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Jones" , Bruno Haible , bug-gnulib@gnu.org References: <20190820152705.GA20597@redhat.com> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: <1ad447f9-7390-a13b-fe3f-74bcd3da65d0@redhat.com> Date: Tue, 20 Aug 2019 11:23:38 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190820152705.GA20597@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wMBzo86AmrRBOmjC7rcDxQivgZHStg8og" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.67]); Tue, 20 Aug 2019 16:23:40 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 X-BeenThere: bug-gnulib@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Gnulib discussion list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnulib-bounces+normalperson=yhbt.net@gnu.org Sender: "bug-gnulib" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --wMBzo86AmrRBOmjC7rcDxQivgZHStg8og Content-Type: multipart/mixed; boundary="pL8YS7WqR5S9wSCqs5xsrRFECAZfJyXUf"; protected-headers="v1" From: Eric Blake To: "Richard W.M. Jones" , Bruno Haible , bug-gnulib@gnu.org Message-ID: <1ad447f9-7390-a13b-fe3f-74bcd3da65d0@redhat.com> Subject: Re: accept4 and SOCK_NONBLOCK References: <20190820152705.GA20597@redhat.com> In-Reply-To: <20190820152705.GA20597@redhat.com> --pL8YS7WqR5S9wSCqs5xsrRFECAZfJyXUf Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 8/20/19 10:27 AM, Richard W.M. Jones wrote: > First of all I'm using Linux 5.0.17 & glibc-2.29-15 so as far as I'm > aware accept4 exists and fully works and gnulib shouldn't be replacing > it at all. I don't understand why it's being replaced. >=20 I think I'm reproducing your setup (Fedora 30), and running: =2E/gnulib-tool --test accept4 shows: =2E.. /usr/bin/mkdir -p sys rm -f sys/socket.h-t sys/socket.h && \ { echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */'; \ sed -e 's|@''GUARD_PREFIX''@|GL|g' \ =2E.. -e 's/@''GNULIB_ACCEPT4''@/1/g' \ =2E.. -e 's|@''HAVE_ACCEPT4''@|1|g' \ =2E.. make[4]: Entering directory '/home/eblake/gnulib/testdir935/build/gllib' gcc -DHAVE_CONFIG_H -I. -I../../gllib -I.. -DGNULIB_STRICT_CHECKING=3D1 -g -O2 -MT accept4.o -MD -MP -MF .deps/accept4.Tpo -c -o accept4.o =2E./../gllib/accept4.c so it is indeed locating the system accept4(), but also compiling the gnulib file. In turn, the gnulib file starts out: #if HAVE_ACCEPT4 Aha - there's the bug. Commit e597d4b8 changed from AC_CHECK_FUNCS_ONCE (defines HAVE_ACCEPT4) to AC_CHECK_DECLS (defines HAVE_DECL_ACCEPT4), but failed to update the =2Ec file. I'll push the obvious fix. > But given that, in libguestfs we call: >=20 > r =3D accept4 (console_sock, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);= >=20 > https://github.com/libguestfs/libguestfs/blob/master/lib/launch-libvi= rt.c#L639 >=20 > This is a valid set of flags according to the Linux man page for > accept4(2). But it fails with EINVAL because of the following test in > gnulib: >=20 > if ((flags & ~(SOCK_CLOEXEC | O_TEXT | O_BINARY)) !=3D 0) > { > errno =3D EINVAL; > return -1; > } >=20 > https://git.savannah.gnu.org/cgit/gnulib.git/tree/lib/accept4.c#n61 Yes, that code is unnecessarily strict; gnulib should be taught to handle SOCK_NONBLOCK, but doing it everywhere correctly is a bigger task, as it also affects the socket() function. >=20 > So I think the set of flags should be broadened to include > SOCK_NONBLOCK + add a call to set_nonblocking_flag. >=20 > As for why accept4 is being replaced at all, the only reference to it > in config.log is: >=20 > configure:25630: checking whether accept4 is declared > configure:25630: gcc -c -O2 -g -pipe -Wall -Werror=3Dformat-security = -Wp,-D_FORTIFY_SOURCE=3D2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-= protector-strong -grecord-gcc-switches -specs=3D/usr/lib/rpm/redhat/redha= t-hardened-cc1 -specs=3D/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtun= e=3Dgeneric -fasynchronous-unwind-tables -fstack-clash-protection -fcf-pr= otection conftest.c >&5 > configure:25630: $? =3D 0 > configure:25630: result: yes --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --pL8YS7WqR5S9wSCqs5xsrRFECAZfJyXUf-- --wMBzo86AmrRBOmjC7rcDxQivgZHStg8og Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAl1cHooACgkQp6FrSiUn Q2qgIAf8CA2dbQUD+UlmKqrEdJRT4cdBu/Y0BMLWx26FVeHe2hhTDt8ZOiggV86O VWg0nsXW1VidbsneQeXQzo+vSxwUSSX80/MachOOKMlfTXPVjShKCmxWzigxQ3Ls H+tE9Z9CmcLzIcy7jSsPPFrRBOR1oCMRlRUL5ccwDKeiJp1HaE08zKhufGGdEoeU Ymaa1jhC2Bb8T/+tpDgEcZ+WyPRxBq7ukcUWPq1IN91h83QWh8iBDEr19OyZLzNa 5XGmsOipfN77tWkpvHRwcjvNU3ehFSSahSDkAkn7AKHNOxUZAwcMbq6nP+DegzSv 9lCc7G5/qVC200IzZlXFiVGLcsYQKw== =DG6D -----END PGP SIGNATURE----- --wMBzo86AmrRBOmjC7rcDxQivgZHStg8og--