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85050ac5a2
this was apparently omitted long ago out of a lack of understanding of its importance and the fact that POSIX doesn't specify it. despite not being officially standardized, however, it turns out that at least AIX, glibc, NetBSD, OpenBSD, QNX, and Solaris document and support it. in certain usage cases, such as implementing a DNS gateway on top of the stub resolver interfaces, it's necessary to distinguish the case where a name does not exit (NxDomain) from one where it exists but has no addresses (or other records) of the requested type (NODATA). in fact, even the legacy gethostbyname API had this distinction, which we were previously unable to support correctly because the backend lacked it. apart from fixing an important functionality gap, adding this distinction helps clarify to users how search domain fallback works (falling back in cases corresponding to EAI_NONAME, not in ones corresponding to EAI_NODATA), a topic that has been a source of ongoing confusion and frustration. as a result of this change, EAI_NONAME is no longer a valid universal error code for getaddrinfo in the case where AI_ADDRCONFIG has suppressed use of all address families. in order to return an accurate result in this case, getaddrinfo is modified to still perform at least one lookup. this will almost surely fail (with a network error, since there is no v4 or v6 network to query DNS over) unless a result comes from the hosts file or from ip literal parsing, but in case it does succeed, the result is replaced by EAI_NODATA. glibc has a related error code, EAI_ADDRFAMILY, that could be used for the AI_ADDRCONFIG case and certain NODATA cases, but distinguishing them properly in full generality seems to require additional DNS queries that are otherwise not useful. on glibc, it is only used for ip literals with mismatching family, not for DNS or hosts file results where the name has addresses only in the opposite family. since this seems misleading and inconsistent, and since EAI_NODATA already covers the semantic case where the "name" exists but doesn't have any addresses in the requested family, we do not adopt EAI_ADDRFAMILY at this time. this could be changed at some point if desired, but the logic for getting all the corner cases with AI_ADDRCONFIG right is slightly nontrivial. |
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| arpa | ||
| net | ||
| netinet | ||
| netpacket | ||
| scsi | ||
| sys | ||
| aio.h | ||
| alloca.h | ||
| alltypes.h.in | ||
| ar.h | ||
| assert.h | ||
| byteswap.h | ||
| complex.h | ||
| cpio.h | ||
| crypt.h | ||
| ctype.h | ||
| dirent.h | ||
| dlfcn.h | ||
| elf.h | ||
| endian.h | ||
| err.h | ||
| errno.h | ||
| fcntl.h | ||
| features.h | ||
| fenv.h | ||
| float.h | ||
| fmtmsg.h | ||
| fnmatch.h | ||
| ftw.h | ||
| getopt.h | ||
| glob.h | ||
| grp.h | ||
| iconv.h | ||
| ifaddrs.h | ||
| inttypes.h | ||
| iso646.h | ||
| langinfo.h | ||
| lastlog.h | ||
| libgen.h | ||
| libintl.h | ||
| limits.h | ||
| link.h | ||
| locale.h | ||
| malloc.h | ||
| math.h | ||
| memory.h | ||
| mntent.h | ||
| monetary.h | ||
| mqueue.h | ||
| netdb.h | ||
| nl_types.h | ||
| paths.h | ||
| poll.h | ||
| pthread.h | ||
| pty.h | ||
| pwd.h | ||
| regex.h | ||
| resolv.h | ||
| sched.h | ||
| search.h | ||
| semaphore.h | ||
| setjmp.h | ||
| shadow.h | ||
| signal.h | ||
| spawn.h | ||
| stdalign.h | ||
| stdarg.h | ||
| stdbool.h | ||
| stdc-predef.h | ||
| stddef.h | ||
| stdint.h | ||
| stdio_ext.h | ||
| stdio.h | ||
| stdlib.h | ||
| stdnoreturn.h | ||
| string.h | ||
| strings.h | ||
| stropts.h | ||
| syscall.h | ||
| sysexits.h | ||
| syslog.h | ||
| tar.h | ||
| termios.h | ||
| tgmath.h | ||
| threads.h | ||
| time.h | ||
| uchar.h | ||
| ucontext.h | ||
| ulimit.h | ||
| unistd.h | ||
| utime.h | ||
| utmp.h | ||
| utmpx.h | ||
| values.h | ||
| wait.h | ||
| wchar.h | ||
| wctype.h | ||
| wordexp.h | ||