From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bregans-1.gladserv.net (bregans-1.gladserv.net [185.128.211.58]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD72C242D8D; Sat, 23 Aug 2025 12:24:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.128.211.58 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755951894; cv=none; b=O9IkNI6Z6PTStsbH+P3n/IrG09SWVJ0I+qEkp5PTCDVbSwO6qBqloe0Pzf3E58buOCHt/4iFuoIxOG2qOIHWeOXSxg4joIfEghuSoP0XpHR1YYQYDJPbtJSMDXK8GMT4kyjXSFU6t/jqfGC1A4MenISkZXcnYXxH8ymNtkvjN48= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755951894; c=relaxed/simple; bh=c7VGgCZa6f+HzVnoJzeCjnygZt875/U69l5XA+/hQEI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ME62g+HtBaep0bWZacx6hps0Qy9LWRjdBpmPGJXSDTiHFhkcm7vQmUcrvZ+IVJRtq+yO3ZwBnqGlGstaUy3cenXO0jBT2grcA2+WZa3F9QC0uXU/+z0/VYNWuR0TncODOx15BE8WKAvXHxwWvBXoGuhbCwooqufutDKdF2hODCg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=librecast.net; spf=pass smtp.mailfrom=librecast.net; arc=none smtp.client-ip=185.128.211.58 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=librecast.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=librecast.net Date: Sat, 23 Aug 2025 14:24:39 +0200 From: Brett Sheffield To: Jakub Kicinski Cc: regressions@lists.linux.dev, netdev@vger.kernel.org, stable@vger.kernel.org, davem@davemloft.net, dsahern@kernel.org, oscmaes92@gmail.com Subject: Re: [REGRESSION][BISECTED][PATCH] net: ipv4: fix regression in broadcast routes Message-ID: References: <20250822165231.4353-4-bacs@librecast.net> <20250822183250.2a9cb92c@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250822183250.2a9cb92c@kernel.org> On 2025-08-22 18:32, Jakub Kicinski wrote: > Thanks for bisecting and fixing! > > > The broadcast_pmtu.sh selftest provided with the original patch still > > passes with this patch applied. > > Hm, yes, AFACT we're losing PMTU discovery but perhaps original commit > wasn't concerned with that. Hopefully Oscar can comment. Indeed. This takes it back to the previous behaviour. > On Fri, 22 Aug 2025 16:50:51 +0000 Brett A C Sheffield wrote: > > + if (type == RTN_BROADCAST) { > > + /* ensure MTU value for broadcast routes is retained */ > > + ip_dst_init_metrics(&rth->dst, res->fi->fib_metrics); > > You need to check if res->fi is actually set before using it Ah, yes. Fixed. > Could you add a selftest / test case for the scenario we broke? > selftests can be in C / bash / Python. If bash hopefully socat > can be used to repro, cause it looks like wakeonlan is not very > widely packaged. Self-test added using socat as requested. If you want this wrapped in namespaces etc. let me know. I started doing that, but decided a simpler test without requiring root was better and cleaner. Thanks for the review Jakub. v2 patches sent. Cheers, Brett -- Brett Sheffield (he/him) Librecast - Decentralising the Internet with Multicast https://librecast.net/ https://blog.brettsheffield.com/