From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=d49o+MXC; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTPS id 243745A0262 for ; Wed, 27 May 2026 21:39:10 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1779910749; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6uKM4+mvqtH4QcSdugjqV2MaHidb4KWeaq+SwuPN3n0=; b=d49o+MXCxv3x4Ce98/TwDVLActfsbSQCZS2ld489AL9bJPDQVN/Sc5u+5RLnikfQaOLfAu S4xoyPzYJINdoVJ8LCRvk+MroR4lqbxhOmoJphPhvU37J0TLreGajzc5lIuwBelBHSDovm ZrBa5afAHz/4iK8TJyJv/V1Ct+j7rJo= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-614-WOnrotAqNIemcxadmtcnuA-1; Wed, 27 May 2026 15:39:06 -0400 X-MC-Unique: WOnrotAqNIemcxadmtcnuA-1 X-Mimecast-MFC-AGG-ID: WOnrotAqNIemcxadmtcnuA_1779910745 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-45e78dd7baaso9739249f8f.0 for ; Wed, 27 May 2026 12:39:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779910745; x=1780515545; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=6uKM4+mvqtH4QcSdugjqV2MaHidb4KWeaq+SwuPN3n0=; b=F9TbhhlNMgMf+qTDVVIy4I+2T2bwd2LqgJrhRiMCcmfVdqVEb5mvMK8FDRLgg1MMbC epStr1NYWfAc8eeVemcKFtblpeaBRbbES0s1p8xEE3+gMlUOyv+CgmvWZ1zqRWcx7lkC aUFP4pGXbxmoa1wLBO8NTSGsE6cSXZ6FnLwUZxpHauAWf+hV8jHti2p4kZbu6Eh8zYX2 dzIDW++K92EQB28PN17pHbSH06JG4+wPzgNxUFdhMjVBQrWgvSvcQ2AWqG1Zh+M4xpR2 4yqn9fw0gDaDrHa0kLcF04Ky0RjDhwRznqXewMg38eC5t8seBvPwWDfdJRRuV634ePMj G4qQ== X-Forwarded-Encrypted: i=1; AFNElJ8YdgoKauaas/6fZVLWoXCDu6ojPVS93dgGudMpC1Hul7km6oaMPGZ2kXV6jySQT8nCl30S1R2Ikg8=@passt.top X-Gm-Message-State: AOJu0YxOhejJO9ntUfktx0IzwvRqNCA/rfZEi1VwWe3pmAW6FQIjQZoW fviByd5aj0tODiCKZAkOmnu8zRPweIIsZhVtxawmBk6yYiGUkc5Lutu6j7KkRO1joreoqsFDUWE H2qMfr6+U/D7ACaHe/od3aw+G4VOLQHYBmdJH92GvEuMzJEr8PeKaaA== X-Gm-Gg: Acq92OFomdW+w4pS8/rJisocPfftx92Q1Yqxc16St1MO2PY4qIOZB4R0XbDs0hjMX3h DivnlMDOyzTU5K3d4+TxSBj2lKjGk/2Cdchs0gnl9LbDlQLqUMNLL0EHqxeMzmL7tCvT58CukTm wgeipa9MbEg8tZgVLdlte2KMjKGxEnCaYYvCzuxyH9UndKPuVWE/RgpFpQDvnAZx+5zfVhTdLAE ci96hCKE4nB+S03yhOmdUuoKjxMfMYHRHW4mmyzf83p25dN7SnfSg+jFNuO4KIvCs4b6vvXcggo 0SQ5pivNu9z5Ol4J3wIdVV3JL28mmMWF29YV4OK8U8fC2KI3ePoChp1c1V3yzjL0gIxSuY4pF+Z SkYOF/CCDux78SqX/jDEvvmYHhFG3iBWifcEtTA== X-Received: by 2002:a05:600c:3b8c:b0:490:480e:266 with SMTP id 5b1f17b1804b1-490480e02eemr438247475e9.26.1779910745266; Wed, 27 May 2026 12:39:05 -0700 (PDT) X-Received: by 2002:a05:600c:3b8c:b0:490:480e:266 with SMTP id 5b1f17b1804b1-490480e02eemr438247115e9.26.1779910744819; Wed, 27 May 2026 12:39:04 -0700 (PDT) Received: from [192.168.188.22] ([80.243.52.133]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4908b427d71sm2811595e9.0.2026.05.27.12.39.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 May 2026 12:39:04 -0700 (PDT) Message-ID: Date: Wed, 27 May 2026 21:39:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Startup fd to avoid busywaits To: Lisanna Dettwyler , passt-dev@passt.top References: From: Paul Holzinger In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: vKxyo25vQW7KFe-MoK6LKh9zNDz5uuSUaWWjbfnkBOk_1779910745 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: RVF47JMYP3KODZICF2TOWWF5OZDNLX7K X-Message-ID-Hash: RVF47JMYP3KODZICF2TOWWF5OZDNLX7K X-MailFrom: pholzing@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 X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Hi, On 27/05/2026 19:08, Lisanna Dettwyler wrote: > Hello! I would like to propose a patch that allows the invoker to pass > a "ready fd" on startup that gets written to once the setup has been > completed, similar to slirp4netns's `--ready-fd` flag. Currently we > have to poll the interface in a loop to wait for setup to be > completed, and it would be much better if we could instead block on fd > activity. > > Just wanted to check if such a contribution would be welcome before > putting in the work of authoring it, or if there's already a better > way to wait for the interface to come up. This is our current > implementation: > https://github.com/NixOS/nix/pull/15919/changes#diff-2a9176262efad1ef345d882b0779646e7a5aaf9ca8db33e9da7fc408594b5377R94-R125 > I am not a pasta maintainer but this is rather simple as we do it in podman. By default pasta forks into the background, when the parent exists the child is ready for connections. So all you need to do is fork/exec and then wait for the exit, that way you also get easily the exit code to know if the setup failed and can read the stderr for errors. From your linked code I see the use of --foreground so the question would be why are you using this over the default? -- Paul Holzinger