Re: [Patch bpf-next v7 4/9] skmsg: move sk_redir from TCP_SKB_CB to skb

On Mon, Mar 1, 2021 at 7:24 AM Lorenz Bauer [off-list ref] wrote:

On Tue, 23 Feb 2021 at 18:49, Cong Wang [off-list ref] wrote:

quoted

From: Cong Wang <redacted>

Currently TCP_SKB_CB() is hard-coded in skmsg code, it certainly
does not work for any other non-TCP protocols. We can move them to
skb ext, but it introduces a memory allocation on fast path.

Fortunately, we only need to a word-size to store all the information,
because the flags actually only contains 1 bit so can be just packed
into the lowest bit of the "pointer", which is stored as unsigned
long.

Inside struct sk_buff, '_skb_refdst' can be reused because skb dst is
no longer needed after ->sk_data_ready() so we can just drop it.

Hi Cong Wang,

I saw this on patchwork:

include/linux/skbuff.h:932: warning: Function parameter or member
'_sk_redir' not described in 'sk_buff'
New warnings added
0a1

quoted

include/linux/skbuff.h:932: warning: Function parameter or member '_sk_redir' not described in 'sk_buff'

Per-file breakdown

Ah, I didn't know the function doc is mandatory now.

Source: https://patchwork.kernel.org/project/netdevbpf/patch/20210223184934.6054-5-xiyou.wangcong@gmail.com/

Maybe something to follow up on, I'm not sure what the conventions are here.

It is already merged, so we definitely need a one-line followup fix.

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bd84f799c952..0503c917d773 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h

@@ -656,6 +656,7 @@ typedef unsigned char *sk_buff_data_t;
  *     @protocol: Packet protocol from driver
  *     @destructor: Destruct function
  *     @tcp_tsorted_anchor: list structure for TCP (tp->tsorted_sent_queue)
+ *     @_sk_redir: socket redirection information for skmsg
  *     @_nfct: Associated connection, if any (with nfctinfo bits)
  *     @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
  *     @skb_iif: ifindex of device we arrived on

Thanks.