As with sys/socket.h and struct sockaddr, most of the files including
netinet/in.h just want struct sockaddr_in or a related type, so
introduce bits/types headers for these.  POSIX specifically allows
arpa/inet.h to include netinet/in.h and I think it makes sense to
preserve that.  The definition of struct sockaddr_in had a dependence
on the definition of struct sockaddr; to avoid that, bits/sockaddr.h
grows a new macro, __SOCKADDR_DATA_SIZE, which is the declared size of
struct sockaddr.sa_data.

On Linux, some kernel headers (notably linux/in.h and linux/in6.h)
attempt to cooperate with a C library’s headers in defining types such
as struct sockaddr_in.  There is a set of macros whose names begin
with __UAPI_DEF_ that indicate that a type has already been defined.
This mechanism doesn’t actually work with the kernel headers as they
are in 5.0, as far as I can tell, but it could be made to work with
straightforward changes, so it makes sense for us to support it to the
extent we can.  To do this sensibly I need to introduce a new bits
header called bits/uapi-compat.h, with a trivial definition for
non-Linux.  This replaces the existing __USE_KERNEL_IPV6_DEFS macro.

	* bits/sockaddr.h (__SOCKADDR_DATA_SIZE): New macro.
	* sysdeps/unix/bsd/bits/sockaddr.h: Likewise.
	* sysdeps/unix/sysv/linux/m68k/bits/sockaddr.h: Likewise.
	* socket/bits/types/struct_sockaddr.h: Use __SOCKADDR_DATA_SIZE as
	array length of sa_data.

	* bits/in.h: Add multiple inclusion guard.
	(__USE_KERNEL_IPV6_DEFS): Don’t define.
	* sysdeps/unix/sysv/linux/bits/in.h: Similarly.
	(IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP): Define when not
	already defined, not conditional on __USE_KERNEL_IPV6_DEFS.

	* bits/uapi-compat.h: New file, trivial generic version.
	* sysdeps/unix/sysv/linux/bits/uapi-compat.h: New file,
	Linux-specific version which recognizes kernel header guard macros
	and defines __UAPI_DEF_* macros as appropriate.
	* misc/Makefile: Install bits/uapi-compat.h.

	* include/bits/types/in_addr_t.h, include/bits/types/in_port_t.h
	* include/bits/types/struct_in_addr.h
	* include/bits/types/struct_in6_addr.h
	* include/bits/types/struct_sockaddr_in.h
	* include/bits/types/struct_sockaddr_in6.h:
	New wrapper headers.

	* inet/bits/types/in_addr_t.h, inet/bits/types/in_port_t.h
	* inet/bits/types/struct_in_addr.h
	* inet/bits/types/struct_in6_addr.h
	* inet/bits/types/struct_sockaddr_in.h
	* inet/bits/types/struct_sockaddr_in6.h
	New single-type headers, factored out of inet/netinet/in.h.
	Add __UAPI_DEF_* conditionals where appropriate, and verify that
	all conditionalized definitions agree with the relevant
	OS-supplied header.  Use __SOCKADDR_DATA_SIZE to set size of sin_zero.
	* inet/Makefile: Install the new single-type headers.

	* inet/netinet/in.h: Include bits/uapi-compat.h.
	Define in_addr_t, in_port_t, struct in_addr, struct in6_addr,
	struct sockaddr_in, and struct sockaddr_in6 by including the
	above single-type headers, not directly.  Replace all
	__USE_KERNEL_IPV6_DEFS conditionals with appropriate __UAPI_DEF_*
	conditionals.  Add appropriate __UAPI_DEF_* conditionals around
	the definitions of the IPPROTO_* constants, the IN_CLASS
	macros, and struct ip_mreq.  Import IN_LOOPBACK macro from
	Linux 5.0 linux/in.h and verify all other conditionalized
	definitions agree with the relevant linux/ header.
	Define IPPORT_RESERVED only if not already defined, and make it a
	macro so we can tell.

