net: ipv6: autoconf routes into per-device tables

Currently, IPv6 router discovery always puts routes into
RT6_TABLE_MAIN. This causes problems for connection managers
that want to support multiple simultaneous network connections
and want control over which one is used by default (e.g., wifi
and wired).

To work around this connection managers typically take the routes
they prefer and copy them to static routes with low metrics in
the main table. This puts the burden on the connection manager
to watch netlink to see if the routes have changed, delete the
routes when their lifetime expires, etc.

Instead, this patch adds a per-interface sysctl to have the
kernel put autoconf routes into different tables. This allows
each interface to have its own autoconf table, and choosing the
default interface (or using different interfaces at the same
time for different types of traffic) can be done using
appropriate ip rules.

The sysctl behaves as follows:

- = 0: default. Put routes into RT6_TABLE_MAIN as before.
- > 0: manual. Put routes into the specified table.
- < 0: automatic. Add the absolute value of the sysctl to the
       device's ifindex, and use that table.

The automatic mode is most useful in conjunction with
net.ipv6.conf.default.accept_ra_rt_table. A connection manager
or distribution could set it to, say, -100 on boot, and
thereafter just use IP rules.

Change-Id: I093d39fb06ec413905dc0d0d5792c1bc5d5c73a9
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

Conflicts:
	net/ipv6/addrconf.c
	net/ipv6/route.c

2 files changed, 99 insertions, 44 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index cf6718f..733bdb2 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -192,6 +192,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.accept_ra_rt_info_max_plen = 0,
 #endif
 #endif
+	.accept_ra_rt_table	= 0,
 	.proxy_ndp		= 0,
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 	.disable_ipv6		= 0,
@@ -226,6 +227,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 	.accept_ra_rt_info_max_plen = 0,
 #endif
 #endif
+	.accept_ra_rt_table	= 0,
 	.proxy_ndp		= 0,
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 	.disable_ipv6		= 0,
@@ -1679,6 +1681,31 @@ static int __ipv6_try_regen_rndid(struct inet6_dev *idev, struct in6_addr *tmpad
 }
 #endif
 
+u32 addrconf_rt_table(const struct net_device *dev, u32 default_table) {
+	/* Determines into what table to put autoconf PIO/RIO/default routes
+	 * learned on this device.
+	 *
+	 * - If 0, use the same table for every device. This puts routes into
+	 *   one of RT_TABLE_{PREFIX,INFO,DFLT} depending on the type of route
+	 *   (but note that these three are currently all equal to
+	 *   RT6_TABLE_MAIN).
+	 * - If > 0, use the specified table.
+	 * - If < 0, put routes into table dev->ifindex + (-rt_table).
+	 */
+	struct inet6_dev *idev = in6_dev_get(dev);
+	u32 table;
+	int sysctl = idev->cnf.accept_ra_rt_table;
+	if (sysctl == 0) {
+		table = default_table;
+	} else if (sysctl > 0) {
+		table = (u32) sysctl;
+	} else {
+		table = (unsigned) dev->ifindex + (-sysctl);
+	}
+	in6_dev_put(idev);
+	return table;
+}
+
 /*
  *	Add prefix route.
  */
@@ -1688,7 +1715,7 @@ addrconf_prefix_route(struct in6_addr *pfx, int plen, struct net_device *dev,
 		      unsigned long expires, u32 flags)
 {
 	struct fib6_config cfg = {
-		.fc_table = RT6_TABLE_PREFIX,
+		.fc_table = addrconf_rt_table(dev, RT6_TABLE_PREFIX),
 		.fc_metric = IP6_RT_PRIO_ADDRCONF,
 		.fc_ifindex = dev->ifindex,
 		.fc_expires = expires,
@@ -1712,6 +1739,39 @@ addrconf_prefix_route(struct in6_addr *pfx, int plen, struct net_device *dev,
 	ip6_route_add(&cfg);
 }
 
+static struct rt6_info *addrconf_get_prefix_route(const struct in6_addr *pfx,
+						  int plen,
+						  const struct net_device *dev,
+						  u32 flags, u32 noflags)
+{
+	struct fib6_node *fn;
+	struct rt6_info *rt = NULL;
+	struct fib6_table *table;
+
+	table = fib6_get_table(dev_net(dev),
+			       addrconf_rt_table(dev, RT6_TABLE_PREFIX));
+	if (table == NULL)
+		return NULL;
+
+	write_lock_bh(&table->tb6_lock);
+	fn = fib6_locate(&table->tb6_root, pfx, plen, NULL, 0);
+	if (!fn)
+		goto out;
+	for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
+		if (rt->dst.dev->ifindex != dev->ifindex)
+			continue;
+		if ((rt->rt6i_flags & flags) != flags)
+			continue;
+		if ((rt->rt6i_flags & noflags) != 0)
+			continue;
+		dst_hold(&rt->dst);
+		break;
+	}
+out:
+	write_unlock_bh(&table->tb6_lock);
+	return rt;
+}
+
 /* Create "default" multicast route to the interface */
 
