Message-Id: <20171006190611.110633-9-tracywwnj@gmail.com>
Date:   Fri,  6 Oct 2017 12:06:03 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>, Wei Wang <weiwan@...gle.com>
Subject: [PATCH net-next 08/16] ipv6: hook up exception table to store dst cache

From: Wei Wang <weiwan@...gle.com>

This commit makes use of the exception hash table implementation to
store dst caches created by pmtu discovery and ip redirect into the hash
table under the rt_info and no longer inserts these routes into fib6
tree.
This makes the fib6 tree only contain static configured routes and could
now be protected by rcu instead of a rw lock.
With this change, in the route lookup related functions, after finding
the rt6_info with the longest prefix, we also need to search for the
exception table before doing backtracking.
In the route delete function, if the route being deleted is not a dst
cache, deletion of this route also need to flush the whole hash table
under it. If it is a dst cache, then only delete the cached dst in the
hash table.

Note: for fib6_walk_continue() function, w->root now is always pointing
to a root node considering that fib6_prune_clones() is removed from the
code. So we add a WARN_ON() msg to make sure w->root always points to a
root node and also removed the update of w->root in fib6_repair_tree().
This is a prerequisite for later patch because we don't need to make
w->root as rcu protected when replacing rwlock with RCU.
Also, we remove all prune related variables as it is no longer used.

Signed-off-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/ip6_fib.h |   1 -
 net/ipv6/addrconf.c   |   1 -
 net/ipv6/ip6_fib.c    |  95 ++++++++------------------------------------
 net/ipv6/route.c      | 108 +++++++++++++++++++++++++-------------------------
 4 files changed, 72 insertions(+), 133 deletions(-)

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 4497a1eb4d41..d0b7283073e3 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -280,7 +280,6 @@ struct fib6_walker {
 	struct fib6_node *root, *node;
 	struct rt6_info *leaf;
 	enum fib6_walk_state state;
-	bool prune;
 	unsigned int skip;
 	unsigned int count;
 	int (*func)(struct fib6_walker *);
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3ccaf52824c9..873afafddfc4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2326,7 +2326,6 @@ static struct rt6_info *addrconf_get_prefix_route(const struct in6_addr *pfx,
 	if (!fn)
 		goto out;
 
-	noflags |= RTF_CACHE;
 	for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
 		if (rt->dst.dev->ifindex != dev->ifindex)
 			continue;
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index b3e4cf0962f8..9c8e704e6af7 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -54,7 +54,6 @@ struct fib6_cleaner {
 #define FWS_INIT FWS_L
 #endif
 
-static void fib6_prune_clones(struct net *net, struct fib6_node *fn);
 static struct rt6_info *fib6_find_prefix(struct net *net, struct fib6_node *fn);
 static struct fib6_node *fib6_repair_tree(struct net *net, struct fib6_node *fn);
 static int fib6_walk(struct net *net, struct fib6_walker *w);
@@ -1101,6 +1100,8 @@ 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))
@@ -1192,11 +1193,8 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
 #endif
 
 	err = fib6_add_rt2node(fn, rt, info, mxc);
-	if (!err) {
+	if (!err)
 		fib6_start_gc(info->nl_net, rt);
-		if (!(rt->rt6i_flags & RTF_CACHE))
-			fib6_prune_clones(info->nl_net, pn);
-	}
 
 out:
 	if (err) {
@@ -1511,19 +1509,12 @@ static struct fib6_node *fib6_repair_tree(struct net *net,
 		read_lock(&net->ipv6.fib6_walker_lock);
 		FOR_WALKERS(net, w) {
 			if (!child) {
-				if (w->root == fn) {
-					w->root = w->node = NULL;
-					RT6_TRACE("W %p adjusted by delroot 1\n", w);
-				} else if (w->node == fn) {
+				if (w->node == fn) {
 					RT6_TRACE("W %p adjusted by delnode 1, s=%d/%d\n", w, w->state, nstate);
 					w->node = pn;
 					w->state = nstate;
 				}
 			} else {
-				if (w->root == fn) {
-					w->root = child;
-					RT6_TRACE("W %p adjusted by delroot 2\n", w);
-				}
 				if (w->node == fn) {
 					w->node = child;
 					if (children&2) {
@@ -1557,12 +1548,17 @@ static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
 
 	RT6_TRACE("fib6_del_route\n");
 
+	WARN_ON_ONCE(rt->rt6i_flags & RTF_CACHE);
+
 	/* Unlink it */
 	*rtp = rt->dst.rt6_next;
 	rt->rt6i_node = NULL;
 	net->ipv6.rt6_stats->fib_rt_entries--;
 	net->ipv6.rt6_stats->fib_discarded_routes++;
 
