datapath: Add loop checking.

[sliver-openvswitch.git] / datapath / vport.c

diff --git a/datapath/vport.c b/datapath/vport.c
index 38c7147..1303950 100644 (file)
--- a/datapath/vport.c
+++ b/datapath/vport.c
@@ -34,6 +34,17 @@ static int n_vport_types;
 static struct hlist_head *dev_table;
 #define VPORT_HASH_BUCKETS 1024
 
+/* We limit the number of times that we pass through vport_send() to
+ * avoid blowing out the stack in the event that we have a loop. There is
+ * a separate counter for each CPU for both interrupt and non-interrupt
+ * context in order to keep the limit deterministic for a given packet. */
+struct percpu_loop_counter {
+       int count[2];
+};
+
+static struct percpu_loop_counter *vport_loop_counter;
+#define VPORT_MAX_LOOPS 5
+
 /* Both RTNL lock and vport_mutex need to be held when updating dev_table.
  *
  * If you use vport_locate and then perform some operations, you need to hold
@@ -107,6 +118,12 @@ vport_init(void)
                goto error_dev_table;
        }
 
+       vport_loop_counter = alloc_percpu(struct percpu_loop_counter);
+       if (!vport_loop_counter) {
+               err = -ENOMEM;
+               goto error_ops_list;
+       }
+
        for (i = 0; i < ARRAY_SIZE(base_vport_ops_list); i++) {
                struct vport_ops *new_ops = base_vport_ops_list[i];
 
@@ -125,6 +142,8 @@ vport_init(void)
 
        return 0;
 
+error_ops_list:
+       kfree(vport_ops_list);
 error_dev_table:
        kfree(dev_table);
 error:
@@ -170,6 +189,7 @@ vport_exit(void)
                        vport_ops_list[i]->exit();
        }
 
+       free_percpu(vport_loop_counter);
        kfree(vport_ops_list);
        kfree(dev_table);
 }
@@ -1267,9 +1287,26 @@ vport_receive(struct vport *vport, struct sk_buff *skb)
 int
 vport_send(struct vport *vport, struct sk_buff *skb)
 {
+       int *loop_count;
        int sent;
 
-       sent = vport->ops->send(vport, skb);
+       loop_count = &per_cpu_ptr(vport_loop_counter, get_cpu())->count[!!in_interrupt()];
+       (*loop_count)++;
+
+       if (likely(*loop_count <= VPORT_MAX_LOOPS)) {
+               sent = vport->ops->send(vport, skb);
+       } else {
+               if (net_ratelimit())
+                       printk(KERN_WARNING "%s: dropping packet that has looped more than %d times\n",
+                              dp_name(vport_get_dp_port(vport)->dp), VPORT_MAX_LOOPS);
+
+               sent = 0;
+               kfree_skb(skb);
+               vport_record_error(vport, VPORT_E_TX_DROPPED);
+       }
+
+       (*loop_count)--;
+       put_cpu();
 
        if (vport->ops->flags & VPORT_F_GEN_STATS && sent > 0) {
                struct vport_percpu_stats *stats;