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Commit c64f7a6a1fb13565687ae5415736095f82557880

Authored by Jon Maloy
Committed by Paul Gortmaker
1 parent 389dd9bcf6
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

tipc: introduce message to synchronize broadcast link 

Upon establishing a first link between two nodes, there is
currently a risk that the two endpoints will disagree on exactly
which sequence number reception and acknowleding of broadcast
packets should start.

The following scenarios may happen:

1: Node A sends an ACTIVATE message to B, telling it to start acking
   packets from sequence number N.
2: Node A sends out broadcast N, but does not expect an acknowledge
   from B, since B is not yet in its broadcast receiver's list.
3: Node A receives ACK for N from all nodes except B, and releases
   packet N.
4: Node B receives the ACTIVATE, activates its link endpoint, and
   stores the value N as sequence number of first expected packet.
5: Node B sends a NAME_DISTR message to A.
6: Node A receives the NAME_DISTR message, and activates its endpoint.
   At this moment B is added to A's broadcast receiver's set.
   Node A also sets sequence number 0 as the first broadcast packet
   to be received from B.
7: Node A sends broadcast N+1.
8: B receives N+1, determines there is a gap in the sequence, since
   it is expecting N, and sends a NACK for N back to A.
9: Node A has already released N, so no retransmission is possible.
   The broadcast link in direction A->B is stale.

In addition to, or instead of, 7-9 above, the following may happen:

10: Node B sends broadcast M > 0 to A.
11: Node A receives M, falsely decides there must be a gap, since
    it is expecting packet 0, and asks for retransmission of packets
    [0,M-1].
12: Node B has already released these packets, so the broadcast
    link is stale in direction B->A.

We solve this problem by introducing a new unicast message type,
BCAST_PROTOCOL/STATE, to convey the sequence number of the next
sent broadcast packet to the other endpoint, at exactly the moment
that endpoint is added to the own node's broadcast receivers list,
and before any other unicast messages are permitted to be sent.

Furthermore, we don't allow any node to start receiving and
processing broadcast packets until this new synchronization
message has been received.

To maintain backwards compatibility, we still open up for
broadcast reception if we receive a NAME_DISTR message without
any preceding broadcast sync message. In this case, we must
assume that the other end has an older code version, and will
never send out the new synchronization message. Hence, for mixed
old and new nodes, the issue arising in 7-12 of the above may
happen with the same probability as before.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

