dex/testing/dcr: fix reorg script

The dcr beta node is only able to add 1 block to the mainchain after
disconnecting from the alpha node, because the beta node has no way to
receive votes while disconnected from alpha. This prevents reorgs on
either nodes since the reorg script ends with both nodes reconnected but
having just 1 divergent mainchain block each.

This is fixed by mining an "extra" block on either node (after reconnection)
to trigger a reorg on the other node.

Additionally, the dcr reorg script is modified to accept 2 optional arguments:
`./reorg (node depth), where
- `node` is the node that should experience a reorg, either "alpha" or "beta"
- `depth` is the number of blocks that should be purged from `node`. Currently,
 due to the beta mining limitation mentioned above, only 1 block can be purged
 from either nodes during reorg, but the reorged node will always see `depth`
 new blocks after the reorg.

dex/testing/dcr/README.md

@@ -30,8 +30,14 @@ allow you to perform RPC calls against each wallet.
 wallets.
 Try `./alpha getbalance`, for example.
 
-`./reorg` will step through a script that causes the alpha node to undergo a
-1-deep reorganization.
+`./reorg` will step through a script that causes the alpha or beta node to
+undergo a 1-deep reorganization. The script takes the following optional
+arguments: `./reorg {node} {depth}`, where:
+- `node` is the node that should undergo a reorg, either "alpha" or "beta" (default: alpha)
+- `depth` is the number of blocks that should be reorged into `node` (default: 1 for alpha, 3 for beta).
+Currently, only 1 block (instead of `depth` blocks) can be purged from either
+nodes during reorg, but the reorged node will always see `depth` new blocks
+after the reorg.
 
 `./quit` shuts down the nodes and closes the tmux session.
 

dex/testing/dcr/harness.sh

@@ -115,19 +115,53 @@ chmod +x "${NODES_ROOT}/harness-ctl/mine-beta"
 # Reorg script
 cat > "${NODES_ROOT}/harness-ctl/reorg" <<EOF
 #!/usr/bin/env bash
+REORG_NODE="alpha"
+VALID_NODE="beta"
+REORG_DEPTH=1
+
+if [ "\$1" = "beta" ]; then
+  REORG_NODE="beta"
+  VALID_NODE="alpha"
+  REORG_DEPTH=3
+fi
+
+if [ "\$2" != "" ]; then
+  REORG_DEPTH=\$2
+fi
+
+# TODO: Cannot currently cause a 1+ block re-org on alpha because
+# beta cannot mine more than 1 main chain block while disconnected
+# from alpha.
+if [ "\${REORG_NODE}" = "alpha" ] && [ \${REORG_DEPTH} -gt 1 ]; then
+  echo "Cannot cause a re-org of more than 1 block on alpha."
+  exit 1
+fi
+
+echo "Current alpha, beta best blocks"
+./alpha getbestblock && ./beta getbestblock
+
 echo "Disconnecting beta from alpha"
-sleep 1
 ./beta addnode 127.0.0.1:${ALPHA_NODE_PORT} remove
-echo "Mining a block on alpha"
 sleep 1
-./mine-alpha 1
-echo "Mining 3 blocks on beta"
-./mine-beta 3
-sleep 2
+
+# Mine equal number of blocks while disconnected.
+for NODE in \${REORG_NODE} \${VALID_NODE}; do
+  echo "Mining \${REORG_DEPTH} blocks on \${NODE}"
+  ./mine-\${NODE} \${REORG_DEPTH}
+  sleep 1
+done
+echo "Diverged alpha, beta best blocks" && ./alpha getbestblock && ./beta getbestblock
+
 echo "Reconnecting beta to alpha"
 ./beta addnode 127.0.0.1:${ALPHA_NODE_PORT} add
+sleep 1
+
+echo "Mining 1 more block on \${VALID_NODE} to trigger re-org on \${REORG_NODE}"
+./mine-\${VALID_NODE} 1
 sleep 2
-grep REORG ${NODES_ROOT}/alpha/logs/simnet/dcrd.log
+echo "Reconnected alpha, beta best blocks" && ./alpha getbestblock && ./beta getbestblock
+
+grep REORG ${NODES_ROOT}/\${REORG_NODE}/logs/simnet/dcrd.log
 EOF
 chmod +x "${NODES_ROOT}/harness-ctl/reorg"