netdev - RE: [Patch bpf-next v8 00/16] sockmap: introduce BPF_SK_SKB

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Date:   Thu, 01 Apr 2021 09:51:16 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, duanxiongchun@...edance.com,
        wangdongdong.6@...edance.com, jiang.wang@...edance.com,
        Cong Wang <cong.wang@...edance.com>
Subject: RE: [Patch bpf-next v8 00/16] sockmap: introduce BPF_SK_SKB_VERDICT
 and support UDP

Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
> 
> We have thousands of services connected to a daemon on every host
> via AF_UNIX dgram sockets, after they are moved into VM, we have to
> add a proxy to forward these communications from VM to host, because
> rewriting thousands of them is not practical. This proxy uses an
> AF_UNIX socket connected to services and a UDP socket to connect to
> the host. It is inefficient because data is copied between kernel
> space and user space twice, and we can not use splice() which only
> supports TCP. Therefore, we want to use sockmap to do the splicing
> without going to user-space at all (after the initial setup).
> 
> Currently sockmap only fully supports TCP, UDP is partially supported
> as it is only allowed to add into sockmap. This patchset, as the second
> part of the original large patchset, extends sockmap with:
> 1) cross-protocol support with BPF_SK_SKB_VERDICT; 2) full UDP support.
> 
> On the high level, ->read_sock() is required for each protocol to support
> sockmap redirection, and in order to do sock proto update, a new ops
> ->psock_update_sk_prot() is introduced, which is also required. And the
> BPF ->recvmsg() is also needed to replace the original ->recvmsg() to
> retrieve skmsg. To make life easier, we have to get rid of lock_sock()
> in sk_psock_handle_skb(), otherwise we would have to implement
> ->sendmsg_locked() on top of ->sendmsg(), which is ugly.
> 
> Please see each patch for more details.
> 
> To see the big picture, the original patchset is available here:
> https://github.com/congwang/linux/tree/sockmap
> this patchset is also available:
> https://github.com/congwang/linux/tree/sockmap2
> 
> ---

This LGTM, thanks for doing this Cong.