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![Jon Paul Maloy](/assets/img/avatar_default.png)
The function tipc_disc_rcv(), which is handling received neighbor discovery messages, is perceived as messy, and it is hard to verify its correctness by code inspection. The fact that the task it is set to resolve is fairly complex does not make the situation better. In this commit we try to take a more systematic approach to the problem. We define a decision machine which takes three state flags as input, and produces three action flags as output. We then walk through all permutations of the state flags, and for each of them we describe verbally what is going on, plus that we set zero or more of the action flags. The action flags indicate what should be done once the decision machine has finished its job, while the last part of the function deals with performing those actions. Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
403 lines
12 KiB
C
403 lines
12 KiB
C
/*
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* net/tipc/discover.c
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*
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* Copyright (c) 2003-2006, 2014, Ericsson AB
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* Copyright (c) 2005-2006, 2010-2011, 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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#include "core.h"
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#include "link.h"
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#include "discover.h"
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#define TIPC_LINK_REQ_INIT 125 /* min delay during bearer start up */
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#define TIPC_LINK_REQ_FAST 1000 /* max delay if bearer has no links */
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#define TIPC_LINK_REQ_SLOW 60000 /* max delay if bearer has links */
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#define TIPC_LINK_REQ_INACTIVE 0xffffffff /* indicates no timer in use */
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/**
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* struct tipc_link_req - information about an ongoing link setup request
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* @bearer_id: identity of bearer issuing requests
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* @dest: destination address for request messages
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* @domain: network domain to which links can be established
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* @num_nodes: number of nodes currently discovered (i.e. with an active link)
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* @lock: spinlock for controlling access to requests
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* @buf: request message to be (repeatedly) sent
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* @timer: timer governing period between requests
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* @timer_intv: current interval between requests (in ms)
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*/
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struct tipc_link_req {
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u32 bearer_id;
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struct tipc_media_addr dest;
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u32 domain;
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int num_nodes;
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spinlock_t lock;
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struct sk_buff *buf;
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struct timer_list timer;
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unsigned int timer_intv;
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};
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/**
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* tipc_disc_init_msg - initialize a link setup message
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* @type: message type (request or response)
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* @b_ptr: ptr to bearer issuing message
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*/
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static void tipc_disc_init_msg(struct sk_buff *buf, u32 type,
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struct tipc_bearer *b_ptr)
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{
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struct tipc_msg *msg;
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u32 dest_domain = b_ptr->domain;
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msg = buf_msg(buf);
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tipc_msg_init(msg, LINK_CONFIG, type, INT_H_SIZE, dest_domain);
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msg_set_non_seq(msg, 1);
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msg_set_node_sig(msg, tipc_random);
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msg_set_dest_domain(msg, dest_domain);
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msg_set_bc_netid(msg, tipc_net_id);
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b_ptr->media->addr2msg(msg_media_addr(msg), &b_ptr->addr);
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}
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/**
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* disc_dupl_alert - issue node address duplication alert
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* @b_ptr: pointer to bearer detecting duplication
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* @node_addr: duplicated node address
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* @media_addr: media address advertised by duplicated node
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*/
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static void disc_dupl_alert(struct tipc_bearer *b_ptr, u32 node_addr,
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struct tipc_media_addr *media_addr)
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{
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char node_addr_str[16];
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char media_addr_str[64];
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tipc_addr_string_fill(node_addr_str, node_addr);
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tipc_media_addr_printf(media_addr_str, sizeof(media_addr_str),
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media_addr);
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pr_warn("Duplicate %s using %s seen on <%s>\n", node_addr_str,
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media_addr_str, b_ptr->name);
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}
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/**
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* tipc_disc_rcv - handle incoming discovery message (request or response)
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* @buf: buffer containing message
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* @bearer: bearer that message arrived on
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*/
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void tipc_disc_rcv(struct sk_buff *buf, struct tipc_bearer *bearer)
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{
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struct tipc_node *node;
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struct tipc_link *link;
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struct tipc_media_addr maddr;
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struct sk_buff *rbuf;
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struct tipc_msg *msg = buf_msg(buf);
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u32 ddom = msg_dest_domain(msg);
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u32 onode = msg_prevnode(msg);
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u32 net_id = msg_bc_netid(msg);
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u32 mtyp = msg_type(msg);
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u32 signature = msg_node_sig(msg);
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bool addr_match = false;
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bool sign_match = false;
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bool link_up = false;
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bool accept_addr = false;
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bool accept_sign = false;
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bool respond = false;
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bearer->media->msg2addr(bearer, &maddr, msg_media_addr(msg));
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kfree_skb(buf);
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/* Ensure message from node is valid and communication is permitted */
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if (net_id != tipc_net_id)
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return;
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if (maddr.broadcast)
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return;
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if (!tipc_addr_domain_valid(ddom))
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return;
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if (!tipc_addr_node_valid(onode))
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return;
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if (in_own_node(onode)) {
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if (memcmp(&maddr, &bearer->addr, sizeof(maddr)))
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disc_dupl_alert(bearer, tipc_own_addr, &maddr);
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return;
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}
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if (!tipc_in_scope(ddom, tipc_own_addr))
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return;
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if (!tipc_in_scope(bearer->domain, onode))
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return;
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/* Locate, or if necessary, create, node: */
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node = tipc_node_find(onode);
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if (!node)
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node = tipc_node_create(onode);
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if (!node)
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return;
