From owner-freebsd-net@FreeBSD.ORG Mon Jul 21 22:37:48 2008 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2E958106564A; Mon, 21 Jul 2008 22:37:48 +0000 (UTC) (envelope-from rehsack@web.de) Received: from fmmailgate02.web.de (fmmailgate02.web.de [217.72.192.227]) by mx1.freebsd.org (Postfix) with ESMTP id AD23C8FC16; Mon, 21 Jul 2008 22:37:47 +0000 (UTC) (envelope-from rehsack@web.de) Received: from smtp08.web.de (fmsmtp08.dlan.cinetic.de [172.20.5.216]) by fmmailgate02.web.de (Postfix) with ESMTP id 5CA60E6AF2AF; Tue, 22 Jul 2008 00:36:56 +0200 (CEST) Received: from [87.149.238.94] (helo=waldorf.muppets.liwing.de) by smtp08.web.de with esmtp (TLSv1:AES256-SHA:256) (WEB.DE 4.109 #226) id 1KL400-00024s-00; Tue, 22 Jul 2008 00:36:56 +0200 Message-ID: <48850F72.90204@web.de> Date: Mon, 21 Jul 2008 22:36:34 +0000 From: Jens Rehsack User-Agent: Thunderbird 2.0.0.14 (X11/20080703) MIME-Version: 1.0 To: Brooks Davis References: <4884F401.4050103@web.de> <20080721204820.GE1699@lor.one-eyed-alien.net> <4884FFFF.9090908@web.de> <20080721222416.GG1699@lor.one-eyed-alien.net> In-Reply-To: <20080721222416.GG1699@lor.one-eyed-alien.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: rehsack@web.de X-Sender: rehsack@web.de X-Provags-ID: V01U2FsdGVkX19cVSb72bhnq2LlCXeug4W2Hiz0y7l631i6o9Zg kQHCzE+2oRsuA7LkQ2DKOA3TZtD37dKv9hl3DWJXOcNxvgUQNY H2wrvydn0= Cc: FreeBSD Net Subject: Re: lo0 not in ioctl( SIOCGIFCONF ) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Jul 2008 22:37:48 -0000 Brooks Davis wrote: > On Mon, Jul 21, 2008 at 09:30:39PM +0000, Jens Rehsack wrote: >> Brooks Davis wrote: >>>> Hi, >>>> >>>> maybe this question is better asked in this list ... >>>> >>>> I was searching why ports/net/p5-Net-Interface was not working as >>>> expected and found some reasons. Most of them I can answer by implementing >>>> some test code as attached, but now I'm wondering why em0 is shown twice >>>> and lo0 is not included. >>>> The same situation on another machine .. >>> The attachment didn't make it through. >>> >>> -- Brooks >> Copy&Paste starts here ... >> #include >> #include >> #include >> #include >> #include >> #include >> #include >> #include >> >> #ifndef _SIZEOF_ADDR_IFREQ >> #define _SIZEOF_ADDR_IFREQ(ifr) \ >> ((ifr).ifr_addr.sa_len > sizeof(struct sockaddr) ? \ >> (sizeof(struct ifreq) - sizeof(struct sockaddr) + \ >> (ifr).ifr_addr.sa_len) : sizeof(struct ifreq)) >> #endif >> >> int >> main() >> { >> struct ifconf ifc; >> struct ifreq *ifr, *lifr; >> int fd; >> unsigned int n; >> >> fd = socket( AF_INET, SOCK_STREAM, 0 ); >> bzero(&ifc, sizeof(ifc)); >> n = 3; >> ifr = calloc( ifc.ifc_len, sizeof(*ifr) ); >> do >> { >> n *= 2; >> ifr = realloc( ifr, sizeof(*ifr) * n ); >> bzero( ifr, sizeof(*ifr) * n ); >> ifc.ifc_req = ifr; >> ifc.ifc_len = n * sizeof(*ifr); >> } while( ( ioctl( fd, SIOCGIFCONF, &ifc ) == -1 ) || ( ifc.ifc_len >> == n * sizeof(*ifr)) ); > > There are several problems with this loop. First, icoctl won't return > an error in the overflow case because that's not how SIOCGIFCONF works. > SIOCGIFCONF is badly designed in a number of ways, but that's how it > is. Second, checking that the array is completely full isn't at all > reliable because what is returned is actually ifreq structures which > might or might not vary in length as they contain addresses. Thus you > need <=. Third, you should start by allocating a significant amount of > space. Yes, your algorithm is O(sqrt(n)), but allocating a larger > value has effectively no cost so you might as well save some system calls > on average. Thanks - that was the information I miss. I'll try tomorrow (it's slightly late here) and send back the result. Using <= should produce an endless loop, but maybe checking if ifc.ifc_len <= (n/2) * sizeof(*ifr) could bring wanted results ... >> lifr = (struct ifreq *)&ifc.ifc_buf[ifc.ifc_len]; >> >> while (ifr < lifr) > { >> printf( "%s\n", ifr->ifr_name ); >> ifr = (struct ifreq *)(((char *)ifr) + _SIZEOF_ADDR_IFREQ(*ifr)); >> } > > This loop has two problems. First, the ifr's are variable length so you > immediately go off into the weeds. The _SIZEOF_ADDR_IFREQ macro should handle that correctly, shouldn't it? > Second, there is at least one per > interface and one per address so you to keep track of the last interface > name and not repeat them. Good point - if it's sure in this order, this is a good way to handle it. > -- Brooks /Jens