 100644 include/uapi/linux/batman_adv.h
 create mode 100644 net/batman-adv/netlink.c
 create mode 100644 net/batman-adv/netlink.h

diff --git a/Makefile b/Makefile
index 5d2c058..f17bde5 100644
--- a/Makefile
+++ b/Makefile
@@ -45,6 +45,7 @@ REVISION= $(shell	if [ -d "$(PWD)/.git" ]; then \
 			fi)
 export NOSTDINC_FLAGS := \
 	-I$(PWD)/compat-include/ \
+	-I$(PWD)/include/ \
 	-include $(PWD)/compat.h \
 	$(CFLAGS)
 
diff --git a/include/uapi/linux/batman_adv.h b/include/uapi/linux/batman_adv.h
new file mode 100644
index 0000000..b9b7dfd
--- /dev/null
+++ b/include/uapi/linux/batman_adv.h
@@ -0,0 +1,49 @@
+/* Copyright (C) 2016 B.A.T.M.A.N. contributors:
+ *
+ * Matthias Schiffer
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _UAPI_LINUX_BATMAN_ADV_H_
+#define _UAPI_LINUX_BATMAN_ADV_H_
+
+#define BATADV_NL_NAME "batadv"
+
+enum {
+	BATADV_ATTR_UNSPEC,
+	BATADV_ATTR_VERSION,
+	BATADV_ATTR_ALGO_NAME,
+	BATADV_ATTR_MESH_IFINDEX,
+	BATADV_ATTR_MESH_IFNAME,
+	BATADV_ATTR_MESH_ADDRESS,
+	BATADV_ATTR_HARD_IFINDEX,
+	BATADV_ATTR_HARD_IFNAME,
+	BATADV_ATTR_HARD_ADDRESS,
+	BATADV_ATTR_ACTIVE,
+	__BATADV_ATTR_MAX,
+};
+
+#define BATADV_ATTR_MAX (__BATADV_ATTR_MAX - 1)
+
+enum {
+	BATADV_CMD_UNSPEC,
+	BATADV_CMD_GET_ROUTING_ALGOS,
+	BATADV_CMD_GET_MESH_INFO,
+	BATADV_CMD_GET_HARDIFS,
+	__BATADV_CMD_MAX,
+};
+
+#define BATADV_CMD_MAX (__BATADV_CMD_MAX - 1)
+
+#endif /* _UAPI_LINUX_BATMAN_ADV_H_ */
diff --git a/net/batman-adv/Makefile b/net/batman-adv/Makefile
index 797cf2f..4e5adba 100644
--- a/net/batman-adv/Makefile
+++ b/net/batman-adv/Makefile
@@ -33,6 +33,7 @@ batman-adv-y += hash.o
 batman-adv-y += icmp_socket.o
 batman-adv-y += main.o
 batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += multicast.o
+batman-adv-y += netlink.o
 batman-adv-$(CONFIG_BATMAN_ADV_NC) += network-coding.o
 batman-adv-y += originator.o
 batman-adv-y += routing.o
diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index 5f2974b..7b5f585 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -35,6 +35,7 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/netdevice.h>
+#include <linux/netlink.h>
 #include <linux/pkt_sched.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
@@ -46,7 +47,10 @@
 #include <linux/string.h>
 #include <linux/workqueue.h>
 #include <net/dsfield.h>
+#include <net/genetlink.h>
+#include <net/netlink.h>
 #include <net/rtnetlink.h>
+#include <uapi/linux/batman_adv.h>
 
