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b4b5610223
linux/net/tipc/node.h
Allan Stephens b4b5610223 tipc: Ensure both nodes recognize loss of contact between them 
Enhances TIPC to ensure that a node that loses contact with a
neighboring node does not allow contact to be re-established until
it sees that its peer has also recognized the loss of contact.

Previously, nodes that were connected by two or more links could
encounter a situation in which node A would lose contact with node B
on all of its links, purge its name table of names published by B,
and then fail to repopulate those names once contact with B was restored.
This would happen because B was able to re-establish one or more links
so quickly that it never reached a point where it had no links to A --
meaning that B never saw a loss of contact with A, and consequently
didn't re-publish its names to A.

This problem is now prevented by enhancing the cleanup done by TIPC
following a loss of contact with a neighboring node to ensure that
node A ignores all messages sent by B until it receives a LINK_PROTOCOL
message that indicates B has lost contact with A, thereby preventing
the (re)establishment of links between the nodes. The loss of contact
is recognized when a RESET or ACTIVATE message is received that has
a "redundant link exists" field of 0, indicating that B's sending link
endpoint is in a reset state and that B has no other working links.

Additionally, TIPC now suppresses the sending of (most) link protocol
messages to a neighboring node while it is cleaning up after an earlier
loss of contact with that node. This stops the peer node from prematurely
activating its link endpoint, which would prevent TIPC from later
activating its own end. TIPC still allows outgoing RESET messages to
occur during cleanup, to avoid problems if its own node recognizes
the loss of contact first and tries to notify the peer of the situation.

Finally, TIPC now recognizes an impending loss of contact with a peer node
as soon as it receives a RESET message on a working link that is the
peer's only link to the node, and ensures that the link protocol
suppression mentioned above goes into effect right away -- that is,
even before its own link endpoints have failed. This is necessary to
ensure correct operation when there are redundant links between the nodes,
since otherwise TIPC would send an ACTIVATE message upon receiving a RESET
on its first link and only begin suppressing when a RESET on its second
link was received, instead of initiating suppression with the first RESET
message as it needs to.

Note: The reworked cleanup code also eliminates a check that prevented
a link endpoint's discovery object from responding to incoming messages
while stale name table entries are being purged. This check is now
unnecessary and would have slowed down re-establishment of communication
between the nodes in some situations.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-09-17 22:55:03 -04:00

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/*
* net/tipc/node.h: Include file for TIPC node management routines
*
* Copyright (c) 2000-2006, Ericsson AB
* Copyright (c) 2005, 2010-2011, Wind River Systems
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the names of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _TIPC_NODE_H
#define _TIPC_NODE_H
#include "node_subscr.h"
#include "addr.h"
#include "net.h"
#include "bearer.h"
/* Flags used to block (re)establishment of contact with a neighboring node */
#define WAIT_PEER_DOWN 0x0001 /* wait to see that peer's links are down */
#define WAIT_NAMES_GONE 0x0002 /* wait for peer's publications to be purged */
#define WAIT_NODE_DOWN 0x0004 /* wait until peer node is declared down */
/**
* struct tipc_node - TIPC node structure
* @addr: network address of node
* @lock: spinlock governing access to structure
* @hash: links to adjacent nodes in unsorted hash chain
* @list: links to adjacent nodes in sorted list of cluster's nodes
* @nsub: list of "node down" subscriptions monitoring node
* @active_links: pointers to active links to node
* @links: pointers to all links to node
* @working_links: number of working links to node (both active and standby)
* @block_setup: bit mask of conditions preventing link establishment to node
* @link_cnt: number of links to node
* @permit_changeover: non-zero if node has redundant links to this system
* @bclink: broadcast-related info
* @supported: non-zero if node supports TIPC b'cast capability
* @acked: sequence # of last outbound b'cast message acknowledged by node
* @last_in: sequence # of last in-sequence b'cast message received from node
* @gap_after: sequence # of last message not requiring a NAK request
* @gap_to: sequence # of last message requiring a NAK request
* @nack_sync: counter that determines when NAK requests should be sent
* @deferred_head: oldest OOS b'cast message received from node
* @deferred_tail: newest OOS b'cast message received from node
* @defragm: list of partially reassembled b'cast message fragments from node
*/
struct tipc_node {
u32 addr;
spinlock_t lock;
struct hlist_node hash;
struct list_head list;
struct list_head nsub;
struct link *active_links[2];
struct link *links[MAX_BEARERS];
int link_cnt;
int working_links;
int block_setup;
int permit_changeover;
struct {
int supported;
u32 acked;
u32 last_in;
u32 gap_after;
u32 gap_to;
u32 nack_sync;
struct sk_buff *deferred_head;
struct sk_buff *deferred_tail;
struct sk_buff *defragm;
} bclink;
};
#define NODE_HTABLE_SIZE 512
extern struct list_head tipc_node_list;
/*
* A trivial power-of-two bitmask technique is used for speed, since this
* operation is done for every incoming TIPC packet. The number of hash table
* entries has been chosen so that no hash chain exceeds 8 nodes and will
* usually be much smaller (typically only a single node).
*/
static inline unsigned int tipc_hashfn(u32 addr)
{
return addr & (NODE_HTABLE_SIZE - 1);
}
extern u32 tipc_own_tag;
struct tipc_node *tipc_node_find(u32 addr);
struct tipc_node *tipc_node_create(u32 addr);
void tipc_node_delete(struct tipc_node *n_ptr);
void tipc_node_attach_link(struct tipc_node *n_ptr, struct link *l_ptr);
void tipc_node_detach_link(struct tipc_node *n_ptr, struct link *l_ptr);
void tipc_node_link_down(struct tipc_node *n_ptr, struct link *l_ptr);
void tipc_node_link_up(struct tipc_node *n_ptr, struct link *l_ptr);
int tipc_node_active_links(struct tipc_node *n_ptr);
int tipc_node_redundant_links(struct tipc_node *n_ptr);
int tipc_node_is_up(struct tipc_node *n_ptr);
struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space);
struct sk_buff *tipc_node_get_nodes(const void *req_tlv_area, int req_tlv_space);
static inline void tipc_node_lock(struct tipc_node *n_ptr)
{
spin_lock_bh(&n_ptr->lock);
}
static inline void tipc_node_unlock(struct tipc_node *n_ptr)
{
spin_unlock_bh(&n_ptr->lock);
}
#endif
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