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Date: Wed, 10 Sep 2014 11:31:28 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <eric.dumazet@...il.com>,
Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: [PATCH net-next] ipv6: implement rt_genid_bump_ipv6 with fn_sernum and remove rt6i_genid
Some special routes will never be cloned in IPv6. Those are mainly
DST_HOST routes without RTF_NONEXTHOP or RTF_GATEWAY flags, thus mostly
routes handling the input path.
rt_genid depends on rt6_info clones being removed from the trie and
recreated with current rt6i_genid, thus bumping the genid would invalidate
all routes cached in the sockets and relookup will recreate them. But in
case a non-cloned route ends up in the per-socket cache, it will never
be recreated, thus will never get a current rt_genid.
After the rt_genid is incremented for the first time all those routes
will always get invalidated by ip6_dst_check on the next check, thus
making early socket demultiplexing absolutely pointless for IPv6. It is
not possible to solve this with rt6i_genid, thus remove it.
In case we need to force the sockets to relookup the routes we now
increase the fn_sernum on all fibnodes in the routing tree. This is a
costly operation but should only happen if we have major routing/policy
changes in the kernel (e.g. manual route adding/removal, xfrm policy
changes). Also this patch optimized the walk over the trie a bit, we
don't touch every rt6_info but only touch the fib6_nodes.
Thanks to Eric Dumazet who noticed this problem.
Fixes: 6f3118b571b8 ("ipv6: use net->rt_genid to check dst validity")
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
Notes:
I based this patch on net-next, because it "only" fixes a performance
problem so far and want it to be a bit more exposed to testing before
a possible submission to stable.
include/net/ip6_fib.h | 5 ++--
include/net/net_namespace.h | 4 +++-
net/core/dst.c | 8 +++++++
net/ipv6/ip6_fib.c | 57 ++++++++++++++++++++++++++++++++++++---------
net/ipv6/route.c | 4 ----
5 files changed, 59 insertions(+), 19 deletions(-)
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 9bcb220..a5e09b8 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -119,8 +119,6 @@ struct rt6_info {
struct inet6_dev *rt6i_idev;
unsigned long _rt6i_peer;
- u32 rt6i_genid;
-
/* more non-fragment space at head required */
unsigned short rt6i_nfheader_len;
@@ -281,7 +279,8 @@ struct fib6_node *fib6_locate(struct fib6_node *root,
const struct in6_addr *daddr, int dst_len,
const struct in6_addr *saddr, int src_len);
-void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg),
+void fib6_clean_all(struct net *net,
+ int (*rt_visit)(struct rt6_info *, void *arg),
void *arg);
int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info,
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 361d260..e0b0476 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -358,9 +358,11 @@ static inline int rt_genid_ipv6(struct net *net)
return atomic_read(&net->ipv6.rt_genid);
}
+extern void (*__rt_genid_bump_ipv6)(struct net *net);
static inline void rt_genid_bump_ipv6(struct net *net)
{
- atomic_inc(&net->ipv6.rt_genid);
+ if (__rt_genid_bump_ipv6)
+ __rt_genid_bump_ipv6(net);
}
#else
static inline int rt_genid_ipv6(struct net *net)
diff --git a/net/core/dst.c b/net/core/dst.c
index a028409..995183b 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -23,6 +23,14 @@
#include <net/dst.h>
+/* as soon as the ipv6 module registers, this function is used to
+ * force all cached routing lookups to relookup
+ */
+#if IS_ENABLED(CONFIG_IPV6)
+void (*__rt_genid_bump_ipv6)(struct net *net);
