From patchwork Mon Sep 27 15:23:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 45475 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id F356D3857C40 for ; Mon, 27 Sep 2021 15:23:55 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F356D3857C40 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1632756236; bh=TvaM6vOEXXYGF6+BVwLSIRiQPydJBsKWGkzaGjlZLiE=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=GvE3aAuKiU4FxFZflTQs4Is8qJNdZHO2VmGsi1l3N1hqPEJGgF0rynfh3GpI5HXU2 vCEM2ErwvKm0PuxYqNvQALE9L0mhX74vpHzI48Y3l0DGNwAq+ClIRf+/YgbWcghMtc g60sYkqI97qzHAuOomAT/lbiE/hdMp++ovNJnQQA= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id C1258385802E for ; Mon, 27 Sep 2021 15:23:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org C1258385802E Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-552-75D7eTDtPZeLlHhkT9qypw-1; Mon, 27 Sep 2021 11:23:22 -0400 X-MC-Unique: 75D7eTDtPZeLlHhkT9qypw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D7110802B9F for ; Mon, 27 Sep 2021 15:23:21 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.176]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 09C801972D for ; Mon, 27 Sep 2021 15:23:20 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH] Linux: Simplify __opensock and fix race condition [BZ #28353] Date: Mon, 27 Sep 2021 17:23:19 +0200 Message-ID: <875yumghzs.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, 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-Patchwork-Original-From: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" 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 - }; -#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; }