From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) by sourceware.org (Postfix) with ESMTPS id A698D3858D3C for ; Mon, 27 Sep 2021 15:33:36 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A698D3858D3C Received: by mail-qk1-x736.google.com with SMTP id x12so3890028qkf.9 for ; Mon, 27 Sep 2021 08:33:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ocfPvhoI1CRarwTST8YsCvjjWxiPWmEl5OUhKoED4lU=; b=fAReLiJYXvln+bQJgugmDheSpcGUhsqefFK+dJaMTPAPj2CaVn0i5Y/lsKXhWoewBH 2TMJ8P6qTrC5oMjCIwGMq7fYVkmBJKGkWu+JRmE/hn4ssmtT3CU93YYmOv/gyjw2znBs a1lByDZRX2V877dlKAR1YzXAIhoNsF9Mm6zNKx/s8/gwjHyFeMBhK/pup3z8oaIGx7xf DCg5130Ps5OmuivyeQ6cBMzPUk2cYZDoLfBRXlqp4dsONCcis+BTtQgoSDyXsB+7bm2y BIwz2Tymn4ZounV5sQD4P7abljG65T3OoKazM1ddPsTnkFqapRy9N778/tYCfGFlYL4t tNdw== X-Gm-Message-State: AOAM531vMqgJWfbl7kV0LB/GhmAxiKUVx6yIp80qIhle04eiR0uNH4GY Rt6kE39qXS/pxnK2ycU0hwnsTdZ0/tpgEA== X-Google-Smtp-Source: ABdhPJxU+ilJ3bTs0P1TWEn4RD3i2wzSyQoPO8Z8j9+QTJB7lD2Va/JrMRGfwuIAgnO+AB++Gc6/HQ== X-Received: by 2002:a37:aac9:: with SMTP id t192mr563590qke.450.1632756816048; Mon, 27 Sep 2021 08:33:36 -0700 (PDT) Received: from ?IPv6:2804:431:c7cb:b338:9c1f:21e4:d45:b086? ([2804:431:c7cb:b338:9c1f:21e4:d45:b086]) by smtp.gmail.com with ESMTPSA id 75sm12522117qkh.121.2021.09.27.08.33.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Sep 2021 08:33:35 -0700 (PDT) Subject: Re: [PATCH] Linux: Simplify __opensock and fix race condition [BZ #28353] To: libc-alpha@sourceware.org, Florian Weimer References: <875yumghzs.fsf@oldenburg.str.redhat.com> From: Adhemerval Zanella Message-ID: <48158338-3d06-72aa-5e1b-0cb34e7325cc@linaro.org> Date: Mon, 27 Sep 2021 12:33:34 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <875yumghzs.fsf@oldenburg.str.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-14.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Sep 2021 15:33:38 -0000 On 27/09/2021 12:23, Florian Weimer via Libc-alpha wrote: > AF_NETLINK support is not quite optional on modern Linux systems > anymore, so it is likely that the first attempt will always succeed. > Consequently, there is no need to cache the result. Keep AF_UNIX > and the Internet address families as a fallback, for the rare case > that AF_NETLINK is fixing. The other address families previously > probed are totally obsolete be now, so remove them. > > --- > Tested on i686-linux-gnu and x86_64-linux-gnu (albeit with all four > address families present). Initial build-many-glibcs.py results look > okay as well. > > sysdeps/unix/sysv/linux/opensock.c | 103 ++++++------------------------------- > 1 file changed, 16 insertions(+), 87 deletions(-) > > diff --git a/sysdeps/unix/sysv/linux/opensock.c b/sysdeps/unix/sysv/linux/opensock.c > index e87d6e58b0..47464d3a30 100644 > --- a/sysdeps/unix/sysv/linux/opensock.c > +++ b/sysdeps/unix/sysv/linux/opensock.c > @@ -15,11 +15,7 @@ > License along with the GNU C Library; if not, see > . */ > > -#include > #include > -#include > -#include > -#include > #include > > /* Return a socket of any type. The socket can be used in subsequent > @@ -27,88 +23,21 @@ > int > __opensock (void) > { > - static int last_family; /* Available socket family we will use. */ > - static int last_type; > - static const struct > - { > - int family; > - const char procname[15]; > - } afs[] = > - { > - { AF_UNIX, "net/unix" }, > - { AF_INET, "" }, > - { AF_INET6, "net/if_inet6" }, > - { AF_AX25, "net/ax25" }, > - { AF_NETROM, "net/nr" }, > - { AF_ROSE, "net/rose" }, > - { AF_IPX, "net/ipx" }, > - { AF_APPLETALK, "net/appletalk" }, > - { AF_ECONET, "sys/net/econet" }, > - { AF_ASH, "sys/net/ash" }, > - { AF_X25, "net/x25" }, > -#ifdef NEED_AF_IUCV > - { AF_IUCV, "net/iucv" } > -#endif With this removal, there is no need to keep the s390 [1]. [1] sysdeps/unix/sysv/linux/s390/opensock.c > - }; > -#define nafs (sizeof (afs) / sizeof (afs[0])) > - char fname[sizeof "/proc/" + 14]; > - int result; > - int has_proc; > - size_t cnt; > - > - /* We already know which family to use from the last call. Use it > - again. */ > - if (last_family != 0) > - { > - assert (last_type != 0); > - > - result = __socket (last_family, last_type | SOCK_CLOEXEC, 0); > - if (result != -1 || errno != EAFNOSUPPORT) > - /* Maybe the socket type isn't supported anymore (module is > - unloaded). In this case again try to find the type. */ > - return result; > - > - /* Reset the values. They seem not valid anymore. */ > - last_family = 0; > - last_type = 0; > - } > - > - /* Check whether the /proc filesystem is available. */ > - has_proc = __access ("/proc/net", R_OK) != -1; > - strcpy (fname, "/proc/"); > - > - /* Iterate over the interface families and find one which is > - available. */ > - for (cnt = 0; cnt < nafs; ++cnt) > - { > - int type = SOCK_DGRAM; > - > - if (has_proc && afs[cnt].procname[0] != '\0') > - { > - strcpy (fname + 6, afs[cnt].procname); > - if (__access (fname, R_OK) == -1) > - /* The /proc entry is not available. I.e., we cannot > - create a socket of this type (without loading the > - module). Don't look for it since this might trigger > - loading the module. */ > - continue; > - } > - > - if (afs[cnt].family == AF_NETROM || afs[cnt].family == AF_X25) > - type = SOCK_SEQPACKET; > - > - result = __socket (afs[cnt].family, type | SOCK_CLOEXEC, 0); > - if (result != -1) > - { > - /* Found an available family. */ > - last_type = type; > - last_family = afs[cnt].family; > - return result; > - } > - } > - > - /* None of the protocol families is available. It is unclear what kind > - of error is returned. ENOENT seems like a reasonable choice. */ > + /* SOCK_DGRAM is supported by all address families. (Netlink does > + not support SOCK_STREAM.) */ > + int type = SOCK_DGRAM | SOCK_CLOEXEC; > + int fd = __socket (AF_NETLINK, type, 0); > + if (fd >= 0) > + return fd; > + fd = __socket (AF_UNIX, type, 0); > + if (fd >= 0) > + return fd; > + fd = __socket (AF_INET, type, 0); > + if (fd >= 0) > + return fd; > + fd = __socket (AF_INET6, type, 0); > + if (fd >= 0) > + return fd; > __set_errno (ENOENT); > - return -1; > + return fd; > } > Wouldn't be better to move it as the generic implementation (and also cleanup it by removing unsualy families like IPX, AX25, and APPLETALK)?