From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-x32e.google.com (mail-wm1-x32e.google.com [IPv6:2a00:1450:4864:20::32e]) by sourceware.org (Postfix) with ESMTPS id E46713858CDA for ; Thu, 30 Mar 2023 17:21:21 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org E46713858CDA Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm1-x32e.google.com with SMTP id o24-20020a05600c511800b003ef59905f26so12255157wms.2 for ; Thu, 30 Mar 2023 10:21:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680196880; x=1682788880; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=fPmrkxP8lA6mm8xNGo07bPYOfkrPR6g3BToZ+bsCS3c=; b=m02NEY4m0MsQBHmg6HVo0I865xOXoUm7zYocyK4yplShm8R13zIPKMTcg/6BkSSSMr fktfULG3scExIKbDaDY118Sm9xa2TiANG4qhpfeZ0r0enku70HrM9f4rFtgpy802m3J8 QKmHn1DFgr1TjxyhRkCmJ+kR7OG+EOd/KPIedzxH5wukU8KuVvGK9A5LJgFkmJDXiP5B eSxNtYAffbXX/+WLi7gH9Cqy3bf8n2dodfIF+tw2ohDZXbsLjNJHdEUlhdufczUWuRO+ eLGHwHp51DtACs7gBHJ1XdnUQid9FyRknaeAO1G7gysTk/xzErj8G5lzYqO+y2HM9dRr uvpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680196880; x=1682788880; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=fPmrkxP8lA6mm8xNGo07bPYOfkrPR6g3BToZ+bsCS3c=; b=1L/MH+j1h8iL/BdA7EZUsfVTivEZh6bcULVrnoQYo4avXLBpBJWE0tCQcaNir9X6JI ZQK730DvyU7z0nu4lFfZav+AfOKi+8sMOBJAQ/wHSLWJcbHVsvKJQkh+yXiHkadnfd3K Z02KHxPlK4pXIKmPmnMbhMxeJM1aLY3Q8w6EtnFcZ9MPO0AcDgRTB2OSOFisWZvDveKu stc6MD+pTiyMs9QpYJL66Crs7GOhp3B0Ft+flVcs4dlkNc8Pu2G2ucdRKH+1FTo5bKN7 KL5SfM8h6uBvwzuwApzFqmxjv1YyRWij+9zmFeg500Huk9L2XkXmjl9ID8KB9v//NZX9 0woA== X-Gm-Message-State: AO0yUKU3rOba4/W56VHYVUK1C/HjUdrtJQ5uNhKPl946b6OMLnSn5C99 qMqK47WRTDF9L/bMAmh6ol8= X-Google-Smtp-Source: AK7set/LoFCPP6hxq7r0EarZskBt24yWXwiE2OSQy9Pm50xlhelnA6s2EadV7BvR8tUsQhYHtccBEQ== X-Received: by 2002:a7b:ca4a:0:b0:3ee:555:ea60 with SMTP id m10-20020a7bca4a000000b003ee0555ea60mr20698202wml.8.1680196880497; Thu, 30 Mar 2023 10:21:20 -0700 (PDT) Received: from asus5775.alejandro-colomar.es ([170.253.51.134]) by smtp.googlemail.com with ESMTPSA id j19-20020a05600c191300b003ee1acdaf95sm6976067wmq.36.2023.03.30.10.21.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 10:21:20 -0700 (PDT) From: Alejandro Colomar X-Google-Original-From: Alejandro Colomar To: linux-man@vger.kernel.org Cc: Alejandro Colomar , =?UTF-8?q?Bastien=20Roucari=C3=A8s?= , glibc , GCC , Eric Blake , Stefan Puiu , Igor Sysoev , Rich Felker , Andrew Clayton , Richard Biener , Zack Weinberg , Florian Weimer , Joseph Myers , Jakub Jelinek , Sam James Subject: [PATCH] sockaddr.3type: Document that sockaddr_storage is the API to be used Date: Thu, 30 Mar 2023 19:13:11 +0200 Message-Id: <20230330171310.12330-1-alx@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-10.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: POSIX.1 Issue 8 will fix the long-standing issue with sockaddr APIs, which inevitably caused UB either on user code, libc, or more likely, both. sockaddr_storage has been clarified to be implemented in a manner that aliasing it is safe (suggesting a unnamed union, or other compiler magic). Link: Reported-by: Bastien Roucariès Reported-by: Alejandro Colomar Cc: glibc Cc: GCC Cc: Eric Blake Cc: Stefan Puiu Cc: Igor Sysoev Cc: Rich Felker Cc: Andrew Clayton Cc: Richard Biener Cc: Zack Weinberg Cc: Florian Weimer Cc: Joseph Myers Cc: Jakub Jelinek Cc: Sam James Signed-off-by: Alejandro Colomar --- Hi all, This is my proposal for documenting the POSIX decission of fixing the definition of sockaddr_storage. Bastien, I believe you had something similar in mind; please review. Eric, thanks again for the fix! Could you please also have a look at this? Cheers, Alex man3type/sockaddr.3type | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/man3type/sockaddr.3type b/man3type/sockaddr.3type index 32c3c5bd0..d1db87d5d 100644 --- a/man3type/sockaddr.3type +++ b/man3type/sockaddr.3type @@ -23,6 +23,14 @@ .SH SYNOPSIS .PP .B struct sockaddr_storage { .BR " sa_family_t ss_family;" " /* Address family */" +.PP +.RS 4 +/* This structure is not really implemented this way. It may be +\& implemented with an unnamed union or some compiler magic to +\& avoid breaking aliasing rules when accessed as any other of the +\& sockaddr_* structures documented in this page. See CAVEATS. +\& */ +.RE .B }; .PP .BR typedef " /* ... */ " socklen_t; @@ -122,6 +130,20 @@ .SH NOTES .I and .IR . +.SH CAVEATS +To avoid breaking aliasing rules, +programs that use functions that receive pointers to +.I sockaddr +structures should declare objects of type +.IR sockaddr_storage , +which is defined in a way that it +can be accessed as any of the different structures defined in this page. +Failure to do so may result in Undefined Behavior. +.PP +New functions should be written to accept pointers to +.I sockaddr_storage +instead of the traditional +.IR sockaddr . .SH SEE ALSO .BR accept (2), .BR bind (2), -- 2.39.2