Merge bitcoin/bitcoin#21825: net: add I2P hardcoded seeds

142e2da net: add I2P seeds to chainparamsseeds (Jon Atack)
e01f173 contrib: add a few I2P seed nodes (Jon Atack)
ea269c7 contrib: parse I2P addresses in generate-seeds.py (Jon Atack)

Pull request description:

  Follow-up to #21560 that updated the fixed seeds infra for BIP155 addresses and then added Tor v3 ones:

  - Update contrib/generate-seeds.py to parse I2P addresses

  - Add a few I2P nodes to contrib/seeds/nodes_main.txt

  - Run generate-seeds.py and add the I2P seeds to chainparamsseeds.h

  Reviewers, see contrib/seeds/README.md for more info and feel free to use the following CLI one-liner to check for and propose additional seeds for contrib/seeds/nodes_main.txt. You can also see how many I2P peers your node knows with cli -addrinfo.

  ```rake
  bitcoin-cli getnodeaddresses 0 | jq '.[] | (select(.address | contains(".b32.i2p"))) | .address' | sort
  ```

  I verified the I2P addresses are correctly BIP155-serialized/deserialized by building with all seeds removed from chainparamsseeds.h except those added here, restarting with `-datadir=newdir -dnsseed=0` and running rpc ` getnodeaddresses 0` that initially returns only the new I2P addresses.

ACKs for top commit:
  laanwj:
    ACK 142e2da
  vasild:
    ACK 142e2da

Tree-SHA512: 040576012d5f1f034e2bd566ad654a6fdfd8ff7f6b12fa40c9fda1e948ebf8417fcea64cfc14938a41439370aa4669bab3e97274f9d4f9a6906fa9520afa9cf8

Author: laanwj

contrib/seeds/generate-seeds.py

@@ -16,6 +16,7 @@
     <ip>:<port>
     [<ipv6>]:<port>
     <onion>.onion:<port>
+    <i2p>.b32.i2p:<port>
 
 The output will be two data structures with the peers in binary format:
 
@@ -52,6 +53,12 @@ def name_to_bip155(addr):
             return (BIP155Network.TORV3, vchAddr[:32])
         else:
             raise ValueError('Invalid onion %s' % vchAddr)
+    elif addr.endswith('.b32.i2p'):
+        vchAddr = b32decode(addr[0:-8] + '====', True)
+        if len(vchAddr) == 32:
+            return (BIP155Network.I2P, vchAddr)
+        else:
+            raise ValueError(f'Invalid I2P {vchAddr}')
     elif '.' in addr: # IPv4
         return (BIP155Network.IPV4, bytes((int(x) for x in addr.split('.'))))
     elif ':' in addr: # IPv6

contrib/seeds/nodes_main.txt

@@ -1188,3 +1188,13 @@ sys54sv4xv3hn3sdiv3oadmzqpgyhd4u4xphv4xqk64ckvaxzm57a7yd.onion:8333
 tddeij4qigtjr6jfnrmq6btnirmq5msgwcsdpcdjr7atftm7cxlqztid.onion:8333
 vi5bnbxkleeqi6hfccjochnn65lcxlfqs4uwgmhudph554zibiusqnad.onion:8333
 xqt25cobm5zqucac3634zfght72he6u3eagfyej5ellbhcdgos7t2had.onion:8333
+
+# manually added 2021-05 for minimal i2p bootstrap support
+72l3ucjkuscrbiiepoehuwqgknyzgo7zuix5ty4puwrkyhtmnsga.b32.i2p:8333
+c4gfnttsuwqomiygupdqqqyy5y5emnk5c73hrfvatri67prd7vyq.b32.i2p:8333
+gehtac45oaghz54ypyopim64mql7oad2bqclla74l6tfeolzmodq.b32.i2p:8333
+h3r6bkn46qxftwja53pxiykntegfyfjqtnzbm6iv6r5mungmqgmq.b32.i2p:8333
+hnbbyjpxx54623l555sta7pocy3se4sdgmuebi5k6reesz5rjp6q.b32.i2p:8333
+pjs7or2ctvteeo5tu4bwyrtydeuhqhvdprtujn4daxr75jpebjxa.b32.i2p:8333
+wwbw7nqr3ahkqv62cuqfwgtneekvvpnuc4i4f6yo7tpoqjswvcwa.b32.i2p:8333
+zsxwyo6qcn3chqzwxnseusqgsnuw3maqnztkiypyfxtya4snkoka.b32.i2p:8333