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tipc_node_lock(node);
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link = node->links[bearer->identity];
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/* Prepare to validate requesting node's signature and media address */
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sign_match = (signature == node->signature);
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addr_match = link && !memcmp(&link->media_addr, &maddr, sizeof(maddr));
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link_up = link && tipc_link_is_up(link);
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/* These three flags give us eight permutations: */
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if (sign_match && addr_match && link_up) {
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/* All is fine. Do nothing. */
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} else if (sign_match && addr_match && !link_up) {
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/* Respond. The link will come up in due time */
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respond = true;
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} else if (sign_match && !addr_match && link_up) {
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/* Peer has changed i/f address without rebooting.
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* If so, the link will reset soon, and the next
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* discovery will be accepted. So we can ignore it.
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* It may also be an cloned or malicious peer having
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* chosen the same node address and signature as an
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* existing one.
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* Ignore requests until the link goes down, if ever.
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*/
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disc_dupl_alert(bearer, onode, &maddr);
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} else if (sign_match && !addr_match && !link_up) {
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/* Peer link has changed i/f address without rebooting.
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* It may also be a cloned or malicious peer; we can't
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* distinguish between the two.
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* The signature is correct, so we must accept.
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*/
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accept_addr = true;
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respond = true;
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} else if (!sign_match && addr_match && link_up) {
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/* Peer node rebooted. Two possibilities:
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* - Delayed re-discovery; this link endpoint has already
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* reset and re-established contact with the peer, before
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* receiving a discovery message from that node.
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* (The peer happened to receive one from this node first).
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* - The peer came back so fast that our side has not
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* discovered it yet. Probing from this side will soon
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* reset the link, since there can be no working link
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* endpoint at the peer end, and the link will re-establish.
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* Accept the signature, since it comes from a known peer.
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*/
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accept_sign = true;
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} else if (!sign_match && addr_match && !link_up) {
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/* The peer node has rebooted.
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* Accept signature, since it is a known peer.
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*/
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accept_sign = true;
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respond = true;
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} else if (!sign_match && !addr_match && link_up) {
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/* Peer rebooted with new address, or a new/duplicate peer.
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* Ignore until the link goes down, if ever.
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*/
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disc_dupl_alert(bearer, onode, &maddr);
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} else if (!sign_match && !addr_match && !link_up) {
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/* Peer rebooted with new address, or it is a new peer.
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* Accept signature and address.
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*/
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accept_sign = true;
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accept_addr = true;
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respond = true;
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}
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if (accept_sign)
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node->signature = signature;
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if (accept_addr) {
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if (!link)
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link = tipc_link_create(node, bearer, &maddr);
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if (link) {
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memcpy(&link->media_addr, &maddr, sizeof(maddr));
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tipc_link_reset(link);
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} else {
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respond = false;
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}
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}
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/* Send response, if necessary */
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if (respond && (mtyp == DSC_REQ_MSG)) {
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rbuf = tipc_buf_acquire(INT_H_SIZE);
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if (rbuf) {
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tipc_disc_init_msg(rbuf, DSC_RESP_MSG, bearer);
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tipc_bearer_send(bearer->identity, rbuf, &maddr);
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kfree_skb(rbuf);
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}
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}
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tipc_node_unlock(node);
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}
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/**
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* disc_update - update frequency of periodic link setup requests
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* @req: ptr to link request structure
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*
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* Reinitiates discovery process if discovery object has no associated nodes
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* and is either not currently searching or is searching at a slow rate
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*/
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static void disc_update(struct tipc_link_req *req)
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{
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if (!req->num_nodes) {
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if ((req->timer_intv == TIPC_LINK_REQ_INACTIVE) ||
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(req->timer_intv > TIPC_LINK_REQ_FAST)) {
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req->timer_intv = TIPC_LINK_REQ_INIT;
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k_start_timer(&req->timer, req->timer_intv);
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}
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}
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}
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/**
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* tipc_disc_add_dest - increment set of discovered nodes
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* @req: ptr to link request structure
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*/
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void tipc_disc_add_dest(struct tipc_link_req *req)
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{
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spin_lock_bh(&req->lock);
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req->num_nodes++;
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spin_unlock_bh(&req->lock);
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}
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/**
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* tipc_disc_remove_dest - decrement set of discovered nodes
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* @req: ptr to link request structure
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*/
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void tipc_disc_remove_dest(struct tipc_link_req *req)
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{
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spin_lock_bh(&req->lock);
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req->num_nodes--;
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disc_update(req);
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spin_unlock_bh(&req->lock);
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}
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/**
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* disc_timeout - send a periodic link setup request
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* @req: ptr to link request structure
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*
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* Called whenever a link setup request timer associated with a bearer expires.
