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https://github.com/espressif/openthread.git
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[mac-frame] helper methods to calculate size of headers/MIC (#4887)
This commit adds new helper methods in `Mac::Frame` to calculate the size (number of bytes) of headers or security MIC. These are used by different methods to simplify the code and avoid repeated patterns: - `CalculateAddrFieldSize(aFcf)` to calculate the size of Address Fields given a Frame Control value. - `CalculateSecurityHeaderSize(aSecurityControl)` to calculate size of Security Header given a Security Control value. - `CalculateMicSize(aSecurityControl)` to get the size of MIC given a Security Control value.
This commit is contained in:
Abtin Keshavarzian
+100
-137
@@ -49,101 +49,33 @@ namespace Mac {
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void Frame::InitMacHeader(uint16_t aFcf, uint8_t aSecurityControl)
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{
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uint8_t *bytes = GetPsdu();
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mLength = 0;
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uint8_t length;
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// Frame Control Field
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Encoding::LittleEndian::WriteUint16(aFcf, bytes);
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mLength += kFcfSize;
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// Sequence Number
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mLength += kDsnSize;
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// Destination PAN
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if (IsDstPanIdPresent(aFcf))
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{
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mLength += sizeof(PanId);
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}
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// Destination Address
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switch (aFcf & kFcfDstAddrMask)
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{
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case kFcfDstAddrNone:
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break;
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case kFcfDstAddrShort:
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mLength += sizeof(ShortAddress);
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break;
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case kFcfDstAddrExt:
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mLength += sizeof(ExtAddress);
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break;
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default:
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OT_ASSERT(false);
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}
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// Source PAN
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if (IsSrcPanIdPresent(aFcf))
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{
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mLength += sizeof(PanId);
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}
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// Source Address
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switch (aFcf & kFcfSrcAddrMask)
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{
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case kFcfSrcAddrNone:
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break;
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case kFcfSrcAddrShort:
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mLength += sizeof(ShortAddress);
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break;
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case kFcfSrcAddrExt:
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mLength += sizeof(ExtAddress);
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break;
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default:
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OT_ASSERT(false);
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}
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length = CalculateAddrFieldSize(aFcf);
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OT_ASSERT(length != kInvalidSize);
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// Security Header
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if (aFcf & kFcfSecurityEnabled)
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{
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bytes[mLength] = aSecurityControl;
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bytes[length] = aSecurityControl;
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if (aSecurityControl & kSecLevelMask)
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{
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mLength += kSecurityControlSize + kFrameCounterSize;
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}
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switch (aSecurityControl & kKeyIdModeMask)
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{
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case kKeyIdMode0:
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mLength += kKeySourceSizeMode0;
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break;
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case kKeyIdMode1:
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mLength += kKeySourceSizeMode1 + kKeyIndexSize;
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break;
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case kKeyIdMode2:
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mLength += kKeySourceSizeMode2 + kKeyIndexSize;
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break;
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case kKeyIdMode3:
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mLength += kKeySourceSizeMode3 + kKeyIndexSize;
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break;
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}
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length += CalculateSecurityHeaderSize(aSecurityControl);
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length += CalculateMicSize(aSecurityControl);
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}
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// Command ID
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if ((aFcf & kFcfFrameTypeMask) == kFcfFrameMacCmd)
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{
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mLength += kCommandIdSize;
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length += kCommandIdSize;
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}
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mLength += GetFooterLength();
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// FCS
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length += GetFcsSize();
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SetPsduLength(length);
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}
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uint16_t Frame::GetFrameControlField(void) const
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@@ -347,7 +279,7 @@ exit:
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return index;
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}
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bool Frame::IsSrcPanIdPresent(uint16_t aFcf) const
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bool Frame::IsSrcPanIdPresent(uint16_t aFcf)
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{
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bool srcPanIdPresent = false;
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@@ -717,39 +649,44 @@ uint8_t Frame::GetHeaderLength(void) const
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uint8_t Frame::GetFooterLength(void) const
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{
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uint8_t footerLength = 0;
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uint8_t footerLength = static_cast<uint8_t>(GetFcsSize());
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uint8_t index = FindSecurityHeaderIndex();
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VerifyOrExit(index != kInvalidIndex, OT_NOOP);
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footerLength += CalculateMicSize((GetPsdu() + index)[0]);
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switch ((GetPsdu() + index)[0] & kSecLevelMask)
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exit:
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return footerLength;
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}
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uint8_t Frame::CalculateMicSize(uint8_t aSecurityControl)
