On 12/20/19 10:26 PM, Martin KaFai Lau wrote: > This patch makes "struct tcp_congestion_ops" to be the first user > of BPF STRUCT_OPS. It allows implementing a tcp_congestion_ops > in bpf. > > The BPF implemented tcp_congestion_ops can be used like > regular kernel tcp-cc through sysctl and setsockopt. e.g. > [root@arch-fb-vm1 bpf]# sysctl -a | egrep congestion > net.ipv4.tcp_allowed_congestion_control = reno cubic bpf_cubic > net.ipv4.tcp_available_congestion_control = reno bic cubic bpf_cubic > net.ipv4.tcp_congestion_control = bpf_cubic > > There has been attempt to move the TCP CC to the user space > (e.g. CCP in TCP). The common arguments are faster turn around, > get away from long-tail kernel versions in production...etc, > which are legit points. > > BPF has been the continuous effort to join both kernel and > userspace upsides together (e.g. XDP to gain the performance > advantage without bypassing the kernel). The recent BPF > advancements (in particular BTF-aware verifier, BPF trampoline, > BPF CO-RE...) made implementing kernel struct ops (e.g. tcp cc) > possible in BPF. It allows a faster turnaround for testing algorithm > in the production while leveraging the existing (and continue growing) > BPF feature/framework instead of building one specifically for > userspace TCP CC. > > This patch allows write access to a few fields in tcp-sock > (in bpf_tcp_ca_btf_struct_access()). > > The optional "get_info" is unsupported now. It can be added > later. One possible way is to output the info with a btf-id > to describe the content. > > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx> Ack from bpf/btf perspective. Acked-by: Yonghong Song <yhs@xxxxxx>