 static void addrconf_add_mroute(struct net_device *dev)
@@ -3863,6 +3923,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 	array[DEVCONF_ACCEPT_RA_RT_INFO_MAX_PLEN] = cnf->accept_ra_rt_info_max_plen;
 #endif
 #endif
+	array[DEVCONF_ACCEPT_RA_RT_TABLE] = cnf->accept_ra_rt_table;
 	array[DEVCONF_PROXY_NDP] = cnf->proxy_ndp;
 	array[DEVCONF_ACCEPT_SOURCE_ROUTE] = cnf->accept_source_route;
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
@@ -4474,6 +4535,13 @@ static struct addrconf_sysctl_table
 #endif
 #endif
 		{
+			.procname	= "accept_ra_rt_table",
+			.data		= &ipv6_devconf.accept_ra_rt_table,
+			.maxlen		= sizeof(int),
+			.mode		= 0644,
+			.proc_handler	= proc_dointvec,
+		},
+		{
 			.procname	= "proxy_ndp",
 			.data		= &ipv6_devconf.proxy_ndp,
 			.maxlen		= sizeof(int),
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 5091740..d6ce355 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -88,13 +88,13 @@ static void		ip6_link_failure(struct sk_buff *skb);
 static void		ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu);
 
 #ifdef CONFIG_IPV6_ROUTE_INFO
-static struct rt6_info *rt6_add_route_info(struct net *net,
+static struct rt6_info *rt6_add_route_info(struct net_device *dev,
 					   const struct in6_addr *prefix, int prefixlen,
-					   const struct in6_addr *gwaddr, int ifindex,
+					   const struct in6_addr *gwaddr,
 					   unsigned pref);
-static struct rt6_info *rt6_get_route_info(struct net *net,
+static struct rt6_info *rt6_get_route_info(struct net_device *dev,
 					   const struct in6_addr *prefix, int prefixlen,
-					   const struct in6_addr *gwaddr, int ifindex);
+					   const struct in6_addr *gwaddr);
 #endif
 
 static u32 *ipv6_cow_metrics(struct dst_entry *dst, unsigned long old)
@@ -533,7 +533,6 @@ static struct rt6_info *rt6_select(struct fib6_node *fn, int oif, int strict)
 int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 		  const struct in6_addr *gwaddr)
 {
-	struct net *net = dev_net(dev);
 	struct route_info *rinfo = (struct route_info *) opt;
 	struct in6_addr prefix_buf, *prefix;
 	unsigned int pref;
@@ -575,8 +574,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 		prefix = &prefix_buf;
 	}
 
-	rt = rt6_get_route_info(net, prefix, rinfo->prefix_len, gwaddr,
-				dev->ifindex);
+	rt = rt6_get_route_info(dev, prefix, rinfo->prefix_len, gwaddr);
 
 	if (rt && !lifetime) {
 		ip6_del_rt(rt);
@@ -584,8 +582,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 	}
 
 	if (!rt && lifetime)
-		rt = rt6_add_route_info(net, prefix, rinfo->prefix_len, gwaddr, dev->ifindex,
-					pref);
+		rt = rt6_add_route_info(dev, prefix, rinfo->prefix_len, gwaddr, pref);
 	else if (rt)
 		rt->rt6i_flags = RTF_ROUTEINFO |
 				 (rt->rt6i_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);
@@ -1768,16 +1765,17 @@ static struct rt6_info * ip6_rt_copy(struct rt6_info *ort)
 }
 
 #ifdef CONFIG_IPV6_ROUTE_INFO
-static struct rt6_info *rt6_get_route_info(struct net *net,
+static struct rt6_info *rt6_get_route_info(struct net_device *dev,
 					   const struct in6_addr *prefix, int prefixlen,
-					   const struct in6_addr *gwaddr, int ifindex)
+					   const struct in6_addr *gwaddr)
 {
 	struct fib6_node *fn;
 	struct rt6_info *rt = NULL;
 	struct fib6_table *table;
 
-	table = fib6_get_table(net, RT6_TABLE_INFO);
-	if (table == NULL)
+	table = fib6_get_table(dev_net(dev),
+			       addrconf_rt_table(dev, RT6_TABLE_INFO));
+	if (!table)
 		return NULL;
 
 	write_lock_bh(&table->tb6_lock);
@@ -1786,7 +1784,7 @@ static struct rt6_info *rt6_get_route_info(struct net *net,
 		goto out;
 
 	for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
-		if (rt->rt6i_dev->ifindex != ifindex)
+		if (rt->rt6i_dev->ifindex != dev->ifindex)
 			continue;
 		if ((rt->rt6i_flags & (RTF_ROUTEINFO|RTF_GATEWAY)) != (RTF_ROUTEINFO|RTF_GATEWAY))
 			continue;
@@ -1800,21 +1798,21 @@ out:
 	return rt;
 }
 
