Re: Question about netinet6/in6.h
- Reply: Mike Karels : "Re: Question about netinet6/in6.h"
- In reply to: Warner Losh : "Question about netinet6/in6.h"
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Fri, 26 Apr 2024 20:49:03 UTC
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. Mike