Subject: [PATCH v2 net-next] Ipvlan should return an error when an address is already in use.

From: Krister Johansen <[email-masked]>
Date: Thu, 8 Jun 2017 13:12:14 -0700

The ipvlan code already knows how to detect when a duplicate address is
about to be assigned to an ipvlan device.  However, that failure is not
propogated outward and leads to a silent failure.

Introduce a validation step at ip address creation time and allow device
drivers to register to validate the incoming ip addresses.  The ipvlan
code is the first consumer.  If it detects an address in use, we can
return an error to the user before beginning to commit the new ifa in
the networking code.

This can be especially useful if it is necessary to provision many
ipvlans in containers.  The provisioning software (or operator) can use
this to detect situations where an ip address is unexpectedly in use.

Signed-off-by: Krister Johansen <[email-masked]>
---
 drivers/net/ipvlan/ipvlan_main.c | 69 ++++++++++++++++++++++++++++++++++++++++
 include/linux/inetdevice.h       |  7 ++++
 include/net/addrconf.h           | 10 +++++-
 net/ipv4/devinet.c               | 33 +++++++++++++++++++
 net/ipv6/addrconf.c              | 17 +++++++++-
 net/ipv6/addrconf_core.c         | 19 +++++++++++
 6 files changed, 153 insertions(+), 2 deletions(-)

Apologies for letting this one languish for so long.  This iteration is
more code than I hoped it would be, but I believe it addresses the
concerns raised in the prior iteration of the review.

Changes v1 -> v2:

- Add a separate validator chain with ipvlan as the first consumer.
  [Address Dave M.'s comment about needing all chain users to agree
  about use of notifier_[to|from]_errno]

- Run validator chain only during address creation.
  [Address Dave M.'s comment about prior version failing to handle
  primary address promotions.]

- Run validator step before the atomic section in the ip address create
  path.
  [Address my own dissatisfaction with having to rollback and
  potentially issue an immediate up and then down RTNETLINK event.]

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 618ed88..e4141d6 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -824,6 +824,33 @@ static int ipvlan_addr6_event(struct notifier_block *unused,
 	return NOTIFY_OK;
 }
 
+static int ipvlan_addr6_validator_event(struct notifier_block *unused,
+					unsigned long event, void *ptr)
+{
+	struct in6_validator_info *i6vi = (struct in6_validator_info *)ptr;
+	struct net_device *dev = (struct net_device *)i6vi->i6vi_dev->dev;
+	struct ipvl_dev *ipvlan = netdev_priv(dev);
+
+	/* FIXME IPv6 autoconf calls us from bh without RTNL */
+	if (in_softirq())
+		return NOTIFY_DONE;
+
+	if (!netif_is_ipvlan(dev))
+		return NOTIFY_DONE;
+
+	if (!ipvlan || !ipvlan->port)
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_UP:
+		if (ipvlan_addr_busy(ipvlan->port, &i6vi->i6vi_addr, true))
+			return notifier_from_errno(-EADDRINUSE);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
 static int ipvlan_add_addr4(struct ipvl_dev *ipvlan, struct in_addr *ip4_addr)
 {
 	if (ipvlan_addr_busy(ipvlan->port, ip4_addr, false)) {
@@ -871,10 +898,37 @@ static int ipvlan_addr4_event(struct notifier_block *unused,
 	return NOTIFY_OK;
 }
 
+static int ipvlan_addr4_validator_event(struct notifier_block *unused,
+					unsigned long event, void *ptr)
+{
+	struct in_validator_info *ivi = (struct in_validator_info *)ptr;
+	struct net_device *dev = (struct net_device *)ivi->ivi_dev->dev;
+	struct ipvl_dev *ipvlan = netdev_priv(dev);
+
+	if (!netif_is_ipvlan(dev))
+		return NOTIFY_DONE;
+
+	if (!ipvlan || !ipvlan->port)
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_UP:
+		if (ipvlan_addr_busy(ipvlan->port, &ivi->ivi_addr, false))
+			return notifier_from_errno(-EADDRINUSE);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
 static struct notifier_block ipvlan_addr4_notifier_block __read_mostly = {
 	.notifier_call = ipvlan_addr4_event,
 };
 
+static struct notifier_block ipvlan_addr4_vtor_notifier_block __read_mostly = {
+	.notifier_call = ipvlan_addr4_validator_event,
+};
+
 static struct notifier_block ipvlan_notifier_block __read_mostly = {
 	.notifier_call = ipvlan_device_event,
 };
@@ -883,6 +937,10 @@ static struct notifier_block ipvlan_addr6_notifier_block __read_mostly = {
 	.notifier_call = ipvlan_addr6_event,
 };
 
