Merge bitcoin/bitcoin#24818: net: improve and address issues in makeseeds.py

c457fb1 improve clarity and up max ipv6 ASNs (Baas)

Pull request description:

  This PR attempts to address some of the areas of improvement raised in #17020 . Concretely, my proposed change is fairly minor but addresses the following changes to [`makeseeds.py`](https://github.com/bitcoin/bitcoin/blob/master/contrib/seeds/makeseeds.py):

  - Increase max seeds per ASN for IPv6 to 10 as recommended [here](bitcoin/bitcoin#16999 (comment)), while keeping max seeds per ASN for IPv4 at 2.
  - Bump `MIN_BLOCKS` to 730000.
  - Improved script clarity: added function types and more docs to functions, added progress indicator when performing ASN lookup, and change string formatting to better align with [bitcoin python style guidelines](https://github.com/bitcoin/bitcoin/blob/master/test/functional/README.md#style-guidelines)

  With the different ASN limits for IPv4 and IPv6, and the new minimum block requirement, the current stats look look like:
  ```
    IPv4   IPv6  Onion Pass
  470689  73238      0 Initial
  470689  73238      0 Skip entries with invalid address
  470689  73238      0 After removing duplicates
  470688  73238      0 Skip entries from suspicious hosts
    6098   1676      0 Enforce minimal number of blocks
    5252   1443      0 Require service bit 1
    3812    898      0 Require minimum uptime
    3738    877      0 Require a known and recent user agent
    3715    869      0 Filter out hosts with multiple bitcoin ports
     512    512      0 Look up ASNs and limit results per ASN and per net
  ```
  The new ASN max seeds of 10 allows for 512 IPv6 addresses to be included, up from the ~150 that was filtered by the previous version.

  While there is more to do for #17020 , these changes I think are fairly isolated from the rest and should make it a bit easier for others to get up to speed with what the functions in the script do.

ACKs for top commit:
  laanwj:
    Concept and code review ACK c457fb1

Tree-SHA512: 3ed67868443cc50544e23b27e2341758c3a8866997b0dba47b137032d5e1a13428855daaeed682626ed471542b44435635178d54848a2cd6fe73777679428032

Author: laanwj

contrib/seeds/makeseeds.py

@@ -10,12 +10,16 @@
 import sys
 import dns.resolver
 import collections
+from typing import List, Dict, Union
 
 NSEEDS=512
 
-MAX_SEEDS_PER_ASN=2
+MAX_SEEDS_PER_ASN = {
+    'ipv4': 2,
+    'ipv6': 10,
+}
 
-MIN_BLOCKS = 337600
+MIN_BLOCKS = 730000
 
 # These are hosts that have been observed to be behaving strangely (e.g.
 # aggressively connecting to every node).
@@ -40,9 +44,13 @@
     r"23.99"
     r")")
 
-def parseline(line):
+def parseline(line: str) -> Union[dict, None]:
+    """ Parses a line from `seeds_main.txt` into a dictionary of details for that line.
+    or `None`, if the line could not be parsed.
+    """
     sline = line.split()
     if len(sline) < 11:
+        # line too short to be valid, skip it.
        return None
     m = PATTERN_IPV4.match(sline[0])
     sortkey = None
@@ -107,25 +115,26 @@ def parseline(line):
         'sortkey': sortkey,
     }
 
-def dedup(ips):
-    '''deduplicate by address,port'''
+def dedup(ips: List[Dict]) -> List[Dict]:
+    """ Remove duplicates from `ips` where multiple ips share address and port. """
     d = {}
     for ip in ips:
         d[ip['ip'],ip['port']] = ip
     return list(d.values())
 
-def filtermultiport(ips):
-    '''Filter out hosts with more nodes per IP'''
+def filtermultiport(ips: List[Dict]) -> List[Dict]:
+    """ Filter out hosts with more nodes per IP"""
     hist = collections.defaultdict(list)
     for ip in ips:
         hist[ip['sortkey']].append(ip)
     return [value[0] for (key,value) in list(hist.items()) if len(value)==1]
 
-def lookup_asn(net, ip):
-    '''
-    Look up the asn for an IP (4 or 6) address by querying cymru.com, or None
-    if it could not be found.
-    '''
+def lookup_asn(net: str, ip: str) -> Union[int, None]:
+    """ Look up the asn for an `ip` address by querying cymru.com
+    on network `net` (e.g. ipv4 or ipv6).
+
+    Returns in integer ASN or None if it could not be found.
+    """
     try:
         if net == 'ipv4':
             ipaddr = ip
@@ -147,20 +156,33 @@ def lookup_asn(net, ip):
         return None
 
 # Based on Greg Maxwell's seed_filter.py
-def filterbyasn(ips, max_per_asn, max_per_net):
+def filterbyasn(ips: List[Dict], max_per_asn: Dict, max_per_net: int) -> List[Dict]:
+    """ Prunes `ips` by
+    (a) trimming ips to have at most `max_per_net` ips from each net (e.g. ipv4, ipv6); and
+    (b) trimming ips to have at most `max_per_asn` ips from each asn in each net.
+    """
     # Sift out ips by type
     ips_ipv46 = [ip for ip in ips if ip['net'] in ['ipv4', 'ipv6']]
     ips_onion = [ip for ip in ips if ip['net'] == 'onion']
 
