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authorJon Paul Maloy <jon.maloy@ericsson.com>2015-07-16 16:54:30 -0400
committerDavid S. Miller <davem@davemloft.net>2015-07-20 20:41:16 -0700
commit1a20cc254e60e79929ef7edb5cf784df86b46e42 (patch)
tree20ace0bcaf31803fe6ffbd048df89be9bb26b8d6 /net/tipc/msg.h
parent8a1577c96f122308ac9b5f195f9f9a7dd74ac541 (diff)
downloadlinux-1a20cc254e60e79929ef7edb5cf784df86b46e42.tar.bz2
tipc: introduce node contact FSM
The logics for determining when a node is permitted to establish and maintain contact with its peer node becomes non-trivial in the presence of multiple parallel links that may come and go independently. A known failure scenario is that one endpoint registers both its links to the peer lost, cleans up it binding table, and prepares for a table update once contact is re-establihed, while the other endpoint may see its links reset and re-established one by one, hence seeing no need to re-synchronize the binding table. To avoid this, a node must not allow re-establishing contact until it has confirmation that even the peer has lost both links. Currently, the mechanism for handling this consists of setting and resetting two state flags from different locations in the code. This solution is hard to understand and maintain. A closer analysis even reveals that it is not completely safe. In this commit we do instead introduce an FSM that keeps track of the conditions for when the node can establish and maintain links. It has six states and four events, and is strictly based on explicit knowledge about the own node's and the peer node's contact states. Only events leading to state change are shown as edges in the figure below. +--------------+ | SELF_UP/ | +---------------->| PEER_COMING |-----------------+ SELF_ | +--------------+ |PEER_ ESTBL_ | | |ESTBL_ CONTACT| SELF_LOST_CONTACT | |CONTACT | v | | +--------------+ | | PEER_ | SELF_DOWN/ | SELF_ | | LOST_ +--| PEER_LEAVING |<--+ LOST_ v +-------------+ CONTACT | +--------------+ | CONTACT +-----------+ | SELF_DOWN/ |<----------+ +----------| SELF_UP/ | | PEER_DOWN |<----------+ +----------| PEER_UP | +-------------+ SELF_ | +--------------+ | PEER_ +-----------+ | LOST_ +--| SELF_LEAVING/|<--+ LOST_ A | CONTACT | PEER_DOWN | CONTACT | | +--------------+ | | A | PEER_ | PEER_LOST_CONTACT | |SELF_ ESTBL_ | | |ESTBL_ CONTACT| +--------------+ |CONTACT +---------------->| PEER_UP/ |-----------------+ | SELF_COMING | +--------------+ Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc/msg.h')
-rw-r--r--net/tipc/msg.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 19c45fb66238..4dc66d9f69cc 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -766,6 +766,13 @@ static inline void msg_set_link_tolerance(struct tipc_msg *m, u32 n)
msg_set_bits(m, 9, 0, 0xffff, n);
}
+static inline bool msg_peer_is_up(struct tipc_msg *m)
+{
+ if (likely(msg_user(m) != LINK_PROTOCOL) || (msg_type(m) == STATE_MSG))
+ return true;
+ return msg_redundant_link(m);
+}
+
struct sk_buff *tipc_buf_acquire(u32 size);
bool tipc_msg_validate(struct sk_buff *skb);
bool tipc_msg_reverse(u32 own_addr, struct sk_buff *buf, u32 *dnode,