path: root/include/linux/if_packet.h
diff options
authorNeil Horman <nhorman@tuxdriver.com>2009-10-02 06:56:41 +0000
committerDavid S. Miller <davem@davemloft.net>2009-10-05 00:21:55 -0700
commit977750076d98c7ff6cbda51858bb5a5894a9d9ab (patch)
tree71b2fca8c6739e7d177996354b99504702a1b946 /include/linux/if_packet.h
parentTI DaVinci EMAC: Minor macro related updates (diff)
af_packet: add interframe drop cmsg (v6)
Add Ancilliary data to better represent loss information I've had a few requests recently to provide more detail regarding frame loss during an AF_PACKET packet capture session. Specifically the requestors want to see where in a packet sequence frames were lost, i.e. they want to see that 40 frames were lost between frames 302 and 303 in a packet capture file. In order to do this we need: 1) The kernel to export this data to user space 2) The applications to make use of it This patch addresses item (1). It does this by doing the following: A) Anytime we drop a frame for which we would increment po->stats.tp_drops, we also no increment a stats called po->stats.tp_gap. B) Every time we successfully enqueue a frame to sk_receive_queue, we record the value of po->stats.tp_gap in skb->mark. skb->cb would nominally be the place to record this, but since all the space there is used up, we're overloading skb->mark. Its safe to do since any enqueued packet is guaranteed to be unshared at this point, and skb->mark isn't used for anything else in the rx path to the application. After we record tp_gap in the skb, we zero po->stats.tp_gap. This allows us to keep a counter of the number of frames lost between any two enqueued packets C) When the application goes to dequeue a frame from the packet socket, we look at skb->mark for that frame. If it is non-zero, we add a cmsg chunk to the msghdr of level SOL_PACKET and type PACKET_GAPDATA. Its a 32 bit integer that represents the number of frames lost between this packet and the last previous frame received. Note there is a chance that if there is frame loss after a receive, and then the socket is closed, some gap data might be lost. This is covered by the use of the PACKET_AUXDATA socket option, which gives total loss data. With a bit of math, the final gap can be determined that way. I've tested this patch myself, and it works well. Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> include/linux/if_packet.h | 2 ++ net/packet/af_packet.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/if_packet.h')
1 files changed, 2 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_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