Check BIP 110 signalling in block headers on your own node

check_bip110_signalling.sh

#!/bin/bash

#
# This shell script allows you to check BIP 110 signalling on your own
# Bitcoin full node, verified by your own node.
#
# BIP 110 (Reduced Data Temporary Softfork) uses modified BIP9 parameters:
#   deployment name:       reduced_data
#   version bit:           4
#   signalling period:     2016 blocks
#   threshold:             1109 blocks (55%)
#   start time:            1764547200 (approximately 2025-12-01 UTC)
#   mandatory signalling:  heights 961632 through 963647, unless already locked in
#   maximum activation:    height 965664
#   active duration:       52416 blocks
#
# Specification: https://github.com/bitcoin/bips/blob/master/bip-0110.mediawiki
#
# DON'T TRUST, VERIFY! :-)
#


# First check if we have the 'bitcoin-cli' and 'jq' commands available.
if ! command -v bitcoin-cli &> /dev/null
then
    echo "command 'bitcoin-cli' could not be found. Are you running this script on a Bitcoin node?"
    exit 1
fi
if ! command -v jq &> /dev/null
then
    echo "command 'jq' could not be found. It is needed to parse JSON output. Please install it."
    exit 1
fi

# Parse optional command-line arguments. They may be supplied in either order:
#   -v                  Enable verbose output.
#   -datadir=/data/     Use a custom Bitcoin data directory.
VERBOSE=0
BITCOIN_DATADIR=""

for ARG in "$@"
do
    case "$ARG" in
        -v)
            VERBOSE=1
            ;;
        -datadir=*)
            BITCOIN_DATADIR=${ARG#-datadir=}
            if [[ -z "$BITCOIN_DATADIR" ]]
            then
                echo "Error: -datadir requires a non-empty path." >&2
                exit 1
            fi
            ;;
        -h|--help)
            echo "Usage: $0 [-v] [-datadir=/path/to/bitcoin/data]"
            exit 0
            ;;
        *)
            echo "Unknown argument: $ARG" >&2
            echo "Usage: $0 [-v] [-datadir=/path/to/bitcoin/data]" >&2
            exit 1
            ;;
    esac
done

# Keep the command and its optional argument in an array so paths containing
# whitespace are passed to bitcoin-cli correctly.
BITCOIN_CLI=(bitcoin-cli)
if [[ -n "$BITCOIN_DATADIR" ]]
then
    BITCOIN_CLI+=("-datadir=$BITCOIN_DATADIR")
fi


#
# Actual script starts HERE:
#

PERIOD_LENGTH=2016
SIGNALLING_THRESHOLD=1109
BIP110_BIT=4
BIP9_TOP_MASK=$((0xE0000000))
BIP9_TOP_BITS=$((0x20000000))

# Get the current validated block height. Unlike the "headers" field, this does
# not include headers for blocks which the node has not downloaded/validated.
CURRENT_BLOCKHEIGHT=$("${BITCOIN_CLI[@]}" getblockcount)

# Find the current retarget/signalling period and its first block.
BLOCK_OFFSET_IN_CURRENT_PERIOD=$((CURRENT_BLOCKHEIGHT % PERIOD_LENGTH))
START_BLOCK_OF_CURRENT_PERIOD=$((CURRENT_BLOCKHEIGHT - BLOCK_OFFSET_IN_CURRENT_PERIOD))
BLOCK_COUNT_IN_CURRENT_PERIOD=$((BLOCK_OFFSET_IN_CURRENT_PERIOD + 1))

# Initialize counters.
BLOCKS_SIGNALLING_FOR_BIP110=0
BLOCKS_NOT_SIGNALLING_FOR_BIP110=0


echo ""
echo "**************************************"
echo " Checking BIP 110 signalling status:"
echo "**************************************"
echo ""
echo "In the current signalling period, $BLOCK_COUNT_IN_CURRENT_PERIOD out of $PERIOD_LENGTH blocks"
echo "have been mined. We will check these $BLOCK_COUNT_IN_CURRENT_PERIOD blocks now to see"
echo "whether they signal for BIP 110."
echo ""


