Merge pull request #1401 from evoskuil/master

Restore bip30, and bip9 checkpoint-based "activations".

include/bitcoin/system/chain/chain_state.hpp

@@ -21,6 +21,7 @@
 
 #include <memory>
 #include <deque>
+#include <bitcoin/system/chain/checkpoint.hpp>
 #include <bitcoin/system/chain/context.hpp>
 #include <bitcoin/system/chain/enums/forks.hpp>
 #include <bitcoin/system/define.hpp>
@@ -79,6 +80,12 @@ class BC_API chain_state
 
         /// (block - (block % 2016 == 0 ? 2016 : block % 2016))
         size_t timestamp_retarget{};
+
+        /// mainnet: 419328, testnet: 770112 (or map::unrequested)
+        size_t bip9_bit0_height;
+
+        /// mainnet: 481824, testnet: 834624 (or map::unrequested)
+        size_t bip9_bit1_height;
     };
 
     /// Values used to populate chain state at the target height.
@@ -90,6 +97,12 @@ class BC_API chain_state
         /// Hash of the candidate block or null_hash for memory pool.
         hash_digest hash{};
 
+        /// Hash of the bip9_bit0 block or null_hash if unrequested.
+        hash_digest bip9_bit0_hash;
+
+        /// Hash of the bip9_bit1 block or null_hash if unrequested.
+        hash_digest bip9_bit1_hash;
+
         /// Values must be ordered by height with high (block - 1) last.
         struct
         {
@@ -193,14 +206,19 @@ class BC_API chain_state
     static size_t bits_count(size_t height, uint32_t forks,
         size_t retargeting_interval) NOEXCEPT;
     static size_t version_count(size_t height, uint32_t forks,
-        size_t activation_sample) NOEXCEPT;
+        size_t bip34_activation_sample) NOEXCEPT;
     static size_t timestamp_count(size_t height, uint32_t forks) NOEXCEPT;
     static size_t retarget_height(size_t height, uint32_t forks,
         size_t retargeting_interval) NOEXCEPT;
+    static size_t bip9_bit0_height(size_t height,
+        const checkpoint& bip9_bit0_active_checkpoint) NOEXCEPT;
+    static size_t bip9_bit1_height(size_t height,
+        const checkpoint& bip9_bit1_active_checkpoint) NOEXCEPT;
 
     static data to_pool(const chain_state& top,
         const system::settings& settings) NOEXCEPT;
-    static data to_block(const chain_state& pool, const block& block) NOEXCEPT;
+    static data to_block(const chain_state& pool, const block& block,
+        const system::settings& settings) NOEXCEPT;
     static data to_header(const chain_state& parent, const header& header,
         const system::settings& settings) NOEXCEPT;
 

include/bitcoin/system/settings.hpp

@@ -102,9 +102,9 @@ class BC_API settings
     uint32_t bip9_version_base;
 
     /// Activation parameters (bip34-style activations).
-    size_t activation_threshold{};
-    size_t enforcement_threshold{};
-    size_t activation_sample{};
+    size_t bip34_activation_threshold{};
+    size_t bip34_enforcement_threshold{};
+    size_t bip34_activation_sample{};
 
     /// Frozen activation heights (frozen_activations).
     size_t bip65_freeze{};

src/chain/block.cpp

@@ -564,7 +564,7 @@ bool block::is_unspent_coinbase_collision() const NOEXCEPT
     if (txs_->empty() || txs_->front()->inputs_ptr()->empty())
         return false;
 
-    // May only commit a coinbase that has already been confirmed spent.
+    // May only commit  duplicate coinbase that is already confirmed spent.
     return !txs_->front()->inputs_ptr()->front()->metadata.spent;
 }
 
@@ -741,10 +741,8 @@ code block::accept(const context& ctx, size_t subsidy_interval,
 code block::confirm(const context& ctx) const NOEXCEPT
 {
     const auto bip30 = ctx.is_enabled(bip30_rule);
-    const auto bip34 = ctx.is_enabled(bip34_rule);
 
-    // confirmations required.
-    if (bip30 && !bip34 && is_unspent_coinbase_collision())
+    if (bip30 && is_unspent_coinbase_collision())
         return error::unspent_coinbase_collision;
 
     return confirm_transactions(ctx);

src/chain/chain_state.cpp

@@ -39,6 +39,7 @@ namespace system {
 namespace chain {
 
 // github.com/bitcoin/bips/blob/master/bip-0030.mediawiki#specification
+// As bip30 exceptions apply only to bitcoin mainnet these can be embedded.
 static const checkpoint mainnet_bip30_exception_checkpoint1
 {
     "00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec", 91842
@@ -51,14 +52,14 @@ static const checkpoint mainnet_bip30_exception_checkpoint2
 // Inlines.
 // ----------------------------------------------------------------------------
 
-constexpr bool is_active(size_t count, size_t activation_threshold) NOEXCEPT
+constexpr bool is_active(size_t count, size_t bip34_activation_threshold) NOEXCEPT
 {
-    return count >= activation_threshold;
+    return count >= bip34_activation_threshold;
 }
 
-constexpr bool is_enforced(size_t count, size_t enforcement_threshold) NOEXCEPT
+constexpr bool is_enforced(size_t count, size_t bip34_enforcement_threshold) NOEXCEPT
 {
-    return count >= enforcement_threshold;
+    return count >= bip34_enforcement_threshold;
 }
 
 // Determine the number of blocks back to the closest retarget height.
@@ -75,6 +76,9 @@ constexpr bool is_retarget_height(size_t height,
     return is_zero(retarget_distance(height, retargeting_interval));
 }
 
+// bip30 is active for all but two mainnet blocks that violate the rule.
+// These two blocks each have a coinbase transaction that exactly duplicates
+// another that is not spent by the arrival of the corresponding duplicate.
 inline bool is_bip30_exception(const checkpoint& check, bool mainnet) NOEXCEPT
 {
     return mainnet &&
@@ -101,10 +105,7 @@ chain_state::activations chain_state::activation(const data& values,
     const auto height = values.height;
     const auto version = values.version.self;
     const auto& history = values.version.ordered;
-    const auto frozen = script::is_enabled(forks, forks::bip90_rule);
-    ////const auto difficult = script::is_enabled(forks, forks::difficult);
-    ////const auto retarget = script::is_enabled(forks, forks::retarget);
-    ////const auto mainnet = retarget && difficult;
+    const auto bip90 = script::is_enabled(forks, forks::bip90_rule);
 
     //*************************************************************************
     // CONSENSUS: Though unspecified in bip34, the satoshi implementation
@@ -124,14 +125,15 @@ chain_state::activations chain_state::activation(const data& values,
         settings.bip65_version); };
 
     // Compute bip34-based activation version summaries.
+    // TODO: avoid these computations if forks not configured.
     const auto count_2 = std::count_if(history.begin(), history.end(), ge_2);
     const auto count_3 = std::count_if(history.begin(), history.end(), ge_3);
     const auto count_4 = std::count_if(history.begin(), history.end(), ge_4);
 
     // Frozen activations (require version and enforce above freeze height).
-    const auto bip34_ice = frozen && height >= settings.bip34_freeze;
-    const auto bip66_ice = frozen && height >= settings.bip66_freeze;
-    const auto bip65_ice = frozen && height >= settings.bip65_freeze;
+    const auto bip90_34 = bip90 && height >= settings.bip34_freeze;
+    const auto bip90_66 = bip90 && height >= settings.bip66_freeze;
+    const auto bip90_65 = bip90 && height >= settings.bip65_freeze;
 
     // Initialize activation results with genesis values.
     activations result{ forks::no_rules, settings.first_version };
@@ -157,60 +159,82 @@ chain_state::activations chain_state::activation(const data& values,
     // scrypt_proof_of_work is activated based on configuration alone (hard fork).
     result.forks |= (forks::scrypt_proof_of_work & forks);
 
-    // bip16 was activated based on manual inspection of history (~55% rule).
+    // bip16 was activated based on manual inspection of signal history (~55% rule).
     if (values.timestamp.self >= settings.bip16_activation_time)
     {
         result.forks |= (forks::bip16_rule & forks);
     }
 
-    ////// bip30 is active for all but two mainnet blocks that violate the rule.
-    ////// These two blocks each have a coinbase transaction that exactly duplicates
-    ////// another that is not spent by the arrival of the corresponding duplicate.
-    ////// This was later applied to the full history in implementation (a no-op).
-    ////if (!is_bip30_exception({ values.hash, height }, mainnet))
-    ////{
-    ////    result.forks |= (forks::bip30_rule & forks);
-    ////}
-
     // bip34 is activated based on 75% of preceding 1000 mainnet blocks.
-    if (bip34_ice || (is_active(count_2, settings.activation_threshold) &&
+    // bip30 is disabled by bip34 or unconditional activation of it by bip90.
+    if (bip90_34 || (is_active(count_2, settings.bip34_activation_threshold) &&
         version >= settings.bip34_version))
     {
+        // TODO: check is_enabled(bip34_rule, forks) before above calculations.
         result.forks |= (forks::bip34_rule & forks);
     }
+    else
+    {
+        const auto difficult = script::is_enabled(forks, forks::difficult);
+        const auto retarget = script::is_enabled(forks, forks::retarget);
+        const auto mainnet = retarget && difficult;
+
+        // If not bip30 exception, existing duplicate coinbase must be spent.
+        if (!is_bip30_exception({ values.hash, height }, mainnet))
+        {
+            result.forks |= (forks::bip30_rule & forks);
+        }
+    }
 
     // bip66 is activated based on 75% of preceding 1000 mainnet blocks.
-    if (bip66_ice || (is_active(count_3, settings.activation_threshold) &&
+    if (bip90_66 || (is_active(count_3, settings.bip34_activation_threshold) &&
         version >= settings.bip66_version))
     {
+        // TODO: check is_enabled(bip66_rule, forks) before above calculations.
         result.forks |= (forks::bip66_rule & forks);
     }
 
     // bip65 is activated based on 75% of preceding 1000 mainnet blocks.
-    if (bip65_ice || (is_active(count_4, settings.activation_threshold) &&
+    if (bip90_65 || (is_active(count_4, settings.bip34_activation_threshold) &&
         version >= settings.bip65_version))
     {
+        // TODO: check is_enabled(bip65_rule, forks) before above calculations.
         result.forks |= (forks::bip65_rule & forks);
     }
 
     // version 4/3/2 enforced based on 95% of preceding 1000 mainnet blocks.
-    if (bip65_ice || is_enforced(count_4, settings.enforcement_threshold))
+    if (bip90_65 || is_enforced(count_4, settings.bip34_enforcement_threshold))
     {
+        // TODO: requires is_enabled(bip65_rule, forks).
         result.minimum_block_version = settings.bip65_version;
     }
-    else if (bip66_ice || is_enforced(count_3, settings.enforcement_threshold))
+    else if (bip90_66 || is_enforced(count_3, settings.bip34_enforcement_threshold))
     {
+        // TODO: requires is_enabled(bip66_rule, forks).
         result.minimum_block_version = settings.bip66_version;
     }
-    else if (bip34_ice || is_enforced(count_2, settings.enforcement_threshold))
+    else if (bip90_34 || is_enforced(count_2, settings.bip34_enforcement_threshold))
     {
+        // TODO: requires is_enabled(bip34_rule, forks).
         result.minimum_block_version = settings.bip34_version;
     }
     else
     {
         result.minimum_block_version = settings.first_version;
     }
 
+    // bip9_bit0 forks are enforced above the bip9_bit0 checkpoint.
+    if (values.bip9_bit0_hash == settings.bip9_bit0_active_checkpoint.hash())
+    {
+        result.forks |= (forks::bip9_bit0_group & forks);
+    }
+
+    // bip9_bit1 forks are enforced above the bip9_bit1 checkpoint.
+    if (values.bip9_bit1_hash == settings.bip9_bit1_active_checkpoint.hash())
+    {
+        result.forks |= (forks::bip9_bit1_group & forks);
+    }
+
     return result;
 }
 
@@ -234,15 +258,15 @@ size_t chain_state::bits_count(size_t height, uint32_t forks,
 }
 
 size_t chain_state::version_count(size_t height, uint32_t forks,
-    size_t activation_sample) NOEXCEPT
+    size_t bip34_activation_sample) NOEXCEPT
 {
     if (script::is_enabled(forks, forks::bip90_rule) ||
         !script::is_enabled(forks, forks::bip34_activations))
     {
         return zero;
     }
 
-    return std::min(height, activation_sample);
+    return std::min(height, bip34_activation_sample);
 }
 
 size_t chain_state::timestamp_count(size_t height, uint32_t) NOEXCEPT
@@ -407,6 +431,24 @@ uint32_t chain_state::easy_work_required(const data& values,
     return proof_of_work_limit;
 }
 
