[PATCH RFC net-next 16/20] net/ipv6: Cleanup exception route handling

[David Ahern <dsahern@gmail.com>]

IPv6 FIB will only contain FIB entries with exception routes added to
the FIB entry. Remove CACHE and dst checks from fib6 add and delete since
they can never happen once the data type changes.

Fixup the lookup functions to use a f6i name for fib lookups and retain
the current rt name for return variables.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 net/ipv6/ip6_fib.c |  16 +------
 net/ipv6/route.c   | 122 ++++++++++++++++++++++++++++++-----------------------
 2 files changed, 71 insertions(+), 67 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 5b03f7e8d850..63a91db61749 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1046,7 +1046,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 static void fib6_start_gc(struct net *net, struct rt6_info *rt)
 {
 	if (!timer_pending(&net->ipv6.ip6_fib_timer) &&
-	    (rt->rt6i_flags & (RTF_EXPIRES | RTF_CACHE)))
+	    (rt->rt6i_flags & RTF_EXPIRES))
 		mod_timer(&net->ipv6.ip6_fib_timer,
 			  jiffies + net->ipv6.sysctl.ip6_rt_gc_interval);
 }
@@ -1097,8 +1097,6 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
 
 	if (WARN_ON_ONCE(!atomic_read(&rt->dst.__refcnt)))
 		return -EINVAL;
-	if (WARN_ON_ONCE(rt->rt6i_flags & RTF_CACHE))
-		return -EINVAL;
 
 	if (info->nlh) {
 		if (!(info->nlh->nlmsg_flags & NLM_F_CREATE))
@@ -1622,8 +1620,6 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
 
 	RT6_TRACE("fib6_del_route\n");
 
-	WARN_ON_ONCE(rt->rt6i_flags & RTF_CACHE);
-
 	/* Unlink it */
 	*rtp = rt->rt6_next;
 	rt->rt6i_node = NULL;
@@ -1692,21 +1688,11 @@ int fib6_del(struct rt6_info *rt, struct nl_info *info)
 	struct rt6_info __rcu **rtp;
 	struct rt6_info __rcu **rtp_next;
 
-#if RT6_DEBUG >= 2
-	if (rt->dst.obsolete > 0) {
-		WARN_ON(fn);
-		return -ENOENT;
-	}
-#endif
 	if (!fn || rt == net->ipv6.fib6_null_entry)
 		return -ENOENT;
 
 	WARN_ON(!(fn->fn_flags & RTN_RTINFO));
 
-	/* remove cached dst from exception table */
-	if (rt->rt6i_flags & RTF_CACHE)
-		return rt6_remove_exception_rt(rt);
-
 	/*
 	 *	Walk the leaf entries looking for ourself
 	 */
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3ea60e932eb9..19b91c60ee55 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1094,35 +1094,36 @@ static struct rt6_info *ip6_pol_route_lookup(struct net *net,
 					     struct fib6_table *table,
 					     struct flowi6 *fl6, int flags)
 {
-	struct rt6_info *rt, *rt_cache;
+	struct rt6_info *f6i;
 	struct fib6_node *fn;
+	struct rt6_info *rt;
 
 	rcu_read_lock();
 	fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
 restart:
-	rt = rcu_dereference(fn->leaf);
-	if (!rt) {
-		rt = net->ipv6.fib6_null_entry;
+	f6i = rcu_dereference(fn->leaf);
+	if (!f6i) {
+		f6i = net->ipv6.fib6_null_entry;
 	} else {
-		rt = rt6_device_match(net, rt, &fl6->saddr,
+		f6i = rt6_device_match(net, f6i, &fl6->saddr,
 				      fl6->flowi6_oif, flags);
-		if (rt->rt6i_nsiblings && fl6->flowi6_oif == 0)
-			rt = rt6_multipath_select(rt, fl6,
+		if (f6i->rt6i_nsiblings && fl6->flowi6_oif == 0)
+			f6i = rt6_multipath_select(f6i, fl6,
 						  fl6->flowi6_oif, flags);
 	}
-	if (rt == net->ipv6.fib6_null_entry) {
+	if (f6i == net->ipv6.fib6_null_entry) {
 		fn = fib6_backtrack(fn, &fl6->saddr);
 		if (fn)
 			goto restart;
 	}
+
 	/* Search through exception table */
-	rt_cache = rt6_find_cached_rt(rt, &fl6->daddr, &fl6->saddr);
-	if (rt_cache) {
-		rt = rt_cache;
+	rt = rt6_find_cached_rt(f6i, &fl6->daddr, &fl6->saddr);
+	if (rt) {
 		if (ip6_hold_safe(net, &rt, true))
 			dst_use_noref(&rt->dst, jiffies);
 	} else {
-		rt = ip6_create_rt_rcu(rt);
+		rt = ip6_create_rt_rcu(f6i);
 	}
 
 	rcu_read_unlock();
@@ -1204,9 +1205,6 @@ static struct rt6_info *ip6_rt_cache_alloc(struct rt6_info *ort,
 	 *	Clone the route.
 	 */
 
