Fix issues with inet type I/O

The inet codec is confusing the network prefix length with the network
mask length, which causes incorrect wire encoding.  This was masked by a
symmetrical bug in the decoder.

Fixes #37.

Author: elprans

asyncpg/protocol/codecs/network.pyx

@@ -18,15 +18,37 @@ _ipaddr = ipaddress.ip_address
 _ipnet = ipaddress.ip_network
 
 
-cdef inline _net_encode(WriteBuffer buf, int32_t version, uint8_t bits,
+cdef inline uint8_t _ip_max_prefix_len(int32_t family):
+    # Maximum number of bits in the network prefix of the specified
+    # IP protocol version.
+    if family == PGSQL_AF_INET:
+        return 32
+    else:
+        return 128
+
+
+cdef inline int32_t _ip_addr_len(int32_t family):
+    # Length of address in bytes for the specified IP protocol version.
+    if family == PGSQL_AF_INET:
+        return 4
+    else:
+        return 16
+
+
+cdef inline int8_t _ver_to_family(int32_t version):
+    if version == 4:
+        return PGSQL_AF_INET
+    else:
+        return PGSQL_AF_INET6
+
+
+cdef inline _net_encode(WriteBuffer buf, int8_t family, uint32_t bits,
                         int8_t is_cidr, bytes addr):
 
     cdef:
         char *addrbytes
         ssize_t addrlen
-        int8_t family
 
-    family = PGSQL_AF_INET if version == 4 else PGSQL_AF_INET6
     cpython.PyBytes_AsStringAndSize(addr, &addrbytes, &addrlen)
 
     buf.write_int32(4 + <int32_t>addrlen)
@@ -41,28 +63,31 @@ cdef net_decode(ConnectionSettings settings, FastReadBuffer buf):
     cdef:
         int32_t family = <int32_t>buf.read(1)[0]
         uint8_t bits = <uint8_t>buf.read(1)[0]
-        uint32_t is_cidr = <uint32_t>buf.read(1)[0]
-        uint32_t addrlen = <uint32_t>buf.read(1)[0]
+        int32_t is_cidr = <int32_t>buf.read(1)[0]
+        int32_t addrlen = <int32_t>buf.read(1)[0]
         bytes addr
+        uint8_t max_prefix_len = _ip_max_prefix_len(family)
 
     if family != PGSQL_AF_INET and family != PGSQL_AF_INET6:
         raise ValueError('invalid address family in "{}" value'.format(
             'cidr' if is_cidr else 'inet'
         ))
 
-    if bits > (32 if family == PGSQL_AF_INET else 128):
-        raise ValueError('invalid bits in "{}" value'.format(
+    max_prefix_len = _ip_max_prefix_len(family)
+
+    if bits > max_prefix_len:
+        raise ValueError('invalid network prefix length in "{}" value'.format(
             'cidr' if is_cidr else 'inet'
         ))
 
-    if addrlen != (4 if family == PGSQL_AF_INET else 16):
-        raise ValueError('invalid length in "{}" value'.format(
+    if addrlen != _ip_addr_len(family):
+        raise ValueError('invalid address length in "{}" value'.format(
             'cidr' if is_cidr else 'inet'
         ))
 
     addr = cpython.PyBytes_FromStringAndSize(buf.read(addrlen), addrlen)
 
-    if is_cidr or bits > 0:
+    if is_cidr or bits != max_prefix_len:
         return _ipnet(addr).supernet(new_prefix=cpython.PyLong_FromLong(bits))
     else:
         return _ipaddr(addr)
@@ -71,15 +96,17 @@ cdef net_decode(ConnectionSettings settings, FastReadBuffer buf):
 cdef cidr_encode(ConnectionSettings settings, WriteBuffer buf, obj):
     cdef:
         object ipnet
+        int8_t family
 
     ipnet = _ipnet(obj)
-    _net_encode(buf, ipnet.version, ipnet.prefixlen, 1,
-                ipnet.network_address.packed)
+    family = _ver_to_family(ipnet.version)
+    _net_encode(buf, family, ipnet.prefixlen, 1, ipnet.network_address.packed)
 
 
 cdef inet_encode(ConnectionSettings settings, WriteBuffer buf, obj):
     cdef:
         object ipaddr
+        int8_t family
 
     try:
         ipaddr = _ipaddr(obj)
@@ -88,7 +115,8 @@ cdef inet_encode(ConnectionSettings settings, WriteBuffer buf, obj):
         # for the host datatype.
         cidr_encode(settings, buf, obj)
     else:
-        _net_encode(buf, ipaddr.version, 0, 0, ipaddr.packed)
+        family = _ver_to_family(ipaddr.version)
+        _net_encode(buf, family, _ip_max_prefix_len(family), 0, ipaddr.packed)
 
 
 cdef init_network_codecs():

tests/test_codecs.py

@@ -302,7 +302,32 @@ def _timezone(offset):
             output=ipaddress.IPv4Network('127.0.0.0/8')),
         dict(
             input='127.0.0.1/32',
-            output=ipaddress.IPv4Network('127.0.0.1/32')),
+            output=ipaddress.IPv4Address('127.0.0.1')),
+        # Postgres appends /32 when casting to text explicitly, but
+        # *not* in inet_out.
+        dict(
+            input='10.11.12.13',
+            textoutput='10.11.12.13/32'
+        ),
+        dict(
+            input=ipaddress.IPv4Address('10.11.12.13'),
+            textoutput='10.11.12.13/32'
+        ),
+        dict(
+            input=ipaddress.IPv4Network('10.11.12.13'),
+            textoutput='10.11.12.13/32'
+        ),
+        dict(
+            textinput='10.11.12.13',
+            output=ipaddress.IPv4Address('10.11.12.13'),
+        ),
+        dict(
+            # Non-zero address bits after the network prefix are permitted
+            # by postgres, but are invalid in Python
+            # (and zeroed out by supernet()).
+            textinput='10.11.12.13/0',
+            output=ipaddress.IPv4Network('0.0.0.0/0'),
+        ),
     ]),
     ('macaddr', 'macaddr', [
         '00:00:00:00:00:00',
@@ -369,20 +394,33 @@ async def test_standard_codecs(self):
                 "SELECT $1::" + typname
             )
 
-            textst = await self.con.prepare(
+            text_in = await self.con.prepare(
                 "SELECT $1::text::" + typname
             )
 
+            text_out = await self.con.prepare(
+                "SELECT $1::" + typname + "::text"
+            )
+
             for sample in sample_data:
                 with self.subTest(sample=sample, typname=typname):
                     stmt = st
                     if isinstance(sample, dict):
                         if 'textinput' in sample:
                             inputval = sample['textinput']
-                            stmt = textst
+                            stmt = text_in
                         else:
                             inputval = sample['input']
-                        outputval = sample['output']
+
+                        if 'textoutput' in sample:
+                            outputval = sample['textoutput']
+                            if stmt is text_in:
+                                raise ValueError(
+                                    'cannot test "textin" and'
+                                    ' "textout" simultaneously')
+                            stmt = text_out
+                        else:
+                            outputval = sample['output']
                     else:
                         inputval = outputval = sample