+static struct notifier_block ipvlan_addr6_vtor_notifier_block __read_mostly = {
+	.notifier_call = ipvlan_addr6_validator_event,
+};
+
 static void ipvlan_ns_exit(struct net *net)
 {
 	struct ipvlan_netns *vnet = net_generic(net, ipvlan_netid);
@@ -907,7 +965,10 @@ static int __init ipvlan_init_module(void)
 	ipvlan_init_secret();
 	register_netdevice_notifier(&ipvlan_notifier_block);
 	register_inet6addr_notifier(&ipvlan_addr6_notifier_block);
+	register_inet6addr_validator_notifier(
+	    &ipvlan_addr6_vtor_notifier_block);
 	register_inetaddr_notifier(&ipvlan_addr4_notifier_block);
+	register_inetaddr_validator_notifier(&ipvlan_addr4_vtor_notifier_block);
 
 	err = register_pernet_subsys(&ipvlan_net_ops);
 	if (err < 0)
@@ -922,7 +983,11 @@ static int __init ipvlan_init_module(void)
 	return 0;
 error:
 	unregister_inetaddr_notifier(&ipvlan_addr4_notifier_block);
+	unregister_inetaddr_validator_notifier(
+	    &ipvlan_addr4_vtor_notifier_block);
 	unregister_inet6addr_notifier(&ipvlan_addr6_notifier_block);
+	unregister_inet6addr_validator_notifier(
+	    &ipvlan_addr6_vtor_notifier_block);
 	unregister_netdevice_notifier(&ipvlan_notifier_block);
 	return err;
 }
@@ -933,7 +998,11 @@ static void __exit ipvlan_cleanup_module(void)
 	unregister_pernet_subsys(&ipvlan_net_ops);
 	unregister_netdevice_notifier(&ipvlan_notifier_block);
 	unregister_inetaddr_notifier(&ipvlan_addr4_notifier_block);
+	unregister_inetaddr_validator_notifier(
+	    &ipvlan_addr4_vtor_notifier_block);
 	unregister_inet6addr_notifier(&ipvlan_addr6_notifier_block);
+	unregister_inet6addr_validator_notifier(
+	    &ipvlan_addr6_vtor_notifier_block);
 }
 
 module_init(ipvlan_init_module);
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index a2e9d6e..e7c04c4 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -150,8 +150,15 @@ struct in_ifaddr {
 	unsigned long		ifa_tstamp; /* updated timestamp */
 };
 
+struct in_validator_info {
+	__be32			ivi_addr;
+	struct in_device	*ivi_dev;
+};
+
 int register_inetaddr_notifier(struct notifier_block *nb);
 int unregister_inetaddr_notifier(struct notifier_block *nb);
+int register_inetaddr_validator_notifier(struct notifier_block *nb);
+int unregister_inetaddr_validator_notifier(struct notifier_block *nb);
 
 void inet_netconf_notify_devconf(struct net *net, int event, int type,
 				 int ifindex, struct ipv4_devconf *devconf);
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index b43a4ee..d0889cb 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -48,11 +48,15 @@ struct prefix_info {
 	struct in6_addr		prefix;
 };
 
-
 #include <linux/netdevice.h>
 #include <net/if_inet6.h>
 #include <net/ipv6.h>
 
+struct in6_validator_info {
+	struct in6_addr		i6vi_addr;
+	struct inet6_dev	*i6vi_dev;
+};
+
 #define IN6_ADDR_HSIZE_SHIFT	4
 #define IN6_ADDR_HSIZE		(1 << IN6_ADDR_HSIZE_SHIFT)
 
@@ -278,6 +282,10 @@ int register_inet6addr_notifier(struct notifier_block *nb);
 int unregister_inet6addr_notifier(struct notifier_block *nb);
 int inet6addr_notifier_call_chain(unsigned long val, void *v);
 
+int register_inet6addr_validator_notifier(struct notifier_block *nb);
+int unregister_inet6addr_validator_notifier(struct notifier_block *nb);
+int inet6addr_validator_notifier_call_chain(unsigned long val, void *v);
+
 void inet6_netconf_notify_devconf(struct net *net, int event, int type,
 				  int ifindex, struct ipv6_devconf *devconf);
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index df14815..a7dd088 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -176,6 +176,7 @@ EXPORT_SYMBOL(__ip_dev_find);
 static void rtmsg_ifa(int event, struct in_ifaddr *, struct nlmsghdr *, u32);
 
 static BLOCKING_NOTIFIER_HEAD(inetaddr_chain);
+static BLOCKING_NOTIFIER_HEAD(inetaddr_validator_chain);
 static void inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 			 int destroy);
 #ifdef CONFIG_SYSCTL
@@ -441,6 +442,8 @@ static int __inet_insert_ifa(struct in_ifaddr *ifa, struct nlmsghdr *nlh,
 {
 	struct in_device *in_dev = ifa->ifa_dev;
 	struct in_ifaddr *ifa1, **ifap, **last_primary;
+	struct in_validator_info ivi;
+	int ret;
 
 	ASSERT_RTNL();
 
