net/packet: tpacket_rcv: do not increment ring index on drop

In one error case, tpacket_rcv drops packets after incrementing the
ring producer index.

If this happens, it does not update tp_status to TP_STATUS_USER and
thus the reader is stalled for an iteration of the ring, causing out
of order arrival.

The only such error path is when virtio_net_hdr_from_skb fails due
to encountering an unknown GSO type.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 30c6879..e5b0986 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2274,6 +2274,13 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
                                        TP_STATUS_KERNEL, (macoff+snaplen));
        if (!h.raw)
                goto drop_n_account;
+
+       if (do_vnet &&
+           virtio_net_hdr_from_skb(skb, h.raw + macoff -
+                                   sizeof(struct virtio_net_hdr),
+                                   vio_le(), true, 0))
+               goto drop_n_account;
+
        if (po->tp_version <= TPACKET_V2) {
                packet_increment_rx_head(po, &po->rx_ring);
        /*
@@ -2286,12 +2293,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
                        status |= TP_STATUS_LOSING;
        }
 
-       if (do_vnet &&
-           virtio_net_hdr_from_skb(skb, h.raw + macoff -
-                                   sizeof(struct virtio_net_hdr),
-                                   vio_le(), true, 0))
-               goto drop_n_account;
-
        po->stats.stats1.tp_packets++;
        if (copy_skb) {
                status |= TP_STATUS_COPY;