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*/
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static void disc_timeout(struct tipc_link_req *req)
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{
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int max_delay;
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spin_lock_bh(&req->lock);
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/* Stop searching if only desired node has been found */
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if (tipc_node(req->domain) && req->num_nodes) {
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req->timer_intv = TIPC_LINK_REQ_INACTIVE;
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goto exit;
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}
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/*
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* Send discovery message, then update discovery timer
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*
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* Keep doubling time between requests until limit is reached;
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* hold at fast polling rate if don't have any associated nodes,
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* otherwise hold at slow polling rate
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*/
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tipc_bearer_send(req->bearer_id, req->buf, &req->dest);
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req->timer_intv *= 2;
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if (req->num_nodes)
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max_delay = TIPC_LINK_REQ_SLOW;
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else
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max_delay = TIPC_LINK_REQ_FAST;
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if (req->timer_intv > max_delay)
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req->timer_intv = max_delay;
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k_start_timer(&req->timer, req->timer_intv);
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exit:
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spin_unlock_bh(&req->lock);
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}
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/**
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* tipc_disc_create - create object to send periodic link setup requests
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* @b_ptr: ptr to bearer issuing requests
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* @dest: destination address for request messages
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* @dest_domain: network domain to which links can be established
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*
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* Returns 0 if successful, otherwise -errno.
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*/
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int tipc_disc_create(struct tipc_bearer *b_ptr, struct tipc_media_addr *dest)
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{
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struct tipc_link_req *req;
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req = kmalloc(sizeof(*req), GFP_ATOMIC);
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if (!req)
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return -ENOMEM;
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req->buf = tipc_buf_acquire(INT_H_SIZE);
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if (!req->buf) {
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kfree(req);
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return -ENOMEM;
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}
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tipc_disc_init_msg(req->buf, DSC_REQ_MSG, b_ptr);
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memcpy(&req->dest, dest, sizeof(*dest));
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req->bearer_id = b_ptr->identity;
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req->domain = b_ptr->domain;
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req->num_nodes = 0;
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req->timer_intv = TIPC_LINK_REQ_INIT;
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spin_lock_init(&req->lock);
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k_init_timer(&req->timer, (Handler)disc_timeout, (unsigned long)req);
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k_start_timer(&req->timer, req->timer_intv);
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b_ptr->link_req = req;
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tipc_bearer_send(req->bearer_id, req->buf, &req->dest);
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return 0;
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}
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/**
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* tipc_disc_delete - destroy object sending periodic link setup requests
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* @req: ptr to link request structure
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*/
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void tipc_disc_delete(struct tipc_link_req *req)
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{
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k_cancel_timer(&req->timer);
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k_term_timer(&req->timer);
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kfree_skb(req->buf);
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kfree(req);
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}
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/**
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* tipc_disc_reset - reset object to send periodic link setup requests
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* @b_ptr: ptr to bearer issuing requests
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* @dest_domain: network domain to which links can be established
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*/
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void tipc_disc_reset(struct tipc_bearer *b_ptr)
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{
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struct tipc_link_req *req = b_ptr->link_req;
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spin_lock_bh(&req->lock);
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tipc_disc_init_msg(req->buf, DSC_REQ_MSG, b_ptr);
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req->bearer_id = b_ptr->identity;
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req->domain = b_ptr->domain;
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req->num_nodes = 0;
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req->timer_intv = TIPC_LINK_REQ_INIT;
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k_start_timer(&req->timer, req->timer_intv);
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tipc_bearer_send(req->bearer_id, req->buf, &req->dest);
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spin_unlock_bh(&req->lock);
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}
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