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. One such use case is the multi-chassis LAG application - 1. The MLAG application runs on peer switches (say Switch0 and Switch1) synchronizing states, forwarding entries etc. between the two switches over the peer-link (this is a link directly connecting the two switches). 2. An MLAG election process designates one of the switches as a primary (for e.g. Switch0 is primary and Switch1 is secondary). 3. The peer link plays a critical role in allowing Switch0-Switch1 to function as a single LAG partner to the downstream dual-connected servers. When the peer-link between the switches goes down we have a split-brain situation. Switch0 and Switch1 are no longer in sync and are acting independently. This can result in traffic loops and traffic black-holing in the network. 4. To prevent these problems the MLAG application on the secondary switch phy-downs the MLAG ports on detecting the peer-link down. This will be seen as a carrier down on servers that are dual-connected to Switch0 and Switch1. 5. Specifically a dual-connected server will see a carrier-down on the port connected to the MLAG secondary, Switch1, and will stop using that port for traffic TX. So traffic black holing is prevented. v6 to v7: Removed some unnecessary code in response to review comments. v5 to v6: Replaced proto_flags with a simple proto_down boolean attribute in response to Dave's comments. v4 to v5: Changed the ip link display format for protodown to match the set as recommended by Stephen. v3 to v4: I have moved protodown out of IFF_XXX and introduced a separate proto_flags field with IF_PROTOF_DOWN bit being used by apps to notify switch port errors. This is in response to Stephen's comments that adding a new IFF_XXX may break user space. I have used rocker as the sample switch driver. And to test this functionality I used the qemu-rocker patch that Scott sent out in response to the v3 posting (needed to set link up/down when phy is enabled/disabled). v1 to v2: Based on Dave's suggestion I have moved out aggregating of error bits across applications to a user space framework. This patch now simply notifies an aggregated error bit to drivers enabling them to handle the error gracefully. Anuradha Karuppiah (4): net core: Add protodown support. netlink: changes for setting and clearing protodown via netlink. rocker: Handle protodown notifications. ip link: proto_down config and display. Signed-off-by: Anuradha Karuppiah <anurad...@cumulusnetworks.com> Signed-off-by: Andy Gospodarek <go...@cumulusnetworks.com> Signed-off-by: Roopa Prabhu <ro...@cumulusnetworks.com> Signed-off-by: Wilson Kok <w...@cumulusnetworks.com> drivers/net/ethernet/rocker/rocker.c | 19 ++++++++++++++++++- include/linux/netdevice.h | 14 ++++++++++++++ include/uapi/linux/if_link.h | 1 + net/core/dev.c | 20 ++++++++++++++++++++ net/core/net-sysfs.c | 14 ++++++++++++++ net/core/rtnetlink.c | 16 ++++++++++++++-- 6 files changed, 81 insertions(+), 3 deletions(-) -- 1.7.10.4 -- 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