@@ -471,6 +474,23 @@ static int __inet_insert_ifa(struct in_ifaddr *ifa, struct nlmsghdr *nlh,
 		}
 	}
 
+	/* Allow any devices that wish to register ifaddr validtors to weigh
+	 * in now, before changes are committed.  The rntl lock is serializing
+	 * access here, so the state should not change between a validator call
+	 * and a final notify on commit.  This isn't invoked on promotion under
+	 * the assumption that validators are checking the address itself, and
+	 * not the flags.
+	 */
+	ivi.ivi_addr = ifa->ifa_address;
+	ivi.ivi_dev = ifa->ifa_dev;
+	ret = blocking_notifier_call_chain(&inetaddr_validator_chain,
+					   NETDEV_UP, &ivi);
+	ret = notifier_to_errno(ret);
+	if (ret) {
+		inet_free_ifa(ifa);
+		return ret;
+	}
+
 	if (!(ifa->ifa_flags & IFA_F_SECONDARY)) {
 		prandom_seed((__force u32) ifa->ifa_local);
 		ifap = last_primary;
@@ -1356,6 +1376,19 @@ int unregister_inetaddr_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_inetaddr_notifier);
 
+int register_inetaddr_validator_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&inetaddr_validator_chain, nb);
+}
+EXPORT_SYMBOL(register_inetaddr_validator_notifier);
+
+int unregister_inetaddr_validator_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&inetaddr_validator_chain,
+	    nb);
+}
+EXPORT_SYMBOL(unregister_inetaddr_validator_notifier);
+
 /* Rename ifa_labels for a device name change. Make some effort to preserve
  * existing alias numbering and to create unique labels if possible.
 */
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 25443fd..0aa36b0 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -963,6 +963,7 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 	struct net *net = dev_net(idev->dev);
 	struct inet6_ifaddr *ifa = NULL;
 	struct rt6_info *rt;
+	struct in6_validator_info i6vi;
 	unsigned int hash;
 	int err = 0;
 	int addr_type = ipv6_addr_type(addr);
@@ -974,6 +975,9 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 		return ERR_PTR(-EADDRNOTAVAIL);
 
 	rcu_read_lock_bh();
+
+	in6_dev_hold(idev);
+
 	if (idev->dead) {
 		err = -ENODEV;			/*XXX*/
 		goto out2;
@@ -984,6 +988,17 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 		goto out2;
 	}
 
+	i6vi.i6vi_addr = *addr;
+	i6vi.i6vi_dev = idev;
+	rcu_read_unlock_bh();
+
+	err = inet6addr_validator_notifier_call_chain(NETDEV_UP, &i6vi);
+
+	rcu_read_lock_bh();
+	err = notifier_to_errno(err);
+	if (err)
+		goto out2;
+
 	spin_lock(&addrconf_hash_lock);
 
 	/* Ignore adding duplicate addresses on an interface */
@@ -1034,7 +1049,6 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 	ifa->rt = rt;
 
 	ifa->idev = idev;
-	in6_dev_hold(idev);
 	/* For caller */
 	in6_ifa_hold(ifa);
 
@@ -1062,6 +1076,7 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 		inet6addr_notifier_call_chain(NETDEV_UP, ifa);
 	else {
 		kfree(ifa);
+		in6_dev_put(idev);
 		ifa = ERR_PTR(err);
 	}
 
diff --git a/net/ipv6/addrconf_core.c b/net/ipv6/addrconf_core.c
index bfa941f..9e3488d 100644
--- a/net/ipv6/addrconf_core.c
+++ b/net/ipv6/addrconf_core.c
@@ -88,6 +88,7 @@ int __ipv6_addr_type(const struct in6_addr *addr)
 EXPORT_SYMBOL(__ipv6_addr_type);
 
 static ATOMIC_NOTIFIER_HEAD(inet6addr_chain);
+static ATOMIC_NOTIFIER_HEAD(inet6addr_validator_chain);
 
 int register_inet6addr_notifier(struct notifier_block *nb)
 {
@@ -107,6 +108,24 @@ int inet6addr_notifier_call_chain(unsigned long val, void *v)
 }
 EXPORT_SYMBOL(inet6addr_notifier_call_chain);
 
+int register_inet6addr_validator_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&inet6addr_validator_chain, nb);
+}
+EXPORT_SYMBOL(register_inet6addr_validator_notifier);
+
+int unregister_inet6addr_validator_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&inet6addr_validator_chain, nb);
+}
+EXPORT_SYMBOL(unregister_inet6addr_validator_notifier);
+
+int inet6addr_validator_notifier_call_chain(unsigned long val, void *v)
+{
+	return atomic_notifier_call_chain(&inet6addr_validator_chain, val, v);
+}
+EXPORT_SYMBOL(inet6addr_validator_notifier_call_chain);
+
 static int eafnosupport_ipv6_dst_lookup(struct net *net, struct sock *u1,
 					struct dst_entry **u2,
 					struct flowi6 *u3)
-- 
2.7.4