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When a link between two nodes come up, both endpoints will initially send out a STATE message to the peer, to increase the probability that the peer endpoint also is up when the first traffic message arrives. Thereafter, if the establishing link is the second link between two nodes, this first "traffic" message is a TUNNEL_PROTOCOL/SYNCH message, helping the peer to perform initial synchronization between the two links. However, the initial STATE message may be lost, in which case the SYNCH message will be the first one arriving at the peer. This should also work, as the SYNCH message itself will be used to take up the link endpoint before initializing synchronization. Unfortunately the code for this case is broken. Currently, the link is brought up through a tipc_link_fsm_evt(ESTABLISHED) when a SYNCH arrives, whereupon __tipc_node_link_up() is called to distribute the link slots and take the link into traffic. But, __tipc_node_link_up() is itself starting with a test for whether the link is up, and if true, returns without action. Clearly, the tipc_link_fsm_evt(ESTABLISHED) call is unnecessary, since tipc_node_link_up() is itself issuing such an event, but also harmful, since it inhibits tipc_node_link_up() to perform the test of its tasks, and the link endpoint in question hence is never taken into traffic. This problem has been exposed when we set up dual links between pre- and post-4.4 kernels, because the former ones don't send out the initial STATE message described above. We fix this by removing the unnecessary event call. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.