Merge #9382: [backport 0.13] Prefer coins that have fewer ancestors, sanity check txn before ATMP

e1ff0db reduce number of lookups in TransactionWithinChainLimit (Gregory Sanders)
4bf2bec Test for fix of txn chaining in wallet (Gregory Sanders)
f00066a CreateTransaction: Don't return success with too-many-ancestor txn (Gregory Sanders)
bdd6d4c SelectCoinsMinConf: Prefer coins with fewer ancestors (Gregory Sanders)

6 files changed, 104 insertions, 43 deletions

diff --git a/qa/rpc-tests/wallet.py b/qa/rpc-tests/wallet.py
index 3c0dc0f4ea..992fb8a2d6 100755
--- a/qa/rpc-tests/wallet.py
+++ b/qa/rpc-tests/wallet.py
@@ -330,10 +330,12 @@ class WalletTest (BitcoinTestFramework):
             # disabled until issue is fixed: https://github.com/bitcoin/bitcoin/issues/7463
             # '-salvagewallet',
         ]
+        chainlimit = 6
         for m in maintenance:
             print("check " + m)
             stop_nodes(self.nodes)
-            self.nodes = start_nodes(3, self.options.tmpdir, [[m]] * 3)
+            # set lower ancestor limit for later
+            self.nodes = start_nodes(3, self.options.tmpdir, [[m, "-limitancestorcount="+str(chainlimit)]] * 3)
             while m == '-reindex' and [block_count] * 3 != [self.nodes[i].getblockcount() for i in range(3)]:
                 # reindex will leave rpc warm up "early"; Wait for it to finish
                 time.sleep(0.1)
@@ -346,5 +348,26 @@ class WalletTest (BitcoinTestFramework):
         assert_equal(coinbase_tx_1["transactions"][0]["blockhash"], blocks[1])
         assert_equal(len(self.nodes[0].listsinceblock(blocks[1])["transactions"]), 0)
 
+        # ==Check that wallet prefers to use coins that don't exceed mempool limits =====
+
+        # Get all non-zero utxos together
+        chain_addrs = [self.nodes[0].getnewaddress(), self.nodes[0].getnewaddress()]
+        singletxid = self.nodes[0].sendtoaddress(chain_addrs[0], self.nodes[0].getbalance(), "", "", True)
+        self.nodes[0].generate(1)
+        node0_balance = self.nodes[0].getbalance()
+        # Split into two chains
+        rawtx = self.nodes[0].createrawtransaction([{"txid":singletxid, "vout":0}], {chain_addrs[0]:node0_balance/2-Decimal('0.01'), chain_addrs[1]:node0_balance/2-Decimal('0.01')})
+        signedtx = self.nodes[0].signrawtransaction(rawtx)
+        singletxid = self.nodes[0].sendrawtransaction(signedtx["hex"])
+        txids = [singletxid, singletxid]
+        self.nodes[0].generate(1)
+
+        # Make a long chain of unconfirmed payments without hitting mempool limit
+        txid_list = []
+        for i in range(chainlimit*2):
+            txid_list.append(self.nodes[0].sendtoaddress(chain_addrs[0], Decimal('0.0001')))
+        assert_equal(self.nodes[0].getmempoolinfo()['size'], chainlimit*2)
+        assert_equal(len(txid_list), chainlimit*2)
+
 if __name__ == '__main__':
     WalletTest().main()
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 59afb2cf5a..63a26da326 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -1134,3 +1134,10 @@ void CTxMemPool::TrimToSize(size_t sizelimit, std::vector<uint256>* pvNoSpendsRe
     if (maxFeeRateRemoved > CFeeRate(0))
         LogPrint("mempool", "Removed %u txn, rolling minimum fee bumped to %s\n", nTxnRemoved, maxFeeRateRemoved.ToString());
 }
+
+bool CTxMemPool::TransactionWithinChainLimit(const uint256& txid, size_t chainLimit) const {
+    LOCK(cs);
+    auto it = mapTx.find(txid);
+    return it == mapTx.end() || (it->GetCountWithAncestors() < chainLimit &&
+       it->GetCountWithDescendants() < chainLimit);
+}
diff --git a/src/txmempool.h b/src/txmempool.h
index afb328b5af..8129a05375 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -595,6 +595,9 @@ public:
     /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
     int Expire(int64_t time);
 
