Merge branch 'improve-bpf-tcp-cc-init'
Neal Cardwell says:
====================
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 ncardwell@google.com
stopped being accepted at netdev@vger.kernel.org mid-way through processing
the v2 patch series (between patches 2 and 3), confusing patchwork about
which patches belonged to the v2 patch series
====================
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>