Commit graph

1656 commits

Author SHA1 Message Date
dak664 a026c94467 Fix compiler warnings 2010-12-14 22:45:22 +00:00
dak664 0a4a0ffb32 Add SICSLOWPAN_CONF_ACK_ALL for hardware autoack testing 2010-12-14 22:18:20 +00:00
dak664 240d478c1f Allow platform to specify COLLECT_CONF_BROADCAST_ANNOUNCEMENT_MAX_TIME 2010-12-14 22:14:33 +00:00
adamdunkels 952dfc9384 Rework of the CSMA layer: instead of using one timer per packet, the module now uses one central timer and a queue of outgoing packets. This helps to keep packets in order, which is extremely useful for TCP transfers, and reduces the amount of congestion since consecutive packets now are spaced in time if there is a collision. Based on the observations and ideas of Simon Duquennoy. 2010-12-14 07:57:14 +00:00
dak664 0e60c99e80 Add defines to set stateful address prefixes. 2010-12-13 23:27:40 +00:00
dak664 9c66df6de1 Fix ancient RAND_MAX compiler warning 2010-12-13 16:52:02 +00:00
joxe 3e293e6cfc updated rpl dio message format to be compliant with latest version 2010-12-13 10:59:37 +00:00
nvt-se c9cc87ef25 Added support for Mode of Operation flags in DIOs. Removed obsolete destination advertisement flags. 2010-12-13 10:54:25 +00:00
joxe b66da85392 fixed comments and initialize flags in dio_output to zero 2010-12-13 09:59:46 +00:00
joxe aa1795d5c2 removed route annotation from rpl - moved to ds6 2010-12-10 22:48:31 +00:00
joxe 2c30b3c6ba added annotation for showing routes and default route during simulation 2010-12-10 22:46:58 +00:00
adamdunkels af21afa750 Make sure that the cycle timing is exact 2010-12-10 13:36:06 +00:00
adamdunkels e4cf633215 Put parenthesis around user-supplied options. Patch by Roger Larsson 2010-12-07 23:33:17 +00:00
adamdunkels c19a967973 Bugfix: with the recent bugfixes, it was no longer possible to turn duty cycling back on after it had been turned off 2010-12-07 23:12:54 +00:00
joxe e1fbb9bba0 changed neighbor state callbacks to occur only at add and remove 2010-12-07 10:36:03 +00:00
nvt-se b2a28e6fc3 Fixed error reported by Pieter Agten. The reachable time is specified in milliseconds, and must thus be divided by 1000. 2010-12-06 09:48:48 +00:00
adamdunkels 4c9793f428 Let ContikiMAC remember the state that the radio should have when duty cycling is turned off. This fixes a bug in which the radio was turned on after sending, even when NETSTACK_RDC.off(0) was enabled. 2010-12-06 09:08:22 +00:00
adamdunkels 433d42e170 Bugfix: if the cc2420_cca() function wasn't able to turn on the radio properly, it should turn it off again if it was off before. 2010-12-05 00:14:24 +00:00
dak664 f34e5ec798 Convert implicit printf to PRINTF 2010-12-04 21:06:04 +00:00
dak664 e54d7d6f9c Fix compiler warnings 2010-12-02 15:55:17 +00:00
adamdunkels 6d556d5c13 Fixed bug with link-layer ACKs. Refactored the ACK reception code. 2010-11-25 08:44:34 +00:00
adamdunkels 2f66db3ded Added a debug mode that keeps track of where individual queuebufs are allocated, which is useful when debugging queuebuf leakage problems. 2010-11-25 08:43:59 +00:00
nifi 3bd78893e5 Renamed nullrdc to nullrdc-noframer and nullrdc-framer to nullrdc.
nullrdc (previously nullrdc-framer) is now a RDC implementation that
does not do any radio duty cycling but supports link layer addresses
and frame format via framer (for example 802.15.4). nullrdc can now be
used in the same way as contikimac, xmac, etc.

