On Fri, Feb 7, 2025 at 10:07 AM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote:
>
> On 2/5/25 10:56 PM, Jason Xing wrote:
> >>> I have to rephrase a bit in case Martin visits here soon: I will
> >>> compare two approaches 1) reply value, 2) bpf kfunc and then see which
> >>> way is better.
> >>
> >> I have already explained in details why the 1) reply value from the bpf prog
> >> won't work. Please go back to that reply which has the context.
> >
> > Yes, of course I saw this, but I said I need to implement and dig more
> > into this on my own. One of my replies includes a little code snippet
> > regarding reply value approach. I didn't expect you to misunderstand
> > that I would choose reply value, so I rephrase it like above :)
>
> I did see the code snippet which is incomplete, so I have to guess. afaik, it is
> not going to work. I was hoping to save some time without detouring to the
> reply-value path in case my earlier message was missed. I will stay quiet and
> wait for v9 first then to avoid extending this long thread further.
FYI, the code I adjusted works, a little bit ugly though.
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ad4f056aff22..44b4f8655668 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -498,10 +498,13 @@ static void tcp_tx_timestamp(struct sock *sk,
struct sockcm_cookie *sockc)
struct skb_shared_info *shinfo = skb_shinfo(skb);
struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
- tcb->txstamp_ack = 2;
- shinfo->tx_flags |= SKBTX_BPF;
shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
- bpf_skops_tx_timestamping(sk, skb, BPF_SOCK_OPS_TS_SND_CB);
+ if (bpf_skops_tx_timestamping(sk, skb,
BPF_SOCK_OPS_TS_SND_CB)) {
+ tcb->txstamp_ack = 2;
+ shinfo->tx_flags |= SKBTX_BPF;
+ } else {
+ shinfo->tskey = 0;
+ }
}
}
I'm not sure if it meets your requirement? The reason why I resorted
to this method is because I failed to attempt to use kfunc and
struggled to read many btf codes :(
So please provide more hints so that I can start again. Thanks.
Thanks,
Jason
