Re: git: 8c0d1eca7834 - main - sockbuf: retain backward compatibility with userland after d59bc188d652

> On 31 May 2022, at 15:33, Mateusz Guzik <mjguzik@gmail.com> wrote:
> 
> On 5/30/22, Alexander V. Chernikov <melifaro@ipfw.ru> wrote:
>> 
>> 
>> 30.05.2022, 16:18, "Mateusz Guzik" <mjguzik@gmail.com>:
>>> 
>>> should probably CTASSERT on size then
>> 
>> Sorry, I’m afraid I don’t get it. Could you please clarify?
>>> 
> 
> diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
> index 249e0800f915..5fc21206b1bf 100644
> --- a/sys/sys/socketvar.h
> +++ b/sys/sys/socketvar.h
> @@ -586,6 +586,14 @@ struct xsocket {
>        } so_rcv, so_snd;
> };
> 
> +#if _LP64
> +_Static_assert(sizeof(struct xsocket) == 240, "bad”)
Ah, got it!
Well, the rationale for the commit was not to absolutely prevent structure size changes - there may be many perfectly valid reasons to do so.
IIRC policy suggests it acceptable between the major revisions.
In the case of original change - removal of mbuf counters - backward compatibility (e.g. keeping structure size the same) does not cost us anything.
sockstat(1) from 13 will work on 14 (at least for now).

> +#elsif _LP32
> +....
> +#else
> +#error "port me"
> +#endif
> +
> #ifdef _KERNEL
> void   sotoxsocket(struct socket *so, struct xsocket *xso);
> void   sbtoxsockbuf(struct sockbuf *sb, struct xsockbuf *xsb);
> 
>>> On 5/30/22, Alexander V. Chernikov <melifaro@freebsd.org> wrote:
>>>> 
>>>> The branch main has been updated by melifaro:
>>>> 
>>>> URL:
>>>> https://cgit.FreeBSD.org/src/commit/?id=8c0d1eca7834bfd5a05c86bf20a7600917057492
>>>> 
>>>> commit 8c0d1eca7834bfd5a05c86bf20a7600917057492
>>>> Author: Alexander V. Chernikov <melifaro@FreeBSD.org>
>>>> AuthorDate: 2022-05-30 14:56:25 +0000
>>>> Commit: Alexander V. Chernikov <melifaro@FreeBSD.org>
>>>> CommitDate: 2022-05-30 15:10:53 +0000
>>>> 
>>>>     sockbuf: retain backward compatibility with userland after
>>>> d59bc188d652
>>>> 
>>>>     Add spare fields to xsockbuf in place of sb_mcnt / sb_ccnt to avoid
>>>>      rebuilding userland binaries like sockstat(1).
>>>> 
>>>>     Reviewed by: glebius
>>>> ---
>>>>  sys/sys/socketvar.h | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>> 
>>>> diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
>>>> index 52b9376f0559..249e0800f915 100644
>>>> --- a/sys/sys/socketvar.h
>>>> +++ b/sys/sys/socketvar.h
>>>> @@ -577,6 +577,8 @@ struct xsocket {
>>>>                  uint32_t sb_cc;
>>>>                  uint32_t sb_hiwat;
>>>>                  uint32_t sb_mbcnt;
>>>> + uint32_t sb_spare0; /* was sb_mcnt */
>>>> + uint32_t sb_spare1; /* was sb_ccnt */
>>>>                  uint32_t sb_mbmax;
>>>>                  int32_t sb_lowat;
>>>>                  int32_t sb_timeo;
>>>> 
>>> 
>>> 
>>> --
>>> Mateusz Guzik <mjguzik gmail.com>
>> 
> 
> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>