nullrdc-noframer (previously nullrdc) is a null RDC implementation
that does not do any radio duty cycling, does not add any header of its
own to the packets, and does not support link layer addresses.
2010-11-23 18:11:00 +00:00
dak664 62d7832fff Fix compiler warning and possible bug 2010-11-13 16:37:42 +00:00
nifi 05d78522d3 Added MAC-layer duplicate message suppression when using 802.15.4 auto ack 2010-11-12 12:53:16 +00:00
nvt-se 1168703506 Minor clarifications in the code and comments. Integrated atches from Frederic Sureau: 1. copy_buf is now an ordinary char pointer. 2. Read directly from a file that is not modified. This reduces the code size when COFFEE_MICRO_LOGS is set to 0. 3. Update the file end value each time it is changed in case a log merge operation occurs later. 4. Avoid possible alignment problem in reading from the dummy_space area when calling cfs_readdir. 2010-11-11 13:08:23 +00:00
adamdunkels 8f745a6ea6 Added a function for obtaining the current parent 2010-11-06 14:32:10 +00:00
adamdunkels 9750eb93bf Turn off debug messages 2010-11-03 15:41:23 +00:00
adamdunkels a891a2ffe8 Bugfix: allow ICMPv6 to send packets larger than those whose length fits in one byte. Bugfix by mathieupouillot 2010-11-03 11:56:11 +00:00
adamdunkels b7df18a96a Turned off streaming by default to save code space; made guard time a little more conservative 2010-11-02 11:00:08 +00:00
adamdunkels 1b5001b226 Bugfix: out-of-order fragments were not handled correctly. minor style fixes 2010-11-02 10:56:57 +00:00
adamdunkels 2a885a476d Bumped version number 2010-11-02 10:55:32 +00:00
adamdunkels 5230e64112 Use the new shared ND-packet queue buffers 2010-10-29 05:36:07 +00:00
joxe 9a1f902881 made rank use full resolution when using OF-ETX 2010-10-28 20:39:06 +00:00
adamdunkels f5031861ac When IPv6 ND kicks in, the packet that caused the ND can either be dropped or saved in a buffer to be send when the NS reply returns. This commit reimplements the buffer management to avoid having one buffer per neighbor, but instead use a buffer pool from which buffers can be allocated for different neighbors. 2010-10-28 15:42:56 +00:00
adamdunkels 677575fc8c Rewrote proactive link estimator to be invoked randomly instead of triggered by an empty queue; this makes network bootups because nodes are not synchronized 2010-10-28 15:36:02 +00:00
joxe 932fed8cc7 improved ETX calculation 2010-10-28 08:54:54 +00:00
nifi 25ceab07d2 Update annotation when removing preferred parent. 2010-10-27 12:27:57 +00:00
nifi d2a3f1f257 We found that the preferred parent should be reset in the rpl_remove_parent function. 2010-10-27 12:20:35 +00:00
nvt-se d528039f9a Created a separate function for local repair. Added a statistics structure. Improved the control of malformed packets. 2010-10-27 00:46:40 +00:00
nvt-se c2c0505402 Increased alpha to 85 in order to get slower changes in the ETX. Put back the start guess to 3. 2010-10-27 00:45:24 +00:00
joxe 43023ab425 made number of transmissions configurable 2010-10-26 13:25:32 +00:00
nvt-se 1fbc651bf3 Lowered the first guess for the ETX of a link. 2010-10-25 20:06:17 +00:00
nvt-se 127c87efcc Fixed debug printfs. Added control of max_rankinc parameter. 2010-10-25 20:03:37 +00:00
nvt-se 19d7543267 Added detection of loops in DAO forwarding. 2010-10-25 19:49:12 +00:00
adamdunkels 9ecc0437f4 Left-over debug printf removed 2010-10-25 12:25:39 +00:00
adamdunkels 42f37ca1d3 Bugfix: removed old leftover code statement 2010-10-25 11:59:09 +00:00
adamdunkels 3bbd6a00a9 Replace old neighbors according to an LRU policy when a new neighbor needs to be added 2010-10-25 11:58:07 +00:00
adamdunkels e680276954 ARP fix for multicast transmissions. (Patch by Robert Quattlebaum.) 2010-10-24 22:29:39 +00:00
adamdunkels a8848517dd UDP checksum is mandatory with IPv6. (Patch by Robert Quattlebaum.) 2010-10-24 22:28:43 +00:00
adamdunkels 77ecfb0366 Rewrote parts of the retransmission logic so that collect is robust against the situation where the MAC layer will fail to callback after a packet has been transmitted. 2010-10-24 21:08:19 +00:00
adamdunkels 8fa7bf6c31 Always restore the queuebuf to the packetbuf before calling the upper layers. Reduce the waiting time between successive MAC layer retransmissions. 2010-10-24 21:07:00 +00:00
adamdunkels 73f5535754 Made the guard time slightly more conservative - found an occasion where this was needed 2010-10-24 21:06:17 +00:00
adamdunkels 8f8741c7f0 Small style fixes 2010-10-24 21:05:42 +00:00
adamdunkels fd4c0e64aa Removed old unused files rand.[ch]. By default, Contiki uses the libc implementations of the rand() and srand() functions. 2010-10-24 21:02:23 +00:00
nvt-se 00a000cca0 Print the rank correctly in the debug output. 2010-10-22 15:40:10 +00:00
nvt-se 86823a84fb Export fix-point representation of the ETX. Make RPL temporarily use the same representation as before. 2010-10-22 13:50:13 +00:00
joxe 804d23e9f4 made DIS Interval configurable 2010-10-22 13:13:40 +00:00
joxe e414c8c5a4 added function for retrieving link etx to neighbor 2010-10-22 11:34:24 +00:00
nvt-se 6e28b1d3fb Reduced ETX_LIMIT in order to avoid overflows. Removed ETX_LOSS_PENALTY and set packet_etx to ETX_LIMIT instead upon packet loss. 2010-10-21 19:46:21 +00:00
adamdunkels 9cb830ed37 Timing bugfix in the waiting period between channel samples to check if the coast is clear before sending a packet. 2010-10-20 22:25:24 +00:00
adamdunkels 06123fefe2 Defensive programming: make sure that a process is actually running before we try to kill it. 2010-10-20 22:24:46 +00:00
adamdunkels 3ffcff0656 Added mechanisms for explicit de-synchronization of synchronized neighbors. Added link-layer ACKs. Fixed bugs with MAC-layer interaction. Now seems to work somewhat (didn't work at all before, in some cases), but there are still problems with packet loss. 2010-10-20 15:23:43 +00:00
adamdunkels 5585d72c86 A simple but substantial change: uIP used the htons()/HTONS() macro
functions for converting between host and network byte order. These
names are the de facto standard names for this functionality because
of the original BSD TCP/IP implementation. But they cause problems for
uIP/Contiki: some platforms define these names themselves (Mac OS,
most notably), causing compilation problems for Contiki on those
platforms.