src/chainparamsseeds.h

@@ -1195,6 +1195,14 @@ static const uint8_t chainparams_seed_main[] = {
     0x04,0x20,0x98,0xc6,0x44,0x27,0x90,0x41,0xa6,0x98,0xf9,0x25,0x6c,0x59,0x0f,0x06,0x6d,0x44,0x59,0x0e,0xb2,0x46,0xb0,0xa4,0x37,0x88,0x69,0x8f,0xc1,0x32,0xcd,0x9f,0x15,0xd7,0x20,0x8d,
     0x04,0x20,0xaa,0x3a,0x16,0x86,0xea,0x59,0x09,0x04,0x78,0xe5,0x10,0x92,0xe1,0x1d,0xad,0xf7,0x56,0x2b,0xac,0xb0,0x97,0x29,0x63,0x30,0xf4,0x1b,0xcf,0xde,0xf3,0x28,0x0a,0x29,0x20,0x8d,
     0x04,0x20,0xbc,0x27,0xae,0x89,0xc1,0x67,0x73,0x0a,0x08,0x02,0xdf,0xb7,0xcc,0x94,0xc7,0x9f,0xf4,0x72,0x7a,0x9b,0x20,0x0c,0x5c,0x11,0x3d,0x22,0xd6,0x13,0x88,0x66,0x74,0xbf,0x20,0x8d,
+    0x05,0x20,0xfe,0x97,0xba,0x09,0x2a,0xa4,0x85,0x10,0xa1,0x04,0x7b,0x88,0x7a,0x5a,0x06,0x53,0x71,0x93,0x3b,0xf9,0xa2,0x2f,0xd9,0xe3,0x8f,0xa5,0xa2,0xac,0x1e,0x6c,0x6c,0x8c,0x20,0x8d,
+    0x05,0x20,0x17,0x0c,0x56,0xce,0x72,0xa5,0xa0,0xe6,0x23,0x06,0xa3,0xc7,0x08,0x43,0x18,0xee,0x3a,0x46,0x35,0x5d,0x17,0xf6,0x78,0x96,0xa0,0x9c,0x51,0xef,0xbe,0x23,0xfd,0x71,0x20,0x8d,
+    0x05,0x20,0x31,0x0f,0x30,0x0b,0x9d,0x70,0x0c,0x7c,0xf7,0x98,0x7e,0x1c,0xf4,0x33,0xdc,0x64,0x17,0xf7,0x00,0x7a,0x0c,0x04,0xb5,0x83,0xfc,0x5f,0xa6,0x52,0x39,0x79,0x63,0x87,0x20,0x8d,
+    0x05,0x20,0x3e,0xe3,0xe0,0xa9,0xbc,0xf4,0x2e,0x59,0xd9,0x20,0xee,0xdf,0x74,0x61,0x4d,0x99,0x0c,0x5c,0x15,0x30,0x9b,0x72,0x16,0x79,0x15,0xf4,0x7a,0xca,0x34,0xcc,0x81,0x99,0x20,0x8d,
+    0x05,0x20,0x3b,0x42,0x1c,0x25,0xf7,0xbf,0x79,0xed,0x6d,0x7d,0xef,0x65,0x30,0x7d,0xee,0x16,0x37,0x22,0x72,0x43,0x33,0x28,0x40,0xa3,0xaa,0xf4,0x48,0x49,0x67,0xb1,0x4b,0xfd,0x20,0x8d,
+    0x05,0x20,0x7a,0x65,0xf7,0x47,0x42,0x9d,0x66,0x42,0x3b,0xb3,0xa7,0x03,0x6c,0x46,0x78,0x19,0x28,0x78,0x1e,0xa3,0x7c,0x67,0x44,0xb7,0x83,0x05,0xe3,0xfe,0xa5,0xe4,0x0a,0x6e,0x20,0x8d,
+    0x05,0x20,0xb5,0x83,0x6f,0xb6,0x11,0xd8,0x0e,0xa8,0x57,0xda,0x15,0x20,0x5b,0x1a,0x6d,0x21,0x15,0x5a,0xbd,0xb4,0x17,0x11,0xc2,0xfb,0x0e,0xfc,0xde,0xe8,0x26,0x56,0xa8,0xac,0x20,0x8d,
+    0x05,0x20,0xcc,0xaf,0x6c,0x3b,0xd0,0x13,0x76,0x23,0xc3,0x36,0xbb,0x64,0x4a,0x4a,0x06,0x93,0x69,0x6d,0xb0,0x10,0x6e,0x66,0xa4,0x61,0xf8,0x2d,0xe7,0x80,0x72,0x4d,0x53,0x94,0x20,0x8d,
 };
 
 static const uint8_t chainparams_seed_test[] = {