On Thu, Jul 30, 2020 at 1:57 PM Martin KaFai Lau <kafai@xxxxxx> wrote: > > The earlier effort in BPF-TCP-CC allows the TCP Congestion Control > algorithm to be written in BPF. It opens up opportunities to allow > a faster turnaround time in testing/releasing new congestion control > ideas to production environment. > > The same flexibility can be extended to writing TCP header option. > It is not uncommon that people want to test new TCP header option > to improve the TCP performance. Another use case is for data-center > that has a more controlled environment and has more flexibility in > putting header options for internal only use. > > For example, we want to test the idea in putting maximum delay > ACK in TCP header option which is similar to a draft RFC proposal [1]. > > This patch introduces the necessary BPF API and use them in the > TCP stack to allow BPF_PROG_TYPE_SOCK_OPS program to parse > and write TCP header options. It currently supports most of > the TCP packet except RST. > > Supported TCP header option: > ─────────────────────────── > This patch allows the bpf-prog to write any option kind. > Different bpf-progs can write its own option by calling the new helper > bpf_store_hdr_opt(). The helper will ensure there is no duplicated > option in the header. > > By allowing bpf-prog to write any option kind, this gives a lot of > flexibility to the bpf-prog. Different bpf-prog can write its > own option kind. It could also allow the bpf-prog to support a > recently standardized option on an older kernel. > > Sockops Callback Flags: > ────────────────────── > The header parsing and writing callback can be turned on > by enabling a few newly added callback flags: > > BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG: > Call bpf when kernel has received a header option that > the kernel cannot handle. It is useful when the peer doesn't > send bpf-options very often. > > The bpf-prog can inspect the received header by sock_ops->skb_data > which covers the whole header (including the fixed fields like > ports, flags...etc) or > use the new bpf_load_hdr_opt() to search for a particular TCP > header option. > > > > > [1]: draft-wang-tcpm-low-latency-opt-00 > https://tools.ietf.org/html/draft-wang-tcpm-low-latency-opt-00 > > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx> > --- > include/linux/bpf-cgroup.h | 25 +++ > include/linux/filter.h | 4 + > include/net/tcp.h | 53 ++++- > include/uapi/linux/bpf.h | 231 ++++++++++++++++++++- > net/core/filter.c | 365 +++++++++++++++++++++++++++++++++ > net/ipv4/tcp_fastopen.c | 2 +- > net/ipv4/tcp_input.c | 86 +++++++- > net/ipv4/tcp_ipv4.c | 3 +- > net/ipv4/tcp_minisocks.c | 1 + > net/ipv4/tcp_output.c | 194 ++++++++++++++++-- > net/ipv6/tcp_ipv6.c | 3 +- > tools/include/uapi/linux/bpf.h | 231 ++++++++++++++++++++- > 12 files changed, 1171 insertions(+), 27 deletions(-) This is a truly gigantic patch. Could you split it in maybe two parts ? This way I could focus on the TCP changes, and let eBPF experts focus on BPF changes.
