On Tue, Apr 28, 2015 at 12:37 PM, Scott Feldman <sfel...@gmail.com> wrote: > 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().
Yes, IFF_DORMANT does seem close to what is needed; in the current/standard interpretation IFF_DORMANT keeps the switch port phy-up and running (and most PDUs are also exchanged in the dormant state). Like you said we could re-interpret IFF_DORMANT in this context to phy-down the switch-port; unfortunately we are already using IFF_DORMANT as well (in its standard interpretation)... We are using the dormant mode (for the MLAG app itself) to hold the MLAG port in a brief/transition-ary suspended state when the switch-port link/carrier up happens. This has been done to co-ordinate states across the MLAG peer switches and to ensure that egress port block masks are programmed on the peer switch before transitioning the local switch port to an OPER_UP state. If we didn't do that the dual-connected server would see duplicate packets every time a link-down to link-up happened on a MLAG port. So IFF_DORMANT re-interpretation is not going to be easily possible for the MLAG use case. -- 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