	* inet/netinet/igmp.h, inet/netinet/ip.h, inet/netinet/ip_icmp.h:
	Include bits/types/struct_in_addr.h, not netinet/in.h.

	* inet/netinet/ip_icmp.h: Hoist all #includes to the top of the file.

	* inet/netinet/icmp6.h, inet/netinet/ip6.h
	* sysdeps/unix/sysv/linux/net/route.h:
	Include bits/types/struct_in6_addr.h, not netinet/in.h.

	* sysdeps/mach/hurd/net/route.h: Include bits/types.h and
	bits/types/struct_in6_addr.h, not netinet/in.h.  Use __uint16_t
	and __uint32_t instead of uint16_t and uint32_t.

	* resolv/bits/types/res_state.h: Include bits/types/struct_in_addr.h
	and bits/types/struct_sockaddr_in.h.  Forward declare struct
	sockaddr_in6.  Don’t include netinet/in.h.

	* resolv/netdb.h: Don’t include netinet/in.h.  Use socklen_t
	instead of __socklen_t.  Define IPPORT_RESERVED only if not
	already defined, with definition matching netinet/in.h.
	When __USE_MISC, include bits/sockaddr.h.
	* resolv/resolv.h: Don’t include netinet/in.h.

	* inet/tst-getni1.c, inet/tst-getni2.c
	* nss/tst-nss-files-hosts-erange.c, nss/tst-nss-files-hosts-getent.c
	* nss/tst-nss-files-hosts-multi.c, posix/tst-getaddrinfo2.c
	* resolv/tst-bug18665-tcp.c, resolv/tst-resolv-ai_idn-common.c
	* resolv/tst-resolv-canonname.c, resolv/tst-resolv-edns.c
	* resolv/tst-resolv-network.c, resolv/tst-resolv-nondecimal.c
	* resolv/tst-resolv-search.c, support/tst-support-namespace.c:
	Include netinet/in.h.
	* support/resolv_test.h: Include stdint.h, not sys/cdefs.h.

	* scripts/check-obsolete-constructs.py (HEADER_ALLOWED_INCLUDES):
	Update.

No standard public header is required to include sys/socket.h,
although some are allowed to.  Several public headers need the
definitions of socklen_t, struct sockaddr, and/or struct
sockaddr_storage, but nothing else from sys/socket.h.  We already have
a single-type header for socklen_t, so this patch adds single-type
headers for struct sockaddr and struct sockaddr_storage.

The definition of struct sockaddr_storage is subtly different on Linux
than on the Hurd; in order to not need two copies of
bits/types/struct_sockaddr_storage.h, bits/sockaddr.h is now
responsible for defining __ss_aligntype if ‘unsigned long int’ is not
the correct definition.

I also added a single-type header for struct linger, even though only
sys/socket.h is expected to define that, just because all three copies
of bits/socket.h were defining it exactly the same way.  There would
also be a case for defining it directly in sys/socket.h but this
seemed tidier.

I did *not* create single-type headers for struct msghdr and struct
cmsghdr, because those and their helper macros are not consistent
among the three copies of bits/socket.h, and, again, only sys/socket.h
is expected to define them.

The large number of .c files that add an `#include <sys/socket.h>`
might make this look like it’s not worth doing.  However, after this
change, only half of the files in the glibc source tree that include
netinet/in.h also need to include sys/socket.h, and only a third of
the files that include netdb.h need to include sys/socket.h.  Before,
all of the files in both groups were getting sys/socket.h.  That seems
like enough justification to me.

While I was at it I noticed that sys/socketvar.h is yet another
backward compatibility header that does nothing but include some other
header (sys/socket.h, in this case) and also doesn’t need to be
system-dependent.

	* socket/bits/types/struct_linger.h
	* socket/bits/types/struct_sockaddr.h
	* socket/bits/types/struct_sockaddr_storage.h:
	New single-type headers, factored out of the various bits/socket.h
	headers.

	* include/bits/types/struct_linger.h
	* include/bits/types/struct_sockaddr.h
	* include/bits/types/struct_sockaddr_storage.h:
	New wrappers.

