On Wed, May 24, 2023 at 10:26:32PM -0700, Yonghong Song wrote:
>
>
> On 5/24/23 8:37 PM, Joe Damato wrote:
> >BPF_PROG_TYPE_SK_REUSEPORT / sk_reuseport ebpf programs do not have
> >access to the queue_mapping or napi_id of the incoming skb. Having
> >this information can help ebpf progs determine which listen socket to
> >select.
> >
> >This patch exposes both queue_mapping and napi_id so that
> >sk_reuseport ebpf programs can use this information to direct incoming
> >connections to the correct listen socket in the SOCKMAP.
> >
> >For example:
> >
> >A multi-threaded userland program with several threads accepting client
> >connections via a reuseport listen socket group might want to direct
> >incoming connections from specific receive queues (or NAPI IDs) to specific
> >listen sockets to maximize locality or for use with epoll busy-poll.
> >
> >Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
> >---
> > include/uapi/linux/bpf.h | 2 ++
> > net/core/filter.c | 10 ++++++++++
> > 2 files changed, 12 insertions(+)
> >
> >diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> >index 9273c654743c..31560b506535 100644
> >--- a/include/uapi/linux/bpf.h
> >+++ b/include/uapi/linux/bpf.h
> >@@ -6286,6 +6286,8 @@ struct sk_reuseport_md {
> > */
> > __u32 eth_protocol;
> > __u32 ip_protocol; /* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
> >+ __u32 rx_queue_mapping; /* Rx queue associated with the skb */
> >+ __u32 napi_id; /* napi id associated with the skb */
> > __u32 bind_inany; /* Is sock bound to an INANY address? */
> > __u32 hash; /* A hash of the packet 4 tuples */
>
> This won't work. You will need to append to the end of data structure
> to keep it backward compatibility.
>
> Also, recent kernel has a kfunc bpf_cast_to_kern_ctx() which converts
> a ctx to a kernel ctx and you can then use tracing-coding-style to
> access those fields. In this particular case, you can do
>
> struct sk_reuseport_kern *kctx = bpf_cast_to_kern_ctx(ctx);
>
> We have
>
> struct sk_reuseport_kern {
> struct sk_buff *skb;
> struct sock *sk;
> struct sock *selected_sk;
> struct sock *migrating_sk;
> void *data_end;
> u32 hash;
> u32 reuseport_id;
> bool bind_inany;
> };
>
> through sk and skb pointer, you should be access the fields presented in
> this patch. You can access more fields too.
>
> So using bpf_cast_to_kern_ctx(), there is no need for more uapi changes.
> Please give a try.
Thanks! I was looking at an LTS kernel tree that didn't have
bpf_cast_to_kern_ctx; this is very helpful and definitely a better way to
go.
Sorry for the noise.
