packet lib: ipv6: simplify the operations of __init__()

before applying this patch:
  - ipv6.parser() uses 'nxt' of the last extension header
  - ipv6.__init__() rewrites 'nxt' in conjunction with extension headers
  - 'nxt' of the extension headers are set automatically, i.e. they are obscure

after applying this patch:
  - ipv6.parser() does not consider 'nxt' of the extension headers
  - ipv6.__init__() does not rewrite 'nxt'
  - 'nxt' of the extension headers are set manually as an argument of __init__()

Signed-off-by: itoyuichi <ito.yuichi0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

2 files changed, 48 insertions, 60 deletions

diff --git a/ryu/lib/packet/ipv6.py b/ryu/lib/packet/ipv6.py
index 8f4b50dd..ca5793d1 100644
--- a/ryu/lib/packet/ipv6.py
+++ b/ryu/lib/packet/ipv6.py
@@ -80,16 +80,8 @@ class ipv6(packet_base.PacketBase):
         self.dst = dst
         if ext_hdrs:
             assert isinstance(ext_hdrs, list)
-            last_hdr = None
             for ext_hdr in ext_hdrs:
                 assert isinstance(ext_hdr, header)
-                if last_hdr:
-                    ext_hdr.set_nxt(last_hdr.nxt)
-                    last_hdr.nxt = ext_hdr.TYPE
-                else:
-                    ext_hdr.set_nxt(self.nxt)
-                    self.nxt = ext_hdr.TYPE
-                last_hdr = ext_hdr
         self.ext_hdrs = ext_hdrs
 
     @classmethod
@@ -111,10 +103,8 @@ class ipv6(packet_base.PacketBase):
             ext_hdrs.append(hdr)
             offset += len(hdr)
             last = hdr.nxt
-        # call ipv6.__init__() using 'nxt' of the last extension
-        # header that points the next protocol.
         msg = cls(version, traffic_class, flow_label, payload_length,
-                  last, hop_limit, addrconv.ipv6.bin_to_text(src),
+                  nxt, hop_limit, addrconv.ipv6.bin_to_text(src),
                   addrconv.ipv6.bin_to_text(dst), ext_hdrs)
         return (msg, ipv6.get_packet_type(last),
                 buf[offset:offset+payload_length])
@@ -148,10 +138,7 @@ class header(stringify.StringifyMixin):
 
     __metaclass__ = abc.ABCMeta
 
-    def __init__(self):
-        self.nxt = None
-
-    def set_nxt(self, nxt):
+    def __init__(self, nxt):
         self.nxt = nxt
 
     @classmethod
@@ -179,8 +166,8 @@ class opt_header(header):
     _FIX_SIZE = 8
 
     @abc.abstractmethod
-    def __init__(self, size, data):
-        super(opt_header, self).__init__()
+    def __init__(self, nxt, size, data):
+        super(opt_header, self).__init__(nxt)
         assert not (size % 8)
         self.size = size
         self.data = data
@@ -200,9 +187,7 @@ class opt_header(header):
                 opt = option.parser(buf[size:])
                 size += len(opt)
             data.append(opt)
-        ret = cls(len_, data)
-        ret.set_nxt(nxt)
-        return ret
+        return cls(nxt, len_, data)
 
     def serialize(self):
         buf = struct.pack(self._PACK_STR, self.nxt, self.size)
@@ -230,6 +215,7 @@ class hop_opts(opt_header):
     ============== =======================================
     Attribute      Description
     ============== =======================================
+    nxt            Next Header
     size           the length of the Hop-by-Hop Options header,
                    not include the first 8 octet.
     data           IPv6 options.
@@ -237,8 +223,8 @@ class hop_opts(opt_header):
     """
     TYPE = inet.IPPROTO_HOPOPTS
 
-    def __init__(self, size, data):
-        super(hop_opts, self).__init__(size, data)
+    def __init__(self, nxt, size, data):
+        super(hop_opts, self).__init__(nxt, size, data)
 