	* socket/Makefile (headers): Add bits/types/struct_linger.h,
	bits/types/struct_sockaddr.h, and bits/types/struct_sockaddr_storage.h.
	Alphabetize the list.

	* bits/socket.h, sysdeps/mach/hurd/bits/socket.h
	* sysdeps/unix/sysv/linux/bits/socket.h:
	Don’t define struct sockaddr, struct sockaddr_storage,
	__ss_aligntype, or struct linger here.  Minimize inclusions.
	* sysdeps/unix/bsd/bits/sockaddr.h: Define __ss_aligntype here.

	* socket/sys/socket.h: Include bits/types/struct_linger.h,
	bits/sockaddr.h, bits/types/struct_sockaddr.h, and
	bits/types/struct_sockaddr_storage.h.  Move inclusion of
	bits/socket.h below forward declaration of struct timespec,
	and update commentary.

	* inet/ifaddrs.h, socket/net/if.h
	* sysdeps/mach/hurd/net/if_arp.h
	* sysdeps/mach/hurd/net/route.h
	* sysdeps/unix/sysv/linux/errqueue.h
	* sysdeps/unix/sysv/linux/net/if_arp.h
	* sysdeps/unix/sysv/linux/net/route.h:
	Include bits/types/struct_sockaddr.h and possibly also bits/types.h,
	not sys/socket.h or sys/types.h.

	* sysdeps/unix/sysv/linux/errqueue.h:
	* sysdeps/unix/sysv/linux/net/route.h:
	Use __uint8_t and __uint32_t instead of uint8_t and uint32_t.

	* inet/arpa/inet.h: Include bits/types/size_t.h.
	* inet/netinet/in.h: Include bits/sockaddr.h,
	bits/types/struct_sockaddr.h, and
	bits/types/struct_sockaddr_storage.h,
	not sys/socket.h.  Use __socklen_t instead of socklen_t.
	* inet/netinet/tcp.h: Include bits/types.h and
	bits/types/struct_sockaddr_storage.h, not sys/socket.h or
	bits/stdint-uintn.h.  Use __uint8_t, __uint16_t, and __uint32_t
	instead of uint8_t, uint16_t and uint32_t.
	* inet/protocols/routed.h: Include features.h and
	bits/types/struct_sockaddr.h, not sys/socket.h.
	* resolv/netdb.h: Include bits/types/socklen_t.h.
	* sysdeps/unix/sysv/linux/netatalk/at.h: Don’t include sys/socket.h.

	* include/ifaddrs.h: Include stddef.h for size_t.
	* include/netdb.h: Use __socklen_t instead of socklen_t.

	* inet/check_pf.c, inet/gethstbynm.c, inet/gethstbynm_r.c
	* inet/getsourcefilter.c, inet/inet6_opt.c, inet/inet6_option.c
        * inet/inet6_rth.c, inet/setsourcefilter.c, inet/test-ifaddrs.c
	* inet/test-inet6_opt.c, inet/tst-inet6_rth.c
	* inet/tst-inet6_scopeid_pton.c, nis/nss_nis/nis-hosts.c
	* nis/nss_nisplus/nisplus-hosts.c, nscd/aicache.c, nscd/cache.c
	* nscd/hstcache.c, nscd/initgrcache.c, nscd/netgroupcache.c
	* nscd/nscd_gethst_r.c, nscd/servicescache.c, nss/digits_dots.c
	* nss/nss_files/files-hosts.c, nss/nss_files/files-network.c
	* nss/tst-nss-files-hosts-erange.c, nss/tst-nss-files-hosts-getent.c
	* nss/tst-nss-files-hosts-multi.c, posix/tst-getaddrinfo3.c
	* resolv/nss_dns/dns-network.c, resolv/resolv_conf.c
	* resolv/tst-bug18665-tcp.c, resolv/tst-bug18665.c
	* resolv/tst-inet_ntop.c, resolv/tst-inet_pton.c
	* resolv/tst-resolv-ai_idn-common.c, resolv/tst-resolv-basic.c
	* resolv/tst-resolv-edns.c, resolv/tst-resolv-network.c
	* resolv/tst-resolv-nondecimal.c, resolv/tst-resolv-search.c
	* resolv/tst-resolv-threads.c, resolv/tst-resolv-trailing.c
	* sunrpc/rpc_gethostbyname.c
	* support/support_format_address_family.c
	* support/support_format_addrinfo.c
	* support/support_format_dns_packet.c
	* support/support_format_hostent.c, support/support_format_netent.c
	* sysdeps/mach/hurd/if_index.c
	* sysdeps/unix/sysv/linux/check_native.c: Include sys/socket.h.

