On Tue, Apr 28, 2015 at 8:39 AM, Anuradha Karuppiah <anurad...@cumulusnetworks.com> wrote: > > > On Mon, Apr 27, 2015 at 10:45 PM, Scott Feldman <sfel...@gmail.com> wrote: >> >> On Mon, Apr 27, 2015 at 10:38 AM, <anurad...@cumulusnetworks.com> wrote: >> > From: Anuradha Karuppiah <anurad...@cumulusnetworks.com> >> > >> > User space daemons can detect errors in the network that need to be >> > notified to the switch device drivers. >> > >> > Drivers can react to this error state by doing a phy-down on the >> > switch-port which would result in a carrier-off locally and on the >> > directly connected switch. Doing that would prevent loops and >> > black-holes in the network. >> >> (Sorry if this was asked earlier) >> >> Can the application simply send a SETLINK with IFF_UP clear and the >> port driver's ndo_stop would bring the PHY link down? > > > Yes, Clearing IFF_UP on detecting errors (PROTO_DOWN) is possible and we > tried > that implementation as well. Unfortunately it failed because of the > following > reasons - > > 1. There is no way to disambiguate between admin_down (!IFF_UP) and an > APP/driver enforced error_down (IFF_PROTO_DOWN). Administrator or > automation-scripts that monitor the config assumed that switch-port > configuration had somehow fallen out of sync (and attempted to reinstate the > admin_up repeatedly). > > 2. Automatic error recovery was not possible; consider the following > scenario > for e.g. > a. The MLAG peer-link is down so the MLAG app on the secondary switch has > proto_down’ed all the MLAG ports (including switch-port swp1) by > clearing > IFF_UP. > b. At the same time the administrator is in the process of making some > changes on the network connected to swp1. To avoid doing it live he > would > admin_disable swp1 (!IFF_UP) by doing an "ip link set swp1 down" (this > is a no-op as event #a has already cleared IFF_UP on swp1). > c. If the MLAG peer-link recovers at this point the MLAG app on the > secondary switch would try to automatically recover the MLAG ports > by clearing proto_down (i.e. setting IFF_UP); including on swp1. Doing > that overrides the administrator’s directive to keep swp1 admin_down. > Overriding an admin-down in a live network can be very dangerous so it > is not possible to do auto-error-recovery unless we have a way to > disambiguate between the admin and error states
That makes sense. Dang, this is so close to IFF_DORMANT. The interface can be IFF_UP and link mode can be DORMANT. Can the port driver kill PHY link if dev->flags&IFF_DORMANT in ndo_set_rx_mode()? Would require IFF_DORMANT is included in dev->flags in __dev_change_flags(). -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
