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([2a01:e0a:b41:c160:4d92:8b8b:5889:ee2f]) by smtp.gmail.com with ESMTPSA id e8-20020a056000178800b00203da3bb4d2sm30687730wrg.41.2022.04.11.09.27.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Apr 2022 09:27:54 -0700 (PDT) Message-ID: <686bf021-e6a4-c77a-33c9-5b01481e12f4@6wind.com> Date: Mon, 11 Apr 2022 18:27:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Reply-To: nicolas.dichtel@6wind.com Subject: Re: What is the purpose of dev->gflags? Content-Language: en-US To: Vladimir Oltean Cc: Jakub Kicinski , netdev@vger.kernel.org, "David S. Miller" , Paolo Abeni References: <20220408183045.wpyx7tqcgcimfudu@skbuf> <20220408115054.7471233b@kernel.org> <20220408191757.dllq7ztaefdyb4i6@skbuf> <797f525b-9b85-9f86-2927-6dfb34e61c31@6wind.com> <20220411153334.lpzilb57wddxlzml@skbuf> <20220411154911.3mjcprftqt6dpqou@skbuf> <41a58ead-9a14-c061-ee12-42050605deff@6wind.com> <20220411162016.sau3gertosgr6mtu@skbuf> From: Nicolas Dichtel Organization: 6WIND In-Reply-To: <20220411162016.sau3gertosgr6mtu@skbuf> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Le 11/04/2022 à 18:20, Vladimir Oltean a écrit : > On Mon, Apr 11, 2022 at 06:10:49PM +0200, Nicolas Dichtel wrote: >> >> Le 11/04/2022 à 17:49, Vladimir Oltean a écrit : >>> On Mon, Apr 11, 2022 at 05:43:01PM +0200, Nicolas Dichtel wrote: >>>> >>>> Le 11/04/2022 à 17:33, Vladimir Oltean a écrit : >>>> [snip] >>>>> Would you agree that the __dev_set_allmulti() -> __dev_notify_flags() >>>>> call path is dead code? If it is, is there any problem it should be >>>>> addressing which it isn't, or can we just delete it? >>>> I probably miss your point, why is it dead code? >>> >>> Because __dev_set_allmulti() doesn't update dev->gflags, it means >>> dev->gflags == old_gflags. In turn, it means dev->gflags ^ old_gflags, >>> passed to "gchanges" of __dev_notify_flags(), is 0. >> I didn't take any assumptions on dev->gflags because two functions are called >> with dev as parameter (dev_change_rx_flags() and dev_set_rx_mode()). > > You mean ops->ndo_change_rx_flags() or ops->ndo_set_rx_mode() are > expected to update dev->gflags? No, I just say that I didn't take any assumptions on what there are expected to do. > >> Even if __dev_notify_flags() is called with 0 for the last arg, it calls >> notifiers. Thus, this is not "dead code". > > The relevant "changes" (dev->flags & old_flags) of the net_device which > may have changed from __dev_set_allmulti() are masked out from > call_netdevice_notifiers(), are they not? > > if (changes & IFF_UP) { > /* doesn't apply */ > } > > if (dev->flags & IFF_UP && > (changes & ~(IFF_UP | IFF_PROMISC | IFF_ALLMULTI | IFF_VOLATILE))) { > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > these changes are masked out Same here. Some complex path are called (eg. dev_change_rx_flags => ops->ndo_change_rx_flags() => vlan_dev_change_rx_flags => dev_set_allmulti => __dev_set_allmulti => etc). Maybe you made an audit to check that other flags cannot be changed. But, if it changes in the future, we will miss them here. Did you see a bug? What is the issue?