[RFC 1/2] fq: support filtering a given tin

[Johannes Berg]

From: Johannes Berg 

Add to the FQ API a way to filter a given tin, in order to
remove frames that fulfil certain criteria according to a
filter function.

This will be used by mac80211 to remove frames belonging to
an AP VLAN interface that's being removed.

Signed-off-by: Johannes Berg 
---
 include/net/fq.h  |  7 
 include/net/fq_impl.h | 92 ++-
 2 files changed, 83 insertions(+), 16 deletions(-)

diff --git a/include/net/fq.h b/include/net/fq.h
index 6d8521a30c5c..ac944a686840 100644
--- a/include/net/fq.h
+++ b/include/net/fq.h
@@ -90,6 +90,13 @@ typedef void fq_skb_free_t(struct fq *,
   struct fq_flow *,
   struct sk_buff *);
 
+/* Return %true to filter (drop) the frame. */
+typedef bool fq_skb_filter_t(struct fq *,
+struct fq_tin *,
+struct fq_flow *,
+struct sk_buff *,
+void *);
+
 typedef struct fq_flow *fq_flow_get_default_t(struct fq *,
  struct fq_tin *,
  int idx,
diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h
index 4e6131cd3f43..b27f13d22a90 100644
--- a/include/net/fq_impl.h
+++ b/include/net/fq_impl.h
@@ -12,24 +12,9 @@
 
 /* functions that are embedded into includer */
 
-static struct sk_buff *fq_flow_dequeue(struct fq *fq,
-  struct fq_flow *flow)
+static void fq_rejigger_backlog(struct fq *fq, struct fq_flow *flow)
 {
-   struct fq_tin *tin = flow->tin;
struct fq_flow *i;
-   struct sk_buff *skb;
-
-   lockdep_assert_held(&fq->lock);
-
-   skb = __skb_dequeue(&flow->queue);
-   if (!skb)
-   return NULL;
-
-   tin->backlog_bytes -= skb->len;
-   tin->backlog_packets--;
-   flow->backlog -= skb->len;
-   fq->backlog--;
-   fq->memory_usage -= skb->truesize;
 
if (flow->backlog == 0) {
list_del_init(&flow->backlogchain);
@@ -43,6 +28,34 @@ static struct sk_buff *fq_flow_dequeue(struct fq *fq,
list_move_tail(&flow->backlogchain,
   &i->backlogchain);
}
+}
+
+static void fq_adjust_removal(struct fq *fq,
+ struct fq_flow *flow,
+ struct sk_buff *skb)
+{
+   struct fq_tin *tin = flow->tin;
+
+   tin->backlog_bytes -= skb->len;
+   tin->backlog_packets--;
+   flow->backlog -= skb->len;
+   fq->backlog--;
+   fq->memory_usage -= skb->truesize;
+}
+
+static struct sk_buff *fq_flow_dequeue(struct fq *fq,
+  struct fq_flow *flow)
+{
+   struct sk_buff *skb;
+
+   lockdep_assert_held(&fq->lock);
+
+   skb = __skb_dequeue(&flow->queue);
+   if (!skb)
+   return NULL;
+
+   fq_adjust_removal(fq, flow, skb);
+   fq_rejigger_backlog(fq, flow);
 
return skb;
 }
@@ -188,6 +201,53 @@ static void fq_tin_enqueue(struct fq *fq,
}
 }
 
+static void fq_flow_filter(struct fq *fq,
+  struct fq_flow *flow,
+  fq_skb_filter_t filter_func,
+  void *filter_data,
+  fq_skb_free_t free_func)
+{
+   struct fq_tin *tin = flow->tin;
+   struct sk_buff *skb, *tmp;
+
+   lockdep_assert_held(&fq->lock);
+
+   skb_queue_walk_safe(&flow->queue, skb, tmp) {
+   if (!filter_func(fq, tin, flow, skb, filter_data))
+   continue;
+
+   __skb_unlink(skb, &flow->queue);
+   fq_adjust_removal(fq, flow, skb);
+   free_func(fq, tin, flow, skb);
+   }
+
+   fq_rejigger_backlog(fq, flow);
+}
+
+static void fq_tin_filter(struct fq *fq,
+ struct fq_tin *tin,
+ fq_skb_filter_t filter_func,
+ void *filter_data,
+ fq_skb_free_t free_func)
+{
+   struct list_head *head;
+   struct fq_flow *flow;
+
+   lockdep_assert_held(&fq->lock);
+
+   for (;;) {
+   head = &tin->new_flows;
+   if (list_empty(head)) {
+   head = &tin->old_flows;
+   if (list_empty(head))
+   break;
+   }
+
+   flow = list_first_entry(head, struct fq_flow, flowchain);
+   fq_flow_filter(fq, flow, filter_func, filter_data, free_func);
+   }
+}
+
 static void fq_flow_reset(struct fq *fq,
  struct fq_flow *flow,
  fq_skb_free_t free_func)
-- 
2.14.2

Re: [RFC 1/2] fq: support filtering a given tin

[Toke Høiland-Jørgensen]

Johannes Berg  writes:

> +static void fq_tin_filter(struct fq *fq,
> +   struct fq_tin *tin,
> +   fq_skb_filter_t filter_func,
> +   void *filter_data,
> +   fq_skb_free_t free_func)
> +{
> + struct list_head *head;
> + struct fq_flow *flow;
> +
> + lockdep_assert_held(&fq->lock);
> +
> + for (;;) {
> + head = &tin->new_flows;
> + if (list_empty(head)) {
> + head = &tin->old_flows;
> + if (list_empty(head))
> + break;
> + }
> +
> + flow = list_first_entry(head, struct fq_flow, flowchain);
> + fq_flow_filter(fq, flow, filter_func, filter_data, free_func);
> + }

Isn't this going to loop forever?

-Toke

Re: [RFC 1/2] fq: support filtering a given tin

[Johannes Berg]

On Thu, 2017-10-05 at 14:24 +0200, Toke Høiland-Jørgensen wrote:

> > +   for (;;) {
> > +   head = &tin->new_flows;
> > +   if (list_empty(head)) {
> > +   head = &tin->old_flows;
> > +   if (list_empty(head))
> > +   break;
> > +   }
> > +
> > +   flow = list_first_entry(head, struct fq_flow, flowchain);
> > +   fq_flow_filter(fq, flow, filter_func, filter_data, free_func);
> > +   }
> 
> Isn't this going to loop forever?

Good question, I'll admit that I copied this without understanding it
from fq_tin_reset(), and didn't think about it much.

I think you're right though - I guess this needs to iterate the
new_flows and old_flows.

johannes