Messages in this thread | | | From | menglong8.dong@gmail ... | Subject | [PATCH net-next v3 0/9] net: add skb drop reasons to TCP packet receive | Date | Sun, 20 Feb 2022 15:06:28 +0800 |
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From: Menglong Dong <imagedong@tencent.com>
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
From the reason 'PROTO_MEM' we can know that the skb is dropped because the memory configured in net.ipv4.tcp_mem is up to the limition.
Changes since v2: - remove the 'inline' of tcp_drop() in the 1th patch, as Jakub suggested
Changes since v1: - enrich the document for this series patches in the cover letter, as Eric suggested - fix compile warning report by Jakub in the 6th patch - let NO_SOCKET trump the XFRM failure in the 2th and 3th patches
Menglong Dong (9): net: tcp: introduce tcp_drop_reason() net: tcp: add skb drop reasons to tcp_v4_rcv() net: tcp: use kfree_skb_reason() for tcp_v6_rcv() net: tcp: add skb drop reasons to tcp_v{4,6}_inbound_md5_hash() net: tcp: add skb drop reasons to tcp_add_backlog() net: tcp: use kfree_skb_reason() for tcp_v{4,6}_do_rcv() net: tcp: use tcp_drop_reason() for tcp_rcv_established() net: tcp: use tcp_drop_reason() for tcp_data_queue() net: tcp: use tcp_drop_reason() for tcp_data_queue_ofo()
include/linux/skbuff.h | 34 ++++++++++++++++++++++++++++++ include/net/tcp.h | 3 ++- include/trace/events/skb.h | 10 +++++++++ net/ipv4/tcp_input.c | 42 +++++++++++++++++++++++++++++--------- net/ipv4/tcp_ipv4.c | 32 +++++++++++++++++++++-------- net/ipv6/tcp_ipv6.c | 39 +++++++++++++++++++++++++++-------- 6 files changed, 132 insertions(+), 28 deletions(-)
-- 2.34.1
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