From: Neal Cardwell <[email protected]>
This patch series reorganizes TCP congestion control initialization so that if
EBPF code called by tcp_init_transfer() sets the congestion control algorithm
by calling setsockopt(TCP_CONGESTION) then the TCP stack initializes the
congestion control module immediately, instead of having tcp_init_transfer()
later initialize the congestion control module.
This increases flexibility for the EBPF code that runs at connection
establishment time, and simplifies the code.
This has the following benefits:
(1) This allows CC module customizations made by the EBPF called in
tcp_init_transfer() to persist, and not be wiped out by a later
call to tcp_init_congestion_control() in tcp_init_transfer().
(2) Does not flip the order of EBPF and CC init, to avoid causing bugs
for existing code upstream that depends on the current order.
(3) Does not cause 2 initializations for for CC in the case where the
EBPF called in tcp_init_transfer() wants to set the CC to a new CC
algorithm.
(4) Allows follow-on simplifications to the code in net/core/filter.c
and net/ipv4/tcp_cong.c, which currently both have some complexity
to special-case CC initialization to avoid double CC
initialization if EBPF sets the CC.
changes in v2:
o rebase onto bpf-next
o add another follow-on simplification suggested by Martin KaFai Lau:
"tcp: simplify tcp_set_congestion_control() load=false case"
changes in v3:
o no change in commits
o resent patch series from @gmail.com, since mail from [email protected]
stopped being accepted at [email protected] mid-way through processing
the v2 patch series (between patches 2 and 3), confusing patchwork about
which patches belonged to the v2 patch series
Neal Cardwell (5):
tcp: only init congestion control if not initialized already
tcp: simplify EBPF TCP_CONGESTION to always init CC
tcp: simplify tcp_set_congestion_control(): always reinitialize
tcp: simplify _bpf_setsockopt(): remove flags argument
tcp: simplify tcp_set_congestion_control() load=false case
include/net/inet_connection_sock.h | 3 ++-
include/net/tcp.h | 2 +-
net/core/filter.c | 18 ++++--------------
net/ipv4/tcp.c | 3 ++-
net/ipv4/tcp_cong.c | 27 +++++++--------------------
net/ipv4/tcp_input.c | 4 +++-
6 files changed, 19 insertions(+), 38 deletions(-)
--
2.28.0.618.gf4bc123cb7-goog