+size_t chain_state::bip9_bit0_height(size_t height,
+    const checkpoint& bip9_bit0_active_checkpoint) NOEXCEPT
+{
+    const auto activation_height = bip9_bit0_active_checkpoint.height();
+
+    // Require bip9_bit0 hash at heights above historical bip9_bit0 activation.
+    return height > activation_height ? activation_height : map::unrequested;
+}
+
+size_t chain_state::bip9_bit1_height(size_t height,
+    const checkpoint& bip9_bit1_active_checkpoint) NOEXCEPT
+{
+    const auto activation_height = bip9_bit1_active_checkpoint.height();
+
+    // Require bip9_bit1 hash at heights above historical bip9_bit1 activation.
+    return height > activation_height ? activation_height : map::unrequested;
+}
+
 // Public static
 // ----------------------------------------------------------------------------
 
@@ -434,10 +476,19 @@ chain_state::map chain_state::get_map(size_t height,
     map.version_self = height;
     map.version.high = sub1(height);
     map.version.count = version_count(height, forks,
-        settings.activation_sample);
+        settings.bip34_activation_sample);
 
     // The most recent past retarget height.
     map.timestamp_retarget = retarget_height(height, forks, interval);
+
+    // The checkpoint above which bip9_bit0 rules are enforced.
+    map.bip9_bit0_height = bip9_bit0_height(height,
+        settings.bip9_bit0_active_checkpoint);
+
+    // The checkpoint above which bip9_bit1 rules are enforced.
+    map.bip9_bit1_height = bip9_bit1_height(height,
+        settings.bip9_bit1_active_checkpoint);
+
     return map;
 }
 
@@ -499,7 +550,7 @@ chain_state::data chain_state::to_pool(const chain_state& top,
 
     // If version collection overflows, dequeue oldest member.
     if (data.version.ordered.size() > version_count(height, forks,
-        settings.activation_sample))
+        settings.bip34_activation_sample))
         data.version.ordered.pop_front();
 
     // If timestamp collection overflows, dequeue oldest member.
@@ -544,7 +595,7 @@ chain_state::chain_state(const chain_state& top,
 }
 
 chain_state::data chain_state::to_block(const chain_state& pool,
-    const block& block) NOEXCEPT
+    const block& block, const system::settings& settings) NOEXCEPT
 {
     // Copy data from presumed same-height pool state.
     chain_state::data data{ pool.data_ };
@@ -557,14 +608,22 @@ chain_state::data chain_state::to_block(const chain_state& pool,
     data.version.self = header.version();
     data.timestamp.self = header.timestamp();
 
+    // Cache hash of bip9 bit0 height block, otherwise use preceding state.
+    if (data.height == settings.bip9_bit0_active_checkpoint.height())
+        data.bip9_bit0_hash = data.hash;
+
+    // Cache hash of bip9 bit1 height block, otherwise use preceding state.
+    if (data.height == settings.bip9_bit1_active_checkpoint.height())
+        data.bip9_bit1_hash = data.hash;
+
     return data;
 }
 
 // Pool to block.
 // This assumes that the pool state is the same height as the block.
 chain_state::chain_state(const chain_state& pool, const block& block,
     const system::settings& settings) NOEXCEPT
-  : data_(to_block(pool, block)),
+  : data_(to_block(pool, block, settings)),
     forks_(pool.forks_),
     active_(activation(data_, forks_, settings)),
     work_required_(work_required(data_, forks_, settings)),
@@ -587,6 +646,14 @@ chain_state::data chain_state::to_header(const chain_state& parent,
     data.version.self = header.version();
     data.timestamp.self = header.timestamp();
 
+    // Cache hash of bip9 bit0 height block, otherwise use preceding state.
+    if (data.height == settings.bip9_bit0_active_checkpoint.height())
+        data.bip9_bit0_hash = data.hash;
+
+    // Cache hash of bip9 bit1 height block, otherwise use preceding state.
+    if (data.height == settings.bip9_bit1_active_checkpoint.height())
+        data.bip9_bit1_hash = data.hash;
+
     return data;
 }
 
@@ -666,16 +733,6 @@ chain::context chain_state::context() const NOEXCEPT
     };
 }
 
-/// Current zulu (utc) time in seconds since epoch, using the wall clock.
-/// Although not defined, epoch is almost always: 00:00, Jan 1 1970 UTC.
-/// BUGBUG: en.wikipedia.org/wiki/Year_2038_problem
-inline uint64_t zulu_time_seconds() NOEXCEPT
-{
-    using wall_clock = std::chrono::system_clock;
-    const auto now = wall_clock::now();
-    return sign_cast<uint64_t>(wall_clock::to_time_t(now));
-}
-
 } // namespace chain
 } // namespace system
 } // namespace libbitcoin