genetlink: make netns aware

This makes generic netlink network namespace aware. No
generic netlink families except for the controller family
are made namespace aware, they need to be checked one by
one and then set the family->netnsok member to true.

A new function genlmsg_multicast_netns() is introduced to
allow sending a multicast message in a given namespace,
for example when it applies to an object that lives in
that namespace, a new function genlmsg_multicast_allns()
to send a message to all network namespaces (for objects
that do not have an associated netns).

The function genlmsg_multicast() is changed to multicast
the message in just init_net, which is currently correct
for all generic netlink families since they only work in
init_net right now. Some will later want to work in all
net namespaces because they do not care about the netns
at all -- those will have to be converted to use one of
the new functions genlmsg_multicast_allns() or
genlmsg_multicast_netns() whenever they are made netns
aware in some way.

After this patch families can easily decide whether or
not they should be available in all net namespaces. Many
genl families us it for objects not related to networking
and should therefore be available in all namespaces, but
that will have to be done on a per family basis.

Note that this doesn't touch on the checkpoint/restart
problem where network namespaces could be used, genl
families and multicast groups are numbered globally and
I see no easy way of changing that, especially since it
must be possible to multicast to all network namespaces
for those families that do not care about netns.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 61 insertions, 7 deletions

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 1b0e3ee4ddd..2a1c06874c4 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -3,6 +3,7 @@
 
 #include <linux/genetlink.h>
 #include <net/netlink.h>
+#include <net/net_namespace.h>
 
 /**
  * struct genl_multicast_group - generic netlink multicast group
@@ -27,6 +28,8 @@ struct genl_multicast_group
  * @name: name of family
  * @version: protocol version
  * @maxattr: maximum number of attributes supported
+ * @netnsok: set to true if the family can handle network
+ *	namespaces and should be presented in all of them
  * @attrbuf: buffer to store parsed attributes
  * @ops_list: list of all assigned operations
  * @family_list: family list
@@ -39,6 +42,7 @@ struct genl_family
 	char			name[GENL_NAMSIZ];
 	unsigned int		version;
 	unsigned int		maxattr;
+	bool			netnsok;
 	struct nlattr **	attrbuf;	/* private */
 	struct list_head	ops_list;	/* private */
 	struct list_head	family_list;	/* private */
@@ -62,8 +66,32 @@ struct genl_info
 	struct genlmsghdr *	genlhdr;
 	void *			userhdr;
 	struct nlattr **	attrs;
+#ifdef CONFIG_NET_NS
+	struct net *		_net;
+#endif
 };
 
+#ifdef CONFIG_NET_NS
+static inline struct net *genl_info_net(struct genl_info *info)
+{
+	return info->_net;
+}
+
+static inline void genl_info_net_set(struct genl_info *info, struct net *net)
+{
+	info->_net = net;
+}
+#else
+static inline struct net *genl_info_net(struct genl_info *info)
+{
+	return &init_net;
+}
+
+static inline void genl_info_net_set(struct genl_info *info, struct net *net)
+{
+}
+#endif
+
 /**
  * struct genl_ops - generic netlink operations
  * @cmd: command identifier
@@ -98,8 +126,6 @@ extern int genl_register_mc_group(struct genl_family *family,
 extern void genl_unregister_mc_group(struct genl_family *family,
 				     struct genl_multicast_group *grp);
 
-extern struct sock *genl_sock;
-
 /**
  * genlmsg_put - Add generic netlink header to netlink message
  * @skb: socket buffer holding the message
@@ -170,7 +196,21 @@ static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
 }
 
 /**
- * genlmsg_multicast - multicast a netlink message
+ * genlmsg_multicast_netns - multicast a netlink message to a specific netns
+ * @net: the net namespace
+ * @skb: netlink message as socket buffer
+ * @pid: own netlink pid to avoid sending to yourself
+ * @group: multicast group id
+ * @flags: allocation flags
+ */
+static inline int genlmsg_multicast_netns(struct net *net, struct sk_buff *skb,
+					  u32 pid, unsigned int group, gfp_t flags)
+{
+	return nlmsg_multicast(net->genl_sock, skb, pid, group, flags);
+}
+
+/**
+ * genlmsg_multicast - multicast a netlink message to the default netns
  * @skb: netlink message as socket buffer
  * @pid: own netlink pid to avoid sending to yourself
  * @group: multicast group id
@@ -179,17 +219,29 @@ static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
 static inline int genlmsg_multicast(struct sk_buff *skb, u32 pid,
 				    unsigned int group, gfp_t flags)
 {
-	return nlmsg_multicast(genl_sock, skb, pid, group, flags);
+	return genlmsg_multicast_netns(&init_net, skb, pid, group, flags);
 }
 
 /**
+ * genlmsg_multicast_allns - multicast a netlink message to all net namespaces
+ * @skb: netlink message as socket buffer
+ * @pid: own netlink pid to avoid sending to yourself
+ * @group: multicast group id
+ * @flags: allocation flags
+ *
+ * This function must hold the RTNL or rcu_read_lock().
+ */
+int genlmsg_multicast_allns(struct sk_buff *skb, u32 pid,
+			    unsigned int group, gfp_t flags);
+
+/**
  * genlmsg_unicast - unicast a netlink message
  * @skb: netlink message as socket buffer
  * @pid: netlink pid of the destination socket
  */
-static inline int genlmsg_unicast(struct sk_buff *skb, u32 pid)
+static inline int genlmsg_unicast(struct net *net, struct sk_buff *skb, u32 pid)
 {
-	return nlmsg_unicast(genl_sock, skb, pid);
+	return nlmsg_unicast(net->genl_sock, skb, pid);
 }
 
 /**
@@ -199,7 +251,7 @@ static inline int genlmsg_unicast(struct sk_buff *skb, u32 pid)
  */
 static inline int genlmsg_reply(struct sk_buff *skb, struct genl_info *info)
 {
-	return genlmsg_unicast(skb, info->snd_pid);
+	return genlmsg_unicast(genl_info_net(info), skb, info->snd_pid);
 }
 
 /**
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index b34a6ee7375..3173d12d946 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -26,6 +26,7 @@ struct net_device;
 struct sock;
 struct ctl_table_header;
 struct net_generic;
+struct sock;
 
 struct net {
 	atomic_t		count;		/* To decided when the network
@@ -57,6 +58,7 @@ struct net {
 	spinlock_t		rules_mod_lock;
 
 	struct sock 		*rtnl;			/* rtnetlink socket */
+	struct sock		*genl_sock;
 
 	struct netns_core	core;
 	struct netns_mib	mib;