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authorHerbert Xu <herbert@gondor.apana.org.au>2010-05-24 00:12:34 -0700
committerDavid S. Miller <davem@davemloft.net>2010-05-24 00:12:34 -0700
commitf845172531fb7410c7fb7780b1a6e51ee6df7d52 (patch)
treeef1030d0ad9d9dbc8fe800a145c587f04be50ade /net/sched/cls_cgroup.c
parenteda6e6f86b5f95b982ac7ebf7cf5be2a29a291e9 (diff)
cls_cgroup: Store classid in struct sock
Up until now cls_cgroup has relied on fetching the classid out of the current executing thread. This runs into trouble when a packet processing is delayed in which case it may execute out of another thread's context. Furthermore, even when a packet is not delayed we may fail to classify it if soft IRQs have been disabled, because this scenario is indistinguishable from one where a packet unrelated to the current thread is processed by a real soft IRQ. In fact, the current semantics is inherently broken, as a single skb may be constructed out of the writes of two different tasks. A different manifestation of this problem is when the TCP stack transmits in response of an incoming ACK. This is currently unclassified. As we already have a concept of packet ownership for accounting purposes in the skb->sk pointer, this is a natural place to store the classid in a persistent manner. This patch adds the cls_cgroup classid in struct sock, filling up an existing hole on 64-bit :) The value is set at socket creation time. So all sockets created via socket(2) automatically gains the ID of the thread creating it. Whenever another process touches the socket by either reading or writing to it, we will change the socket classid to that of the process if it has a valid (non-zero) classid. For sockets created on inbound connections through accept(2), we inherit the classid of the original listening socket through sk_clone, possibly preceding the actual accept(2) call. In order to minimise risks, I have not made this the authoritative classid. For now it is only used as a backup when we execute with soft IRQs disabled. Once we're completely happy with its semantics we can use it as the sole classid. Footnote: I have rearranged the error path on cls_group module creation. If we didn't do this, then there is a window where someone could create a tc rule using cls_group before the cgroup subsystem has been registered. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/cls_cgroup.c')
-rw-r--r--net/sched/cls_cgroup.c50
1 files changed, 34 insertions, 16 deletions
diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index 221180384fd7..78ef2c5e130b 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -16,14 +16,11 @@
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/cgroup.h>
+#include <linux/rcupdate.h>
#include <net/rtnetlink.h>
#include <net/pkt_cls.h>
-
-struct cgroup_cls_state
-{
- struct cgroup_subsys_state css;
- u32 classid;
-};
+#include <net/sock.h>
+#include <net/cls_cgroup.h>
static struct cgroup_subsys_state *cgrp_create(struct cgroup_subsys *ss,
struct cgroup *cgrp);
@@ -112,6 +109,10 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp,
struct cls_cgroup_head *head = tp->root;
u32 classid;
+ rcu_read_lock();
+ classid = task_cls_state(current)->classid;
+ rcu_read_unlock();
+
/*
* Due to the nature of the classifier it is required to ignore all
* packets originating from softirq context as accessing `current'
@@ -122,12 +123,12 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp,
* calls by looking at the number of nested bh disable calls because
* softirqs always disables bh.
*/
- if (softirq_count() != SOFTIRQ_OFFSET)
- return -1;
-
- rcu_read_lock();
- classid = task_cls_state(current)->classid;
- rcu_read_unlock();
+ if (softirq_count() != SOFTIRQ_OFFSET) {
+ /* If there is an sk_classid we'll use that. */
+ if (!skb->sk)
+ return -1;
+ classid = skb->sk->sk_classid;
+ }
if (!classid)
return -1;
@@ -289,18 +290,35 @@ static struct tcf_proto_ops cls_cgroup_ops __read_mostly = {
static int __init init_cgroup_cls(void)
{
- int ret = register_tcf_proto_ops(&cls_cgroup_ops);
- if (ret)
- return ret;
+ int ret;
+
ret = cgroup_load_subsys(&net_cls_subsys);
if (ret)
- unregister_tcf_proto_ops(&cls_cgroup_ops);
+ goto out;
+
+#ifndef CONFIG_NET_CLS_CGROUP
+ /* We can't use rcu_assign_pointer because this is an int. */
+ smp_wmb();
+ net_cls_subsys_id = net_cls_subsys.subsys_id;
+#endif
+
+ ret = register_tcf_proto_ops(&cls_cgroup_ops);
+ if (ret)
+ cgroup_unload_subsys(&net_cls_subsys);
+
+out:
return ret;
}
static void __exit exit_cgroup_cls(void)
{
unregister_tcf_proto_ops(&cls_cgroup_ops);
+
+#ifndef CONFIG_NET_CLS_CGROUP
+ net_cls_subsys_id = -1;
+ synchronize_rcu();
+#endif
+
cgroup_unload_subsys(&net_cls_subsys);
}