This commit changes all htons to uip_htons instead. Same goes for
htonl, ntohs, and ntohl. All-caps versions as well.
2010-10-19 18:29:03 +00:00
adamdunkels 34cba78ca8 Bugfix: bump advertisements only when a parent changes, not because of an upstream parent change 2010-10-19 07:34:29 +00:00
nifi e2b4956a7f Bug fix: release the packet and notify the sender if RDC returned an error 2010-10-14 19:08:39 +00:00
oliverschmidt 2f89e69ff7 Fixed build for platforms which use the default value for QUEUEBUF_NUM. 2010-10-12 19:51:28 +00:00
adamdunkels 020da4e8ba Added a function for obtaining beacon intervals 2010-10-11 23:44:24 +00:00
adamdunkels ec716ea62d Do not reduce transmission interval, unless explicitly told so with the bump flag 2010-10-11 23:43:01 +00:00
adamdunkels 37adf130b4 Rewrite of the congestion logic. A node now report it being congested
when half the transmission queue is full. When a neighbor is heard to
be congested, the rtmetric of that node is inflated to avoid sending
more traffic in its direction.

Fixed problems with beacon intervals: intervals are now not reduced
when a path gets significantly worse, only when they get better.
2010-10-11 23:42:01 +00:00
adamdunkels d821ba5e22 Added a lifetime for link estimates: if they are too old, they are
reset so that a new probing period can produce more up-to-date
estimates. Added a congestion mechanism whereby a neighbor can be
marked as being congested for a period of time, during which the ETX
for the neighbor will be artificially inflated.
2010-10-11 23:38:46 +00:00
adamdunkels 5eb4a0fe8d Rewrote the initial link estimate logic: link estimates are now
computed only over the actual samples, not over the entire
buffer. Also, the initial link estimate is much more conservative now
(16 transmissions) to favor links that have been probed, and which
therefore are likely to have better ETXs.
2010-10-11 23:34:02 +00:00
adamdunkels 0cabe483c3 Don't call sink recv function for zero-size packets, since these most likely are link estimate probes or keepalive packets. Explicitly set eseqno to zero when opening a new connection. 2010-10-07 15:52:28 +00:00
adamdunkels ad35c54473 Bugfix: when a node's rtmetric was lower than SIGNIFICANT_RTMETRIC_PARENT_CHANGE, its beacon timers would always be bumped to its lowest value 2010-10-05 20:06:47 +00:00
adamdunkels 52e9a6f1fb Turned the DRAW_TREE debug flag off by default 2010-10-04 22:36:47 +00:00
adamdunkels 65d640ac53 Several bugfixes to the proactive link estimate maintenance code, which is now enabled by default. Simplified DRAW_TREE code for drawing routing graph in Cooja. Added routing metric penalty to parents that are congested or that drop packets. 2010-10-04 20:27:50 +00:00
adamdunkels 212e73faa6 Removed old netsim code. Added a function for obtaining the packet attributes of a queuebuf packet. 2010-10-04 20:26:01 +00:00
joxe 4f3fc1c404 fixed xmac to use new channel check define name 2010-10-03 22:46:53 +00:00
adamdunkels ceebd7020a Bugfix: the return value sometimes was wrong when a collision was detected. 2010-10-03 20:39:24 +00:00
adamdunkels ae88ed04f1 Moved the definition of the channel check rate used by the radio duty
cycling layer. This definition was previously held in net/mac/mac.h,
with the name MAC_CONF_CHANNEL_CHECK_RATE. But since the rate is used
by the radio duty cycling layer, it makes more sense to change its
name to reflect this. Also, the configuration option should be tied to
the netstack configuration instead.

So the new configuration option is called
NETSTACK_CONF_RDC_CHANNEL_CHECK_RATE.
2010-10-03 20:37:32 +00:00