	* resolv/tst-resolv-binary.c: Include sys/types.h.

	* sysdeps/generic/sys/socketvar.h: Move to socket/sys/socketvar.h.
	* include/sys/socketvar.h: New wrapper.

	* scripts/check-obsolete-constructs.py (HEADER_ALLOWED_INCLUDES):
	Update.

Also, change sources.redhat.com to sourceware.org.
This patch was automatically generated by running the following shell
script, which uses GNU sed, and which avoids modifying files imported
from upstream:

sed -ri '
  s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g
  s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g
' \
  $(find $(git ls-files) -prune -type f \
      ! -name '*.po' \
      ! -name 'ChangeLog*' \
      ! -path COPYING ! -path COPYING.LIB \
      ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \
      ! -path manual/texinfo.tex ! -path scripts/config.guess \
      ! -path scripts/config.sub ! -path scripts/install-sh \
      ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \
      ! -path INSTALL ! -path  locale/programs/charmap-kw.h \
      ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \
      ! '(' -name configure \
            -execdir test -f configure.ac -o -f configure.in ';' ')' \
      ! '(' -name preconfigure \
            -execdir test -f preconfigure.ac ';' ')' \
      -print)

and then by running 'make dist-prepare' to regenerate files built
from the altered files, and then executing the following to cleanup:

  chmod a+x sysdeps/unix/sysv/linux/riscv/configure
  # Omit irrelevant whitespace and comment-only changes,
  # perhaps from a slightly-different Autoconf version.
  git checkout -f \
    sysdeps/csky/configure \
    sysdeps/hppa/configure \
    sysdeps/riscv/configure \
    sysdeps/unix/sysv/linux/csky/configure
  # Omit changes that caused a pre-commit check to fail like this:
  # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines
  git checkout -f \
    sysdeps/powerpc/powerpc64/ppc-mcount.S \
    sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
  # Omit change that caused a pre-commit check to fail like this:
  # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline
  git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

Several network-related structures are defined conditionally under
__USE_MISC, but unconditionally used by other headers.  The path of
least resistance is usually to condition the uses on __USE_MISC as
well.

	* sysdeps/mach/hurd/net/if_ppp.h
	* sysdeps/unix/sysv/linux/net/if_ppp.h:
        Only define struct ifpppstatsreq and struct ifpppcstatsreq
        if __USE_MISC is defined, to ensure struct ifreq is declared.

	* inet/netinet/ether.h: Condition all function prototypes
        on __USE_MISC, to ensure struct ether_addr is declared.

sys/socket.h defines struct osockaddr only under __USE_MISC, whereas
protocols/talkd.h requires it unconditionally.  Here it doesn't make
sense to condition the entire body of protocols/talkd.h on __USE_MISC.
Rather than complicate sys/socket.h with a __need macro or duplicate
the definition, I am introducing a new concept: tiny headers named
bits/types/TYPE.h that define TYPE and nothing else.  This can, I hope,
ultimately replace *all* the __need macros.  The guard macro for such
headers will be __TYPE_defined, just in case application or third-party
library code is looking at them.

	* socket/bits/types/struct_osockaddr.h: New header.
	* include/bits/types/struct_osockaddr.h: New wrapper.
	* socket/Makefile: Install the new header.
	* socket/sys/socket.h,  inet/protocols/talkd.h:
	Refer to bits/types/struct_osockaddr.h for the definition of
	struct osockaddr.