From owner-freebsd-net@freebsd.org Thu Jan 4 16:54:53 2018 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 70C76EA4BC0 for ; Thu, 4 Jan 2018 16:54:53 +0000 (UTC) (envelope-from lew@perftech.com) Received: from smtp-gw.pt.net (smtp-gw.pt.net [206.210.194.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "smtp-gw.pt.net", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 40474736EE for ; Thu, 4 Jan 2018 16:54:52 +0000 (UTC) (envelope-from lew@perftech.com) X-ASG-Debug-ID: 1515084832-09411a0f9912d47b0001-QdxwpM Received: from mail.pt.net (mail.pt.net [206.210.194.11]) by smtp-gw.pt.net with ESMTP id N6uP43Fu48EFdzZF (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 04 Jan 2018 10:53:52 -0600 (CST) X-Barracuda-Envelope-From: lew@perftech.com X-Barracuda-Effective-Source-IP: mail.pt.net[206.210.194.11] X-Barracuda-Apparent-Source-IP: 206.210.194.11 Received: from localhost (localhost [IPv6:::1]) by mail.pt.net (Postfix) with ESMTP id AD9A98426C7; Thu, 4 Jan 2018 10:53:52 -0600 (CST) Received: from mail.pt.net ([IPv6:::1]) by localhost (mail.pt.net [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id G8m4VIgi5OP2; Thu, 4 Jan 2018 10:53:52 -0600 (CST) Received: from localhost (localhost [IPv6:::1]) by mail.pt.net (Postfix) with ESMTP id 22F278426C8; Thu, 4 Jan 2018 10:53:52 -0600 (CST) X-Virus-Scanned: amavisd-new at pt.net Received: from mail.pt.net ([IPv6:::1]) by localhost (mail.pt.net [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id FoQGUUFGXoz0; Thu, 4 Jan 2018 10:53:52 -0600 (CST) Received: from dhcp-221-110.perftech.com (dhcp-221-110.perftech.com [206.210.221.110]) (Authenticated sender: lew@pt.net) by mail.pt.net (Postfix) with ESMTPSA id 0FF98842697; Thu, 4 Jan 2018 10:53:52 -0600 (CST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.2 \(3445.5.20\)) Subject: Re: IP networking single socket, both IPv4 and V6? From: Lewis Donzis X-ASG-Orig-Subj: Re: IP networking single socket, both IPv4 and V6? In-Reply-To: Date: Thu, 4 Jan 2018 10:53:51 -0600 Cc: freebsd-net@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: <64BFEA30-EF91-4AAB-9E4F-5937CCAEB92B@perftech.com> References: <2b3944fc-df1a-9998-876e-ad74f8cc073d@denninger.net> To: Karl Denninger X-Mailer: Apple Mail (2.3445.5.20) X-Barracuda-Connect: mail.pt.net[206.210.194.11] X-Barracuda-Start-Time: 1515084832 X-Barracuda-Encrypted: ECDHE-RSA-AES256-GCM-SHA384 X-Barracuda-URL: https://smtp-gw.pt.net:443/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at pt.net X-Barracuda-Scan-Msg-Size: 2411 X-Barracuda-BRTS-Status: 1 X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.46545 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Jan 2018 16:54:53 -0000 > On Jan 4, 2018, at 10:32 AM, Lewis Donzis wrote: >=20 > On Jan 4, 2018, at 10:17 AM, Karl Denninger = wrote: >>=20 >> I've written a fair bit of code that binds to both Ipv4 and v6 for >> incoming connections, using two sockets (one for each.) >>=20 >> Perusing around the 'net I see an implementation note written by IBM >> that implies that on their Unix implementation you can set up an = INET6 >> listener and it will open listeners on *both* IPv4 and v6; you code = it >> as an Ipv6 socket/bind/listen/accept, and if an Ipv4 connection comes = in >> you get a prefix'd IPv4 address back when you call getpeername(). >>=20 >> This would obviously shorten up code and remove the need to open the >> second listener socket, but playing with this on FreeBSD it doesn't >> appear to work -- I only get the IPv6 listener in "netstat -a -n" >> showing up and as expected a connection to a v4 address on that port >> fails (refused, since there's no listener.) >>=20 >> Is this something that *should* work on FreeBSD? >=20 > It works. We do it all the time. You either have to set the sysctl: >=20 > net.inet6.ip6.v6only=3D0 >=20 > which you can do in /etc/sysctl.conf or with the sysctl utility, or, = in your program, use setsockopt to turn off the V6ONLY option, e.g.: >=20 > setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof (int)); = // Turn off v6-only >=20 > We use the first method, which is broken in FreeBSD 11.1 prior to = patch level 5 or 6, I can=E2=80=99t remember which, but works in all = others. The second method is considered to be more portable. >=20 > FWIW, Linux, by default, sets v6only off, so it doesn't require = anything special. I forgot about one other option, which we used to get around the = regression in 11.1 until the kernel gets fixed. Because libc functions = are generally published with a weak reference, you can overload the = socket() function in your own code, like this: int socket (int domain, int type, int protocol) { extern int _socket(int domain, int type, int protocol); int s =3D _socket(domain, type, protocol); if (s >=3D 0 && domain =3D=3D PF_INET6) setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof (int)); = // Turn off v6-only return s; } We put that in one of our own shared libraries that we bind all of our = programs to, and that solves it without having to change a lot of code.=