+    /** Returns false if the transaction is in the mempool and not within the chain limit specified. */
+    bool TransactionWithinChainLimit(const uint256& txid, size_t chainLimit) const;
+
     unsigned long size()
     {
         LOCK(cs);
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index c6c5058984..38637b2d5c 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -78,24 +78,24 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         empty_wallet();
 
         // with an empty wallet we can't even pay one cent
-        BOOST_CHECK(!wallet.SelectCoinsMinConf( 1 * CENT, 1, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf( 1 * CENT, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
 
         add_coin(1*CENT, 4);        // add a new 1 cent coin
 
         // with a new 1 cent coin, we still can't find a mature 1 cent
-        BOOST_CHECK(!wallet.SelectCoinsMinConf( 1 * CENT, 1, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf( 1 * CENT, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
 
         // but we can find a new 1 cent
-        BOOST_CHECK( wallet.SelectCoinsMinConf( 1 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf( 1 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 1 * CENT);
 
         add_coin(2*CENT);           // add a mature 2 cent coin
 
         // we can't make 3 cents of mature coins
-        BOOST_CHECK(!wallet.SelectCoinsMinConf( 3 * CENT, 1, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf( 3 * CENT, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
 
         // we can make 3 cents of new  coins
-        BOOST_CHECK( wallet.SelectCoinsMinConf( 3 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf( 3 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 3 * CENT);
 
         add_coin(5*CENT);           // add a mature 5 cent coin,
@@ -105,33 +105,33 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         // now we have new: 1+10=11 (of which 10 was self-sent), and mature: 2+5+20=27.  total = 38
 
         // we can't make 38 cents only if we disallow new coins:
-        BOOST_CHECK(!wallet.SelectCoinsMinConf(38 * CENT, 1, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf(38 * CENT, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
         // we can't even make 37 cents if we don't allow new coins even if they're from us
-        BOOST_CHECK(!wallet.SelectCoinsMinConf(38 * CENT, 6, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf(38 * CENT, 6, 6, 0, vCoins, setCoinsRet, nValueRet));
         // but we can make 37 cents if we accept new coins from ourself
-        BOOST_CHECK( wallet.SelectCoinsMinConf(37 * CENT, 1, 6, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(37 * CENT, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 37 * CENT);
         // and we can make 38 cents if we accept all new coins
-        BOOST_CHECK( wallet.SelectCoinsMinConf(38 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(38 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 38 * CENT);
 
         // try making 34 cents from 1,2,5,10,20 - we can't do it exactly
-        BOOST_CHECK( wallet.SelectCoinsMinConf(34 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(34 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 35 * CENT);       // but 35 cents is closest
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);     // the best should be 20+10+5.  it's incredibly unlikely the 1 or 2 got included (but possible)
 
         // when we try making 7 cents, the smaller coins (1,2,5) are enough.  We should see just 2+5
-        BOOST_CHECK( wallet.SelectCoinsMinConf( 7 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf( 7 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 7 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
         // when we try making 8 cents, the smaller coins (1,2,5) are exactly enough.
-        BOOST_CHECK( wallet.SelectCoinsMinConf( 8 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf( 8 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK(nValueRet == 8 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         // when we try making 9 cents, no subset of smaller coins is enough, and we get the next bigger coin (10)
-        BOOST_CHECK( wallet.SelectCoinsMinConf( 9 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf( 9 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 10 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -145,30 +145,30 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin(30*CENT); // now we have 6+7+8+20+30 = 71 cents total
 
         // check that we have 71 and not 72
-        BOOST_CHECK( wallet.SelectCoinsMinConf(71 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
-        BOOST_CHECK(!wallet.SelectCoinsMinConf(72 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(71 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!wallet.SelectCoinsMinConf(72 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
 
         // now try making 16 cents.  the best smaller coins can do is 6+7+8 = 21; not as good at the next biggest coin, 20
-        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 20 * CENT); // we should get 20 in one coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
         add_coin( 5*CENT); // now we have 5+6+7+8+20+30 = 75 cents total
 
         // now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, better than the next biggest coin, 20
-        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 18 * CENT); // we should get 18 in 3 coins
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         add_coin( 18*CENT); // now we have 5+6+7+8+18+20+30
 
         // and now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, the same as the next biggest coin, 18
-        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(16 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 18 * CENT);  // we should get 18 in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U); // because in the event of a tie, the biggest coin wins
 