 #include "bat_algo.h"
 #include "bridge_loop_avoidance.h"
@@ -57,6 +61,7 @@
 #include "hard-interface.h"
 #include "icmp_socket.h"
 #include "multicast.h"
+#include "netlink.h"
 #include "network-coding.h"
 #include "originator.h"
 #include "packet.h"
@@ -101,6 +106,7 @@ static int __init batadv_init(void)
 
 	register_netdevice_notifier(&batadv_hard_if_notifier);
 	rtnl_link_register(&batadv_link_ops);
+	batadv_netlink_register();
 
 	pr_info("B.A.T.M.A.N. advanced %s (compatibility version %i) loaded\n",
 		BATADV_SOURCE_VERSION, BATADV_COMPAT_VERSION);
@@ -111,6 +117,7 @@ static int __init batadv_init(void)
 static void __exit batadv_exit(void)
 {
 	batadv_debugfs_destroy();
+	batadv_netlink_unregister();
 	rtnl_link_unregister(&batadv_link_ops);
 	unregister_netdevice_notifier(&batadv_hard_if_notifier);
 	batadv_hardif_remove_interfaces();
@@ -610,6 +617,50 @@ int batadv_algo_seq_print_text(struct seq_file *seq, void *offset)
 	return 0;
 }
 
+static int batadv_algo_dump_entry(struct sk_buff *msg, u32 portid, u32 seq,
+				  struct batadv_algo_ops *bat_algo_ops)
+{
+	void *hdr;
+
+	hdr = genlmsg_put(msg, portid, seq, &batadv_netlink_family, NLM_F_MULTI,
+			  BATADV_CMD_GET_ROUTING_ALGOS);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_string(msg, BATADV_ATTR_ALGO_NAME, bat_algo_ops->name))
+		goto nla_put_failure;
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+ nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+int batadv_algo_dump(struct sk_buff *msg, struct netlink_callback *cb)
+{
+	int portid = NETLINK_CB(cb->skb).portid;
+	struct batadv_algo_ops *bat_algo_ops;
+	int skip = cb->args[0];
+	int i = 0;
+
+	hlist_for_each_entry(bat_algo_ops, &batadv_algo_list, list) {
+		if (i++ < skip)
+			continue;
+
+		if (batadv_algo_dump_entry(msg, portid, cb->nlh->nlmsg_seq,
+					   bat_algo_ops)) {
+			i--;
+			break;
+		}
+	}
+
+	cb->args[0] = i;
+
+	return msg->len;
+}
+
 /**
  * batadv_skb_crc32 - calculate CRC32 of the whole packet and skip bytes in
  *  the header
diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index 7692526..3b770df 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -191,6 +191,7 @@ enum batadv_uev_type {
 #include "types.h"
 
 struct batadv_ogm_packet;
+struct netlink_callback;
 struct seq_file;
 struct sk_buff;
 
@@ -221,6 +222,7 @@ void batadv_recv_handler_unregister(u8 packet_type);
 int batadv_algo_register(struct batadv_algo_ops *bat_algo_ops);
 int batadv_algo_select(struct batadv_priv *bat_priv, char *name);
 int batadv_algo_seq_print_text(struct seq_file *seq, void *offset);
+int batadv_algo_dump(struct sk_buff *msg, struct netlink_callback *cb);
 __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr);
 
