From nobody Tue Aug 5 15:00:29 2025 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4bxGnV0Tsrz63L0g for ; Tue, 05 Aug 2025 15:00:30 +0000 (UTC) (envelope-from ivy@freebsd.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2610:1c1:1:6074::16:84]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "freefall.freebsd.org", Issuer "R11" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4bxGnT5Tkmz3Nf4; Tue, 05 Aug 2025 15:00:29 +0000 (UTC) (envelope-from ivy@freebsd.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1754406029; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6WtV8QyfMBJpNMo64ETDbdnYANgxU5G6GNM8KMQ1F+k=; b=Uov0m3VT8LvPKyxaxcGpe3O/dVWV9Jc0AI8NSBzENcgCofX3EXtkA8pBqarRPm9PGm1nXn MakjHH81CJ1KYjAlO2u4RqDo0hRy12Uu/ZQYEwpmYmkfDYDnB7Vx7BUyU79L7PsOqSw0Tj tTKPzBbnQJf1vMH6ZHx1HF7OQS86RGTk6rVCu5vwMZdyPAovh6xh/zlEyZ0nIt8UYypZn1 MTBAQaBL4cQtQXomZlx350IpIR2ndcHyujKyZFmuxx+u5EiYOXlmaeaKEDhlcGHaP4PWIO JZPaUnXycyJ5j3PzYeRcZEFxb4GlwM6wTDe3Olq+7hEDJnB3sxAihm6/JrdeAA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1754406029; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6WtV8QyfMBJpNMo64ETDbdnYANgxU5G6GNM8KMQ1F+k=; b=gAzVUXzNeqjRetyXLPyrfndKJBKcVBgtrWKL2GI6PY5SLRzvdY0TdzZEMTt8UpzgNCZOso 7+wryPiESuoKF9fdBU7pp4VUctS4t0gAlmQAQPMaElplW8W0cGwZSZ7bQm+oN0AilhORY1 PGp838HYHzziO2VT9OK3Txzo83wLYNZTMfQNzRJumvReTTKhxEptMS49s+sZ/3CeBJe9dR ZYchhSQT9HJMX6yX7QYn7Nek68zMGc7IAEMnF9HmT76Hh9E/Ly8FwEtIZyqWafarvEaXrW NClXeoDUgAkfI703nJuMN+VwJMDV+bmN1Ev0MX3/YeTkCDrwOKhWAmCG2ThqrA== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1754406029; a=rsa-sha256; cv=none; b=Zt/GFg8YCS/CHGa/+xJdosKkdNHElHs3OxEOrUzsygS4GOLZAhHqEao4k5fj5uJ89XtC3M KAdpVZXO8w9swhSvm+89Sp3bHCoYBJLM1zHSwzotNPF3zAx82wTuVCrIlbwvpGjVL84Y5a YnxZeWCvippmemO2z2GZ4pCb0p9VpFodyDnaSWvnAV9fbg/LY/vdFANIZsbF6+1Gt+JkGr ppXOqsxavhiG1ICKchEUy1N90yK7OwP8RgOBP01UtOW1eAznOGMepyQTmrP2eQ+ODX1Ko5 P2ZKm+s6lDtdti7ViWkbE2Wqy7kqH3A43mxVI3Knsyi2KDGO8/ne4XLhg0yAew== Received: by freefall.freebsd.org (Postfix, from userid 1532) id 926C4E993; Tue, 05 Aug 2025 15:00:29 +0000 (UTC) Date: Tue, 5 Aug 2025 16:00:29 +0100 From: Lexi Winter To: Felix Cc: freebsd-net@freebsd.org Subject: Re: Source address selection failure when using RFC5549-style (v4-via-v6) routes Message-ID: Mail-Followup-To: Felix , freebsd-net@freebsd.org References: List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@FreeBSD.org MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="pXIecegGtuzM2uyz" Content-Disposition: inline In-Reply-To: --pXIecegGtuzM2uyz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Felix: > I've been experimenting a bit with routing IPv4 via IPv6 next-hops, >[...] > What I've discovered: trying to /originate/ a connection from a machine with > such a route doesn't seem to work properly. you can fix this by assigning your IPv4 loopback address to every interface with such a route: ifconfig ix0 inet 192.168.0.1/32 ifconfig ix1 inet 192.168.0.1/32 ifconfig ix2 inet 192.168.0.1/32 ... after doing that, you need to re-install any routes via these interfaces to pick up the new source address. > I'm not sure what the right thing for FreeBSD to do in this circumstance is. > What do you think? i prefer the Linux behaviour. however, when i've raised this in the past it seems like this opinion is far from universal. as this matches historical behaviour for legacy IP and there is a workaround, i'm not sure it's important enough to fix. > I also haven't tested whether this same issue affects the generation of ICMP > responses (e.g. TTL expired, packet too big). If it does, that seems like > much more of a concern for using FreeBSD on real routers. it does. the host will send ICMP errors from 0.0.0.0 unless you apply the workaround above. --pXIecegGtuzM2uyz Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQSyjTg96lp3RifySyn1nT63mIK/YAUCaJIciQAKCRD1nT63mIK/ YJq/AP9Yslk98rNbA6HEVa99KHNA//RRv4l14TYsHIzNKhwUrAEA6mql+Dqinkku uUBTPcmgHm4cfO0jdXrI+1j6OZ1iOQM= =6kOE -----END PGP SIGNATURE----- --pXIecegGtuzM2uyz--