 
 @ipv6.register_header_type(inet.IPPROTO_DSTOPTS)
@@ -256,6 +242,7 @@ class dst_opts(opt_header):
     ============== =======================================
     Attribute      Description
     ============== =======================================
+    nxt            Next Header
     size           the length of the destination header,
                    not include the first 8 octet.
     data           IPv6 options.
@@ -263,8 +250,8 @@ class dst_opts(opt_header):
     """
     TYPE = inet.IPPROTO_DSTOPTS
 
-    def __init__(self, size, data):
-        super(dst_opts, self).__init__(size, data)
+    def __init__(self, nxt, size, data):
+        super(dst_opts, self).__init__(nxt, size, data)
 
 
 class option(stringify.StringifyMixin):
@@ -341,6 +328,7 @@ class fragment(header):
     ============== =======================================
     Attribute      Description
     ============== =======================================
+    nxt            Next Header
     offset         offset, in 8-octet units, relative to
                    the start of the fragmentable part of
                    the original packet.
@@ -354,8 +342,8 @@ class fragment(header):
     _PACK_STR = '!BxHI'
     _MIN_LEN = struct.calcsize(_PACK_STR)
 
-    def __init__(self, offset, more, id_):
-        super(fragment, self).__init__()
+    def __init__(self, nxt, offset, more, id_):
+        super(fragment, self).__init__(nxt)
         self.offset = offset
         self.more = more
         self.id_ = id_
@@ -365,9 +353,7 @@ class fragment(header):
         (nxt, off_m, id_) = struct.unpack_from(cls._PACK_STR, buf)
         offset = off_m >> 3
         more = off_m & 0x1
-        ret = cls(offset, more, id_)
-        ret.set_nxt(nxt)
-        return ret
+        return cls(nxt, offset, more, id_)
 
     def serialize(self):
         off_m = (self.offset << 3 | self.more)
@@ -393,6 +379,7 @@ class auth(header):
     ============== =======================================
     Attribute      Description
     ============== =======================================
+    nxt            Next Header
     size           the length of the Authentication Header
                    in 64-bit words, subtracting 1.
     spi            security parameters index.
@@ -405,8 +392,8 @@ class auth(header):
     _PACK_STR = '!BB2xII'
     _MIN_LEN = struct.calcsize(_PACK_STR)
 
-    def __init__(self, size, spi, seq, data):
-        super(auth, self).__init__()
+    def __init__(self, nxt, size, spi, seq, data):
+        super(auth, self).__init__(nxt)
         self.size = size
         self.spi = spi
         self.seq = seq
@@ -421,9 +408,7 @@ class auth(header):
         (nxt, size, spi, seq) = struct.unpack_from(cls._PACK_STR, buf)
         form = "%ds" % (cls._get_size(size) - cls._MIN_LEN)
         (data, ) = struct.unpack_from(form, buf, cls._MIN_LEN)
-        ret = cls(size, spi, seq, data)
-        ret.set_nxt(nxt)
-        return ret
+        return cls(nxt, size, spi, seq, data)
 