+EXPORT_SYMBOL(__rt_genid_bump_ipv6);
+#endif
+
/*
* Theory of operations:
* 1) We use a list, protected by a spinlock, to add
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 76b7f5e..d23b76f 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -106,10 +106,15 @@ static inline void fib6_walker_unlink(struct fib6_walker_t *w)
}
static __inline__ u32 fib6_new_sernum(void)
{
- u32 n = ++rt_sernum;
- if ((__s32)n <= 0)
- rt_sernum = n = 1;
- return n;
+ u32 new, old;
+
+ do {
+ old = ACCESS_ONCE(rt_sernum);
+ new = old + 1;
+ if ((s32)new <= 0)
+ new = 1;
+ } while (cmpxchg(&rt_sernum, old, new) != old);
+ return new;
}
/*
@@ -1553,25 +1558,28 @@ static int fib6_clean_node(struct fib6_walker_t *w)
*/
static void fib6_clean_tree(struct net *net, struct fib6_node *root,
- int (*func)(struct rt6_info *, void *arg),
+ int (*node_visit)(struct fib6_walker_t *),
+ int (*rt_visit)(struct rt6_info *, void *arg),
int prune, void *arg)
{
struct fib6_cleaner_t c;
c.w.root = root;
- c.w.func = fib6_clean_node;
+ c.w.func = node_visit;
c.w.prune = prune;
c.w.count = 0;
c.w.skip = 0;
- c.func = func;
+ c.func = rt_visit;
c.arg = arg;
c.net = net;
fib6_walk(&c.w);
}
-void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg),
- void *arg)
+static void __fib6_clean_all(struct net *net,
+ int (*node_visit)(struct fib6_walker_t *),
+ int (*rt_visit)(struct rt6_info *, void *arg),
+ void *arg)
{
struct fib6_table *table;
struct hlist_head *head;
@@ -1583,13 +1591,20 @@ void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg),
hlist_for_each_entry_rcu(table, head, tb6_hlist) {
write_lock_bh(&table->tb6_lock);
fib6_clean_tree(net, &table->tb6_root,
- func, 0, arg);
+ node_visit, rt_visit, 0, arg);
write_unlock_bh(&table->tb6_lock);
}
}
rcu_read_unlock();
}
+void fib6_clean_all(struct net *net,
+ int (*rt_visit)(struct rt6_info *, void *arg),
+ void *arg)
+{
+ __fib6_clean_all(net, fib6_clean_node, rt_visit, arg);
+}
+
static int fib6_prune_clone(struct rt6_info *rt, void *arg)
{
if (rt->rt6i_flags & RTF_CACHE) {
@@ -1602,7 +1617,25 @@ static int fib6_prune_clone(struct rt6_info *rt, void *arg)
static void fib6_prune_clones(struct net *net, struct fib6_node *fn)
{
- fib6_clean_tree(net, fn, fib6_prune_clone, 1, NULL);
+ fib6_clean_tree(net, fn, fib6_clean_node, fib6_prune_clone, 1, NULL);
+}
+
+static int fib6_upd_sernum(struct fib6_walker_t *w)
+{
+ struct fib6_cleaner_t *c = container_of(w, struct fib6_cleaner_t, w);
+ int *sernum = c->arg;
+
+ w->node->fn_sernum = *sernum;
+ w->leaf = NULL;
+ return 0;
+}
+
+static void fib6_genid_bump(struct net *net)
+{
+ int sernum;
+
+ sernum = fib6_new_sernum();
+ __fib6_clean_all(net, fib6_upd_sernum, NULL, &sernum);
}
/*
@@ -1788,6 +1821,8 @@ int __init fib6_init(void)
NULL);
if (ret)
goto out_unregister_subsys;
+
+ __rt_genid_bump_ipv6 = fib6_genid_bump;
out:
return ret;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f74b041..a318dd89 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -314,7 +314,6 @@ static inline struct rt6_info *ip6_dst_alloc(struct net *net,
memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
rt6_init_peer(rt, table ? &table->tb6_peers : net->ipv6.peers);
- rt->rt6i_genid = rt_genid_ipv6(net);
INIT_LIST_HEAD(&rt->rt6i_siblings);
}
return rt;
@@ -1096,9 +1095,6 @@ static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
* DST_OBSOLETE_FORCE_CHK which forces validation calls down
* into this function always.
*/
- if (rt->rt6i_genid != rt_genid_ipv6(dev_net(rt->dst.dev)))
- return NULL;
-
if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie))
return NULL;
--
1.9.3
--
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