net: fix problem in dequeuing from input_pkt_queue

Fix some issues introduced in batch skb dequeuing for input_pkt_queue.
The primary issue it that the queue head must be incremented only
after a packet has been processed, that is only after
__netif_receive_skb has been called.  This is needed for the mechanism
to prevent OOO packet in RFS.  Also when flushing the input_pkt_queue
and process_queue, the process queue should be done first to prevent
OOO packets.

Because the input_pkt_queue has been effectively split into two queues,
the calculation of the tail ptr is no longer correct.  The correct value
would be head+input_pkt_queue->len+process_queue->len.  To avoid
this calculation we added an explict input_queue_tail in softnet_data.
The tail value is simply incremented when queuing to input_pkt_queue.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a1bff65..2564195 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1407,17 +1407,25 @@ struct softnet_data {
 	struct softnet_data	*rps_ipi_next;
 	unsigned int		cpu;
 	unsigned int		input_queue_head;
+	unsigned int		input_queue_tail;
 #endif
 	unsigned		dropped;
 	struct sk_buff_head	input_pkt_queue;
 	struct napi_struct	backlog;
 };
 
-static inline void input_queue_head_add(struct softnet_data *sd,
-					unsigned int len)
+static inline void input_queue_head_incr(struct softnet_data *sd)
 {
 #ifdef CONFIG_RPS
-	sd->input_queue_head += len;
+	sd->input_queue_head++;
+#endif
+}
+
+static inline void input_queue_tail_incr_save(struct softnet_data *sd,
+					      unsigned int *qtail)
+{
+#ifdef CONFIG_RPS
+	*qtail = ++sd->input_queue_tail;
 #endif
 }