Date: Sun, 16 May 2021 21:18:55 +1000 From: Peter Jeremy <peter@rulingia.com> To: "Patrick M. Hausen" <hausen@punkt.de> Cc: freebsd-net@freebsd.org Subject: Re: sender source IP address on UDP socket bound to INADDR_ANY in golang Message-ID: <YKD/n0Wvz5gwKiso@server.rulingia.com> In-Reply-To: <D72535AB-1CC4-4091-8446-356DE83812A9@punkt.de> References: <2B26D5AB-0F77-4E36-AD9A-D7D6CE5F173C@punkt.de> <YJpenW9tB7LzlyS9@server.rulingia.com> <846FFF4A-0D81-4F04-8358-1B14F996C0A2@punkt.de> <YJvEsc9MED9rOFBV@server.rulingia.com> <D72535AB-1CC4-4091-8446-356DE83812A9@punkt.de>
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--Fy7fqJva2Z+yZ6Q2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Patrick, On 2021-May-14 23:40:04 +0200, "Patrick M. Hausen" <hausen@punkt.de> wrote: >do you have some spare time and would you be so kind to look at our discus= sion >here: https://github.com/AdguardTeam/AdGuardHome/issues/3015 > >Andrey from the AdGuard team references this golang issue: >https://github.com/golang/go/issues/8329 > >Which references this FreeBSD issue: >https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D193246 I've skimmed through all three issues. >What I as a sysadmin can observe is that the test code Andrey gave me >binds to *.53 on IPv4 and IPv6 although I start it with `-l 0.0.0.0` which= is >clearly an IPv4 "any" address. > >I am not 100% familiar with the API but as I understand you can treat >IPv4 as IPv6 via the socket interface by using an IPv4-mapped IPv6 >address. So far so good. Yes. >But then of course you have an AF_INET6 socket and it seems that >FreeBSD does not allow setting IPv4 specific options via setsockopt() >because it's an IPv6 socket. Correct? That's my reading of the FreeBSD issue. >Why can you have a single socket on both address families, anyway? >IPv4 and IPv6 are as "related" as IP and IPX - if you go dual stack, >treat them both separately - no? This is getting outside my expertise but my understanding is that the idea behind using IPv4-mapped addressed is to simplify building dual-stack applications, particularly during the early introduction of IPv6. The main benefit is that it made it possible to support both IPv4 and IPv6 without needing 2 sockets - which means you can stick to doing an accept() on a blocking socket, rather than needing to use poll() or select() etc with a pair of non-blocking sockets. I'm not sure how to solve your problem, sorry. --=20 Peter Jeremy --Fy7fqJva2Z+yZ6Q2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE7rKYbDBnHnTmXCJ+FqWXoOSiCzQFAmCg/5RfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEVF QjI5ODZDMzA2NzFFNzRFNjVDMjI3RTE2QTU5N0EwRTRBMjBCMzQACgkQFqWXoOSi CzSLqA//b5p4Ec/UOsqe4tLRvvQhhLjIHVUdmn7lfQwmn0I5luDQ1mz8nNl7kGeU BsDKOdfUXc6mhzHFW+rA4uD0//3GWnnz/wbSoOJFH+olAa91Heggyx15DgbodTuG LaxKY79jBsjKXpuaWtTOhnr955/FgyfXx28yVLdm541KAJ8kOMKDWaxBV2xJSRYR e46ww3kak/k6wm5xuc91NzYL3fU01Rrkbl1bEr39kOb8r/Wm9pk5JGWmpjeeRuWC mWAwXFIP/C315AZdMx4lI/vS9YidusvHZP79hGATm7VT1+64A5lTFNaObXnPHQE0 Iq9A4aBidLE2tYPWCBqB2Re/P/7TWo2It4cgiHW/w7uIjsa7tJSPTPlGSS+u7q2H WRfcurfaINw6h8d/3RIA/rSMyi21iutnERVAgK9LD8cwcDuUjejtCEyd5UfEYFdk uAyusWvizdgeKMBtL8YJ7eXZ5QkXoLhAbSNGHdsdnwEsOM7Y5Gsvq+i3y1S3NpjU kx2L6pAwq6An8jPidvF4h/PCdtPVS+z1wOiSDMhovbE8Ld0SzrNKoXCGNpBopaod I7lHfAPZehuqAdYy4yx5WCAIkJmyGyqV8l6o5NB2vZ6J47PI6c1B5LH67Art3YJT Wg2tFTJS29PENkL+bOiEum8K4l/mf7U8pcHWrQcJHJwuiBDUBho= =QdIG -----END PGP SIGNATURE----- --Fy7fqJva2Z+yZ6Q2--
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