1 files changed, 111 insertions, 108 deletions

diff --git a/net/tipc/discover.c b/net/tipc/discover.c
index b15cbedfea13..aa722a42ef8b 100644
--- a/net/tipc/discover.c
+++ b/net/tipc/discover.c
@@ -1,7 +1,7 @@
 /*
  * net/tipc/discover.c
  *
- * Copyright (c) 2003-2006, Ericsson AB
+ * Copyright (c) 2003-2006, 2014, Ericsson AB
  * Copyright (c) 2005-2006, 2010-2011, Wind River Systems
  * All rights reserved.
  *
@@ -106,147 +106,150 @@ static void disc_dupl_alert(struct tipc_bearer *b_ptr, u32 node_addr,
 }
 
 /**
- * tipc_disc_rcv - handle incoming link setup message (request or response)
+ * tipc_disc_rcv - handle incoming discovery message (request or response)
  * @buf: buffer containing message
- * @b_ptr: bearer that message arrived on
+ * @bearer: bearer that message arrived on
  */
-void tipc_disc_rcv(struct sk_buff *buf, struct tipc_bearer *b_ptr)
+void tipc_disc_rcv(struct sk_buff *buf, struct tipc_bearer *bearer)
 {
-	struct tipc_node *n_ptr;
+	struct tipc_node *node;
 	struct tipc_link *link;
-	struct tipc_media_addr media_addr;
+	struct tipc_media_addr maddr;
 	struct sk_buff *rbuf;
 	struct tipc_msg *msg = buf_msg(buf);
-	u32 dest = msg_dest_domain(msg);
-	u32 orig = msg_prevnode(msg);
+	u32 ddom = msg_dest_domain(msg);
+	u32 onode = msg_prevnode(msg);
 	u32 net_id = msg_bc_netid(msg);
-	u32 type = msg_type(msg);
+	u32 mtyp = msg_type(msg);
 	u32 signature = msg_node_sig(msg);
-	int addr_mismatch;
-	int link_fully_up;
-
-	media_addr.broadcast = 1;
-	b_ptr->media->msg2addr(b_ptr, &media_addr, msg_media_addr(msg));
+	bool addr_match = false;
+	bool sign_match = false;
+	bool link_up = false;
+	bool accept_addr = false;
+	bool accept_sign = false;
+	bool respond = false;
+
+	bearer->media->msg2addr(bearer, &maddr, msg_media_addr(msg));
 	kfree_skb(buf);
 
 	/* Ensure message from node is valid and communication is permitted */
 	if (net_id != tipc_net_id)
 		return;
-	if (media_addr.broadcast)
+	if (maddr.broadcast)
 		return;
-	if (!tipc_addr_domain_valid(dest))
+	if (!tipc_addr_domain_valid(ddom))
 		return;
-	if (!tipc_addr_node_valid(orig))
+	if (!tipc_addr_node_valid(onode))
 		return;
-	if (orig == tipc_own_addr) {
-		if (memcmp(&media_addr, &b_ptr->addr, sizeof(media_addr)))
-			disc_dupl_alert(b_ptr, tipc_own_addr, &media_addr);
+
+	if (in_own_node(onode)) {
+		if (memcmp(&maddr, &bearer->addr, sizeof(maddr)))
+			disc_dupl_alert(bearer, tipc_own_addr, &maddr);
 		return;
 	}
-	if (!tipc_in_scope(dest, tipc_own_addr))
+	if (!tipc_in_scope(ddom, tipc_own_addr))
 		return;
-	if (!tipc_in_scope(b_ptr->domain, orig))
+	if (!tipc_in_scope(bearer->domain, onode))
 		return;
 
-	/* Locate structure corresponding to requesting node */
-	n_ptr = tipc_node_find(orig);
-	if (!n_ptr) {
-		n_ptr = tipc_node_create(orig);
-		if (!n_ptr)
-			return;
-	}
-	tipc_node_lock(n_ptr);
+	/* Locate, or if necessary, create, node: */
+	node = tipc_node_find(onode);
+	if (!node)
+		node = tipc_node_create(onode);
+	if (!node)
+		return;
 
-	/* Prepare to validate requesting node's signature and media address */
-	link = n_ptr->links[b_ptr->identity];
-	addr_mismatch = (link != NULL) &&
-		memcmp(&link->media_addr, &media_addr, sizeof(media_addr));
+	tipc_node_lock(node);
+	link = node->links[bearer->identity];
 