adamdunkels 40583fe112 Removed the polite announcement code, since it was not used, and enabled the broadcast announcement code by default. Increased the default intervals for broadcast announcements. 2010-10-03 20:10:22 +00:00
adamdunkels 605392522f Bugfixes and improvements: rtmetrics are now 16-bit clean. Added experimental feature that proactively probes neighbors that have not yet been tried out, in order to get an initial ETX for them. 2010-10-03 20:08:44 +00:00
adamdunkels d0579c8a81 Cleaned up the collect neighbor management code 2010-10-03 20:07:10 +00:00
adamdunkels b23a364397 rtmetric values should always be computed as 16-bit values 2010-10-03 20:06:25 +00:00
nvt-se 909569f834 Must check if load_file succeeded 2010-10-01 20:14:14 +00:00
adamdunkels 32ba90ea4c Bugfix: make sure that neighbor exists before attempting to update tx
count.
2010-09-28 06:53:02 +00:00
joxe 77c5187a2e fixed bug where context is null but still referenced 2010-09-23 19:57:50 +00:00
joxe 494d2a3073 only compare with global addresses when selecting source for a specific destination 2010-09-23 18:17:27 +00:00
nifi e242fb28bf Reverted radio API change in CC2420 (not yet fully integrated with Contiki core) 2010-09-23 08:26:06 +00:00
adamdunkels eed22a6f3c A number of changes to the collect code:
* Added an optional "keep alive" mechanism whereby an idle network is
periodically probed by dummy packets to maintain a recent quality
metric when there is no traffic.
* Bugfix in when new routing metrics should be advertised
* Rewrote the ACK logic so that a queuebuf is not allocated for each
ack, only for those acks generated by the sink node.
* Updated the wrap-around logic for sequence numbers: when a sequence
number wraps, it won't go back to 0. Instead, it wraps to 128. This
allows us to understand when a node has rebooted: when its seqno is <
128, it has recently rebooted.
2010-09-22 22:08:08 +00:00
adamdunkels 2cae71e89b Added a function for obtaining the link estimate and rtmetric for a neighbor 2010-09-22 22:04:55 +00:00
adamdunkels 46b2451969 Made the initial link estimate explicit 2010-09-22 22:03:21 +00:00
adamdunkels 40ee35e8c8 Rewrote all busy waits with a new macro, which has a built-in timeout to ensure that busy waits won't hang the CPU 2010-09-22 22:01:53 +00:00
joxe 1dc5366b15 fixed buggy comment 2010-09-21 13:15:25 +00:00
joxe f1d19a5f9a no callback to rpl if rpl is not used 2010-09-21 13:13:09 +00:00
joxe 63ab1ffce0 clear default route when neighbour is removed 2010-09-20 15:30:12 +00:00
nvt-se 58db04ee64 Set a high penalty for packet losses. 2010-09-15 15:59:52 +00:00
nvt-se 098f4001e0 Use fixed point arithmetic in the calculations of the ETX EWMA 2010-09-15 15:10:25 +00:00
nvt-se adf6961a85 Various bug fixes and adjustments for rpl-11 2010-09-15 13:22:22 +00:00
dak664 b9a9e7695d Add option to remove process name strings to save RAM 2010-09-14 18:55:04 +00:00
adamdunkels 18e31f33b9 Minor tweaks. Removed debug output from CVS. 2010-09-14 06:48:36 +00:00
nifi 095f700b63 Moved down inclusion of rtimer-arch.h to allow rtimer_clock_t to be used in rtimer-arch.h 2010-09-13 20:46:02 +00:00
adamdunkels eb58968459 Added a timer to each phase structure that keeps track of for how long
a particular receiver has not ACKed packets. After some time
(currently 16 seconds), the sender will begin sending full strobe
periods again.
2010-09-13 13:39:05 +00:00
adamdunkels 3ae774c91a Added a way to for specifying lists as parts of structs. These lists
must be initialized with a special LIST_STRUCT_INIT() call before
using.
2010-09-13 13:31:00 +00:00
adamdunkels 591766e663 Significant improvements to the Collect protocol:
* Loop detection and untangling. Now uses in-band loop detection that
  works.

