From 9d5ef190e5615a7b63af89f88c4106a5bc127974 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Fri, 5 Feb 2021 15:37:10 +0200 Subject: [PATCH] net: dsa: automatically bring up DSA master when opening user port 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) knocking at an open door. Even if there still was an issue with promiscuity while down, DSA could still just open the master and avoid it. 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. Tested with two cascaded DSA switches: $ ip link set sw0p2 up fsl_enetc 0000:00:00.2 eno2: configuring for fixed/internal link mode fsl_enetc 0000:00:00.2 eno2: Link is Up - 1Gbps/Full - flow control rx/tx mscc_felix 0000:00:00.5 swp0: configuring for fixed/sgmii link mode mscc_felix 0000:00:00.5 swp0: Link is Up - 1Gbps/Full - flow control off 8021q: adding VLAN 0 to HW filter on device swp0 sja1105 spi2.0 sw0p2: configuring for phy/rgmii-id link mode IPv6: ADDRCONF(NETDEV_CHANGE): eno2: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): swp0: link becomes ready Signed-off-by: Vladimir Oltean Reviewed-by: Andrew Lunn Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski --- Documentation/networking/dsa/dsa.rst | 4 ---- net/dsa/slave.c | 7 +++++-- 2 files changed, 5 insertions(+), 6 deletions(-) --- a/Documentation/networking/dsa/dsa.rst +++ b/Documentation/networking/dsa/dsa.rst @@ -273,10 +273,6 @@ will not make us go through the switch t 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 ================================== --- a/net/dsa/slave.c +++ b/net/dsa/slave.c @@ -68,8 +68,11 @@ static int dsa_slave_open(struct net_dev struct dsa_port *dp = dsa_slave_to_port(dev); int err; - if (!(master->flags & IFF_UP)) - return -ENETDOWN; + err = dev_open(master, 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);