-static struct rt6_info *rt6_add_route_info(struct net *net,
+static struct rt6_info *rt6_add_route_info(struct net_device *dev,
 					   const struct in6_addr *prefix, int prefixlen,
-					   const struct in6_addr *gwaddr, int ifindex,
+					   const struct in6_addr *gwaddr,
 					   unsigned pref)
 {
 	struct fib6_config cfg = {
-		.fc_table	= RT6_TABLE_INFO,
+		.fc_table	= addrconf_rt_table(dev, RT6_TABLE_INFO),
 		.fc_metric	= IP6_RT_PRIO_USER,
-		.fc_ifindex	= ifindex,
+		.fc_ifindex	= dev->ifindex,
 		.fc_dst_len	= prefixlen,
 		.fc_flags	= RTF_GATEWAY | RTF_ADDRCONF | RTF_ROUTEINFO |
 				  RTF_UP | RTF_PREF(pref),
 		.fc_nlinfo.pid = 0,
 		.fc_nlinfo.nlh = NULL,
-		.fc_nlinfo.nl_net = net,
+		.fc_nlinfo.nl_net = dev_net(dev),
 	};
 
 	ipv6_addr_copy(&cfg.fc_dst, prefix);
@@ -1826,7 +1824,7 @@ static struct rt6_info *rt6_add_route_info(struct net *net,
 
 	ip6_route_add(&cfg);
 
-	return rt6_get_route_info(net, prefix, prefixlen, gwaddr, ifindex);
+	return rt6_get_route_info(dev, prefix, prefixlen, gwaddr);
 }
 #endif
 
@@ -1835,8 +1833,9 @@ struct rt6_info *rt6_get_dflt_router(const struct in6_addr *addr, struct net_dev
 	struct rt6_info *rt;
 	struct fib6_table *table;
 
-	table = fib6_get_table(dev_net(dev), RT6_TABLE_DFLT);
-	if (table == NULL)
+	table = fib6_get_table(dev_net(dev),
+			       addrconf_rt_table(dev, RT6_TABLE_MAIN));
+	if (!table)
 		return NULL;
 
 	write_lock_bh(&table->tb6_lock);
@@ -1857,7 +1856,7 @@ struct rt6_info *rt6_add_dflt_router(const struct in6_addr *gwaddr,
 				     unsigned int pref)
 {
 	struct fib6_config cfg = {
-		.fc_table	= RT6_TABLE_DFLT,
+		.fc_table	= addrconf_rt_table(dev, RT6_TABLE_DFLT),
 		.fc_metric	= IP6_RT_PRIO_USER,
 		.fc_ifindex	= dev->ifindex,
 		.fc_flags	= RTF_GATEWAY | RTF_ADDRCONF | RTF_DEFAULT |
@@ -1874,28 +1873,16 @@ struct rt6_info *rt6_add_dflt_router(const struct in6_addr *gwaddr,
 	return rt6_get_dflt_router(gwaddr, dev);
 }
 
+int rt6_addrconf_purge(struct rt6_info *rt, void *arg) {
+	if (rt->rt6i_flags & (RTF_DEFAULT | RTF_ADDRCONF) &&
+	    (!rt->rt6i_idev || rt->rt6i_idev->cnf.accept_ra != 2))
+		return -1;
+	return 0;
+}
+
 void rt6_purge_dflt_routers(struct net *net)
 {
-	struct rt6_info *rt;
-	struct fib6_table *table;
-
-	/* NOTE: Keep consistent with rt6_get_dflt_router */
-	table = fib6_get_table(net, RT6_TABLE_DFLT);
-	if (table == NULL)
-		return;
-
-restart:
-	read_lock_bh(&table->tb6_lock);
-	for (rt = table->tb6_root.leaf; rt; rt = rt->dst.rt6_next) {
-		if (rt->rt6i_flags & (RTF_DEFAULT | RTF_ADDRCONF) &&
-		    (!rt->rt6i_idev || rt->rt6i_idev->cnf.accept_ra != 2)) {
-			dst_hold(&rt->dst);
-			read_unlock_bh(&table->tb6_lock);
-			ip6_del_rt(rt);
-			goto restart;
-		}
-	}
-	read_unlock_bh(&table->tb6_lock);
+	fib6_clean_all(net, rt6_addrconf_purge, 0, NULL);
 }
 
 static void rtmsg_to_fib6_config(struct net *net,