packet lib: ipv6: Fix to calculate AH length

RFC2402 says:

    All IPv6 extension headers, as per RFC 1883, encode the "Hdr Ext Len" field by first
    subtracting 1 (64-bit word) from the header length (measured in 64-bit words).
    AH is an IPv6 extension header.  However, since its length is measured in 32-bit words,
    the "Payload Length" is calculated by subtracting 2 (32 bit words).

This patch fixes as follows:

    return (int(size) - 1) * 8 ->
    return (int(size) + 2) * 4
                      ^ ^    ^
And, this patch also fixes a default argument of length.

Signed-off-by: TAKAHASHI Minoru <takahashi.minoru7@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

2 files changed, 11 insertions, 4 deletions

diff --git a/ryu/lib/packet/ipv6.py b/ryu/lib/packet/ipv6.py
index 960f1acb..b02ca51c 100644
--- a/ryu/lib/packet/ipv6.py
+++ b/ryu/lib/packet/ipv6.py
@@ -409,7 +409,7 @@ class auth(header):
     _PACK_STR = '!BB2xII'
     _MIN_LEN = struct.calcsize(_PACK_STR)
 
-    def __init__(self, nxt=inet.IPPROTO_TCP, size=3, spi=0, seq=0,
+    def __init__(self, nxt=inet.IPPROTO_TCP, size=2, spi=0, seq=0,
                  data='\x00\x00\x00\x00'):
         super(auth, self).__init__(nxt)
         assert data is not None
@@ -420,7 +420,7 @@ class auth(header):
 
     @classmethod
     def _get_size(cls, size):
-        return (int(size) - 1) * 8
+        return (int(size) + 2) * 4
 
     @classmethod
     def parser(cls, buf):
diff --git a/ryu/tests/unit/packet/test_ipv6.py b/ryu/tests/unit/packet/test_ipv6.py
index a2a13433..4229b18c 100644
--- a/ryu/tests/unit/packet/test_ipv6.py
+++ b/ryu/tests/unit/packet/test_ipv6.py
@@ -786,7 +786,14 @@ class Test_auth(unittest.TestCase):
         eq_(self.data, res[4])
 
     def test_len(self):
-        eq_((4 - 1) * 8, len(self.auth))
+        eq_((4 + 2) * 4, len(self.auth))
+
+    def test_len_re(self):
+        size = 5
+        auth = ipv6.auth(
+            0, size, 256, 1,
+            '\x21\xd3\xa9\x5c\x5f\xfd\x4d\x18\x46\x22\xb9\xf8\xf8\xf8\xf8\xf8')
+        eq_((size + 2) * 4, len(auth))
 
     def test_default_args(self):
         hdr = ipv6.auth()
@@ -796,7 +803,7 @@ class Test_auth(unittest.TestCase):
         LOG.info(res)
 
         eq_(res[0], 6)
-        eq_(res[1], 3)
+        eq_(res[1], 2)
         eq_(res[2], 0)
         eq_(res[3], 0)
         eq_(buf[ipv6.auth._MIN_LEN:], '\x00\x00\x00\x00')