-	if (ort->rt6i_flags & (RTF_CACHE | RTF_PCPU))
-		ort = ort->from;
-
 	rcu_read_lock();
 	dev = ip6_rt_get_dev_rcu(ort);
 	rt = __ip6_dst_alloc(dev_net(dev), dev, 0);
@@ -1432,11 +1430,6 @@ static int rt6_insert_exception(struct rt6_info *nrt,
 	struct rt6_exception *rt6_ex;
 	int err = 0;
 
-	/* ort can't be a cache or pcpu route */
-	if (ort->rt6i_flags & (RTF_CACHE | RTF_PCPU))
-		ort = ort->from;
-	WARN_ON_ONCE(ort->rt6i_flags & (RTF_CACHE | RTF_PCPU));
-
 	spin_lock_bh(&rt6_exception_lock);
 
 	if (ort->exception_bucket_flushed) {
@@ -1815,7 +1808,8 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 			       int oif, struct flowi6 *fl6, int flags)
 {
 	struct fib6_node *fn, *saved_fn;
-	struct rt6_info *rt, *rt_cache;
+	struct rt6_info *f6i;
+	struct rt6_info *rt;
 	int strict = 0;
 
 	strict |= flags & RT6_LOOKUP_F_IFACE;
@@ -1832,10 +1826,10 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 		oif = 0;
 
 redo_rt6_select:
-	rt = rt6_select(net, fn, oif, strict);
-	if (rt->rt6i_nsiblings)
-		rt = rt6_multipath_select(rt, fl6, oif, strict);
-	if (rt == net->ipv6.fib6_null_entry) {
+	f6i = rt6_select(net, fn, oif, strict);
+	if (f6i->rt6i_nsiblings)
+		f6i = rt6_multipath_select(f6i, fl6, oif, strict);
+	if (f6i == net->ipv6.fib6_null_entry) {
 		fn = fib6_backtrack(fn, &fl6->saddr);
 		if (fn)
 			goto redo_rt6_select;
@@ -1847,18 +1841,17 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 		}
 	}
 
-	/*Search through exception table */
-	rt_cache = rt6_find_cached_rt(rt, &fl6->daddr, &fl6->saddr);
-	if (rt_cache)
-		rt = rt_cache;
-
-	if (rt == net->ipv6.fib6_null_entry) {
+	if (f6i == net->ipv6.fib6_null_entry) {
 		rt = net->ipv6.ip6_null_entry;
 		rcu_read_unlock();
 		dst_hold(&rt->dst);
 		trace_fib6_table_lookup(net, rt, table, fl6);
 		return rt;
-	} else if (rt->rt6i_flags & RTF_CACHE) {
+	}
+
+	/*Search through exception table */
+	rt = rt6_find_cached_rt(f6i, &fl6->daddr, &fl6->saddr);
+	if (rt) {
 		if (ip6_hold_safe(net, &rt, true))
 			dst_use_noref(&rt->dst, jiffies);
 
@@ -1866,7 +1859,7 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 		trace_fib6_table_lookup(net, rt, table, fl6);
 		return rt;
 	} else if (unlikely((fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH) &&
-			    !(rt->rt6i_flags & RTF_GATEWAY))) {
+			    !(f6i->rt6i_flags & RTF_GATEWAY))) {
 		/* Create a RTF_CACHE clone which will not be
 		 * owned by the fib6 tree.  It is for the special case where
 		 * the daddr in the skb during the neighbor look-up is different
@@ -1875,16 +1868,16 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 
 		struct rt6_info *uncached_rt;
 
-		if (ip6_hold_safe(net, &rt, true)) {
-			dst_use_noref(&rt->dst, jiffies);
+		if (ip6_hold_safe(net, &f6i, true)) {
+			dst_use_noref(&f6i->dst, jiffies);
 		} else {
 			rcu_read_unlock();
-			uncached_rt = rt;
+			uncached_rt = f6i;
 			goto uncached_rt_out;
 		}
 		rcu_read_unlock();
 
-		uncached_rt = ip6_rt_cache_alloc(rt, &fl6->daddr, NULL);
+		uncached_rt = ip6_rt_cache_alloc(f6i, &fl6->daddr, NULL);
 		dst_release(&rt->dst);
 
 		if (uncached_rt) {
@@ -1907,18 +1900,18 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 
 		struct rt6_info *pcpu_rt;
 