         // now try making 11 cents.  we should get 5+6
-        BOOST_CHECK( wallet.SelectCoinsMinConf(11 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(11 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 11 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
@@ -177,11 +177,11 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin( 2*COIN);
         add_coin( 3*COIN);
         add_coin( 4*COIN); // now we have 5+6+7+8+18+20+30+100+200+300+400 = 1094 cents
-        BOOST_CHECK( wallet.SelectCoinsMinConf(95 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(95 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 1 * COIN);  // we should get 1 BTC in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
-        BOOST_CHECK( wallet.SelectCoinsMinConf(195 * CENT, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(195 * CENT, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 2 * COIN);  // we should get 2 BTC in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -196,14 +196,14 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
 
         // try making 1 * MIN_CHANGE from the 1.5 * MIN_CHANGE
         // we'll get change smaller than MIN_CHANGE whatever happens, so can expect MIN_CHANGE exactly
-        BOOST_CHECK( wallet.SelectCoinsMinConf(MIN_CHANGE, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(MIN_CHANGE, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE);
 
         // but if we add a bigger coin, small change is avoided
         add_coin(1111*MIN_CHANGE);
 
         // try making 1 from 0.1 + 0.2 + 0.3 + 0.4 + 0.5 + 1111 = 1112.5
-        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 1 * MIN_CHANGE); // we should get the exact amount
 
         // if we add more small coins:
@@ -211,7 +211,7 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin(MIN_CHANGE * 7 / 10);
 
         // and try again to make 1.0 * MIN_CHANGE
-        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 1 * MIN_CHANGE); // we should get the exact amount
 
         // run the 'mtgox' test (see http://blockexplorer.com/tx/29a3efd3ef04f9153d47a990bd7b048a4b2d213daaa5fb8ed670fb85f13bdbcf)
@@ -220,7 +220,7 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         for (int i = 0; i < 20; i++)
             add_coin(50000 * COIN);
 
-        BOOST_CHECK( wallet.SelectCoinsMinConf(500000 * COIN, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(500000 * COIN, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 500000 * COIN); // we should get the exact amount
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 10U); // in ten coins
 
@@ -233,7 +233,7 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin(MIN_CHANGE * 6 / 10);
         add_coin(MIN_CHANGE * 7 / 10);
         add_coin(1111 * MIN_CHANGE);
-        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(1 * MIN_CHANGE, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 1111 * MIN_CHANGE); // we get the bigger coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -243,7 +243,7 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin(MIN_CHANGE * 6 / 10);
         add_coin(MIN_CHANGE * 8 / 10);
         add_coin(1111 * MIN_CHANGE);
-        BOOST_CHECK( wallet.SelectCoinsMinConf(MIN_CHANGE, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( wallet.SelectCoinsMinConf(MIN_CHANGE, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE);   // we should get the exact amount
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U); // in two coins 0.4+0.6
 
@@ -254,12 +254,12 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
         add_coin(MIN_CHANGE * 100);
 
         // trying to make 100.01 from these three coins
-        BOOST_CHECK(wallet.SelectCoinsMinConf(MIN_CHANGE * 10001 / 100, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(wallet.SelectCoinsMinConf(MIN_CHANGE * 10001 / 100, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE * 10105 / 100); // we should get all coins
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         // but if we try to make 99.9, we should take the bigger of the two small coins to avoid small change
-        BOOST_CHECK(wallet.SelectCoinsMinConf(MIN_CHANGE * 9990 / 100, 1, 1, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(wallet.SelectCoinsMinConf(MIN_CHANGE * 9990 / 100, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
         BOOST_CHECK_EQUAL(nValueRet, 101 * MIN_CHANGE);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
@@ -269,7 +269,7 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
              // Create 676 inputs (= MAX_STANDARD_TX_SIZE / 148 bytes per input)
              for (uint16_t j = 0; j < 676; j++)
                  add_coin(amt);
-             BOOST_CHECK(wallet.SelectCoinsMinConf(2000, 1, 1, vCoins, setCoinsRet, nValueRet));
+             BOOST_CHECK(wallet.SelectCoinsMinConf(2000, 1, 1, 0, vCoins, setCoinsRet, nValueRet));
              if (amt - 2000 < MIN_CHANGE) {
                  // needs more than one input:
                  uint16_t returnSize = std::ceil((2000.0 + MIN_CHANGE)/amt);
@@ -291,8 +291,8 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
 