Showing 2 changed files with 60 additions and 6 deletions Side-by-side Diff

1 1 /*
2 2 * net/tipc/link.c: TIPC link code
3 3 *
4   - * Copyright (c) 1996-2007, Ericsson AB
  4 + * Copyright (c) 1996-2007, 2012, Ericsson AB
5 5 * Copyright (c) 2004-2007, 2010-2011, Wind River Systems
6 6 * All rights reserved.
7 7 *
... ... @@ -103,6 +103,8 @@
103 103 static void link_print(struct tipc_link *l_ptr, const char *str);
104 104 static void link_start(struct tipc_link *l_ptr);
105 105 static int link_send_long_buf(struct tipc_link *l_ptr, struct sk_buff *buf);
  106 +static void tipc_link_send_sync(struct tipc_link *l);
  107 +static void tipc_link_recv_sync(struct tipc_node *n, struct sk_buff *buf);
106 108  
107 109 /*
108 110 * Simple link routines
... ... @@ -712,6 +714,8 @@
712 714 link_activate(l_ptr);
713 715 tipc_link_send_proto_msg(l_ptr, STATE_MSG, 1, 0, 0, 0, 0);
714 716 l_ptr->fsm_msg_cnt++;
  717 + if (l_ptr->owner->working_links == 1)
  718 + tipc_link_send_sync(l_ptr);
715 719 link_set_timer(l_ptr, cont_intv);
716 720 break;
717 721 case RESET_MSG:
... ... @@ -745,6 +749,8 @@
745 749 link_activate(l_ptr);
746 750 tipc_link_send_proto_msg(l_ptr, STATE_MSG, 1, 0, 0, 0, 0);
747 751 l_ptr->fsm_msg_cnt++;
  752 + if (l_ptr->owner->working_links == 1)
  753 + tipc_link_send_sync(l_ptr);
748 754 link_set_timer(l_ptr, cont_intv);
749 755 break;
750 756 case RESET_MSG:
... ... @@ -941,7 +947,48 @@
941 947 return res;
942 948 }
943 949  
944   -/**
  950 +/*
  951 + * tipc_link_send_sync - synchronize broadcast link endpoints.
  952 + *
  953 + * Give a newly added peer node the sequence number where it should
  954 + * start receiving and acking broadcast packets.
  955 + *
  956 + * Called with node locked
  957 + */
  958 +static void tipc_link_send_sync(struct tipc_link *l)
  959 +{
  960 + struct sk_buff *buf;
  961 + struct tipc_msg *msg;
  962 +
  963 + buf = tipc_buf_acquire(INT_H_SIZE);
  964 + if (!buf)
  965 + return;
  966 +
  967 + msg = buf_msg(buf);
  968 + tipc_msg_init(msg, BCAST_PROTOCOL, STATE_MSG, INT_H_SIZE, l->addr);
  969 + msg_set_last_bcast(msg, l->owner->bclink.acked);
  970 + link_add_chain_to_outqueue(l, buf, 0);
  971 + tipc_link_push_queue(l);
  972 +}
  973 +
  974 +/*
  975 + * tipc_link_recv_sync - synchronize broadcast link endpoints.
  976 + * Receive the sequence number where we should start receiving and
  977 + * acking broadcast packets from a newly added peer node, and open
  978 + * up for reception of such packets.
  979 + *
  980 + * Called with node locked
  981 + */
  982 +static void tipc_link_recv_sync(struct tipc_node *n, struct sk_buff *buf)
  983 +{
  984 + struct tipc_msg *msg = buf_msg(buf);
  985 +
  986 + n->bclink.last_sent = n->bclink.last_in = msg_last_bcast(msg);
  987 + n->bclink.recv_permitted = true;
  988 + kfree_skb(buf);
  989 +}
  990 +
  991 +/*
945 992 * tipc_link_send_names - send name table entries to new neighbor
946 993 *
947 994 * Send routine for bulk delivery of name table messages when contact
948 995  
... ... @@ -1691,9 +1738,14 @@
1691 1738 tipc_link_recv_bundle(buf);
1692 1739 continue;
1693 1740 case NAME_DISTRIBUTOR:
  1741 + n_ptr->bclink.recv_permitted = true;
1694 1742 tipc_node_unlock(n_ptr);
1695 1743 tipc_named_recv(buf);
1696 1744 continue;
  1745 + case BCAST_PROTOCOL:
  1746 + tipc_link_recv_sync(n_ptr, buf);
  1747 + tipc_node_unlock(n_ptr);
  1748 + continue;
1697 1749 case CONN_MANAGER:
1698 1750 tipc_node_unlock(n_ptr);
1699 1751 tipc_port_recv_proto_msg(buf);
1700 1752  
1701 1753  
... ... @@ -1736,16 +1788,19 @@
1736 1788 continue;
1737 1789 }
1738 1790  
  1791 + /* Link is not in state WORKING_WORKING */
1739 1792 if (msg_user(msg) == LINK_PROTOCOL) {
1740 1793 link_recv_proto_msg(l_ptr, buf);
1741 1794 head = link_insert_deferred_queue(l_ptr, head);
1742 1795 tipc_node_unlock(n_ptr);
1743 1796 continue;
1744 1797 }
  1798 +
  1799 + /* Traffic message. Conditionally activate link */
1745 1800 link_state_event(l_ptr, TRAFFIC_MSG_EVT);
1746 1801  
1747 1802 if (link_working_working(l_ptr)) {
1748   - /* Re-insert in front of queue */
  1803 + /* Re-insert buffer in front of queue */
1749 1804 buf->next = head;
1750 1805 head = buf;
1751 1806 tipc_node_unlock(n_ptr);
1 1 /*
2 2 * net/tipc/node.c: TIPC node management routines
3 3 *
4   - * Copyright (c) 2000-2006, Ericsson AB
  4 + * Copyright (c) 2000-2006, 2012 Ericsson AB
5 5 * Copyright (c) 2005-2006, 2010-2011, Wind River Systems
6 6 * All rights reserved.
7 7 *
8 8  
... ... @@ -263,10 +263,9 @@
263 263 static void node_established_contact(struct tipc_node *n_ptr)
264 264 {
265 265 tipc_k_signal((Handler)tipc_named_node_up, n_ptr->addr);
266   -
  266 + n_ptr->bclink.oos_state = 0;
267 267 n_ptr->bclink.acked = tipc_bclink_get_last_sent();
268 268 tipc_bclink_add_node(n_ptr->addr);
269   - n_ptr->bclink.recv_permitted = true;
270 269 }
271 270  
272 271 static void node_name_purge_complete(unsigned long node_addr)