     def serialize(self):
         buf = struct.pack(self._PACK_STR, self.nxt, self.size, self.spi,
diff --git a/ryu/tests/unit/packet/test_ipv6.py b/ryu/tests/unit/packet/test_ipv6.py
index 8ca7bda6..0810086b 100644
--- a/ryu/tests/unit/packet/test_ipv6.py
+++ b/ryu/tests/unit/packet/test_ipv6.py
@@ -66,16 +66,17 @@ class Test_ipv6(unittest.TestCase):
             ipv6.option(self.opt1_type, self.opt1_len, self.opt1_data),
             ipv6.option(self.opt2_type, self.opt2_len, self.opt2_data),
         ]
+        self.hop_opts_nxt = 6
         self.hop_opts_size = 0
-        self.hop_opts = ipv6.hop_opts(self.hop_opts_size, self.options)
+        self.hop_opts = ipv6.hop_opts(
+            self.hop_opts_nxt, self.hop_opts_size, self.options)
         self.ext_hdrs = [self.hop_opts]
         self.payload_length += len(self.hop_opts)
+        self.nxt = ipv6.hop_opts.TYPE
         self.ip = ipv6.ipv6(
             self.version, self.traffic_class, self.flow_label,
             self.payload_length, self.nxt, self.hop_limit, self.src,
             self.dst, self.ext_hdrs)
-        self.hop_opts.nxt = self.nxt
-        self.nxt = self.hop_opts.TYPE
         self.buf = struct.pack(
             ipv6.ipv6._PACK_STR, self.v_tc_flow,
             self.payload_length, self.nxt, self.hop_limit,
@@ -94,16 +95,17 @@ class Test_ipv6(unittest.TestCase):
             ipv6.option(self.opt1_type, self.opt1_len, self.opt1_data),
             ipv6.option(self.opt2_type, self.opt2_len, self.opt2_data),
         ]
+        self.dst_opts_nxt = 6
         self.dst_opts_size = 0
-        self.dst_opts = ipv6.dst_opts(self.dst_opts_size, self.options)
+        self.dst_opts = ipv6.dst_opts(
+            self.dst_opts_nxt, self.dst_opts_size, self.options)
         self.ext_hdrs = [self.dst_opts]
         self.payload_length += len(self.dst_opts)
+        self.nxt = ipv6.dst_opts.TYPE
         self.ip = ipv6.ipv6(
             self.version, self.traffic_class, self.flow_label,
             self.payload_length, self.nxt, self.hop_limit, self.src,
             self.dst, self.ext_hdrs)
-        self.dst_opts.nxt = self.nxt
-        self.nxt = self.dst_opts.TYPE
         self.buf = struct.pack(
             ipv6.ipv6._PACK_STR, self.v_tc_flow,
             self.payload_length, self.nxt, self.hop_limit,
@@ -112,19 +114,20 @@ class Test_ipv6(unittest.TestCase):
         self.buf += self.dst_opts.serialize()
 
     def setUp_with_fragment(self):
+        self.fragment_nxt = 6
         self.fragment_offset = 50
         self.fragment_more = 1
         self.fragment_id = 123
         self.fragment = ipv6.fragment(
-            self.fragment_offset, self.fragment_more, self.fragment_id)
+            self.fragment_nxt, self.fragment_offset, self.fragment_more,
+            self.fragment_id)
         self.ext_hdrs = [self.fragment]
         self.payload_length += len(self.fragment)
+        self.nxt = ipv6.fragment.TYPE
         self.ip = ipv6.ipv6(
             self.version, self.traffic_class, self.flow_label,
             self.payload_length, self.nxt, self.hop_limit, self.src,
             self.dst, self.ext_hdrs)
-        self.fragment.nxt = self.nxt
-        self.nxt = self.fragment.TYPE
         self.buf = struct.pack(
             ipv6.ipv6._PACK_STR, self.v_tc_flow,
             self.payload_length, self.nxt, self.hop_limit,
@@ -133,20 +136,21 @@ class Test_ipv6(unittest.TestCase):
         self.buf += self.fragment.serialize()
 