* Link quality estimation. Now starts with a conservative /
  pessimistic estimate for new links.

* Retransmissions. MAC layer and network layer retransmissions are now
  decoupled.

* Loss handling. Deals better with losses now.

* Concurrent applications. Each connection now maintains its own
  neighbor table with separated cost to sink estimates for each
  connection.
2010-09-13 13:28:14 +00:00
oliverschmidt a0b8927777 Allow to exit the process owning the foreground window by pressing ctrl-c. This is especially useful if there's no closebutton on the window frames (or no windows at all). 2010-09-09 20:21:26 +00:00
adamdunkels 4e0744954a Rewrite of important parts of the Collect logic: link estimation
calculation and parent selection.  This fixes a severe bug that caused
loops when packets were erroneously retransmitted due to ACK loss.
2010-09-08 19:21:45 +00:00
nifi f05952c926 Changed packet id to use 8 bit instead of 4 bit 2010-08-31 13:14:49 +00:00
nifi d06a1ecc0c corrected include path 2010-08-25 18:35:52 +00:00
dak664 12479c32bc Fix compiler warnings 2010-08-01 21:18:07 +00:00
oliverschmidt 89f6235c13 Using wherex() to determine the length of the string printed with cputsn() fails if the right edge of the screen was reached as wherex() then returns 0.
Therefore we rather count the chars actually printed in cputsn() and return that value thus avoiding usage of wherex() in those scenarios altogether.
2010-07-20 22:19:23 +00:00
nvt-se 11760059d3 The second predicate is not needed. 2010-07-03 23:52:02 +00:00
nifi 3e6113be72 removed debug output 2010-06-30 09:03:20 +00:00
nvt-se 007d4a4001 Improved logic for processing DIOs 2010-06-28 14:51:23 +00:00
nifi c44cf73e4f Adapted to new SPI and CC2420 naming 2010-06-24 11:25:55 +00:00
nifi f609cb0f7c Added macro to read from CC2420 RAM 2010-06-24 11:25:07 +00:00
nifi 30db4eff52 Made QUEUEBUF_STATS configurable 2010-06-24 09:48:21 +00:00
nifi 49a2ca6b1e Fixed naming of CC2420 macros 2010-06-24 09:28:38 +00:00
nifi fb3c2e75cf removed obsolete definitions 2010-06-24 09:28:12 +00:00
nifi c6b6b6625c removed obsolete header file for CC2420 2010-06-24 09:20:28 +00:00
joxe f7a82a9145 split SPI code into generic and CC2420-related and renamed constants in CC2420 2010-06-23 10:15:28 +00:00
joxe bc398ca546 removed platform dependent loop-count from cc2420 - moved to platform config instead 2010-06-21 19:48:00 +00:00
joxe a5d7b197eb added support for the Z1 platform and its 8Mhz 2010-06-21 19:09:35 +00:00
joxe 1f0a43bf01 fixed timer bug - did not do equality comparison 2010-06-21 19:07:24 +00:00
joxe 546504516b changed timer comparison to avoid crashing mspgcc4 2010-06-21 09:41:49 +00:00
nifi e965b74cf5 added missing include 2010-06-18 08:28:56 +00:00
nifi 4741b95858 added missing include 2010-06-16 10:10:10 +00:00
nifi 21828ad782 Changed the retransmission time to be based on the configured MAC channel check rate when the RDC has no channel check interval. 2010-06-16 10:08:30 +00:00
adamdunkels 7647cbd8aa Use the list_item_next() API 2010-06-15 19:22:25 +00:00
adamdunkels 560c84a2fe Added a function for getting the first global IPv6 address 2010-06-15 19:16:22 +00:00
adamdunkels a84cc7c8a0 Added a function for obtaining the next item on the list. This makes list iterations nicer, as the ->next pointer now is hidden within the list abstraction. 2010-06-15 18:54:27 +00:00
nifi 01b1359b1f removed unused (and slightly problematic) code 2010-06-15 14:19:22 +00:00
nifi 46f9f7e6c0 corrected include path 2010-06-15 13:31:22 +00:00
adamdunkels 3fa8ffda1a Moved the modules packetbuf, queuebuf, and packetqueue from net/rime to net/, since they are not Rime-specific 2010-06-14 19:19:16 +00:00
adamdunkels 951fd78f6c ctimer moved from net/rime to sys/ 2010-06-14 18:58:45 +00:00
nvt-se fad2b1def9 Clarified the function naming for neighbor information callbacks - names now indicate where the information is from. 2010-06-14 18:35:04 +00:00
nifi adc38568ad Minor optimization: replaced init loops with memset to reduce code size 2010-06-14 13:51:13 +00:00
nifi 7499939c94 removed debug output 2010-06-14 13:07:09 +00:00
nvt-se e000b1abf3 A major update to ContikiRPL resulting in a reduced code footprint by
300 bytes, as well as cleaner protocol logic.

