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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conflicting, publication has already been withdrawn by the other node.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>
79 lines
3.1 KiB
C
79 lines
3.1 KiB
C
/*
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* net/tipc/name_distr.h: Include file for TIPC name distribution code
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*
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* Copyright (c) 2000-2006, Ericsson AB
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* Copyright (c) 2005, Wind River Systems
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the names of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* Alternatively, this software may be distributed under the terms of the
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* GNU General Public License ("GPL") version 2 as published by the Free
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* Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _TIPC_NAME_DISTR_H
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#define _TIPC_NAME_DISTR_H
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#include "name_table.h"
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#define ITEM_SIZE sizeof(struct distr_item)
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/**
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* struct distr_item - publication info distributed to other nodes
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* @type: name sequence type
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* @lower: name sequence lower bound
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* @upper: name sequence upper bound
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* @ref: publishing port reference
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* @key: publication key
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*
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* ===> All fields are stored in network byte order. <===
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*
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* First 3 fields identify (name or) name sequence being published.
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* Reference field uniquely identifies port that published name sequence.
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* Key field uniquely identifies publication, in the event a port has
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* multiple publications of the same name sequence.
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*
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* Note: There is no field that identifies the publishing node because it is
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* the same for all items contained within a publication message.
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*/
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struct distr_item {
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__be32 type;
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__be32 lower;
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__be32 upper;
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__be32 ref;
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__be32 key;
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};
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struct sk_buff *tipc_named_publish(struct publication *publ);
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struct sk_buff *tipc_named_withdraw(struct publication *publ);
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void named_cluster_distribute(struct sk_buff *buf);
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void tipc_named_node_up(u32 dnode);
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void tipc_named_rcv(struct sk_buff *buf);
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void tipc_named_reinit(void);
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void tipc_named_process_backlog(void);
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#endif
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