-	/*
-	 * Ensure discovery message's signature is correct
-	 *
-	 * If signature is incorrect and there is no working link to the node,
-	 * accept the new signature but invalidate all existing links to the
-	 * node so they won't re-activate without a new discovery message.
-	 *
-	 * If signature is incorrect and the requested link to the node is
-	 * working, accept the new signature. (This is an instance of delayed
-	 * rediscovery, where a link endpoint was able to re-establish contact
-	 * with its peer endpoint on a node that rebooted before receiving a
-	 * discovery message from that node.)
-	 *
-	 * If signature is incorrect and there is a working link to the node
-	 * that is not the requested link, reject the request (must be from
-	 * a duplicate node).
-	 */
-	if (signature != n_ptr->signature) {
-		if (n_ptr->working_links == 0) {
-			struct tipc_link *curr_link;
-			int i;
-
-			for (i = 0; i < MAX_BEARERS; i++) {
-				curr_link = n_ptr->links[i];
-				if (curr_link) {
-					memset(&curr_link->media_addr, 0,
-					       sizeof(media_addr));
-					tipc_link_reset(curr_link);
-				}
-			}
-			addr_mismatch = (link != NULL);
-		} else if (tipc_link_is_up(link) && !addr_mismatch) {
-			/* delayed rediscovery */
-		} else {
-			disc_dupl_alert(b_ptr, orig, &media_addr);
-			tipc_node_unlock(n_ptr);
-			return;
-		}
-		n_ptr->signature = signature;
+	/* Prepare to validate requesting node's signature and media address */
+	sign_match = (signature == node->signature);
+	addr_match = link && !memcmp(&link->media_addr, &maddr, sizeof(maddr));
+	link_up = link && tipc_link_is_up(link);
+
+
+	/* These three flags give us eight permutations: */
+
+	if (sign_match && addr_match && link_up) {
+		/* All is fine. Do nothing. */
+	} else if (sign_match && addr_match && !link_up) {
+		/* Respond. The link will come up in due time */
+		respond = true;
+	} else if (sign_match && !addr_match && link_up) {
+		/* Peer has changed i/f address without rebooting.
+		 * If so, the link will reset soon, and the next
+		 * discovery will be accepted. So we can ignore it.
+		 * It may also be an cloned or malicious peer having
+		 * chosen the same node address and signature as an
+		 * existing one.
+		 * Ignore requests until the link goes down, if ever.
+		 */
+		disc_dupl_alert(bearer, onode, &maddr);
+	} else if (sign_match && !addr_match && !link_up) {
+		/* Peer link has changed i/f address without rebooting.
+		 * It may also be a cloned or malicious peer; we can't
+		 * distinguish between the two.
+		 * The signature is correct, so we must accept.
+		 */
+		accept_addr = true;
+		respond = true;
+	} else if (!sign_match && addr_match && link_up) {
+		/* Peer node rebooted. Two possibilities:
+		 *  - Delayed re-discovery; this link endpoint has already
+		 *    reset and re-established contact with the peer, before
+		 *    receiving a discovery message from that node.
+		 *    (The peer happened to receive one from this node first).
+		 *  - The peer came back so fast that our side has not
+		 *    discovered it yet. Probing from this side will soon
+		 *    reset the link, since there can be no working link
+		 *    endpoint at the peer end, and the link will re-establish.
+		 *  Accept the signature, since it comes from a known peer.
+		 */
+		accept_sign = true;
+	} else if (!sign_match && addr_match && !link_up) {
+		/*  The peer node has rebooted.
+		 *  Accept signature, since it is a known peer.
+		 */
+		accept_sign = true;
+		respond = true;
+	} else if (!sign_match && !addr_match && link_up) {
+		/* Peer rebooted with new address, or a new/duplicate peer.
+		 * Ignore until the link goes down, if ever.
+		 */
+		disc_dupl_alert(bearer, onode, &maddr);
+	} else if (!sign_match && !addr_match && !link_up) {
+		/* Peer rebooted with new address, or it is a new peer.
+		 * Accept signature and address.
+		*/
+		accept_sign = true;
+		accept_addr = true;
+		respond = true;
 	}
 
-	/*
-	 * Ensure requesting node's media address is correct
-	 *
-	 * If media address doesn't match and the link is working, reject the
-	 * request (must be from a duplicate node).
-	 *
-	 * If media address doesn't match and the link is not working, accept
-	 * the new media address and reset the link to ensure it starts up
-	 * cleanly.
-	 */
-	if (addr_mismatch) {
-		if (tipc_link_is_up(link)) {
-			disc_dupl_alert(b_ptr, orig, &media_addr);
-			tipc_node_unlock(n_ptr);
-			return;
-		} else {
-			memcpy(&link->media_addr, &media_addr,
-			       sizeof(media_addr));
-			tipc_link_reset(link);
-		}
-	}
+	if (accept_sign)
+		node->signature = signature;
 
-	/* Create a link endpoint for this bearer, if necessary */
-	if (!link) {
-		link = tipc_link_create(n_ptr, b_ptr, &media_addr);
-		if (!link) {
-			tipc_node_unlock(n_ptr);
-			return;
+	if (accept_addr) {
+		if (!link)
+			link = tipc_link_create(node, bearer, &maddr);
+		if (link) {
+			memcpy(&link->media_addr, &maddr, sizeof(maddr));
+			tipc_link_reset(link);
+		} else {
+			respond = false;
 		}
 	}
 
-	/* Accept discovery message & send response, if necessary */
-	link_fully_up = link_working_working(link);
-
-	if ((type == DSC_REQ_MSG) && !link_fully_up) {
+	/* Send response, if necessary */
+	if (respond && (mtyp == DSC_REQ_MSG)) {
 		rbuf = tipc_buf_acquire(INT_H_SIZE);
 		if (rbuf) {
-			tipc_disc_init_msg(rbuf, DSC_RESP_MSG, b_ptr);
-			tipc_bearer_send(b_ptr->identity, rbuf, &media_addr);
+			tipc_disc_init_msg(rbuf, DSC_RESP_MSG, bearer);
+			tipc_bearer_send(bearer->identity, rbuf, &maddr);
 			kfree_skb(rbuf);
 		}
 	}
-
-	tipc_node_unlock(n_ptr);
+	tipc_node_unlock(node);
 }
 
 /**