[net-next,v7,0/7] Implement reset reason mechanism to detect

Message

Jason Xing April 22, 2024, 3:01 a.m. UTC

From: Jason Xing <[e-mail]>

In production, there are so many cases about why the RST skb is sent but
we don't have a very convenient/fast method to detect the exact underlying
reasons.

RST is implemented in two kinds: passive kind (like tcp_v4_send_reset())
and active kind (like tcp_send_active_reset()). The former can be traced
carefully 1) in TCP, with the help of drop reasons, which is based on
Eric's idea[1], 2) in MPTCP, with the help of reset options defined in
RFC 8684. The latter is relatively independent, which should be
implemented on our own, such as active reset reasons which can not be
replace by skb drop reason or something like this.

In this series, I focus on the fundamental implement mostly about how
the rstreason mechnism works and give the detailed passive part as an
example, not including the active reset part. In future, we can go
further and refine those NOT_SPECIFIED reasons.

Here are some examples when tracing:
<idle>-0       [002] ..s1.  1830.262425: tcp_send_reset: skbaddr=x
        skaddr=x src=x dest=x state=x reason=NOT_SPECIFIED
<idle>-0       [002] ..s1.  1830.262425: tcp_send_reset: skbaddr=x
        skaddr=x src=x dest=x state=x reason=NO_SOCKET

[1]
Link: https://lore.kernel.org/all/CANn89iJw8x-LqgsWOeJQQvgVg6DnL5aBRLi10QN2WBdr+X4k=[e-mail]/

v7
Link: https://lore.kernel.org/all/[e-mail]/
1. get rid of enum casts which could bring potential issues (Eric)
2. use switch-case method to map between reset reason in MPTCP and sk reset
reason (Steven)
3. use switch-case method to map between skb drop reason and sk reset
reason

v6
1. add back casts, or else they are treated as error.

v5
Link: https://lore.kernel.org/all/[e-mail]/
1. address format issue (like reverse xmas tree) (Eric, Paolo)
2. remove unnecessary casts. (Eric)
3. introduce a helper used in mptcp active reset. See patch 6. (Paolo)

v4
Link: https://lore.kernel.org/all/[e-mail]/
1. passing 'enum sk_rst_reason' for readability when tracing (Antoine)

v3
Link: https://lore.kernel.org/all/[e-mail]/
1. rebase (mptcp part) and address what Mat suggested.

v2
Link: https://lore.kernel.org/all/[e-mail]/
1. rebase against the latest net-next tree


Jason Xing (7):
  net: introduce rstreason to detect why the RST is sent
  rstreason: prepare for passive reset
  rstreason: prepare for active reset
  tcp: support rstreason for passive reset
  mptcp: support rstreason for passive reset
  mptcp: introducing a helper into active reset logic
  rstreason: make it work in trace world

 include/net/request_sock.h |   4 +-
 include/net/rstreason.h    | 144 +++++++++++++++++++++++++++++++++++++
 include/net/tcp.h          |   3 +-
 include/trace/events/tcp.h |  26 +++++--
 net/dccp/ipv4.c            |  10 +--
 net/dccp/ipv6.c            |  10 +--
 net/dccp/minisocks.c       |   3 +-
 net/ipv4/tcp.c             |  15 ++--
 net/ipv4/tcp_ipv4.c        |  15 ++--
 net/ipv4/tcp_minisocks.c   |   3 +-
 net/ipv4/tcp_output.c      |   5 +-
 net/ipv4/tcp_timer.c       |   9 ++-
 net/ipv6/tcp_ipv6.c        |  18 +++--
 net/mptcp/protocol.c       |   2 +-
 net/mptcp/protocol.h       |  11 +++
 net/mptcp/subflow.c        |  27 +++++--
 16 files changed, 258 insertions(+), 47 deletions(-)
 create mode 100644 include/net/rstreason.h