 /**
diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
new file mode 100644
index 0000000..e302de3
--- /dev/null
+++ b/net/batman-adv/netlink.c
@@ -0,0 +1,260 @@
+/* Copyright (C) 2016 B.A.T.M.A.N. contributors:
+ *
+ * Matthias Schiffer
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "main.h"
+#include "netlink.h"
+
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/if_ether.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/netlink.h>
+#include <linux/printk.h>
+#include <linux/rculist.h>
+#include <linux/rcupdate.h>
+#include <linux/skbuff.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+#include <net/sock.h>
+#include <uapi/linux/batman_adv.h>
+
+#include "hard-interface.h"
+#include "soft-interface.h"
+
+struct genl_family batadv_netlink_family = {
+	.id = GENL_ID_GENERATE,
+	.hdrsize = 0,
+	.name = BATADV_NL_NAME,
+	.version = 1,
+	.maxattr = BATADV_ATTR_MAX,
+};
+
+static int
+batadv_netlink_mesh_info_put(struct sk_buff *msg, struct net_device *soft_iface)
+{
+	int ret = -ENOBUFS;
+	struct batadv_priv *bat_priv = netdev_priv(soft_iface);
+	struct batadv_hard_iface *primary_if = NULL;
+	struct net_device *hard_iface;
+
+	if (nla_put_string(msg, BATADV_ATTR_VERSION, BATADV_SOURCE_VERSION) ||
+	    nla_put_string(msg, BATADV_ATTR_ALGO_NAME,
+			   bat_priv->bat_algo_ops->name) ||
+	    nla_put_u32(msg, BATADV_ATTR_MESH_IFINDEX, soft_iface->ifindex) ||
+	    nla_put_string(msg, BATADV_ATTR_MESH_IFNAME, soft_iface->name) ||
+	    nla_put(msg, BATADV_ATTR_MESH_ADDRESS, ETH_ALEN,
+		    soft_iface->dev_addr))
+		goto out;
+
+	primary_if = batadv_primary_if_get_selected(bat_priv);
+	if (primary_if && primary_if->if_status == BATADV_IF_ACTIVE) {
+		hard_iface = primary_if->net_dev;
+
+		if (nla_put_u32(msg, BATADV_ATTR_HARD_IFINDEX,
+				hard_iface->ifindex) ||
+		    nla_put_string(msg, BATADV_ATTR_HARD_IFNAME,
+				   hard_iface->name) ||
+		    nla_put(msg, BATADV_ATTR_HARD_ADDRESS, ETH_ALEN,
+			    hard_iface->dev_addr))
+			goto out;
+	}
+
+	ret = 0;
+
+ out:
+	if (primary_if)
+		batadv_hardif_put(primary_if);
+
+	return ret;
+}
+
+static int
+batadv_netlink_get_mesh_info(struct sk_buff *skb, struct genl_info *info)
+{
+	struct net *net = genl_info_net(info);
+	int ret;
+	struct sk_buff *msg = NULL;
+	void *msg_head;
+	int ifindex;
+	struct net_device *soft_iface;
+
+	if (!info->attrs[BATADV_ATTR_MESH_IFINDEX])
+		return -EINVAL;
+
+	ifindex = nla_get_u32(info->attrs[BATADV_ATTR_MESH_IFINDEX]);
+	if (!ifindex)
+		return -EINVAL;
+
+	soft_iface = dev_get_by_index(net, ifindex);
+	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	msg_head = genlmsg_put(msg, info->snd_portid, info->snd_seq,
+			       &batadv_netlink_family, 0,
+			       BATADV_CMD_GET_MESH_INFO);
+	if (!msg_head) {
+		ret = -ENOBUFS;
+		goto out;
+	}
+
+	ret = batadv_netlink_mesh_info_put(msg, soft_iface);
+
+ out:
+	if (soft_iface)
+		dev_put(soft_iface);
+
+	if (ret) {
+		if (msg)
+			nlmsg_free(msg);
+		return ret;
+	}
+
+	genlmsg_end(msg, msg_head);
+	return genlmsg_reply(msg, info);
+}
+
+static int
+batadv_netlink_dump_hardif_entry(struct sk_buff *msg, u32 portid, u32 seq,
+				 struct batadv_hard_iface *hard_iface)
+{
+	struct net_device *net_dev = hard_iface->net_dev;
+	void *hdr;
+
+	hdr = genlmsg_put(msg, portid, seq, &batadv_netlink_family, NLM_F_MULTI,
