From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 17978 invoked from network); 10 May 2022 10:52:21 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 10 May 2022 10:52:21 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id DE78393D2D; Tue, 10 May 2022 20:52:19 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 8353D93D28; Tue, 10 May 2022 20:49:14 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id A078893D28; Tue, 10 May 2022 20:49:09 +1000 (AEST) Received: from relay05.pair.com (relay05.pair.com [216.92.24.67]) by minnie.tuhs.org (Postfix) with ESMTPS id 1372393D1B for ; Tue, 10 May 2022 20:49:06 +1000 (AEST) Received: from orac.inputplus.co.uk (unknown [87.112.46.167]) by relay05.pair.com (Postfix) with ESMTP id CD5E31A2750 for ; Tue, 10 May 2022 06:49:04 -0400 (EDT) Received: from orac.inputplus.co.uk (orac.inputplus.co.uk [IPv6:::1]) by orac.inputplus.co.uk (Postfix) with ESMTP id DF66E221AE for ; Tue, 10 May 2022 11:49:03 +0100 (BST) To: tuhs@minnie.tuhs.org From: Ralph Corderoy MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit In-reply-to: <20220509140846.Qaxea%steffen@sdaoden.eu> References: <20220508102208.50A2822158@orac.inputplus.co.uk> <20220509140846.Qaxea%steffen@sdaoden.eu> Date: Tue, 10 May 2022 11:49:03 +0100 Message-Id: <20220510104903.DF66E221AE@orac.inputplus.co.uk> Subject: Re: [TUHS] conventions around zero padding in ip4 X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" Hi Steffen, > > It has been standardised; see inet_addr(3p) where ‘p’ means the > > POSIX version of the man page or > > https://pubs.opengroup.org/onlinepubs/9699919799/functions/inet_addr.html > > > > Briefly, the string must be one of > > > > a.b.c.d > > a.b.cd > > a.bcd > > abcd ... > "However", RFC 2553 says > > RFC 2553 Basic Socket Interface Extensions for IPv6 March 1999 > > The address conversion functions -- inet_ntoa() and inet_addr() -- > convert IPv4 addresses between binary and printable form. These > functions are quite specific to 32-bit IPv4 addresses. We have > designed two analogous functions that convert both IPv4 and IPv6 > addresses So that RFC added inet_pton(3) and inet_ntop(3). > And for this POSIX says > > If the af argument of inet_pton( ) is AF_INET, the src string > shall be in the standard IPv4 dotted-decimal form: > ddd.ddd.ddd.ddd where "ddd" is a one to three digit decimal > number between 0 and 255 (see inet_addr( )). The inet_pton() > function does not accept other formats [.] True. The non-POSIX inet_pton(3) here points out it only accepts IPv4 in decimal 3.1.4.1 form and pushes the programmer to getaddrinfo(3) instead. NOTES Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6 addresses. On the other hand, inet_pton() accepts only IPv4 addresses in dotted-decimal notation, whereas inet_aton(3) and inet_addr(3) allow the more general numbers-and-dots notation (hexadecimal and octal number formats, and formats that don't require all four bytes to be explicitly written). For an interface that handles both IPv6 addresses, and IPv4 addresses in numbers-and-dots notation, see getaddrinfo(3). And POSIX's getaddrinfo(3p) punts to inet_addr(3p) for describing what IPv4 formats are accepted, so we've gone full circle. If the specified address family is AF_INET or AF_UNSPEC, address strings using Internet standard dot notation as specified in inet_addr() are valid. It looks to me that the RFC introduced a limited format which then had to be standardised but the older interface is still being spread by newer functions like getaddrinfo(). -- Cheers, Ralph.