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Thu, 10 Jul 2025 07:17:01 -0700 (PDT) Received: from localhost.localdomain ([45.128.133.228]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454d5133183sm60150125e9.40.2025.07.10.07.16.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Jul 2025 07:17:01 -0700 (PDT) Date: Thu, 10 Jul 2025 16:16:48 +0200 From: Oscar Maes To: Jakub Kicinski Cc: netdev@vger.kernel.org, davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2 1/2] net: ipv4: fix incorrect MTU in broadcast routes Message-ID: <20250710141648-oscmaes92@gmail.com> References: <20250703152838.2993-1-oscmaes92@gmail.com> <20250708185430.68f143a2@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: <20250708185430.68f143a2@kernel.org> On Tue, Jul 08, 2025 at 06:54:30PM -0700, Jakub Kicinski wrote: > On Thu, 3 Jul 2025 17:28:37 +0200 Oscar Maes wrote: > > if (type == RTN_BROADCAST) { > > flags |= RTCF_BROADCAST | RTCF_LOCAL; > > - fi = NULL; > > } else if (type == RTN_MULTICAST) { > > flags |= RTCF_MULTICAST | RTCF_LOCAL; > > if (!ip_check_mc_rcu(in_dev, fl4->daddr, fl4->saddr, > > Not super familiar with this code, but do we not need to set > do_cache = false; ? I'm guessing cache interactions may have > been the reason fib_info was originally cleared, not sure if > that's still relevant.. > > I'd also target this at net-next, unless you can pinpoint > some kernel version where MTU on bcast routes worked.. > -- > pw-bot: cr The caching mechanism was introduced after this line, back when nhc was embedded in fib_info. (see https://lore.kernel.org/netdev/20120720.142612.691540831359186107.davem@davemloft.net/) I'll resend to net-next.