2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/if_packet.h b/include/linux/if_packet.h
index dea7d6b7cf98..e5d200f53fc3 100644
--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -48,11 +48,13 @@ struct sockaddr_ll
 #define PACKET_RESERVE                  12
 #define PACKET_TX_RING                  13
 #define PACKET_LOSS                     14
+#define PACKET_GAPDATA                  15
 
 struct tpacket_stats
 {
         unsigned int    tp_packets;
         unsigned int    tp_drops;
+        unsigned int    tp_gap;
 };
 
 struct tpacket_auxdata
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d7ecca0a0c07..d398a9bf6903 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -524,6 +524,31 @@ static inline unsigned int run_filter(struct sk_buff *skb, struct sock *sk,
 }
 
 /*
+ * If we've lost frames since the last time we queued one to the
+ * sk_receive_queue, we need to record it here.
+ * This must be called under the protection of the socket lock
+ * to prevent racing with other softirqs and user space
+ */
+static inline void record_packet_gap(struct sk_buff *skb,
+                                        struct packet_sock *po)
+{
+        /*
+         * We overload the mark field here, since we're about
+         * to enqueue to a receive queue and no body else will
+         * use this field at this point
+         */
+        skb->mark = po->stats.tp_gap;
+        po->stats.tp_gap = 0;
+        return;
+
+}
+
+static inline __u32 check_packet_gap(struct sk_buff *skb)
+{
+        return skb->mark;
+}
+
+/*
    This function makes lazy skb cloning in hope that most of packets
    are discarded by BPF.
 
@@ -626,6 +651,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 
         spin_lock(&sk->sk_receive_queue.lock);
         po->stats.tp_packets++;
+        record_packet_gap(skb, po);
         __skb_queue_tail(&sk->sk_receive_queue, skb);
         spin_unlock(&sk->sk_receive_queue.lock);
         sk->sk_data_ready(sk, skb->len);
@@ -634,6 +660,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 drop_n_acct:
         spin_lock(&sk->sk_receive_queue.lock);
         po->stats.tp_drops++;
+        po->stats.tp_gap++;
         spin_unlock(&sk->sk_receive_queue.lock);
 
 drop_n_restore:
@@ -811,6 +838,7 @@ drop:
 
 ring_is_full:
         po->stats.tp_drops++;
+        po->stats.tp_gap++;
         spin_unlock(&sk->sk_receive_queue.lock);
 
         sk->sk_data_ready(sk, 0);
@@ -1418,6 +1446,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
         struct sk_buff *skb;
         int copied, err;
         struct sockaddr_ll *sll;
+        __u32 gap;
 
         err = -EINVAL;
         if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT))
@@ -1496,6 +1525,10 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
                 put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
         }
 
+        gap = check_packet_gap(skb);
+        if (gap)
+                put_cmsg(msg, SOL_PACKET, PACKET_GAPDATA, sizeof(__u32), &gap);
+
         /*
          *      Free or return the buffer as appropriate. Again this
          *      hides all the races and re-entrancy issues from us.