* Made parent management uniform.

* Simplified the DIO processing.

* Improved the Objective Function API and its documentation.

* Removed redundant code at various places.

* Improved identifier naming.

* Switched visualization from candidate parents to preferred parents only.

* Made DAO ACK transmissions configurable.

* Improved initial ETX guess by using a cached local confidence value.

* Added a periodical rank recalculation function to reduce
  the maximum stack depth.

* Increased the Trickle redundancy constant to ensure faster
  topological updates.
2010-06-14 12:44:37 +00:00
adamdunkels a890cd3d49 Moved ctimer.[ch] from their old and illogical location in core/net/rime to a more appropriate place in core/sys 2010-06-14 11:33:58 +00:00
adamdunkels 97708d6235 Documentation group set accordingly 2010-06-14 07:35:53 +00:00
adamdunkels 8f8393aadc Moved ctimer.[ch] from their old and illogical location in core/net/rime to a more appropriate place in core/sys 2010-06-14 07:34:36 +00:00
adamdunkels baa62e9314 Addresses are not const 2010-06-14 06:55:26 +00:00
adamdunkels 2647f879c2 Bugfix: select the best parent if current parent is NULL 2010-06-14 06:54:47 +00:00
adamdunkels 8d1680fed5 Filter duplicate packets 2010-06-14 06:52:41 +00:00
adamdunkels a6bd51f361 If a packet is lost due to NOACK or TXERR, we count the number of transmissions and we add an additional loss penalty (currently one) 2010-06-14 06:51:58 +00:00
joxe 1095997b66 made DIOs and OCP 09 compliant 2010-06-12 10:55:46 +00:00
nvt-se 75b624eb71 Refactored the code, removed void pointer arithmetic, and fixed invalid list removal after freeing of memb object. 2010-06-11 12:32:48 +00:00
nvt-se 8a43743a42 Updated declaration for rpl_alloc_dag. 2010-06-08 21:41:02 +00:00
nvt-se b1521e4950 Check correctly if a DAG already exists in the same instance. 2010-06-08 21:37:22 +00:00