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>

1 files changed, 146 insertions, 40 deletions

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index eed4c6a..575c643 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -18,8 +18,6 @@
 #include <net/sock.h>
 #include <net/genetlink.h>
 
-struct sock *genl_sock = NULL;
-
 static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
 
 static inline void genl_lock(void)
@@ -175,10 +173,31 @@ int genl_register_mc_group(struct genl_family *family,
 		mc_groups_longs++;
 	}
 
-	err = netlink_change_ngroups(genl_sock,
-				     mc_groups_longs * BITS_PER_LONG);
-	if (err)
-		goto out;
+	if (family->netnsok) {
+		struct net *net;
+
+		rcu_read_lock();
+		for_each_net_rcu(net) {
+			err = netlink_change_ngroups(net->genl_sock,
+					mc_groups_longs * BITS_PER_LONG);
+			if (err) {
+				/*
+				 * No need to roll back, can only fail if
+				 * memory allocation fails and then the
+				 * number of _possible_ groups has been
+				 * increased on some sockets which is ok.
+				 */
+				rcu_read_unlock();
+				goto out;
+			}
+		}
+		rcu_read_unlock();
+	} else {
+		err = netlink_change_ngroups(init_net.genl_sock,
+					     mc_groups_longs * BITS_PER_LONG);
+		if (err)
+			goto out;
+	}
 
 	grp->id = id;
 	set_bit(id, mc_groups);
@@ -195,8 +214,14 @@ EXPORT_SYMBOL(genl_register_mc_group);
 static void __genl_unregister_mc_group(struct genl_family *family,
 				       struct genl_multicast_group *grp)
 {
+	struct net *net;
 	BUG_ON(grp->family != family);
-	netlink_clear_multicast_users(genl_sock, grp->id);
+
+	rcu_read_lock();
+	for_each_net_rcu(net)
+		netlink_clear_multicast_users(net->genl_sock, grp->id);
+	rcu_read_unlock();
+
 	clear_bit(grp->id, mc_groups);
 	list_del(&grp->list);
 	genl_ctrl_event(CTRL_CMD_DELMCAST_GRP, grp);
@@ -467,6 +492,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct genl_ops *ops;
 	struct genl_family *family;
+	struct net *net = sock_net(skb->sk);
 	struct genl_info info;
 	struct genlmsghdr *hdr = nlmsg_data(nlh);
 	int hdrlen, err;
@@ -475,6 +501,10 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (family == NULL)
 		return -ENOENT;
 
+	/* this family doesn't exist in this netns */
+	if (!family->netnsok && !net_eq(net, &init_net))
+		return -ENOENT;
+
 	hdrlen = GENL_HDRLEN + family->hdrsize;
 	if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 		return -EINVAL;
@@ -492,7 +522,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 			return -EOPNOTSUPP;
 
 		genl_unlock();
-		err = netlink_dump_start(genl_sock, skb, nlh,
+		err = netlink_dump_start(net->genl_sock, skb, nlh,
 					 ops->dumpit, ops->done);
 		genl_lock();
 		return err;
@@ -514,6 +544,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 	info.genlhdr = nlmsg_data(nlh);
 	info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 	info.attrs = family->attrbuf;
+	genl_info_net_set(&info, net);
 
 	return ops->doit(skb, &info);
 }
@@ -534,6 +565,7 @@ static struct genl_family genl_ctrl = {
 	.name = "nlctrl",
 	.version = 0x2,
 	.maxattr = CTRL_ATTR_MAX,
+	.netnsok = true,
 };
 
 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
@@ -650,6 +682,7 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 
 	int i, n = 0;
 	struct genl_family *rt;
+	struct net *net = sock_net(skb->sk);
 	int chains_to_skip = cb->args[0];
 	int fams_to_skip = cb->args[1];
 
@@ -658,6 +691,8 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 			continue;
 		n = 0;
 		list_for_each_entry(rt, genl_family_chain(i), family_list) {
+			if (!rt->netnsok && !net_eq(net, &init_net))
+				continue;
 			if (++n < fams_to_skip)
 				continue;
 			if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
@@ -729,6 +764,7 @@ static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 	if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
 		u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
 		res = genl_family_find_byid(id);
+		err = -ENOENT;
 	}
 
 	if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
@@ -736,49 +772,61 @@ static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 
 		name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
 		res = genl_family_find_byname(name);
+		err = -ENOENT;
 	}
 
-	if (res == NULL) {
-		err = -ENOENT;
-		goto errout;
+	if (res == NULL)
+		return err;
+
+	if (!res->netnsok && !net_eq(genl_info_net(info), &init_net)) {
+		/* family doesn't exist here */
+		return -ENOENT;
 	}
 
 	msg = ctrl_build_family_msg(res, info->snd_pid, info->snd_seq,
 				    CTRL_CMD_NEWFAMILY);
-	if (IS_ERR(msg)) {
-		err = PTR_ERR(msg);
-		goto errout;
-	}
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
 
