linux/net/tipc/msg.c, branch v4.1

tipc: eliminate delayed link deletion at link failover

2015-04-02T20:27:12Z

When a bearer is disabled manually, all its links have to be reset and deleted. However, if there is a remaining, parallel link ready to take over a deleted link's traffic, we currently delay the delete of the removed link until the failover procedure is finished. This is because the remaining link needs to access state from the reset link, such as the last received packet number, and any partially reassembled buffer, in order to perform a successful failover. In this commit, we do instead move the state data over to the new link, so that it can fulfill the procedure autonomously, without accessing any data on the old link. This means that we can now proceed and delete all pertaining links immediately when a bearer is disabled. This saves us from some unnecessary complexity in such situations. We also choose to change the confusing definitions CHANGEOVER_PROTOCOL, ORIGINAL_MSG and DUPLICATE_MSG to the more descriptive TUNNEL_PROTOCOL, FAILOVER_MSG and SYNCH_MSG respectively. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: fix two bugs in secondary destination lookup

2015-03-29T20:47:36Z

A message sent to a node after a successful name table lookup may still find that the destination socket has disappeared, because distribution of name table updates is non-atomic. If so, the message will be rejected back to the sender with error code TIPC_ERR_NO_PORT. If the source socket of the message has disappeared in the meantime, the message should be dropped. However, in the currrent code, the message will instead be subject to an unwanted tertiary lookup, because the function tipc_msg_lookup_dest() doesn't check if there is an error code present in the message before performing the lookup. In the worst case, the message may now find the old destination again, and be redirected once more, instead of being dropped directly as it should be. A second bug in this function is that the "prev_node" field in the message is not updated after successful lookup, something that may have unpredictable consequences. The problems arising from those bugs occur very infrequently. The third change in this function; the test on msg_reroute_msg_cnt() is purely cosmetic, reflecting that the returned value never can be negative. This commit corrects the two bugs described above. Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: clean up handling of message priorities

2015-03-14T18:38:32Z

Messages transferred by TIPC are assigned an "importance priority", -an integer value indicating how to treat the message when there is link or destination socket congestion. There is no separate header field for this value. Instead, the message user values have been chosen in ascending order according to perceived importance, so that the message user field can be used for this. This is not a good solution. First, we have many more users than the needed priority levels, so we end up with treating more priority levels than necessary. Second, the user field cannot always accurately reflect the priority of the message. E.g., a message fragment packet should really have the priority of the enveloped user data message, and not the priority of the MSG_FRAGMENTER user. Until now, we have been working around this problem in different ways, but it is now time to implement a consistent way of handling such priorities, although still within the constraint that we cannot allocate any more bits in the regular data message header for this. In this commit, we define a new priority level, TIPC_SYSTEM_IMPORTANCE, that will be the only one used apart from the four (lower) user data levels. All non-data messages map down to this priority. Furthermore, we take some free bits from the MSG_FRAGMENTER header and allocate them to store the priority of the enveloped message. We then adjust the functions msg_importance()/msg_set_importance() so that they read/set the correct header fields depending on user type. This small protocol change is fully compatible, because the code at the receiving end of a link currently reads the importance level only from user data messages, where there is no change. Reviewed-by: Erik Hugne Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: split link outqueue

2015-03-14T18:38:32Z

struct tipc_link contains one single queue for outgoing packets, where both transmitted and waiting packets are queued. This infrastructure is hard to maintain, because we need to keep a number of fields to keep track of which packets are sent or unsent, and the number of packets in each category. A lot of code becomes simpler if we split this queue into a transmission queue, where sent/unacknowledged packets are kept, and a backlog queue, where we keep the not yet sent packets. In this commit we do this separation. Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: extract bundled buffers by cloning instead of copying

2015-03-14T18:38:32Z

When we currently extract a bundled buffer from a message bundle in the function tipc_msg_extract(), we allocate a new buffer and explicitly copy the linear data area. This is unnecessary, since we can just clone the buffer and do skb_pull() on the clone to move the data pointer to the correct position. This is what we do in this commit. Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: eliminate unnecessary linearization of incoming buffers

2015-03-14T18:38:32Z

Currently, TIPC linearizes all incoming buffers directly at reception before passing them upwards in the stack. This is clearly a waste of CPU resources, and must be avoided. In this commit, we eliminate this unnecessary linearization. We still ensure that at least the message header is linear, and that the buffer is linearized where this is still needed, i.e. when unbundling and when reversing messages. In addition, we ensure that fragmented messages are validated after reassembly before delivering them upwards in the stack. Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: move message validation function to msg.c

2015-03-14T18:38:32Z

The function link_buf_validate() is in reality re-entrant and context independent, and will in later commits be called from several locations. Therefore, we move it to msg.c, make it outline and rename the it to tipc_msg_validate(). We also redesign the function to make proper use of pskb_may_pull() Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: resolve race problem at unicast message reception

2015-02-06T00:00:02Z

TIPC handles message cardinality and sequencing at the link layer, before passing messages upwards to the destination sockets. During the upcall from link to socket no locks are held. It is therefore possible, and we see it happen occasionally, that messages arriving in different threads and delivered in sequence still bypass each other before they reach the destination socket. This must not happen, since it violates the sequentiality guarantee. We solve this by adding a new input buffer queue to the link structure. Arriving messages are added safely to the tail of that queue by the link, while the head of the queue is consumed, also safely, by the receiving socket. Sequentiality is secured per socket by only allowing buffers to be dequeued inside the socket lock. Since there may be multiple simultaneous readers of the queue, we use a 'filter' parameter to reduce the risk that they peek the same buffer from the queue, hence also reducing the risk of contention on the receiving socket locks. This solves the sequentiality problem, and seems to cause no measurable performance degradation. A nice side effect of this change is that lock handling in the functions tipc_rcv() and tipc_bcast_rcv() now becomes uniform, something that will enable future simplifications of those functions. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: split up function tipc_msg_eval()

2015-02-06T00:00:02Z

The function tipc_msg_eval() is in reality doing two related, but different tasks. First it tries to find a new destination for named messages, in case there was no first lookup, or if the first lookup failed. Second, it does what its name suggests, evaluating the validity of the message and its destination, and returning an appropriate error code depending on the result. This is confusing, and in this commit we choose to break it up into two functions. A new function, tipc_msg_lookup_dest(), first attempts to find a new destination, if the message is of the right type. If this lookup fails, or if the message should not be subject to a second lookup, the already existing tipc_msg_reverse() is called. This function performs prepares the message for rejection, if applicable. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: reduce usage of context info in socket and link

2015-02-06T00:00:01Z

The most common usage of namespace information is when we fetch the own node addess from the net structure. This leads to a lot of passing around of a parameter of type 'struct net *' between functions just to make them able to obtain this address. However, in many cases this is unnecessary. The own node address is readily available as a member of both struct tipc_sock and tipc_link, and can be fetched from there instead. The fact that the vast majority of functions in socket.c and link.c anyway are maintaining a pointer to their respective base structures makes this option even more compelling. In this commit, we introduce the inline functions tsk_own_node() and link_own_node() to make it easy for functions to fetch the node address from those structs instead of having to pass along and dereference the namespace struct. In particular, we make calls to the msg_xx() functions in msg.{h,c} context independent by directly passing them the own node address as parameter when needed. Those functions should be regarded as leaves in the code dependency tree, and it is hence desirable to keep them namspace unaware. Apart from a potential positive effect on cache behavior, these changes make it easier to introduce the changes that will follow later in this series. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller