Date: Fri, 26 Apr 2024 17:21:08 -0500 From: Mike Karels <mike@karels.net> To: Warner Losh <imp@bsdimp.com> Cc: FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: Question about netinet6/in6.h Message-ID: <AA706B2F-1C77-47B7-915E-6574E1F3654C@karels.net> In-Reply-To: <229EB3F8-FB68-461C-BF1F-3B2846510EBA@karels.net> References: <CANCZdfrDTktpyW9Ad=3-K9qnVYmY_wCnrmyizvgwJktVfHfV3Q@mail.gmail.com> <229EB3F8-FB68-461C-BF1F-3B2846510EBA@karels.net>
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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] = 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). Oddly,
> 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.
Mike
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