From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D1CEC433ED for ; Sat, 10 Apr 2021 09:25:51 +0000 (UTC) Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A102B61182 for ; Sat, 10 Apr 2021 09:25:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A102B61182 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=wireguard-bounces@lists.zx2c4.com Received: by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTP id bbe97c1d; Sat, 10 Apr 2021 09:25:48 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id bae298b9 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO) for ; Sat, 10 Apr 2021 09:25:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Mime-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=THuhIzVWxgfF32ArPV86JIBpqiTe6YDqvD78mKLQzzE=; b=Ralz7tBmqRBpXvBIw4IzFWxUFk IVaoqZHXm8J4I8zPk30Ndahuiebv8T2y6r6UuiMFGOUTsD8BXSS20JleedU59/FqSI3627OWOhlrJ lkkQdHYR1WO8WdXUvnO1k7kAsBLk+f9IFVPmhop0ZZvNj7+RWBbgKmLvz+EPKd87wh4SQg8I9dLA+ Ox2qhSYAK/OshmMOpmeJGlV4dAbeL0fn8wFkRFbcirPiO3cx+xrKNdRLYVoXsXvhIRerggFjHTH0c SwnqfAKi9EUWARLYwbTYzDxETSAtHyR+qhZwtEZmaMVgmZUU2YKBWL+NxMVfwpjvNQXhFkGe/wNd/ qKGF6QWw==; Received: from dyn-234.woodhou.se ([90.155.92.234] helo=u3832b3a9db3152.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lV9s3-002XZZ-5v; Sat, 10 Apr 2021 09:25:41 +0000 Message-ID: <731dfc961cc071b9ea25f3ef8fb04105956bafe5.camel@infradead.org> Subject: Re: Duplicate IP address, and permissions problems on Windows From: David Woodhouse To: Daniel Lenski Cc: "Jason A. Donenfeld" , WireGuard mailing list Date: Sat, 10 Apr 2021 10:25:38 +0100 In-Reply-To: References: <432300ddb79fffb1586ccac6852fade4c2d47db0.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-+8H7aFvUOq7S/2qyuKL1" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" --=-+8H7aFvUOq7S/2qyuKL1 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-04-08 at 10:53 -0700, Daniel Lenski wrote: > On Thu, Apr 8, 2021 at 9:59 AM David Woodhouse wrot= e: > > Hm, your description doesn't match the code I see at that link. > >=20 > > You're using GetAdaptersAddresses() which gives you the UP/DOWN status > > as well as the addresses, and you iterate over those. The loop is > >=20 > > =E2=88=80 adapter, =E2=88=80 Unicast address on that adapter: > > Check if it's our Legacy IP or IPv6 address. > >=20 > > That isn't O(n=C2=B2), is it? It's still O(n) of the total number of un= icast > > addresses in the system? >=20 > It's O(n=C2=B2) the number of unicast addresses, because there's an extra= layer=E2=80=A6 >=20 > =E2=88=80 adapter, =E2=88=80 Unicast address on that adapter (iterating= via > GetAdaptersAddresses) > 1. Check if it's using our Legacy IP or IPv6 address. > 2. If yes, then check if the other adapter is UP or non-UP > 3. If non-UP, then=E2=80=A6 > =E2=88=80 Unicast address on the system (iterating via > GetUnicastIpAddressTable(), since the other one maddeningly lacks an > API to delete addresses) > 2. If non-UP, then steal/delete/reclaim the desired address fro= m it. Nah, that doesn't make it O(n=C2=B2) because anything after step 1 doesn't actually happen for *every* address. It only happens for the one or two addresses which match our Legacy IP or IPv6 address. And we *know* there can be only one match for each because that's the whole point of this exercise, right? So it's O(n) for checking all the addresses in the system against our own address(es), then O(n) for each of up to two addresses that get matches. O(3n) is still O(n). And I still think you can fix it just to be O(1n) this way anyway, can't you: > > Alternatively, can't we start with GetUnicastIpAddressTable() as my > > original code did, and if we want to check whether an interface is down > > before we steal the address from it, use GetIfEntry2() to find out? > >=20 > > Using GetIfEntry2() is probably a saner way to find the InterfaceIndex > > for the Wintun itself, which I was dredging the registry for manually. > Let's save the OpenConnect-specific decisions, but=E2=80=A6 >=20 > It seems to me that we've identifying a couple of tasks that many > users of Wintun would need, and which are (in my opinion) quite > tedious to implement robustly in Windows: >=20 > 1. Identifying the =E2=80=9Cinterface index=E2=80=9D of the newly-created= adapter (for > use with 'netsh', etc.). > 2. Reclaiming desired Layer3 (IP) addresses from other non-UP adapters > to which they may already be assigned. >=20 > If the Wintun developers are amenable to it, these both seem like they > could be useful additions to Wintun itself. Along with the driver extension to add headroom/tailroom to TUN_PACKET, I agree. I'd be interested to hear Jason's and Simon's thoughts about those in principle, before we rephrase those suggestions in the form of a pull request. --=-+8H7aFvUOq7S/2qyuKL1 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTkwMTAyMDAwMDAwWhcNMjIwMTAxMjM1 OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRlYWQub3JnMIIBIjANBgkqhkiG9w0B AQEFAAOCAQ8AMIIBCgKCAQEAsv3wObLTCbUA7GJqKj9vHGf+Fa+tpkO+ZRVve9EpNsMsfXhvFpb8 RgL8vD+L133wK6csYoDU7zKiAo92FMUWaY1Hy6HqvVr9oevfTV3xhB5rQO1RHJoAfkvhy+wpjo7Q 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