     def setUp_with_auth(self):
+        self.auth_nxt = 6
         self.auth_size = 4
         self.auth_spi = 256
         self.auth_seq = 1
         self.auth_data = '\xa0\xe7\xf8\xab\xf9\x69\x1a\x8b\xf3\x9f\x7c\xae'
         self.auth = ipv6.auth(
-            self.auth_size, self.auth_spi, self.auth_seq, self.auth_data)
+            self.auth_nxt, self.auth_size, self.auth_spi, self.auth_seq,
+            self.auth_data)
         self.ext_hdrs = [self.auth]
         self.payload_length += len(self.auth)
+        self.nxt = ipv6.auth.TYPE
         self.ip = ipv6.ipv6(
             self.version, self.traffic_class, self.flow_label,
             self.payload_length, self.nxt, self.hop_limit, self.src,
             self.dst, self.ext_hdrs)
-        self.auth.nxt = self.nxt
-        self.nxt = self.auth.TYPE
         self.buf = struct.pack(
             ipv6.ipv6._PACK_STR, self.v_tc_flow,
             self.payload_length, self.nxt, self.hop_limit,
@@ -165,24 +169,25 @@ class Test_ipv6(unittest.TestCase):
             ipv6.option(self.opt1_type, self.opt1_len, self.opt1_data),
             ipv6.option(self.opt2_type, self.opt2_len, self.opt2_data),
         ]
+        self.hop_opts_nxt = ipv6.auth.TYPE
         self.hop_opts_size = 0
-        self.hop_opts = ipv6.hop_opts(self.hop_opts_size, self.options)
+        self.hop_opts = ipv6.hop_opts(
+            self.hop_opts_nxt, self.hop_opts_size, self.options)
+        self.auth_nxt = 6
         self.auth_size = 4
         self.auth_spi = 256
         self.auth_seq = 1
         self.auth_data = '\xa0\xe7\xf8\xab\xf9\x69\x1a\x8b\xf3\x9f\x7c\xae'
         self.auth = ipv6.auth(
-            self.auth_size, self.auth_spi, self.auth_seq, self.auth_data)
+            self.auth_nxt, self.auth_size, self.auth_spi, self.auth_seq,
+            self.auth_data)
         self.ext_hdrs = [self.hop_opts, self.auth]
         self.payload_length += len(self.hop_opts) + len(self.auth)
+        self.nxt = ipv6.hop_opts.TYPE
         self.ip = ipv6.ipv6(
             self.version, self.traffic_class, self.flow_label,
             self.payload_length, self.nxt, self.hop_limit, self.src,
             self.dst, self.ext_hdrs)
-        self.hop_opts.nxt = self.nxt
-        self.nxt = self.hop_opts.TYPE
-        self.auth.nxt = self.hop_opts.nxt
-        self.hop_opts.nxt = self.auth.TYPE
         self.buf = struct.pack(
             ipv6.ipv6._PACK_STR, self.v_tc_flow,
             self.payload_length, self.nxt, self.hop_limit,
@@ -403,8 +408,7 @@ class Test_hop_opts(unittest.TestCase):
             ipv6.option(0xc2, 4, '\x00\x01\x00\x00'),
             ipv6.option(1, 0, None),
         ]
-        self.hop = ipv6.hop_opts(self.size, self.data)
-        self.hop.set_nxt(self.nxt)
+        self.hop = ipv6.hop_opts(self.nxt, self.size, self.data)
         self.form = '!BB'
         self.buf = struct.pack(self.form, self.nxt, self.size) \
             + self.data[0].serialize() \
@@ -475,8 +479,7 @@ class Test_dst_opts(unittest.TestCase):
             ipv6.option(0xc2, 4, '\x00\x01\x00\x00'),
             ipv6.option(1, 0, None),
         ]
-        self.dst = ipv6.dst_opts(self.size, self.data)
-        self.dst.set_nxt(self.nxt)
+        self.dst = ipv6.dst_opts(self.nxt, self.size, self.data)
         self.form = '!BB'
         self.buf = struct.pack(self.form, self.nxt, self.size) \
             + self.data[0].serialize() \
@@ -615,8 +618,8 @@ class Test_fragment(unittest.TestCase):
         self.offset = 50
         self.more = 1
         self.id_ = 123
-        self.fragment = ipv6.fragment(self.offset, self.more, self.id_)
-        self.fragment.set_nxt(self.nxt)
+        self.fragment = ipv6.fragment(
+            self.nxt, self.offset, self.more, self.id_)
 
         self.off_m = (self.offset << 3 | self.more)
         self.form = '!BxHI'
@@ -658,8 +661,8 @@ class Test_auth(unittest.TestCase):
         self.spi = 256
         self.seq = 1
         self.data = '\x21\xd3\xa9\x5c\x5f\xfd\x4d\x18\x46\x22\xb9\xf8'
-        self.auth = ipv6.auth(self.size, self.spi, self.seq, self.data)
-        self.auth.set_nxt(self.nxt)
+        self.auth = ipv6.auth(
+            self.nxt, self.size, self.spi, self.seq, self.data)
         self.form = '!BB2xII12s'
         self.buf = struct.pack(self.form, self.nxt, self.size, self.spi,
                                self.seq, self.data)