[PATCH net-next v2 0/9] net: add skb drop reasons to TCP packet receive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Menglong Dong <imagedong@xxxxxxxxxxx>

In the commit c504e5c2f964 ("net: skb: introduce kfree_skb_reason()"),
we added the support of reporting the reasons of skb drops to kfree_skb
tracepoint. And in this series patches, reasons for skb drops are added
to TCP layer (both TCPv4 and TCPv6 are considered).
Following functions are processed:

tcp_v4_rcv()
tcp_v6_rcv()
tcp_v4_inbound_md5_hash()
tcp_v6_inbound_md5_hash()
tcp_add_backlog()
tcp_v4_do_rcv()
tcp_v6_do_rcv()
tcp_rcv_established()
tcp_data_queue()
tcp_data_queue_ofo()

The functions we handled are mostly for packet ingress, as skb drops
hardly happens in the egress path of TCP layer. However, it's a little
complex for TCP state processing, as I find that it's hard to report skb
drop reasons to where it is freed. For example, when skb is dropped in
tcp_rcv_state_process(), the reason can be caused by the call of
tcp_v4_conn_request(), and it's hard to return a drop reason from
tcp_v4_conn_request(). So such cases are skipped  for this moment.

Following new drop reasons are introduced (what they mean can be see
in the document for them):

/* SKB_DROP_REASON_TCP_MD5* corresponding to LINUX_MIB_TCPMD5* */
SKB_DROP_REASON_TCP_MD5NOTFOUND
SKB_DROP_REASON_TCP_MD5UNEXPECTED
SKB_DROP_REASON_TCP_MD5FAILURE
SKB_DROP_REASON_SOCKET_BACKLOG
SKB_DROP_REASON_TCP_FLAGS
SKB_DROP_REASON_TCP_ZEROWINDOW
SKB_DROP_REASON_TCP_OLD_DATA
SKB_DROP_REASON_TCP_OVERWINDOW
/* corresponding to LINUX_MIB_TCPOFOMERGE */
SKB_DROP_REASON_TCP_OFOMERGE

Here is a example to get TCP packet drop reasons from ftrace:

$ echo 1 > /sys/kernel/debug/tracing/events/skb/kfree_skb/enable
$ cat /sys/kernel/debug/tracing/trace
$ <idle>-0       [036] ..s1.   647.428165: kfree_skb: skbaddr=000000004d037db6 protocol=2048 location=0000000074cd1243 reason: NO_SOCKET
$ <idle>-0       [020] ..s2.   639.676674: kfree_skb: skbaddr=00000000bcbfa42d protocol=2048 location=00000000bfe89d35 reason: PROTO_MEM


[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux