From ff5e9cd74dba04880427c397d6b3d58dad8316c0 Mon Sep 17 00:00:00 2001
From: Gregory Sanders <gsanders87@gmail.com>
Date: Fri, 15 Sep 2017 14:47:57 -0400
Subject: [PATCH] mempool and policy support for peg-in inputs

---
 src/policy/policy.cpp |  6 +++++-
 src/txmempool.cpp     |  3 ++-
 src/validation.cpp    | 28 ++++++++++++++++++++++++++--
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
index ce3f037666..2d0299a62d 100644
--- a/src/policy/policy.cpp
+++ b/src/policy/policy.cpp
@@ -120,6 +120,10 @@ bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
 
     for (unsigned int i = 0; i < tx.vin.size(); i++)
     {
+        if (tx.vin[i].m_is_pegin) {
+            // This deals with p2sh in general only
+            continue;
+        }
         const CTxOut& prev = mapInputs.GetOutputFor(tx.vin[i]);
 
         // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
@@ -169,7 +173,7 @@ bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
         if (tx.wit.vtxinwit.size() <= i || tx.wit.vtxinwit[i].scriptWitness.IsNull())
             continue;
 
-        const CTxOut &prev = mapInputs.GetOutputFor(tx.vin[i]);
+        const CTxOut &prev = tx.vin[i].m_is_pegin ? GetPeginOutputFromWitness(tx.wit.vtxinwit[i].m_pegin_witness) :  mapInputs.GetOutputFor(tx.vin[i]);
 
         // get the scriptPubKey corresponding to this input:
         CScript prevScript = prev.scriptPubKey;
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 722d89764b..6610015ba0 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -709,8 +709,9 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
                     parentSigOpCost += it2->GetSigOpCost();
                 }
             } else {
+                // peg-in inputs are not sanity-checked to be valid
                 const CCoins* coins = pcoins->AccessCoins(txin.prevout.hash);
-                assert(coins && coins->IsAvailable(txin.prevout.n));
+                assert(txin.m_is_pegin || (coins && coins->IsAvailable(txin.prevout.n)));
             }
             // Check whether its inputs are marked in mapNextTx.
             auto it3 = mapNextTx.find(txin.prevout);
diff --git a/src/validation.cpp b/src/validation.cpp
index 4b03dd31a4..7e4c12501c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1124,6 +1124,10 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         // Note that this does not check for the presence of actual outputs (see the next check for that),
         // and only helps with filling in pfMissingInputs (to determine missing vs spent).
         BOOST_FOREACH(const CTxIn txin, tx.vin) {
+            // Don't look for coins that only exist in parent chain
+            if (txin.m_is_pegin) {
+                continue;
+            }
             if (!pcoinsTip->HaveCoinsInCache(txin.prevout.hash))
                 vHashTxnToUncache.push_back(txin.prevout.hash);
             if (!view.HaveCoins(txin.prevout.hash)) {
@@ -1137,6 +1141,22 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         if (!view.HaveInputs(tx))
             return state.Invalid(false, REJECT_DUPLICATE, "bad-txns-inputs-spent");
 
+        // Extract peg-in inputs, pass set to mempool entry. Validity of pegins checked in CheckInputs
+        for (unsigned int i = 0; i < tx.vin.size(); i++) {
+            if (tx.vin[i].m_is_pegin) {
+                // Quick check of pegin witness and prevout to extract db entry
+                if (tx.wit.vtxinwit.size() <= i || tx.wit.vtxinwit[i].m_pegin_witness.stack.size() < 6 || uint256(tx.wit.vtxinwit[i].m_pegin_witness.stack[2]).IsNull() || tx.vin[i].prevout.hash.IsNull()) {
+                    return state.Invalid(false, REJECT_INVALID, "pegin-no-witness");
+                }
+                std::pair<uint256, COutPoint> pegin = std::make_pair(uint256(tx.wit.vtxinwit[i].m_pegin_witness.stack[2]), tx.vin[i].prevout);
+                // This assumes non-null prevout and genesis block hash
+                if (view.IsWithdrawSpent(pegin)) {
+                    return state.Invalid(false, REJECT_CONFLICT, "pegin-already-claimed");
+                }
+                setPeginsSpent.insert(pegin);
+            }
+        }
+
         // Bring the best block into scope
         view.GetBestBlock();
 
@@ -1171,14 +1191,18 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         double nPriorityDummy = 0;
         pool.ApplyDeltas(hash, nPriorityDummy, nModifiedFees);
 
-        CAmount inChainInputValue;
-        double dPriority = view.GetPriority(tx, chainActive.Height(), inChainInputValue);
+        // Neuter priority in mempool
+        CAmount inChainInputValue = 0;
+        double dPriority = 0;
 
         // Keep track of transactions that spend a coinbase, which we re-scan
         // during reorgs to ensure COINBASE_MATURITY is still met.
         // Also track withdraw lock spends to allow them through free relay
         bool fSpendsCoinbase = false;
         BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+            if (txin.m_is_pegin) {
+                continue;
+            }
             const CCoins *coins = view.AccessCoins(txin.prevout.hash);
             if (coins->IsCoinBase()) {
                 fSpendsCoinbase = true;