| Message ID | 20220218083133.18031-1-imagedong@tencent.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | net: add skb drop reasons to TCP packet receive | expand |
On Fri, Feb 18, 2022 at 12:32 AM <menglong8.dong@gmail.com> wrote: > > 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: > > > /* 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 > For the whole series: Reviewed-by: Eric Dumazet <edumazet@google.com> Thanks !
On 2/18/22 1:31 AM, menglong8.dong@gmail.com wrote: > 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 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(-) > LGTM. for the set: Reviewed-by: David Ahern <dsahern@kernel.org>
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 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(-)