+			  BATADV_CMD_GET_HARDIFS);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(msg, BATADV_ATTR_HARD_IFINDEX,
+			net_dev->ifindex) ||
+	    nla_put_string(msg, BATADV_ATTR_HARD_IFNAME,
+			   net_dev->name) ||
+	    nla_put(msg, BATADV_ATTR_HARD_ADDRESS, ETH_ALEN,
+		    net_dev->dev_addr))
+		goto nla_put_failure;
+
+	if (hard_iface->if_status == BATADV_IF_ACTIVE) {
+		if (nla_put_flag(msg, BATADV_ATTR_ACTIVE))
+			goto nla_put_failure;
+	}
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+ nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+static int
+batadv_netlink_dump_hardifs(struct sk_buff *msg, struct netlink_callback *cb)
+{
+	struct net *net = sock_net(cb->skb->sk);
+	struct net_device *soft_iface;
+	struct batadv_hard_iface *hard_iface;
+	int ifindex;
+	int portid = NETLINK_CB(cb->skb).portid;
+	int seq = cb->nlh->nlmsg_seq;
+	int skip = cb->args[0];
+	int i = 0;
+
+	ifindex = batadv_netlink_get_ifindex(cb->nlh, BATADV_ATTR_MESH_IFINDEX);
+	if (!ifindex)
+		return -EINVAL;
+
+	soft_iface = dev_get_by_index(net, ifindex);
+	if (!soft_iface)
+		return -ENODEV;
+
+	if (!batadv_softif_is_valid(soft_iface)) {
+		dev_put(soft_iface);
+		return -ENODEV;
+	}
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
+		if (hard_iface->soft_iface != soft_iface)
+			continue;
+
+		if (i++ < skip)
+			continue;
+
+		if (batadv_netlink_dump_hardif_entry(msg, portid, seq,
+						     hard_iface)) {
+			i--;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+
+	dev_put(soft_iface);
+
+	cb->args[0] = i;
+
+	return msg->len;
+}
+
+static struct nla_policy batadv_netlink_policy[BATADV_ATTR_MAX + 1] = {
+	[BATADV_ATTR_MESH_IFINDEX]	= { .type = NLA_U32 },
+};
+
+static struct genl_ops batadv_netlink_ops[] = {
+	{
+		.cmd = BATADV_CMD_GET_ROUTING_ALGOS,
+		.flags = GENL_ADMIN_PERM,
+		.policy = batadv_netlink_policy,
+		.dumpit = batadv_algo_dump,
+	},
+	{
+		.cmd = BATADV_CMD_GET_MESH_INFO,
+		.flags = GENL_ADMIN_PERM,
+		.policy = batadv_netlink_policy,
+		.doit = batadv_netlink_get_mesh_info,
+	},
+	{
+		.cmd = BATADV_CMD_GET_HARDIFS,
+		.flags = GENL_ADMIN_PERM,
+		.policy = batadv_netlink_policy,
+		.dumpit = batadv_netlink_dump_hardifs,
+	},
+};
+
+void __init batadv_netlink_register(void)
+{
+	int ret;
+
+	ret = genl_register_family_with_ops(&batadv_netlink_family,
+					    batadv_netlink_ops);
+	if (ret)
+		pr_warn("unable to register netlink family");
+}
+
+void batadv_netlink_unregister(void)
+{
+	genl_unregister_family(&batadv_netlink_family);
+}
diff --git a/net/batman-adv/netlink.h b/net/batman-adv/netlink.h
new file mode 100644
index 0000000..ae0eeb9
--- /dev/null
+++ b/net/batman-adv/netlink.h
@@ -0,0 +1,41 @@
+/* Copyright (C) 2016 B.A.T.M.A.N. contributors:
+ *
+ * Matthias Schiffer
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _NET_BATMAN_ADV_NETLINK_H_
+#define _NET_BATMAN_ADV_NETLINK_H_
+
+#include <linux/compiler.h>
+#include <linux/genetlink.h>
+#include <net/genetlink.h>
+#include <net/netlink.h>
+
+struct nlmsghdr;
+
+void batadv_netlink_register(void);
+void batadv_netlink_unregister(void);
+
+static inline int
+batadv_netlink_get_ifindex(const struct nlmsghdr *nlh, int attrtype)
+{
+	struct nlattr *attr = nlmsg_find_attr(nlh, GENL_HDRLEN, attrtype);
+
+	return attr ? nla_get_u32(attr) : 0;
+}
+
+extern struct genl_family batadv_netlink_family;
+
+#endif /* _NET_BATMAN_ADV_NETLINK_H_ */
-- 
2.8.0.rc3