dns: add dns seed provider filtering based on supported flags

Author: naiyoma

check-dnsseeds.py

@@ -4,6 +4,22 @@
 Seeds are available from https://github.com/bitcoin/bitcoin/blob/master/src/kernel/chainparams.cpp
 '''
 import subprocess
+from itertools import combinations
+
+NODE_NONE = 0
+NODE_NETWORK = (1 << 0)
+NODE_BLOOM = (1 << 2)
+NODE_WITNESS = (1 << 3)
+NODE_COMPACT_FILTERS = (1 << 6)
+NODE_NETWORK_LIMITED = (1 << 10)
+NODE_P2P_V2 = (1 << 11)
+
+DNS_SEED_PROVIDERS = [
+    "seed.bitcoin.sipa.be.",
+    "dnsseed.bluematt.me.",
+    "dnsseed.bitcoin.dashjr.org.",
+    "seed.bitcoinstats.com.",
+]
 
 SEEDS_PER_NETWORK={
     'mainnet': [
@@ -43,11 +59,55 @@ def check_seed(x):
     else:
         print(f"\x1b[91mFAIL\x1b[0m {x}")
 
-if __name__ == '__main__':
+def has_answer_section(domain):
+    """
+    Executes a dig command for the given domain and checks for an answer section.
+    """
+    command = ["dig", domain]
+    try:
+        result = subprocess.run(command, capture_output=True, check=True)
+        output = result.stdout.decode("utf-8")
+        return "ANSWER SECTION" in output
+    except subprocess.CalledProcessError:
+        return False  
+
+def get_hex_from_combination(*flags):
+    """
+    Calculates the hexadecimal representation of the combination value.
+    """
+    combination_value = sum(flags)
+    hex_value = hex(combination_value)[2:].upper()
+    return f"x{hex_value}" 
+
+if __name__ == "__main__":
+    print("\nBitcoin Core DNS Seed Status Check:\n")
+
     for (network, seeds) in SEEDS_PER_NETWORK.items():
         print(f"\x1b[90m* \x1b[97m{network}\x1b[0m")
 
         for hostname in seeds:
             check_seed(hostname)
 
         print()
+
+    print("\n")
+
+    all_flags = [NODE_NONE, NODE_NETWORK, NODE_BLOOM, NODE_WITNESS, NODE_COMPACT_FILTERS, NODE_NETWORK_LIMITED, NODE_P2P_V2]
+    all_combinations = []
+
+    for i in range(1, len(all_flags) + 1):  
+        for combo in combinations(all_flags, i):
+            combination = sum(combo)  
+            hex_value = get_hex_from_combination(*combo)
+            all_combinations.append((combo, hex_value))  
+
+    print("All possible combinations and their hexadecimal values:")
+    for combination, hex_value in all_combinations:
+        combination_names = [flag_name for flag_name, flag_value in zip(["NODE_NONE", "NODE_NETWORK", "NODE_BLOOM", "NODE_WITNESS", "NODE_COMPACT_FILTERS", "NODE_NETWORK_LIMITED", "NODE_P2P_V2"], combination) if flag_value != 0]
+        combination_string = ", ".join(combination_names)
+        print(f"Combination: {combination_string} => Hexadecimal Value: {hex_value}")
+
+        for provider in DNS_SEED_PROVIDERS:
+            domain = f"{hex_value}.{provider}"
+            has_answer = has_answer_section(domain)
+            print(f"  {domain}: {has_answer}")