Date: Tue, 11 May 2021 13:40:44 +0200 From: "Patrick M. Hausen" <hausen@punkt.de> To: Peter Jeremy <peter@rulingia.com> Cc: freebsd-net@freebsd.org Subject: Re: sender source IP address on UDP socket bound to INADDR_ANY in golang Message-ID: <846FFF4A-0D81-4F04-8358-1B14F996C0A2@punkt.de> In-Reply-To: <YJpenW9tB7LzlyS9@server.rulingia.com> References: <2B26D5AB-0F77-4E36-AD9A-D7D6CE5F173C@punkt.de> <YJpenW9tB7LzlyS9@server.rulingia.com>
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--Apple-Mail=_D570B725-284C-47E1-9CFE-A86D10271DD7 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 Hi! > Am 11.05.2021 um 12:38 schrieb Peter Jeremy <peter@rulingia.com>: >=20 > On 2021-May-08 19:05:56 +0200, "Patrick M. Hausen" <hausen@punkt.de> = wrote: >> I am facing a problem that is perfectly explained by the semantics >> of the socket interface for UDP, if one assumes that the application >> in question binds to INADDR_ANY and does not specifically set the >> sender address when sending datagrams. > ... >> Their code in question is here: >> = https://github.com/AdguardTeam/dnsproxy/blob/1163404e605c3dfbeab360fc3540f= c290f61a321/proxyutil/udp_unix.go#L47 >=20 > So, they say that they retrieve "the net interface IP the packet was > sent to (dst addr) from the socket's OOB data" and I agree that's what > the referenced code does. I hadn't heard of that behaviour before and > went digging... Thank you. I received some code with internal debugging added from the AdGuard core team and will try that today or tomorrow. If I read the = quote from the documentation correctly, on possible explanation would be them calling recvmsg() but forgetting to setsockopt()? Kind regards, Patrick -- punkt.de GmbH Patrick M. Hausen .infrastructure Kaiserallee 13a 76133 Karlsruhe Tel. +49 721 9109500 https://infrastructure.punkt.de info@punkt.de AG Mannheim 108285 Gesch=C3=A4ftsf=C3=BChrer: J=C3=BCrgen Egeling, Daniel Lienert, Fabian = Stein --Apple-Mail=_D570B725-284C-47E1-9CFE-A86D10271DD7 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEgzqrjO/mj9CSsTg2kG8u4u3aiVwFAmCabTwACgkQkG8u4u3a iVziTwf/QUvq7YXWreIzK7uO486J3pk/pjWqazNAsfioPcIECJEq0O3s8PY7H8Wy GcP0IzS4gi5AdHEo8PE02yqB1DZxnTL1yjL7kpOIi4pssE4fEBMmrPa6bR9604nb dF80d1bq9PxiUaZeh9wUTksxfntnnnhOSOBADXBqvjR/2G0jZyQNKT0k7QWNIQi2 ReLhsUBKmk3TDdFY29RVGx5RqonQmjVgynSZSScdVFxOBCW6iCXvydk8elf9xKnG O0fIcneXQjJSRQ3i6OqDl8j77DvySvlgMgrqk6cKPtgwjUtSy6x1kbEepiZ6yBQN b1pRadbFAmp+5ok0Yjdrdb3nN7VFEA== =xU/M -----END PGP SIGNATURE----- --Apple-Mail=_D570B725-284C-47E1-9CFE-A86D10271DD7--
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