             // picking 50 from 100 coins doesn't depend on the shuffle,
             // but does depend on randomness in the stochastic approximation code
-            BOOST_CHECK(wallet.SelectCoinsMinConf(50 * COIN, 1, 6, vCoins, setCoinsRet , nValueRet));
-            BOOST_CHECK(wallet.SelectCoinsMinConf(50 * COIN, 1, 6, vCoins, setCoinsRet2, nValueRet));
+            BOOST_CHECK(wallet.SelectCoinsMinConf(50 * COIN, 1, 6, 0, vCoins, setCoinsRet , nValueRet));
+            BOOST_CHECK(wallet.SelectCoinsMinConf(50 * COIN, 1, 6, 0, vCoins, setCoinsRet2, nValueRet));
             BOOST_CHECK(!equal_sets(setCoinsRet, setCoinsRet2));
 
             int fails = 0;
@@ -300,8 +300,8 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
             {
                 // selecting 1 from 100 identical coins depends on the shuffle; this test will fail 1% of the time
                 // run the test RANDOM_REPEATS times and only complain if all of them fail
-                BOOST_CHECK(wallet.SelectCoinsMinConf(COIN, 1, 6, vCoins, setCoinsRet , nValueRet));
-                BOOST_CHECK(wallet.SelectCoinsMinConf(COIN, 1, 6, vCoins, setCoinsRet2, nValueRet));
+                BOOST_CHECK(wallet.SelectCoinsMinConf(COIN, 1, 6, 0, vCoins, setCoinsRet , nValueRet));
+                BOOST_CHECK(wallet.SelectCoinsMinConf(COIN, 1, 6, 0, vCoins, setCoinsRet2, nValueRet));
                 if (equal_sets(setCoinsRet, setCoinsRet2))
                     fails++;
             }
@@ -321,8 +321,8 @@ BOOST_AUTO_TEST_CASE(coin_selection_tests)
             {
                 // selecting 1 from 100 identical coins depends on the shuffle; this test will fail 1% of the time
                 // run the test RANDOM_REPEATS times and only complain if all of them fail
-                BOOST_CHECK(wallet.SelectCoinsMinConf(90*CENT, 1, 6, vCoins, setCoinsRet , nValueRet));
-                BOOST_CHECK(wallet.SelectCoinsMinConf(90*CENT, 1, 6, vCoins, setCoinsRet2, nValueRet));
+                BOOST_CHECK(wallet.SelectCoinsMinConf(90*CENT, 1, 6, 0, vCoins, setCoinsRet , nValueRet));
+                BOOST_CHECK(wallet.SelectCoinsMinConf(90*CENT, 1, 6, 0, vCoins, setCoinsRet2, nValueRet));
                 if (equal_sets(setCoinsRet, setCoinsRet2))
                     fails++;
             }
@@ -346,7 +346,7 @@ BOOST_AUTO_TEST_CASE(ApproximateBestSubset)
         add_coin(1000 * COIN);
     add_coin(3 * COIN);
 
-    BOOST_CHECK(wallet.SelectCoinsMinConf(1003 * COIN, 1, 6, vCoins, setCoinsRet, nValueRet));
+    BOOST_CHECK(wallet.SelectCoinsMinConf(1003 * COIN, 1, 6, 0, vCoins, setCoinsRet, nValueRet));
     BOOST_CHECK_EQUAL(nValueRet, 1003 * COIN);
     BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 }
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 7f62402625..7bcb9aaf11 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1921,7 +1921,7 @@ static void ApproximateBestSubset(vector<pair<CAmount, pair<const CWalletTx*,uns
     }
 }
 
-bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int nConfTheirs, vector<COutput> vCoins,
+bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const int nConfMine, const int nConfTheirs, const uint64_t nMaxAncestors, vector<COutput> vCoins,
                                  set<pair<const CWalletTx*,unsigned int> >& setCoinsRet, CAmount& nValueRet) const
 {
     setCoinsRet.clear();
@@ -1946,6 +1946,9 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int
         if (output.nDepth < (pcoin->IsFromMe(ISMINE_ALL) ? nConfMine : nConfTheirs))
             continue;
 
+        if (!mempool.TransactionWithinChainLimit(pcoin->GetHash(), nMaxAncestors))
+            continue;
+
         int i = output.i;
         CAmount n = pcoin->vout[i].nValue;
 
@@ -2071,10 +2074,17 @@ bool CWallet::SelectCoins(const vector<COutput>& vAvailableCoins, const CAmount&
             ++it;
     }
 
