Date: Fri, 26 Apr 2024 17:06:31 -0600 From: Warner Losh <imp@bsdimp.com> To: Mike Karels <mike@karels.net> Cc: FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: Question about netinet6/in6.h Message-ID: <CANCZdfrtxsGKKn3bzaWRDhYphYb0DuZ7VTOWeTbR_8X980u_1A@mail.gmail.com> In-Reply-To: <AA706B2F-1C77-47B7-915E-6574E1F3654C@karels.net> References: <CANCZdfrDTktpyW9Ad=3-K9qnVYmY_wCnrmyizvgwJktVfHfV3Q@mail.gmail.com> <229EB3F8-FB68-461C-BF1F-3B2846510EBA@karels.net> <AA706B2F-1C77-47B7-915E-6574E1F3654C@karels.net>
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On Fri, Apr 26, 2024 at 4:21=E2=80=AFPM Mike Karels <mike@karels.net> wrote=
:
> On 26 Apr 2024, at 15:49, Mike Karels wrote:
>
> > On 26 Apr 2024, at 15:01, Warner Losh wrote:
> >
> >> This has to be a FAQ
> >>
> >> I'm porting a program from Linux, I often see an error like:
> >> ./test/mock-ifaddrs.c:95:19: error: no member named 's6_addr32' in
> 'struct
> >> in6_addr'
> >> 95 | ipv6->sin6_addr.s6_addr32[3] =3D 0;
> >> | ~~~~~~~~~~~~~~~ ^
> >> but yet, we kinda define them, but only for the kernel and boot loader=
:
> >> /*
> >> * IPv6 address
> >> */
> >> struct in6_addr {
> >> union {
> >> uint8_t __u6_addr8[16];
> >> uint16_t __u6_addr16[8];
> >> uint32_t __u6_addr32[4];
> >> } __u6_addr; /* 128-bit IP6 address */
> >> };
> >>
> >> #define s6_addr __u6_addr.__u6_addr8
> >> #if defined(_KERNEL) || defined(_STANDALONE) /* XXX nonstandard */
> >> #define s6_addr8 __u6_addr.__u6_addr8
> >> #define s6_addr16 __u6_addr.__u6_addr16
> >> #define s6_addr32 __u6_addr.__u6_addr32
> >> #endif
> >>
> >> I'm wondering if anybody why it's like that? git blame suggests we
> imported
> >> that from kame, with
> >> only tweaks by people that are now deceased*.*
> >>
> >> Why not just expose them?
> >
> > Looks like only s6_addr is specified in the RFCs (2553 and 3493). Oddl=
y,
> > though, the RFCs give an example implementation using that union with
> > different element names (like _S6_u8), and show the one #define.
> > Similarly, POSIX specifies only s6_addr, but it allows other members
> > of the structure, so I don't see a problem with exposing them all even
> > in a POSIX environment.
> >
> > I would have no objection to exposing all four definitions, especially
> > if Linux apps use them.
>
> I put the change, along with an explanatory comment, in
> https://reviews.freebsd.org/D44979. Comments welcome.
>
Thanks! I was testing a similar change, but I like yours better... though
maybe
we should just make it visible when __BSD_VISIBLE is true.... I'll have to
look
closely at what Linux does here... I think they have it always visible, or
at least
musl does that (glibc is harder to track down due to the many layers of
indirection).
Warner
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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Fri, Apr 26, 2024 at 4:21=E2=80=AF=
PM Mike Karels <<a href=3D"mailto:mike@karels.net">mike@karels.net</a>&g=
t; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0p=
x 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 26 =
Apr 2024, at 15:49, Mike Karels wrote:<br>
<br>
> On 26 Apr 2024, at 15:01, Warner Losh wrote:<br>
><br>
>> This has to be a FAQ<br>
>><br>
>> I'm porting a program from Linux, I often see an error like:<b=
r>
>> ./test/mock-ifaddrs.c:95:19: error: no member named 's6_addr32=
' in 'struct<br>
>> in6_addr'<br>
>>=C2=A0 =C2=A0 95 |=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0ipv6->sin6_addr.s6_addr32[3] =3D 0;<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0|=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0~~~~~~~~~~~~~~~ ^<br>
>> but yet, we kinda define them, but only for the kernel and boot lo=
ader:<br>
>> /*<br>
>>=C2=A0 * IPv6 address<br>
>>=C2=A0 */<br>
>> struct in6_addr {<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0union {<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0uint8=
_t=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0__u6_addr8[16];<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0uint1=
6_t=C2=A0 =C2=A0 =C2=A0 =C2=A0 __u6_addr16[8];<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0uint3=
2_t=C2=A0 =C2=A0 =C2=A0 =C2=A0 __u6_addr32[4];<br>
>>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0} __u6_addr;=C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 /* 128-bit IP6 address */<=
br>
>> };<br>
>><br>
>> #define s6_addr=C2=A0 =C2=A0__u6_addr.__u6_addr8<br>
>> #if defined(_KERNEL) || defined(_STANDALONE) /* XXX nonstandard */=
<br>
>> #define s6_addr8=C2=A0 __u6_addr.__u6_addr8<br>
>> #define s6_addr16 __u6_addr.__u6_addr16<br>
>> #define s6_addr32 __u6_addr.__u6_addr32<br>
>> #endif<br>
>><br>
>> I'm wondering if anybody why it's like that? git blame sug=
gests we imported<br>
>> that from kame, with<br>
>> only tweaks by people that are now deceased*.*<br>
>><br>
>> Why not just expose them?<br>
><br>
> Looks like only s6_addr is specified in the RFCs (2553 and 3493).=C2=
=A0 Oddly,<br>
> though, the RFCs give an example implementation using that union with<=
br>
> different element names (like _S6_u8), and show the one #define.<br>
> Similarly, POSIX specifies only s6_addr, but it allows other members<b=
r>
> of the structure, so I don't see a problem with exposing them all =
even<br>
> in a POSIX environment.<br>
><br>
> I would have no objection to exposing all four definitions, especially=
<br>
> if Linux apps use them.<br>
<br>
I put the change, along with an explanatory comment, in<br>
<a href=3D"https://reviews.freebsd.org/D44979" rel=3D"noreferrer" target=3D=
"_blank">https://reviews.freebsd.org/D44979</a>.=C2=A0 Comments welcome.<br=
></blockquote><div><br></div><div>Thanks! I was testing a similar change, b=
ut I like yours better... though maybe</div><div>we should just make it vis=
ible when __BSD_VISIBLE is true.... I'll have to look</div><div>closely=
at what Linux does here... I think they have it always visible, or at leas=
t</div><div>musl does that (glibc is harder to track down due to the many l=
ayers of indirection).</div><div><br></div><div>Warner<br></div></div></div=
>
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