+	/* Flush all cached dst in exception table */
+	rt6_flush_exceptions(rt);
+
 	/* Reset round-robin state, if necessary */
 	if (fn->rr_ptr == rt)
 		fn->rr_ptr = NULL;
@@ -1625,18 +1621,9 @@ int fib6_del(struct rt6_info *rt, struct nl_info *info)
 
 	WARN_ON(!(fn->fn_flags & RTN_RTINFO));
 
-	if (!(rt->rt6i_flags & RTF_CACHE)) {
-		struct fib6_node *pn = fn;
-#ifdef CONFIG_IPV6_SUBTREES
-		/* clones of this route might be in another subtree */
-		if (rt->rt6i_src.plen) {
-			while (!(pn->fn_flags & RTN_ROOT))
-				pn = pn->parent;
-			pn = pn->parent;
-		}
-#endif
-		fib6_prune_clones(info->nl_net, pn);
-	}
+	/* 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
@@ -1679,16 +1666,14 @@ static int fib6_walk_continue(struct fib6_walker *w)
 {
 	struct fib6_node *fn, *pn;
 
+	/* w->root should always be table->tb6_root */
+	WARN_ON_ONCE(!(w->root->fn_flags & RTN_TL_ROOT));
+
 	for (;;) {
 		fn = w->node;
 		if (!fn)
 			return 0;
 
-		if (w->prune && fn != w->root &&
-		    fn->fn_flags & RTN_RTINFO && w->state < FWS_C) {
-			w->state = FWS_C;
-			w->leaf = fn->leaf;
-		}
 		switch (w->state) {
 #ifdef CONFIG_IPV6_SUBTREES
 		case FWS_S:
@@ -1820,20 +1805,16 @@ static int fib6_clean_node(struct fib6_walker *w)
  *	func is called on each route.
  *		It may return -1 -> delete this route.
  *		              0  -> continue walking
- *
- *	prune==1 -> only immediate children of node (certainly,
- *	ignoring pure split nodes) will be scanned.
  */
 
 static void fib6_clean_tree(struct net *net, struct fib6_node *root,
 			    int (*func)(struct rt6_info *, void *arg),
-			    bool prune, int sernum, void *arg)
+			    int sernum, void *arg)
 {
 	struct fib6_cleaner c;
 
 	c.w.root = root;
 	c.w.func = fib6_clean_node;
-	c.w.prune = prune;
 	c.w.count = 0;
 	c.w.skip = 0;
 	c.func = func;
@@ -1858,7 +1839,7 @@ static void __fib6_clean_all(struct net *net,
 		hlist_for_each_entry_rcu(table, head, tb6_hlist) {
 			write_lock_bh(&table->tb6_lock);
 			fib6_clean_tree(net, &table->tb6_root,
-					func, false, sernum, arg);
+					func, sernum, arg);
 			write_unlock_bh(&table->tb6_lock);
 		}
 	}
@@ -1871,22 +1852,6 @@ void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *),
 	__fib6_clean_all(net, func, FIB6_NO_SERNUM_CHANGE, arg);
 }
 
-static int fib6_prune_clone(struct rt6_info *rt, void *arg)
-{
-	if (rt->rt6i_flags & RTF_CACHE) {
-		RT6_TRACE("pruning clone %p\n", rt);
-		return -1;
-	}
-
-	return 0;
-}
-
-static void fib6_prune_clones(struct net *net, struct fib6_node *fn)
-{
-	fib6_clean_tree(net, fn, fib6_prune_clone, true,
-			FIB6_NO_SERNUM_CHANGE, NULL);
-}
-
 static void fib6_flush_trees(struct net *net)
 {
 	int new_sernum = fib6_new_sernum(net);
@@ -1914,32 +1879,6 @@ static int fib6_age(struct rt6_info *rt, void *arg)
 			return -1;
 		}
 		gc_args->more++;
-	/* The following part will soon be removed when the exception
-	 * table is hooked up to store all cached routes.
-	 */
-	} else if (rt->rt6i_flags & RTF_CACHE) {
-		if (time_after_eq(now, rt->dst.lastuse + gc_args->timeout))
-			rt->dst.obsolete = DST_OBSOLETE_KILL;
-		if (atomic_read(&rt->dst.__refcnt) == 1 &&
-		    rt->dst.obsolete == DST_OBSOLETE_KILL) {
-			RT6_TRACE("aging clone %p\n", rt);
-			return -1;
-		} else if (rt->rt6i_flags & RTF_GATEWAY) {
-			struct neighbour *neigh;
-			__u8 neigh_flags = 0;
-
-			neigh = dst_neigh_lookup(&rt->dst, &rt->rt6i_gateway);
-			if (neigh) {
-				neigh_flags = neigh->flags;
-				neigh_release(neigh);
-			}
-			if (!(neigh_flags & NTF_ROUTER)) {
-				RT6_TRACE("purging route %p via non-router but gateway\n",
-					  rt);
-				return -1;
-			}
-		}
-		gc_args->more++;
 	}
 
