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2014-09-02tipc: add name distributor resiliency queueErik Hugne1-0/+7
TIPC name table updates are distributed asynchronously in a cluster, entailing a risk of certain race conditions. E.g., if two nodes simultaneously issue conflicting (overlapping) publications, this may not be detected until both publications have reached a third node, in which case one of the publications will be silently dropped on that node. Hence, we end up with an inconsistent name table. In most cases this conflict is just a temporary race, e.g., one node is issuing a publication under the assumption that a previous, conflicting, publication has already been withdrawn by the other node. However, because of the (rtt related) distributed update delay, this may not yet hold true on all nodes. The symptom of this failure is a syslog message: "tipc: Cannot publish {%u,%u,%u}, overlap error". In this commit we add a resiliency queue at the receiving end of the name table distributor. When insertion of an arriving publication fails, we retain it in this queue for a short amount of time, assuming that another update will arrive very soon and clear the conflict. If so happens, we insert the publication, otherwise we drop it. The (configurable) retention value defaults to 2000 ms. Knowing from experience that the situation described above is extremely rare, there is no risk that the queue will accumulate any large number of items. Signed-off-by: Erik Hugne <erik.hugne@ericsson.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-06-18tipc: change socket buffer overflow control to respect sk_rcvbufYing Xue1-0/+64
As per feedback from the netdev community, we change the buffer overflow protection algorithm in receiving sockets so that it always respects the nominal upper limit set in sk_rcvbuf. Instead of scaling up from a small sk_rcvbuf value, which leads to violation of the configured sk_rcvbuf limit, we now calculate the weighted per-message limit by scaling down from a much bigger value, still in the same field, according to the importance priority of the received message. To allow for administrative tunability of the socket receive buffer size, we create a tipc_rmem sysctl variable to allow the user to configure an even bigger value via sysctl command. It is a size of three (min/default/max) to be consistent with things like tcp_rmem. By default, the value initialized in tipc_rmem[1] is equal to the receive socket size needed by a TIPC_CRITICAL_IMPORTANCE message. This value is also set as the default value of sk_rcvbuf. Originally-by: Jon Maloy <jon.maloy@ericsson.com> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Jon Maloy <jon.maloy@ericsson.com> [Ying: added sysctl variation to Jon's original patch] Signed-off-by: Ying Xue <ying.xue@windriver.com> [PG: don't compile sysctl.c if not config'd; add Documentation] Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>