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Sat, 16 May 2026 01:48:54 -0700 (PDT) Received: from [192.168.1.3] ([213.55.168.64]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45da15a666fsm19176815f8f.36.2026.05.16.01.48.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 16 May 2026 01:48:54 -0700 (PDT) Message-ID: <358e950b-4019-4d47-81a4-0a06dc32be1d@gmail.com> Date: Sat, 16 May 2026 10:48:53 +0200 Precedence: bulk X-Mailing-List: xenomai@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [EVL] Kernel WARNING: notifier callback netevent_handler already registered To: Florian Bezdeka , Philippe Gerum , Tobias Schaffner Cc: xenomai@lists.linux.dev References: <8e08bda6-1fed-4a5a-9bb3-74f019b05855@gmail.com> <87340ij2lx.fsf@xenomai.org> <201a7d9c-e1dc-4686-8a5e-adc7c921ba14@gmail.com> <87jytt34q7.fsf@2a01cb0804738000b42250ae26cae50b.ipv6.abo.wanadoo.fr> <2686ae4a-c63e-418e-8b4a-be49a22db83f@gmail.com> Content-Language: de-CH, en-US From: Hannes Diethelm In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Am 27.04.26 um 11:18 schrieb Florian Bezdeka: > On Sun, 2026-04-26 at 23:32 +0200, Hannes Diethelm wrote: >> Am 26.04.26 um 21:24 schrieb Philippe Gerum: >>> Hannes Diethelm writes: >>> >>>> Am 25.04.26 um 20:50 schrieb Philippe Gerum: >>>>> Hannes Diethelm writes: >>>>> >>>>>> Hello >>>>>> >>>>>> There is a Kernel WARNING: "notifier callback netevent_handler already registered right after boot". It is repeated 5 times. >>>>>> >>>>>> Config: >>>>>> Debian Trixie with xfce4 Desktop >>>>>> libevl: r56 >>>>>> linux-evl: v6.12.67-evl2-rebase >>>>>> >>>>>> I traced the issue already trough the following code: >>>>>> net/core/net_namespace.c:355 >>>>>> kernel/evl/net/net.c:35 >>>>>> kernel/evl/net/ipv4/ipv4.c:41 >>>>>> kernel/evl/net/ipv4/arp.c:323 >>>>>> >>>>>> However, I lack the knowledge to do a proper fix. One way would be to just check in evl_net_init_arp() if it is already >>>>>> registered and don't do it more than once but that doesn't feel right. >>>>> It looks like the system is instantiating multiple network >>>>> namespaces, >>>>> for each of which we set up an ARP front cache by calling >>>>> evl_net_init_arp(). Bad idea to hook a system-wide handler there as >>>>> well. Could you confirm this fix [1] works for you? >>>>> Thanks for reporting this. >>>>> [1] >>>>> https://gitlab.com/Xenomai/xenomai4/linux-evl/-/commit/569beef061321c2c00d775b13ad0aec1a1d2a416 >>>>> >>>> >>>> Thanks, that was fast. The WARNING is gone now. >>>> >>>> But now after just updating to the kernel including your fix, I have a different behavior on >>>> incoming packages. It seams that the default when no filter is set has changed from EVL_RX_SKIP to EVL_RX_ACCEPT. >>>> >>>> linux-evl: v6.12.67-evl2-rebase >>>> -After evl net -ei enp7s0, I can ping another host. >>>> -oob-net-icmp does only receive packages when I use an eBPF filter with EVL_RX_ACCEPT >>>> -After that, ping doesn't work any more >>>> >>>> linux-evl: v6.12.y-cip-evl-rebase >>>> -After evl net -ei enp7s0, I can NOT ping another host. >>>> -oob-net-icmp does receive packages >>>> -If I use an eBPF filter returning EVL_RX_SKIP, I can ping again >>>> >>>> I am not using VLAN's. >>>> >>>> Was that changed on purpose? >>> >>> Yes, this is implemented by this commit [1]. The rationale here is that >>> if you turn on the oob port directly on a base device, then the evl net >>> stack may assume that the device is entirely dedicated to oob traffic, >>> as opposed to enabling such port on some upper device based on the >>> former (e.g. a VLAN interface). As a result, all ingress traffic >>> received by such base device is diverted (RX_ACCEPT) to the evl net >>> stack. >>> >>> [1] https://gitlab.com/Xenomai/xenomai4/linux-evl/-/commit/3026e69cee2a1de047818fa06ad8c44623461a0d >>> >> >> This makes sense. It took me some time to get evl reading packages by >> activating an eBPF filter and it's mostly save to assume that you don't >> have mixed traffic on an real time network interface. With this change, >> a filter is not needed any more. >> >> A bit off topic: >> >> Is there anything like rtping for evl? I have seen oob-net-icmp.c but >> this is answering requests. >> >> In Xenomai3, there is a debian package configuration. Any interest in >> one for libevl? I have one working but it's still very basic. If it's >> presentable, I can send a patch. > > There is a debianization for x4 in xenomai-images already. See [1]. > Can't tell why it hasn't been upstreamed yet. Maybe Tobias or Philippe > can comment on that. > > [1] https://gitlab.com/Xenomai/xenomai-images/-/tree/master/recipes-xenomai/libevl/files/debian Thanks for the hint. This debianization is also basic, looks like it is only built for CI purpose. But it helps to improve my version. There are a few things missing: - Build dependency's - Optional: evl group + udev rules to allow non-root usage - Probably much more for being a install & use debian package