 	/*	Also age clones in the exception table.
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 855b4ceec349..65130dde276a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -878,8 +878,8 @@ 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 fib6_node *fn;
-	struct rt6_info *rt;
 
 	read_lock_bh(&table->tb6_lock);
 	fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
@@ -893,6 +893,11 @@ static struct rt6_info *ip6_pol_route_lookup(struct net *net,
 		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;
+
 	dst_use(&rt->dst, jiffies);
 	read_unlock_bh(&table->tb6_lock);
 
@@ -1592,7 +1597,7 @@ 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;
+	struct rt6_info *rt, *rt_cache;
 	int strict = 0;
 
 	strict |= flags & RT6_LOOKUP_F_IFACE;
@@ -1624,6 +1629,10 @@ 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.ip6_null_entry || (rt->rt6i_flags & RTF_CACHE)) {
 		dst_use(&rt->dst, jiffies);
@@ -1988,23 +1997,17 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
 
 	if (!rt6_cache_allowed_for_pmtu(rt6)) {
 		rt6_do_update_pmtu(rt6, mtu);
+		/* update rt6_ex->stamp for cache */
+		if (rt6->rt6i_flags & RTF_CACHE)
+			rt6_update_exception_stamp_rt(rt6);
 	} else if (daddr) {
 		struct rt6_info *nrt6;
 
 		nrt6 = ip6_rt_cache_alloc(rt6, daddr, saddr);
 		if (nrt6) {
 			rt6_do_update_pmtu(nrt6, mtu);
-
-			/* ip6_ins_rt(nrt6) will bump the
-			 * rt6->rt6i_node->fn_sernum
-			 * which will fail the next rt6_check() and
-			 * invalidate the sk->sk_dst_cache.
-			 */
-			ip6_ins_rt(nrt6);
-			/* Release the reference taken in
-			 * ip6_rt_cache_alloc()
-			 */
-			dst_release(&nrt6->dst);
+			if (rt6_insert_exception(nrt6, rt6))
+				dst_release_immediate(&nrt6->dst);
 		}
 	}
 }
@@ -2068,7 +2071,7 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 					     int flags)
 {
 	struct ip6rd_flowi *rdfl = (struct ip6rd_flowi *)fl6;
-	struct rt6_info *rt;
+	struct rt6_info *rt, *rt_cache;
 	struct fib6_node *fn;
 
 	/* Get the "current" route for this destination and
@@ -2093,8 +2096,23 @@ static struct rt6_info *__ip6_route_redirect(struct net *net,
 			continue;
 		if (fl6->flowi6_oif != rt->dst.dev->ifindex)
 			continue;
-		if (!ipv6_addr_equal(&rdfl->gateway, &rt->rt6i_gateway))
+		/* rt_cache's gateway might be different from its 'parent'
+		 * in the case of an ip redirect.
+		 * So we keep searching in the exception table if the gateway
+		 * is different.
+		 */
+		if (!ipv6_addr_equal(&rdfl->gateway, &rt->rt6i_gateway)) {
+			rt_cache = rt6_find_cached_rt(rt,
+						      &fl6->daddr,
+						      &fl6->saddr);
+			if (rt_cache &&
+			    ipv6_addr_equal(&rdfl->gateway,
+					    &rt_cache->rt6i_gateway)) {
+				rt = rt_cache;
+				break;
+			}
 			continue;
+		}
 		break;
 	}
 