     # Filter IPv46 by ASN, and limit to max_per_net per network
     result = []
-    net_count = collections.defaultdict(int)
-    asn_count = collections.defaultdict(int)
-    for ip in ips_ipv46:
+    net_count: Dict[str, int] = collections.defaultdict(int)
+    asn_count: Dict[int, int] = collections.defaultdict(int)
+
+    for i, ip in enumerate(ips_ipv46):
+        if i % 10 == 0:
+            # give progress update
+            print(f"{i:6d}/{len(ips_ipv46)} [{100*i/len(ips_ipv46):04.1f}%]\r", file=sys.stderr, end='', flush=True)
+
         if net_count[ip['net']] == max_per_net:
+            # do not add this ip as we already too many
+            # ips from this network
             continue
         asn = lookup_asn(ip['net'], ip['ip'])
-        if asn is None or asn_count[asn] == max_per_asn:
+        if asn is None or asn_count[asn] == max_per_asn[ip['net']]:
+            # do not add this ip as we already have too many
+            # ips from this ASN on this network
             continue
         asn_count[asn] += 1
         net_count[ip['net']] += 1
@@ -170,54 +192,55 @@ def filterbyasn(ips, max_per_asn, max_per_net):
     result.extend(ips_onion[0:max_per_net])
     return result
 
-def ip_stats(ips):
-    hist = collections.defaultdict(int)
+def ip_stats(ips: List[Dict]) -> str:
+    """ Format and return pretty string from `ips`. """
+    hist: Dict[str, int] = collections.defaultdict(int)
     for ip in ips:
         if ip is not None:
             hist[ip['net']] += 1
 
-    return '%6d %6d %6d' % (hist['ipv4'], hist['ipv6'], hist['onion'])
+    return f"{hist['ipv4']:6d} {hist['ipv6']:6d} {hist['onion']:6d}"
 
 def main():
     lines = sys.stdin.readlines()
     ips = [parseline(line) for line in lines]
 
     print('\x1b[7m  IPv4   IPv6  Onion Pass                                               \x1b[0m', file=sys.stderr)
-    print('%s Initial' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Initial', file=sys.stderr)
     # Skip entries with invalid address.
     ips = [ip for ip in ips if ip is not None]
-    print('%s Skip entries with invalid address' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Skip entries with invalid address', file=sys.stderr)
     # Skip duplicates (in case multiple seeds files were concatenated)
     ips = dedup(ips)
-    print('%s After removing duplicates' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} After removing duplicates', file=sys.stderr)
     # Skip entries from suspicious hosts.
     ips = [ip for ip in ips if ip['ip'] not in SUSPICIOUS_HOSTS]
-    print('%s Skip entries from suspicious hosts' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Skip entries from suspicious hosts', file=sys.stderr)
     # Enforce minimal number of blocks.
     ips = [ip for ip in ips if ip['blocks'] >= MIN_BLOCKS]
-    print('%s Enforce minimal number of blocks' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Enforce minimal number of blocks', file=sys.stderr)
     # Require service bit 1.
     ips = [ip for ip in ips if (ip['service'] & 1) == 1]
-    print('%s Require service bit 1' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Require service bit 1', file=sys.stderr)
     # Require at least 50% 30-day uptime for clearnet, 10% for onion.
     req_uptime = {
         'ipv4': 50,
         'ipv6': 50,
         'onion': 10,
     }
     ips = [ip for ip in ips if ip['uptime'] > req_uptime[ip['net']]]
-    print('%s Require minimum uptime' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Require minimum uptime', file=sys.stderr)
     # Require a known and recent user agent.
     ips = [ip for ip in ips if PATTERN_AGENT.match(ip['agent'])]
-    print('%s Require a known and recent user agent' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Require a known and recent user agent', file=sys.stderr)
     # Sort by availability (and use last success as tie breaker)
     ips.sort(key=lambda x: (x['uptime'], x['lastsuccess'], x['ip']), reverse=True)
     # Filter out hosts with multiple bitcoin ports, these are likely abusive
     ips = filtermultiport(ips)
-    print('%s Filter out hosts with multiple bitcoin ports' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Filter out hosts with multiple bitcoin ports', file=sys.stderr)
     # Look up ASNs and limit results, both per ASN and globally.
     ips = filterbyasn(ips, MAX_SEEDS_PER_ASN, NSEEDS)
-    print('%s Look up ASNs and limit results per ASN and per net' % (ip_stats(ips)), file=sys.stderr)
+    print(f'{ip_stats(ips):s} Look up ASNs and limit results per ASN and per net', file=sys.stderr)
     # Sort the results by IP address (for deterministic output).
     ips.sort(key=lambda x: (x['net'], x['sortkey']))
     for ip in ips: