On Wed, Apr 10, 2024 at 9:21 PM Antoine Tenart <aten...@kernel.org> wrote:
>
> Quoting Jason Xing (2024-04-10 14:54:51)
> > Hi Antoine,
> >
> > On Wed, Apr 10, 2024 at 8:14 PM Antoine Tenart <aten...@kernel.org> wrote:
> > >
> > > Quoting Jason Xing (2024-04-09 12:09:30)
> > > > void (*send_reset)(const struct sock *sk,
> > > > - struct sk_buff *skb);
> > > > + struct sk_buff *skb,
> > > > + int reason);
> >
> > > what should be 'reason' harder. Eg. when looking at the code or when
> > > using BTF (to then install debugging probes with BPF) this is not
> > > obvious.
> >
> > Only one number if we want to extract the reason with BPF, right? I
> > haven't tried it.
>
> Yes, we can get 'reason'. Knowing the type helps.
>
> > > A similar approach could be done as the one used for drop reasons: enum
> > > skb_drop_reason is used for parameters (eg. kfree_skb_reason) but other
> > > valid values (subsystem drop reasons) can be used too if casted (to
> > > u32). We could use 'enum sk_rst_reason' and cast the other values. WDYT?
> >
> > I have been haunted by this 'issue' for a long time...
> >
> > Are you suggesting doing so as below for readability:
> > 1) replace the reason parameter in all the related functions (like
> > .send_reset(), tcp_v4_send_reset(), etc) by using 'enum sk_rst_reason'
> > type?
> > 2) in patch [4/6], when it needs to pass the specific reason in those
> > functions, we can cast it to 'enum sk_rst_reason'?
> >
> > One modification I just made based on this patchset if I understand
> > correctly:
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > index 4889fccbf754..e0419b8496b5 100644
> > --- a/net/ipv4/tcp_ipv4.c
> > +++ b/net/ipv4/tcp_ipv4.c
> > @@ -725,7 +725,7 @@ static bool tcp_v4_ao_sign_reset(const struct sock
> > *sk, struct sk_buff *skb,
> > */
> >
> > static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb,
> > - int reason)
> > + enum sk_rst_reason reason)
> > {
> > const struct tcphdr *th = tcp_hdr(skb);
> > struct {
> > @@ -1935,7 +1935,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff
> > *skb)
> > return 0;
> >
> > reset:
> > - tcp_v4_send_reset(rsk, skb, reason);
> > + tcp_v4_send_reset(rsk, skb, (enum sk_rst_reason)reason);
> > discard:
> > kfree_skb_reason(skb, reason);
> > /* Be careful here. If this function gets more complicated and
> >
>
> That's right. I think (u32) can also be used for the cast to make the
> compiler happy in 2), but the above makes sense.
Got it :) Will update soon.
Thanks,
Jason