@@ -2785,9 +2803,9 @@ static int __ip6_del_rt_siblings(struct rt6_info *rt, struct fib6_config *cfg)
 static int ip6_route_del(struct fib6_config *cfg,
 			 struct netlink_ext_ack *extack)
 {
+	struct rt6_info *rt, *rt_cache;
 	struct fib6_table *table;
 	struct fib6_node *fn;
-	struct rt6_info *rt;
 	int err = -ESRCH;
 
 	table = fib6_get_table(cfg->fc_nlinfo.nl_net, cfg->fc_table);
@@ -2801,13 +2819,17 @@ static int ip6_route_del(struct fib6_config *cfg,
 	fn = fib6_locate(&table->tb6_root,
 			 &cfg->fc_dst, cfg->fc_dst_len,
 			 &cfg->fc_src, cfg->fc_src_len,
-			 true);
+			 !(cfg->fc_flags & RTF_CACHE));
 
 	if (fn) {
 		for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
-			if ((rt->rt6i_flags & RTF_CACHE) &&
-			    !(cfg->fc_flags & RTF_CACHE))
-				continue;
+			if (cfg->fc_flags & RTF_CACHE) {
+				rt_cache = rt6_find_cached_rt(rt, &cfg->fc_dst,
+							      &cfg->fc_src);
+				if (!rt_cache)
+					continue;
+				rt = rt_cache;
+			}
 			if (cfg->fc_ifindex &&
 			    (!rt->dst.dev ||
 			     rt->dst.dev->ifindex != cfg->fc_ifindex))
@@ -2933,8 +2955,14 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
 	nrt->rt6i_protocol = RTPROT_REDIRECT;
 	nrt->rt6i_gateway = *(struct in6_addr *)neigh->primary_key;
 
-	if (ip6_ins_rt(nrt))
-		goto out_release;
+	/* No need to remove rt from the exception table if rt is
+	 * a cached route because rt6_insert_exception() will
+	 * takes care of it
+	 */
+	if (rt6_insert_exception(nrt, rt)) {
+		dst_release_immediate(&nrt->dst);
+		goto out;
+	}
 
 	netevent.old = &rt->dst;
 	netevent.new = &nrt->dst;
@@ -2942,17 +2970,6 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
 	netevent.neigh = neigh;
 	call_netevent_notifiers(NETEVENT_REDIRECT, &netevent);
 
-	if (rt->rt6i_flags & RTF_CACHE) {
-		rt = (struct rt6_info *) dst_clone(&rt->dst);
-		ip6_del_rt(rt);
-	}
-
-out_release:
-	/* Release the reference taken in
-	 * ip6_rt_cache_alloc()
-	 */
-	dst_release(&nrt->dst);
-
 out:
 	neigh_release(neigh);
 }
@@ -3344,12 +3361,8 @@ static int fib6_clean_tohost(struct rt6_info *rt, void *arg)
 {
 	struct in6_addr *gateway = (struct in6_addr *)arg;
 
-	/* RTF_CACHE_GATEWAY case will be removed once the exception
-	 * table is hooked up to store all cached routes.
-	 */
-	if ((((rt->rt6i_flags & RTF_RA_ROUTER) == RTF_RA_ROUTER) ||
-	     ((rt->rt6i_flags & RTF_CACHE_GATEWAY) == RTF_CACHE_GATEWAY)) &&
-	     ipv6_addr_equal(gateway, &rt->rt6i_gateway)) {
+	if (((rt->rt6i_flags & RTF_RA_ROUTER) == RTF_RA_ROUTER) &&
+	    ipv6_addr_equal(gateway, &rt->rt6i_gateway)) {
 		return -1;
 	}
 
@@ -3438,20 +3451,9 @@ static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
 	    dst_metric_raw(&rt->dst, RTAX_MTU) &&
 	    !dst_metric_locked(&rt->dst, RTAX_MTU)) {
 		spin_lock_bh(&rt6_exception_lock);
-		/* This case will be removed once the exception table
-		 * is hooked up.
-		 */
-		if (rt->rt6i_flags & RTF_CACHE) {
-			/* For RTF_CACHE with rt6i_pmtu == 0
-			 * (i.e. a redirected route),
-			 * the metrics of its rt->dst.from has already
-			 * been updated.
-			 */
-			if (rt->rt6i_pmtu && rt->rt6i_pmtu > arg->mtu)
-				rt->rt6i_pmtu = arg->mtu;
-		} else if (dst_mtu(&rt->dst) >= arg->mtu ||
-			   (dst_mtu(&rt->dst) < arg->mtu &&
-			    dst_mtu(&rt->dst) == idev->cnf.mtu6)) {
+		if (dst_mtu(&rt->dst) >= arg->mtu ||
+		    (dst_mtu(&rt->dst) < arg->mtu &&
+		     dst_mtu(&rt->dst) == idev->cnf.mtu6)) {
 			dst_metric_set(&rt->dst, RTAX_MTU, arg->mtu);
 		}
 		rt6_exceptions_update_pmtu(rt, arg->mtu);
-- 
2.14.2.920.gcf0c67979c-goog

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