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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4325c052d34sm15047458f8f.25.2025.12.22.14.51.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Dec 2025 14:51:18 -0800 (PST) Date: Mon, 22 Dec 2025 23:51:17 +0100 From: Stefano Brivio To: Felix Rubio Subject: Re: Connecting back to the host through a dummy veth interface Message-ID: <20251222235117.2264ae71@elisabeth> In-Reply-To: <2379954.irdbgypaU6@altair> References: <176606116131.2775.3279769610610037541@maja> <5105334.31r3eYUQgx@altair> <20251221114722.2a613e94@elisabeth> <2379954.irdbgypaU6@altair> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: lp2gi6KVkM5HOJpkCpSERu8fURcXGA7ypuX2GKvJ8rE_1766443880 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: VASENHKA36RN4DFIGLWYVAGHIFPW35W3 X-Message-ID-Hash: VASENHKA36RN4DFIGLWYVAGHIFPW35W3 X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-user@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: "For passt users: support, questions and answers" Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Mon, 22 Dec 2025 13:48:03 +0100 Felix Rubio wrote: > Ok, things are starting to get clear. The problem was, I think, between the > desk and the keyboard. The chair! I think it was the chair. :) > * I have everything on a VM that I configure with Ansible. I have just taken > everything down and started from scratch > > * I still have my containers without any ad-hoc network. They are binding only > to network interface 10.255.255.1, which is a dummy ethernet. > > * My error was that I am running an LDAP server in one of these containers, > and I was checking if it was working with a ldapwhoami. The client was > replying that could not reach the server, which triggered all subsequent > investigation, but the real cause was that the certificate offered by the server > was not trusted by the client, and the latter broke the connection (without > giving a more proper message - facepalm). > > Once fixed the problem with the certificates, everything seems to work. This > means that: > * I have a dns server in 10.255.255.1 that resolves ldap.host.internal to > 10.255.255.1 > * ldap server rootless container is listening to 10.255.255.1:1636 > * ldap client is in another rootless container, and can reach directly > ldap.host.internal:1636. > > ... Is this last point expected? the ldap server is started through podman as > a regular user, without any network options... nothing fancy. Yes, it's expected, because 10.255.255.1 is not a loopback address. > The reason for me asking is that all I have read points in the direction that > from a rootless container I should not be able to loopback to the host... but > maybe this dummy interface is not identified as "the host" and therefore I can It's rather not identified as "loopback". > connect to services bound to it? On the LDAP side, the logs show that these > connections are coming from the same 10.255.255.1. That would be actually > convenient, because then I can put firewall rules in place that prevent > connecting from that dummy ethernet back to the host at all. You don't need a whole new interface for that, by the way. You could just add that address to an existing interface, assuming that the LDAP server lets you bind to a specific address and not just a specific interface. -- Stefano