CoAP option update (#1523)

* Do not drop CoAP requests with unknown options

If packets are dropped due to unrecognized options, then it should be done
according to RFC7252 Section 5.4.1., otherwise leave it for the user.

* Implement CoAP Header GetFirstOption

* Implement in Header
* Add to CoAP API
* Use in code

* Remove CoAP Header GetCurrentOption

* Correction in the comments

* Initialize CoAP Header before parsing

include/openthread/coap.h

@@ -136,6 +136,7 @@ typedef struct otCoapHeader
     } mHeader;                                      ///< The CoAP header encoding
     uint8_t mHeaderLength;                          ///< The CoAP header length (bytes)
     uint16_t mOptionLast;                           ///< The last CoAP Option Number value
+    uint16_t mFirstOptionOffset;                    ///< The byte offset for the first CoAP Option
     uint16_t mNextOptionOffset;                     ///< The byte offset for the next CoAP Option
     otCoapOption mOption;                           ///< A structure representing the current CoAP Option.
 } otCoapHeader;
@@ -344,14 +345,14 @@ uint8_t otCoapHeaderGetTokenLength(const otCoapHeader *aHeader);
 const uint8_t *otCoapHeaderGetToken(const otCoapHeader *aHeader);
 
 /**
- * This function returns a pointer to the current option.
+ * This function returns a pointer to the first option.
  *
  * @param[in]  aHeader  A pointer to the CoAP header.
  *
- * @returns A pointer to the current option. If no option is present NULL pointer is returned.
+ * @returns A pointer to the first option. If no option is present NULL pointer is returned.
  *
  */
-const otCoapOption *otCoapHeaderGetCurrentOption(const otCoapHeader *aHeader);
+const otCoapOption *otCoapHeaderGetFirstOption(otCoapHeader *aHeader);
 
 /**
  * This function returns a pointer to the next option.

src/core/api/coap_api.cpp

@@ -116,9 +116,9 @@ const uint8_t *otCoapHeaderGetToken(const otCoapHeader *aHeader)
     return static_cast<const Coap::Header *>(aHeader)->GetToken();
 }
 
-const otCoapOption *otCoapHeaderGetCurrentOption(const otCoapHeader *aHeader)
+const otCoapOption *otCoapHeaderGetFirstOption(otCoapHeader *aHeader)
 {
-    return static_cast<const otCoapOption *>(static_cast<const Coap::Header *>(aHeader)->GetCurrentOption());
+    return static_cast<const otCoapOption *>(static_cast<Coap::Header *>(aHeader)->GetFirstOption());
 }
 
 const otCoapOption *otCoapHeaderGetNextOption(otCoapHeader *aHeader)

src/core/coap/coap_header.cpp

@@ -46,6 +46,7 @@ void Header::Init(void)
 {
     mHeaderLength = kMinHeaderLength;
     mOptionLast = 0;
+    mFirstOptionOffset = 0;
     mNextOptionOffset = 0;
     memset(&mOption, 0, sizeof(mOption));
     memset(&mHeader, 0, sizeof(mHeader));
@@ -71,6 +72,8 @@ ThreadError Header::FromMessage(const Message &aMessage, uint16_t aMetadataSize)
 
     length -= aMetadataSize;
 
+    Init();
+
     VerifyOrExit(length >= kTokenOffset, error = kThreadError_Parse);
     aMessage.Read(offset, kTokenOffset, mHeader.mBytes);
     mHeaderLength = kTokenOffset;
@@ -96,6 +99,11 @@ ThreadError Header::FromMessage(const Message &aMessage, uint16_t aMetadataSize)
             ExitNow(error = kThreadError_None);
         }
 
+        if (firstOption)
+        {
+            mFirstOptionOffset = mHeaderLength;
+        }
+
         optionDelta = mHeader.mBytes[mHeaderLength] >> 4;
         optionLength = mHeader.mBytes[mHeaderLength] & 0xf;
         mHeaderLength += sizeof(uint8_t);
@@ -173,6 +181,13 @@ ThreadError Header::FromMessage(const Message &aMessage, uint16_t aMetadataSize)
     }
 
 exit:
+
+    // In case any step failed, prevent access to corrupt Option
+    if (error != kThreadError_None)
+    {
+        mFirstOptionOffset = 0;
+    }
+
     return error;
 }
 
@@ -328,9 +343,19 @@ ThreadError Header::AppendUriQueryOption(const char *aUriQuery)
     return AppendOption(coapOption);
 }
 
-const Header::Option *Header::GetCurrentOption(void) const
+const Header::Option *Header::GetFirstOption(void)
 {
-    return static_cast<const Header::Option *>(&mOption);
+    const Option *rval = NULL;
+
+    VerifyOrExit(mFirstOptionOffset > 0,);
+
+    memset(&mOption, 0, sizeof(mOption));
+    mNextOptionOffset = mFirstOptionOffset;
+
+    rval = GetNextOption();
+
+exit:
+    return rval;
 }
 
 const Header::Option *Header::GetNextOption(void)

src/core/coap/coap_header.hpp

@@ -340,12 +340,12 @@ public:
     ThreadError AppendUriQueryOption(const char *aUriQuery);
 
     /**
-     * This method returns a pointer to the current option.
+     * This method returns a pointer to the first option.
      *
-     * @returns A pointer to the current option.
+     * @returns A pointer to the first option.
      *
      */
-    const Option *GetCurrentOption(void) const;
+    const Option *GetFirstOption(void);
 
     /**
      * This method returns a pointer to the next option.

src/core/coap/coap_server.cpp

@@ -173,7 +173,7 @@ void Server::ProcessReceivedMessage(Message &aMessage, const Ip6::MessageInfo &a
         break;
     }
 
-    coapOption = header.GetCurrentOption();
+    coapOption = header.GetFirstOption();
 
     while (coapOption != NULL)
     {
@@ -191,11 +191,8 @@ void Server::ProcessReceivedMessage(Message &aMessage, const Ip6::MessageInfo &a
             curUriPath += coapOption->mLength;
             break;
 
-        case kCoapOptionContentFormat:
-            break;
-
         default:
-            ExitNow();
+            break;
         }
 
         coapOption = header.GetNextOption();