On Wed, Oct 23, 2024 at 9:01 PM Eric Dumazet <[email protected]> wrote:
>
> On Wed, Oct 23, 2024 at 2:33 PM Yafang Shao <[email protected]> wrote:
> >
> > We previously hooked the tcp_drop_reason() function using BPF to monitor
> > TCP drop reasons. However, after upgrading our compiler from GCC 9 to GCC
> > 11, tcp_drop_reason() is now inlined, preventing us from hooking into it.
> > To address this, it would be beneficial to introduce a dedicated tracepoint
> > for monitoring.
>
> This patch would require changes in user space tracers.
> I am surprised no one came up with a noinline variant.
>
> __bpf_kfunc is using
>
> #define __bpf_kfunc __used __retain noinline
>
> I would rather not have include/trace/events/tcp.h becoming the
> biggest file in TCP stack...
I’d prefer not to introduce a new tracepoint if we can easily hook it
with BPF. Does the following change look good to you?
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 092456b8f8af..ebea844cc974 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4720,7 +4720,7 @@ static bool tcp_ooo_try_coalesce(struct sock *sk,
return res;
}
-static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
+noinline static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
enum skb_drop_reason reason)
{
sk_drops_add(sk, skb);
--
Regards
Yafang
