net: relay I2P addresses even if not reachable (by us)

src/netaddress.h

@@ -222,7 +222,7 @@ class CNetAddr
          */
         bool IsRelayable() const
         {
-            return IsIPv4() || IsIPv6() || IsTor();
+            return IsIPv4() || IsIPv6() || IsTor() || IsI2P();
         }
 
         /**

test/functional/p2p_addrv2_relay.py

@@ -18,12 +18,19 @@
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal
 
+I2P_ADDR = "c4gfnttsuwqomiygupdqqqyy5y5emnk5c73hrfvatri67prd7vyq.b32.i2p"
+
 ADDRS = []
 for i in range(10):
     addr = CAddress()
     addr.time = int(time.time()) + i
     addr.nServices = NODE_NETWORK | NODE_WITNESS
-    addr.ip = "123.123.123.{}".format(i % 256)
+    # Add one I2P address at an arbitrary position.
+    if i == 5:
+        addr.net = addr.NET_I2P
+        addr.ip = I2P_ADDR
+    else:
+        addr.ip = f"123.123.123.{i % 256}"
     addr.port = 8333 + i
     ADDRS.append(addr)
 
@@ -35,11 +42,8 @@ def __init__(self):
         super().__init__(support_addrv2 = True)
 
     def on_addrv2(self, message):
-        for addr in message.addrs:
-            assert_equal(addr.nServices, 9)
-            assert addr.ip.startswith('123.123.123.')
-            assert (8333 <= addr.port < 8343)
-        self.addrv2_received_and_checked = True
+        if ADDRS == message.addrs:
+            self.addrv2_received_and_checked = True
 
     def wait_for_addrv2(self):
         self.wait_until(lambda: "addrv2" in self.last_message)
@@ -64,15 +68,18 @@ def run_test(self):
         addr_receiver = self.nodes[0].add_p2p_connection(AddrReceiver())
         msg.addrs = ADDRS
         with self.nodes[0].assert_debug_log([
-                'Added 10 addresses from 127.0.0.1: 0 tried',
-                'received: addrv2 (131 bytes) peer=0',
-                'sending addrv2 (131 bytes) peer=1',
+                # The I2P address is not added to node's own addrman because it has no
+                # I2P reachability (thus 10 - 1 = 9).
+                'Added 9 addresses from 127.0.0.1: 0 tried',
+                'received: addrv2 (159 bytes) peer=0',
+                'sending addrv2 (159 bytes) peer=1',
         ]):
             addr_source.send_and_ping(msg)
             self.nodes[0].setmocktime(int(time.time()) + 30 * 60)
             addr_receiver.wait_for_addrv2()
 
         assert addr_receiver.addrv2_received_and_checked
+        assert_equal(len(self.nodes[0].getnodeaddresses(count=0, network="i2p")), 0)
 
 
 if __name__ == '__main__':

test/functional/test_framework/messages.py

@@ -18,6 +18,7 @@
 Classes use __slots__ to ensure extraneous attributes aren't accidentally added
 by tests, compromising their intended effect.
 """
+from base64 import b32decode, b32encode
 from codecs import encode
 import copy
 import hashlib
@@ -207,22 +208,30 @@ class CAddress:
 
     # see https://github.com/bitcoin/bips/blob/master/bip-0155.mediawiki
     NET_IPV4 = 1
+    NET_I2P = 5
 
     ADDRV2_NET_NAME = {
-        NET_IPV4: "IPv4"
+        NET_IPV4: "IPv4",
+        NET_I2P: "I2P"
     }
 
     ADDRV2_ADDRESS_LENGTH = {
-        NET_IPV4: 4
+        NET_IPV4: 4,
+        NET_I2P: 32
     }
 
+    I2P_PAD = "===="
+
     def __init__(self):
         self.time = 0
         self.nServices = 1
         self.net = self.NET_IPV4
         self.ip = "0.0.0.0"
         self.port = 0
 
+    def __eq__(self, other):
+        return self.net == other.net and self.ip == other.ip and self.nServices == other.nServices and self.port == other.port and self.time == other.time
+
     def deserialize(self, f, *, with_time=True):
         """Deserialize from addrv1 format (pre-BIP155)"""
         if with_time:
@@ -255,24 +264,33 @@ def deserialize_v2(self, f):
         self.nServices = deser_compact_size(f)
 
         self.net = struct.unpack("B", f.read(1))[0]
-        assert self.net == self.NET_IPV4
+        assert self.net in (self.NET_IPV4, self.NET_I2P)
 
         address_length = deser_compact_size(f)
         assert address_length == self.ADDRV2_ADDRESS_LENGTH[self.net]
 
-        self.ip = socket.inet_ntoa(f.read(4))
+        addr_bytes = f.read(address_length)
+        if self.net == self.NET_IPV4:
+            self.ip = socket.inet_ntoa(addr_bytes)
+        else:
+            self.ip = b32encode(addr_bytes)[0:-len(self.I2P_PAD)].decode("ascii").lower() + ".b32.i2p"
 
         self.port = struct.unpack(">H", f.read(2))[0]
 
     def serialize_v2(self):
         """Serialize in addrv2 format (BIP155)"""
-        assert self.net == self.NET_IPV4
+        assert self.net in (self.NET_IPV4, self.NET_I2P)
         r = b""
         r += struct.pack("<I", self.time)
         r += ser_compact_size(self.nServices)
         r += struct.pack("B", self.net)
         r += ser_compact_size(self.ADDRV2_ADDRESS_LENGTH[self.net])
-        r += socket.inet_aton(self.ip)
+        if self.net == self.NET_IPV4:
+            r += socket.inet_aton(self.ip)
+        else:
+            sfx = ".b32.i2p"
+            assert self.ip.endswith(sfx)
+            r += b32decode(self.ip[0:-len(sfx)] + self.I2P_PAD, True)
         r += struct.pack(">H", self.port)
         return r