+    size_t nMaxChainLength = std::min(GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT), GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT));
+    bool fRejectLongChains = GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS);
+
     bool res = nTargetValue <= nValueFromPresetInputs ||
-        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 6, vCoins, setCoinsRet, nValueRet) ||
-        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 1, vCoins, setCoinsRet, nValueRet) ||
-        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, vCoins, setCoinsRet, nValueRet));
+        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 6, 0, vCoins, setCoinsRet, nValueRet) ||
+        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 1, 0, vCoins, setCoinsRet, nValueRet) ||
+        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, 2, vCoins, setCoinsRet, nValueRet)) ||
+        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, std::min((size_t)4, nMaxChainLength/3), vCoins, setCoinsRet, nValueRet)) ||
+        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, nMaxChainLength/2, vCoins, setCoinsRet, nValueRet)) ||
+        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, nMaxChainLength, vCoins, setCoinsRet, nValueRet)) ||
+        (bSpendZeroConfChange && !fRejectLongChains && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, std::numeric_limits<uint64_t>::max(), vCoins, setCoinsRet, nValueRet));
 
     // because SelectCoinsMinConf clears the setCoinsRet, we now add the possible inputs to the coinset
     setCoinsRet.insert(setPresetCoins.begin(), setPresetCoins.end());
@@ -2442,6 +2452,21 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
         }
     }
 
+    if (GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS)) {
+        // Lastly, ensure this tx will pass the mempool's chain limits
+        LockPoints lp;
+        CTxMemPoolEntry entry(txNew, 0, 0, 0, 0, false, 0, false, 0, lp);
+        CTxMemPool::setEntries setAncestors;
+        size_t nLimitAncestors = GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT);
+        size_t nLimitAncestorSize = GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT)*1000;
+        size_t nLimitDescendants = GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT);
+        size_t nLimitDescendantSize = GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT)*1000;
+        std::string errString;
+        if (!mempool.CalculateMemPoolAncestors(entry, setAncestors, nLimitAncestors, nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, errString)) {
+            strFailReason = _("Transaction has too long of a mempool chain");
+            return false;
+        }
+    }
     return true;
 }
 
@@ -3263,6 +3288,7 @@ std::string CWallet::GetWalletHelpString(bool showDebug)
         strUsage += HelpMessageOpt("-dblogsize=<n>", strprintf("Flush wallet database activity from memory to disk log every <n> megabytes (default: %u)", DEFAULT_WALLET_DBLOGSIZE));
         strUsage += HelpMessageOpt("-flushwallet", strprintf("Run a thread to flush wallet periodically (default: %u)", DEFAULT_FLUSHWALLET));
         strUsage += HelpMessageOpt("-privdb", strprintf("Sets the DB_PRIVATE flag in the wallet db environment (default: %u)", DEFAULT_WALLET_PRIVDB));
+        strUsage += HelpMessageOpt("-walletrejectlongchains", strprintf(_("Wallet will not create transactions that violate mempool chain limits (default: %u"), DEFAULT_WALLET_REJECT_LONG_CHAINS));
     }
 
     return strUsage;
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 056dcc5daf..10f6ea8fed 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -51,6 +51,8 @@ static const CAmount MIN_CHANGE = CENT;
 static const bool DEFAULT_SPEND_ZEROCONF_CHANGE = true;
 //! Default for -sendfreetransactions
 static const bool DEFAULT_SEND_FREE_TRANSACTIONS = false;
+//! Default for -walletrejectlongchains
+static const bool DEFAULT_WALLET_REJECT_LONG_CHAINS = false;
 //! -txconfirmtarget default
 static const unsigned int DEFAULT_TX_CONFIRM_TARGET = 2;
 //! Largest (in bytes) free transaction we're willing to create
@@ -668,7 +670,7 @@ public:
      * completion the coin set and corresponding actual target value is
      * assembled
      */
-    bool SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int nConfTheirs, std::vector<COutput> vCoins, std::set<std::pair<const CWalletTx*,unsigned int> >& setCoinsRet, CAmount& nValueRet) const;
+    bool SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int nConfTheirs, uint64_t nMaxAncestors, std::vector<COutput> vCoins, std::set<std::pair<const CWalletTx*,unsigned int> >& setCoinsRet, CAmount& nValueRet) const;
 
     bool IsSpent(const uint256& hash, unsigned int n) const;