-	err = genlmsg_reply(msg, info);
-errout:
-	return err;
+	return genlmsg_reply(msg, info);
 }
 
 static int genl_ctrl_event(int event, void *data)
 {
 	struct sk_buff *msg;
+	struct genl_family *family;
+	struct genl_multicast_group *grp;
 
-	if (genl_sock == NULL)
+	/* genl is still initialising */
+	if (!init_net.genl_sock)
 		return 0;
 
 	switch (event) {
 	case CTRL_CMD_NEWFAMILY:
 	case CTRL_CMD_DELFAMILY:
-		msg = ctrl_build_family_msg(data, 0, 0, event);
-		if (IS_ERR(msg))
-			return PTR_ERR(msg);
-
-		genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
+		family = data;
+		msg = ctrl_build_family_msg(family, 0, 0, event);
 		break;
 	case CTRL_CMD_NEWMCAST_GRP:
 	case CTRL_CMD_DELMCAST_GRP:
+		grp = data;
+		family = grp->family;
 		msg = ctrl_build_mcgrp_msg(data, 0, 0, event);
-		if (IS_ERR(msg))
-			return PTR_ERR(msg);
-
-		genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
 		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
+
+	if (!family->netnsok) {
+		genlmsg_multicast_netns(&init_net, msg, 0,
+					GENL_ID_CTRL, GFP_KERNEL);
+	} else {
+		rcu_read_lock();
+		genlmsg_multicast_allns(msg, 0, GENL_ID_CTRL, GFP_ATOMIC);
+		rcu_read_unlock();
 	}
 
 	return 0;
@@ -795,6 +843,33 @@ static struct genl_multicast_group notify_grp = {
 	.name		= "notify",
 };
 
+static int __net_init genl_pernet_init(struct net *net)
+{
+	/* we'll bump the group number right afterwards */
+	net->genl_sock = netlink_kernel_create(net, NETLINK_GENERIC, 0,
+					       genl_rcv, &genl_mutex,
+					       THIS_MODULE);
+
+	if (!net->genl_sock && net_eq(net, &init_net))
+		panic("GENL: Cannot initialize generic netlink\n");
+
+	if (!net->genl_sock)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void __net_exit genl_pernet_exit(struct net *net)
+{
+	netlink_kernel_release(net->genl_sock);
+	net->genl_sock = NULL;
+}
+
+static struct pernet_operations genl_pernet_ops = {
+	.init = genl_pernet_init,
+	.exit = genl_pernet_exit,
+};
+
 static int __init genl_init(void)
 {
 	int i, err;
@@ -804,36 +879,67 @@ static int __init genl_init(void)
 
 	err = genl_register_family(&genl_ctrl);
 	if (err < 0)
-		goto errout;
+		goto problem;
 
 	err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
 	if (err < 0)
-		goto errout_register;
+		goto problem;
 
 	netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
 
-	/* we'll bump the group number right afterwards */
-	genl_sock = netlink_kernel_create(&init_net, NETLINK_GENERIC, 0,
-					  genl_rcv, &genl_mutex, THIS_MODULE);
-	if (genl_sock == NULL)
-		panic("GENL: Cannot initialize generic netlink\n");
+	err = register_pernet_subsys(&genl_pernet_ops);
+	if (err)
+		goto problem;
 
 	err = genl_register_mc_group(&genl_ctrl, &notify_grp);
 	if (err < 0)
-		goto errout_register;
+		goto problem;
 
 	return 0;
 
-errout_register:
-	genl_unregister_family(&genl_ctrl);
-errout:
+problem:
 	panic("GENL: Cannot register controller: %d\n", err);
 }
 
 subsys_initcall(genl_init);
 
-EXPORT_SYMBOL(genl_sock);
 EXPORT_SYMBOL(genl_register_ops);
 EXPORT_SYMBOL(genl_unregister_ops);
 EXPORT_SYMBOL(genl_register_family);
 EXPORT_SYMBOL(genl_unregister_family);
+
+static int genlmsg_mcast(struct sk_buff *skb, u32 pid, unsigned long group,
+			 gfp_t flags)
+{
+	struct sk_buff *tmp;
+	struct net *net, *prev = NULL;
+	int err;
+
+	for_each_net_rcu(net) {
+		if (prev) {
+			tmp = skb_clone(skb, flags);
+			if (!tmp) {
+				err = -ENOMEM;
+				goto error;
+			}
+			err = nlmsg_multicast(prev->genl_sock, tmp,
+					      pid, group, flags);
+			if (err)
+				goto error;
+		}
+
+		prev = net;
+	}
+
+	return nlmsg_multicast(prev->genl_sock, skb, pid, group, flags);
+ error:
+	kfree_skb(skb);
+	return err;
+}
+
+int genlmsg_multicast_allns(struct sk_buff *skb, u32 pid, unsigned int group,
+			    gfp_t flags)
+{
+	return genlmsg_mcast(skb, pid, group, flags);
+}
+EXPORT_SYMBOL(genlmsg_multicast_allns);