ipv6: Only create RTF_CACHE routes after encountering pmtu exception
This patch creates a RTF_CACHE routes only after encountering a pmtu
exception.
After ip6_rt_update_pmtu() has inserted the RTF_CACHE route to the fib6
tree, the rt->rt6i_node->fn_sernum is bumped which will fail the
ip6_dst_check() and trigger a relookup.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f199d63..e7ae243 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -873,16 +873,13 @@
struct flowi6 *fl6, int flags)
{
struct fib6_node *fn, *saved_fn;
- struct rt6_info *rt, *nrt;
+ struct rt6_info *rt;
int strict = 0;
- int attempts = 3;
- int err;
strict |= flags & RT6_LOOKUP_F_IFACE;
if (net->ipv6.devconf_all->forwarding == 0)
strict |= RT6_LOOKUP_F_REACHABLE;
-redo_fib6_lookup_lock:
read_lock_bh(&table->tb6_lock);
fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
@@ -901,46 +898,12 @@
strict &= ~RT6_LOOKUP_F_REACHABLE;
fn = saved_fn;
goto redo_rt6_select;
- } else {
- dst_hold(&rt->dst);
- read_unlock_bh(&table->tb6_lock);
- goto out2;
}
}
dst_hold(&rt->dst);
read_unlock_bh(&table->tb6_lock);
- if (rt->rt6i_flags & RTF_CACHE)
- goto out2;
-
- if (!rt6_is_gw_or_nonexthop(rt) ||
- !(rt->dst.flags & DST_HOST) || !(rt->rt6i_flags & RTF_LOCAL))
- nrt = ip6_rt_cache_alloc(rt, &fl6->daddr, &fl6->saddr);
- else
- goto out2;
-
- ip6_rt_put(rt);
- rt = nrt ? : net->ipv6.ip6_null_entry;
-
- dst_hold(&rt->dst);
- if (nrt) {
- err = ip6_ins_rt(nrt);
- if (!err)
- goto out2;
- }
-
- if (--attempts <= 0)
- goto out2;
-
- /*
- * Race condition! In the gap, when table->tb6_lock was
- * released someone could insert this route. Relookup.
- */
- ip6_rt_put(rt);
- goto redo_fib6_lookup_lock;
-
-out2:
rt6_dst_from_metrics_check(rt);
rt->dst.lastuse = jiffies;
rt->dst.__use++;
@@ -1113,24 +1076,63 @@
}
}
-static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
- struct sk_buff *skb, u32 mtu)
+static void rt6_do_update_pmtu(struct rt6_info *rt, u32 mtu)
+{
+ struct net *net = dev_net(rt->dst.dev);
+
+ rt->rt6i_flags |= RTF_MODIFIED;
+ rt->rt6i_pmtu = mtu;
+ rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);
+}
+
+static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
+ const struct ipv6hdr *iph, u32 mtu)
{
struct rt6_info *rt6 = (struct rt6_info *)dst;
+ if (rt6->rt6i_flags & RTF_LOCAL)
+ return;
+
dst_confirm(dst);
- if (mtu < dst_mtu(dst) && (rt6->rt6i_flags & RTF_CACHE)) {
- struct net *net = dev_net(dst->dev);
+ mtu = max_t(u32, mtu, IPV6_MIN_MTU);
+ if (mtu >= dst_mtu(dst))
+ return;
- rt6->rt6i_flags |= RTF_MODIFIED;
- if (mtu < IPV6_MIN_MTU)
- mtu = IPV6_MIN_MTU;
+ if (rt6->rt6i_flags & RTF_CACHE) {
+ rt6_do_update_pmtu(rt6, mtu);
+ } else {
+ const struct in6_addr *daddr, *saddr;
+ struct rt6_info *nrt6;
- rt6->rt6i_pmtu = mtu;
- rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
+ if (iph) {
+ daddr = &iph->daddr;
+ saddr = &iph->saddr;
+ } else if (sk) {
+ daddr = &sk->sk_v6_daddr;
+ saddr = &inet6_sk(sk)->saddr;
+ } else {
+ return;
+ }
+ 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);
+ }
}
}
+static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
+ struct sk_buff *skb, u32 mtu)
+{
+ __ip6_rt_update_pmtu(dst, sk, skb ? ipv6_hdr(skb) : NULL, mtu);
+}
+
void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
int oif, u32 mark)
{
@@ -1147,7 +1149,7 @@
dst = ip6_route_output(net, NULL, &fl6);
if (!dst->error)
- ip6_rt_update_pmtu(dst, NULL, skb, ntohl(mtu));
+ __ip6_rt_update_pmtu(dst, NULL, iph, ntohl(mtu));
dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_update_pmtu);