ofp_handler: Handle empty data field in OFPErrorMsg

OpenFlow Spec defines that the data field should contain at least
64 bytes of the failed request that caused the error message to be
generated, unless otherwise specified.
But, the data field can be empty in some switch implementation,
this patch checks the data field length and skips parsing it if the
field does not contain enough bytes to parse.

Reported-by: Yury Yurochko <y.yurochko@brain4net.com>
Signed-off-by: IWASE Yusuke <iwase.yusuke0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

1 files changed, 25 insertions, 18 deletions

diff --git a/ryu/controller/ofp_handler.py b/ryu/controller/ofp_handler.py
index b3c63dfd..7ec1c955 100644
--- a/ryu/controller/ofp_handler.py
+++ b/ryu/controller/ofp_handler.py
@@ -243,22 +243,29 @@ class OFPHandler(ryu.base.app_manager.RyuApp):
     def error_msg_handler(self, ev):
         msg = ev.msg
         ofp = msg.datapath.ofproto
-        (version, msg_type, msg_len, xid) = ofproto_parser.header(msg.data)
-        self.logger.debug('EventOFPErrorMsg received.')
         self.logger.debug(
-            'version=%s, msg_type=%s, msg_len=%s, xid=%s', hex(msg.version),
-            hex(msg.msg_type), hex(msg.msg_len), hex(msg.xid))
-        self.logger.debug(
-            ' `-- msg_type: %s', ofp.ofp_msg_type_to_str(msg.msg_type))
-        self.logger.debug(
-            "OFPErrorMsg(type=%s, code=%s, data=b'%s')", hex(msg.type),
-            hex(msg.code), utils.binary_str(msg.data))
-        self.logger.debug(
-            ' |-- type: %s', ofp.ofp_error_type_to_str(msg.type))
-        self.logger.debug(
-            ' |-- code: %s', ofp.ofp_error_code_to_str(msg.type, msg.code))
-        self.logger.debug(
-            ' `-- data: version=%s, msg_type=%s, msg_len=%s, xid=%s',
-            hex(version), hex(msg_type), hex(msg_len), hex(xid))
-        self.logger.debug(
-            '     `-- msg_type: %s', ofp.ofp_msg_type_to_str(msg_type))
+            "EventOFPErrorMsg received.\n"
+            "version=%s, msg_type=%s, msg_len=%s, xid=%s\n"
+            " `-- msg_type: %s\n"
+            "OFPErrorMsg(type=%s, code=%s, data=b'%s')\n"
+            " |-- type: %s\n"
+            " |-- code: %s",
+            hex(msg.version), hex(msg.msg_type), hex(msg.msg_len),
+            hex(msg.xid), ofp.ofp_msg_type_to_str(msg.msg_type),
+            hex(msg.type), hex(msg.code), utils.binary_str(msg.data),
+            ofp.ofp_error_type_to_str(msg.type),
+            ofp.ofp_error_code_to_str(msg.type, msg.code))
+        if len(msg.data) >= ofp.OFP_HEADER_SIZE:
+            (version, msg_type, msg_len, xid) = ofproto_parser.header(msg.data)
+            self.logger.debug(
+                " `-- data: version=%s, msg_type=%s, msg_len=%s, xid=%s\n"
+                "     `-- msg_type: %s",
+                hex(version), hex(msg_type), hex(msg_len), hex(xid),
+                ofp.ofp_msg_type_to_str(msg_type))
+        else:
+            self.logger.warning(
+                "The data field sent from the switch is too short: "
+                "len(msg.data) < OFP_HEADER_SIZE\n"
+                "The OpenFlow Spec says that the data field should contain "
+                "at least 64 bytes of the failed request.\n"
+                "Please check the settings or implementation of your switch.")