-		dst_use_noref(&rt->dst, jiffies);
+		dst_use_noref(&f6i->dst, jiffies);
 		local_bh_disable();
-		pcpu_rt = rt6_get_pcpu_route(rt);
+		pcpu_rt = rt6_get_pcpu_route(f6i);
 
 		if (!pcpu_rt) {
 			/* atomic_inc_not_zero() is needed when using rcu */
-			if (atomic_inc_not_zero(&rt->rt6i_ref)) {
+			if (atomic_inc_not_zero(&f6i->rt6i_ref)) {
 				/* No dst_hold() on rt is needed because grabbing
 				 * rt->rt6i_ref makes sure rt can't be released.
 				 */
-				pcpu_rt = rt6_make_pcpu_route(net, rt);
-				rt6_release(rt);
+				pcpu_rt = rt6_make_pcpu_route(net, f6i);
+				rt6_release(f6i);
 			} else {
 				/* rt is already removed from tree */
 				pcpu_rt = net->ipv6.ip6_null_entry;
@@ -2296,7 +2289,8 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 					     int flags)
 {
 	struct ip6rd_flowi *rdfl = (struct ip6rd_flowi *)fl6;
-	struct rt6_info *rt, *rt_cache;
+	struct rt6_info *ret = NULL, *rt_cache;
+	struct rt6_info *rt;
 	struct fib6_node *fn;
 
 	/* Get the "current" route for this destination and
@@ -2335,7 +2329,7 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 			if (rt_cache &&
 			    ipv6_addr_equal(&rdfl->gateway,
 					    &rt_cache->rt6i_gateway)) {
-				rt = rt_cache;
+				ret = rt_cache;
 				break;
 			}
 			continue;
@@ -2346,7 +2340,7 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 	if (!rt)
 		rt = net->ipv6.fib6_null_entry;
 	else if (rt->rt6i_flags & RTF_REJECT) {
-		rt = net->ipv6.ip6_null_entry;
+		ret = net->ipv6.ip6_null_entry;
 		goto out;
 	}
 
@@ -2357,12 +2351,15 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 	}
 
 out:
-	ip6_hold_safe(net, &rt, true);
+	if (ret)
+		dst_hold(&ret->dst);
+	else
+		ret = ip6_create_rt_rcu(rt);
 
 	rcu_read_unlock();
 
-	trace_fib6_table_lookup(net, rt, table, fl6);
-	return rt;
+	trace_fib6_table_lookup(net, ret, table, fl6);
+	return ret;
 };
 
 static struct dst_entry *ip6_route_redirect(struct net *net,
@@ -3031,6 +3028,22 @@ static int __ip6_del_rt_siblings(struct rt6_info *rt, struct fib6_config *cfg)
 	return err;
 }
 
+static int ip6_del_cached_rt(struct rt6_info *rt, struct fib6_config *cfg)
+{
+	int rc = -ESRCH;
+
+	if (cfg->fc_ifindex && rt->dst.dev->ifindex != cfg->fc_ifindex)
+		goto out;
+
+	if (cfg->fc_flags & RTF_GATEWAY &&
+	    !ipv6_addr_equal(&cfg->fc_gateway, &rt->rt6i_gateway))
+		goto out;
+	if (dst_hold_safe(&rt->dst))
+		rc = rt6_remove_exception_rt(rt);
+out:
+	return rc;
+}
+
 static int ip6_route_del(struct fib6_config *cfg,
 			 struct netlink_ext_ack *extack)
 {
@@ -3055,11 +3068,16 @@ static int ip6_route_del(struct fib6_config *cfg,
 	if (fn) {
 		for_each_fib6_node_rt_rcu(fn) {
 			if (cfg->fc_flags & RTF_CACHE) {
+				int rc;
+
 				rt_cache = rt6_find_cached_rt(rt, &cfg->fc_dst,
 							      &cfg->fc_src);
-				if (!rt_cache)
-					continue;
-				rt = rt_cache;
+				if (rt_cache) {
+					rc = ip6_del_cached_rt(rt_cache, cfg);
+					if (rc != -ESRCH)
+						return rc;
+				}
+				continue;
 			}
 			if (cfg->fc_ifindex &&
 			    (!rt->fib6_nh.nh_dev ||
@@ -3176,7 +3194,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
 				     NEIGH_UPDATE_F_ISROUTER)),
 		     NDISC_REDIRECT, &ndopts);
 
-	nrt = ip6_rt_cache_alloc(rt, &msg->dest, NULL);
+	nrt = ip6_rt_cache_alloc(rt->from, &msg->dest, NULL);
 	if (!nrt)
 		goto out;
 
-- 
2.11.0