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[5.12.227.87]) by smtp.gmail.com with ESMTPSA id ko23sm115897ejc.35.2021.01.26.17.00.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Jan 2021 17:00:42 -0800 (PST) From: Vladimir Oltean To: "David S . Miller" , Jakub Kicinski , netdev@vger.kernel.org Cc: Andrew Lunn , Florian Fainelli , Vivien Didelot , Hideaki YOSHIFUJI Subject: [PATCH net-next 1/4] net: dsa: automatically bring up DSA master when opening user port Date: Wed, 27 Jan 2021 03:00:25 +0200 Message-Id: <20210127010028.1619443-2-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210127010028.1619443-1-olteanv@gmail.com> References: <20210127010028.1619443-1-olteanv@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Vladimir Oltean DSA wants the master interface to be open before the user port is due to historical reasons. The promiscuity of interfaces that are down used to have issues, as referenced Lennert Buytenhek in commit df02c6ff2e39 ("dsa: fix master interface allmulti/promisc handling"). The bugfix mentioned there, commit b6c40d68ff64 ("net: only invoke dev->change_rx_flags when device is UP"), was basically a "don't do that" approach to working around the promiscuity while down issue. Further work done by Vlad Yasevich in commit d2615bf45069 ("net: core: Always propagate flag changes to interfaces") has resolved the underlying issue, and it is strictly up to the DSA and 8021q drivers now, it is no longer mandated by the networking core that the master interface must be up when changing its promiscuity. >From DSA's point of view, deciding to error out in dsa_slave_open because the master isn't up is (a) a bad user experience and (b) missing the forest for the trees. Even if there still was an issue with promiscuity while down, DSA could still do this and avoid it: open the DSA master manually, then do whatever. Voila, the DSA master is now up, no need to error out. Doing it this way has the additional benefit that user space can now remove DSA-specific workarounds, like systemd-networkd with BindCarrier: https://github.com/systemd/systemd/issues/7478 And we can finally remove one of the 2 bullets in the "Common pitfalls using DSA setups" chapter. Signed-off-by: Vladimir Oltean --- Documentation/networking/dsa/dsa.rst | 4 ---- net/dsa/slave.c | 10 ++++++++-- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/Documentation/networking/dsa/dsa.rst b/Documentation/networking/dsa/dsa.rst index a8d15dd2b42b..e9517af5fe02 100644 --- a/Documentation/networking/dsa/dsa.rst +++ b/Documentation/networking/dsa/dsa.rst @@ -273,10 +273,6 @@ will not make us go through the switch tagging protocol transmit function, so the Ethernet switch on the other end, expecting a tag will typically drop this frame. -Slave network devices check that the master network device is UP before allowing -you to administratively bring UP these slave network devices. A common -configuration mistake is forgetting to bring UP the master network device first. - Interactions with other subsystems ================================== diff --git a/net/dsa/slave.c b/net/dsa/slave.c index f2fb433f3828..393294a53834 100644 --- a/net/dsa/slave.c +++ b/net/dsa/slave.c @@ -68,8 +68,14 @@ static int dsa_slave_open(struct net_device *dev) struct dsa_port *dp = dsa_slave_to_port(dev); int err; - if (!(master->flags & IFF_UP)) - return -ENETDOWN; + if (!(master->flags & IFF_UP)) { + err = dev_change_flags(master, master->flags | IFF_UP, NULL); + if (err < 0) { + netdev_err(dev, "failed to open master %s\n", + master->name); + goto out; + } + } if (!ether_addr_equal(dev->dev_addr, master->dev_addr)) { err = dev_uc_add(master, dev->dev_addr); -- 2.25.1