# Loop through all blocks mined in the current period.
for (( height=START_BLOCK_OF_CURRENT_PERIOD; height<=CURRENT_BLOCKHEIGHT; height++ ))
do
    BLOCK_HASH=$("${BITCOIN_CLI[@]}" getblockhash "$height")
    BLOCK_VERSION=$("${BITCOIN_CLI[@]}" getblockheader "$BLOCK_HASH" | jq -r .version)

    # Modified BIP9 signalling requires the versionbits top pattern (001) and
    # version bit 4. Merely finding bit 4 set is not sufficient.
    if (( (BLOCK_VERSION & BIP9_TOP_MASK) == BIP9_TOP_BITS &&
          (BLOCK_VERSION & (1 << BIP110_BIT)) != 0 ))
    then
        SIGNALS_BIP110=1
    else
        SIGNALS_BIP110=0
    fi

    # In default mode, insert a newline after every 56 blocks (2016 / 56 = 36).
    BLOCK_NUMBER_IN_PERIOD=$((height - START_BLOCK_OF_CURRENT_PERIOD + 1))
    if [[ $VERBOSE -eq 0 && $BLOCK_NUMBER_IN_PERIOD -gt 1 && $(((BLOCK_NUMBER_IN_PERIOD - 1) % 56)) -eq 0 ]]
    then
        echo ""
    fi

    if [[ $VERBOSE -eq 1 ]]
    then
        echo -n "[$((CURRENT_BLOCKHEIGHT-height)) blocks left to check]: "
    fi

    if [[ $SIGNALS_BIP110 -eq 1 ]]
    then
        BLOCKS_SIGNALLING_FOR_BIP110=$((BLOCKS_SIGNALLING_FOR_BIP110 + 1))

        if [[ $VERBOSE -eq 1 ]]; then
            echo "Block number $height: ✅"
        else
            echo -n "✅"
        fi
    else
        BLOCKS_NOT_SIGNALLING_FOR_BIP110=$((BLOCKS_NOT_SIGNALLING_FOR_BIP110 + 1))

        if [[ $VERBOSE -eq 1 ]]; then
            echo "Block number $height: 🛑 The block does NOT signal BIP 110 support."
        else
            echo -n "🛑"
        fi
    fi
done


# Display a summary.
echo ""
echo ""
echo "*********************************************************************"
echo "  SUMMARY:"
echo ""
echo "  In the current period, $BLOCK_COUNT_IN_CURRENT_PERIOD out of $PERIOD_LENGTH blocks have been mined."
echo "  Of these, $BLOCKS_SIGNALLING_FOR_BIP110 signal BIP 110 support and"
echo "  $BLOCKS_NOT_SIGNALLING_FOR_BIP110 do not."
echo ""

if [[ $BLOCKS_SIGNALLING_FOR_BIP110 -lt $SIGNALLING_THRESHOLD ]]
then
    echo "  The BIP 110 lock-in threshold has not been reached in this period."
    echo "  $SIGNALLING_THRESHOLD blocks must signal, so $((SIGNALLING_THRESHOLD-BLOCKS_SIGNALLING_FOR_BIP110))"
    echo "  more signalling blocks are needed."
else
    echo "  🎉 The BIP 110 threshold of $SIGNALLING_THRESHOLD signalling blocks has been reached!"
    echo "  The deployment can enter LOCKED_IN at the start of the next retarget period."
    echo "  It becomes ACTIVE one retarget period after LOCKED_IN."
fi

echo ""
if (( CURRENT_BLOCKHEIGHT >= 961632 && CURRENT_BLOCKHEIGHT <= 963647 ))
then
    echo "  NOTE: BIP 110's mandatory-signalling window is in progress."
    echo "  Unless already LOCKED_IN, non-signalling blocks at heights 961632-963647"
    echo "  are invalid under the proposal."
elif (( CURRENT_BLOCKHEIGHT < 961632 ))
then
    echo "  Mandatory signalling is scheduled for heights 961632-963647 if lock-in"
    echo "  has not already occurred."
fi
echo "*********************************************************************"
echo ""