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{
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uint8_t micSize = 0;
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switch (aSecurityControl & kSecLevelMask)
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{
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case kSecNone:
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case kSecEnc:
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footerLength += kMic0Size;
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micSize = kMic0Size;
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break;
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case kSecMic32:
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case kSecEncMic32:
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footerLength += kMic32Size;
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micSize = kMic32Size;
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break;
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case kSecMic64:
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case kSecEncMic64:
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footerLength += kMic64Size;
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micSize = kMic64Size;
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break;
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case kSecMic128:
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case kSecEncMic128:
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footerLength += kMic128Size;
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micSize = kMic128Size;
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break;
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}
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exit:
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// Frame Check Sequence
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footerLength += GetFcsSize();
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return footerLength;
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return micSize;
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}
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uint16_t Frame::GetMaxPayloadLength(void) const
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@@ -769,104 +706,130 @@ void Frame::SetPayloadLength(uint16_t aLength)
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uint8_t Frame::SkipSecurityHeaderIndex(void) const
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{
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uint8_t index = SkipAddrFieldIndex();
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uint16_t fcf;
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uint8_t index = SkipAddrFieldIndex();
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VerifyOrExit(index != kInvalidIndex, OT_NOOP);
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fcf = GetFrameControlField();
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// Security Control + Frame Counter + Key Identifier
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if ((fcf & kFcfSecurityEnabled) != 0)
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if (GetSecurityEnabled())
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{
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uint8_t securityControl;
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uint8_t headerSize;
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VerifyOrExit(index < GetPsduLength(), index = kInvalidIndex);
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uint8_t securityControl = *(GetPsdu() + index);
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securityControl = *(GetPsdu() + index);
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index += kSecurityControlSize + kFrameCounterSize;
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headerSize = CalculateSecurityHeaderSize(securityControl);
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VerifyOrExit(headerSize != kInvalidSize, index = kInvalidIndex);
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switch (securityControl & kKeyIdModeMask)
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{
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case kKeyIdMode0:
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index += kKeySourceSizeMode0;
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break;
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index += headerSize;
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case kKeyIdMode1:
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index += kKeySourceSizeMode1 + kKeyIndexSize;
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break;
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case kKeyIdMode2:
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index += kKeySourceSizeMode2 + kKeyIndexSize;
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break;
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case kKeyIdMode3:
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index += kKeySourceSizeMode3 + kKeyIndexSize;
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break;
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}
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VerifyOrExit(index <= GetPsduLength(), index = kInvalidIndex);
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}
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exit:
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return index;
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}
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uint8_t Frame::SkipAddrFieldIndex(void) const
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uint8_t Frame::CalculateSecurityHeaderSize(uint8_t aSecurityControl)
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{
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uint8_t index = kFcfSize + kDsnSize; // Frame Control field and Sequence Number field
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uint16_t fcf;
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uint8_t size = kSecurityControlSize + kFrameCounterSize;
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VerifyOrExit((index + GetFcsSize()) <= GetPsduLength(), index = kInvalidIndex);
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fcf = GetFrameControlField();
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VerifyOrExit((aSecurityControl & kSecLevelMask) != kSecNone, size = kInvalidSize);
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// Destination PAN
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if (IsDstPanIdPresent(fcf))
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switch (aSecurityControl & kKeyIdModeMask)
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{
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index += sizeof(PanId);
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case kKeyIdMode0:
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size += kKeySourceSizeMode0;
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break;
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case kKeyIdMode1:
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size += kKeySourceSizeMode1 + kKeyIndexSize;
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break;
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case kKeyIdMode2:
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size += kKeySourceSizeMode2 + kKeyIndexSize;
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break;
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case kKeyIdMode3:
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size += kKeySourceSizeMode3 + kKeyIndexSize;
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break;
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}
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// Destination Address
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switch (fcf & kFcfDstAddrMask)
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exit:
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return size;
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}
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uint8_t Frame::SkipAddrFieldIndex(void) const
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{
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uint8_t index;
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VerifyOrExit(kFcfSize + kDsnSize + GetFcsSize() <= GetPsduLength(), index = kInvalidIndex);
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index = CalculateAddrFieldSize(GetFrameControlField());
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exit:
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return index;
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}
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uint8_t Frame::CalculateAddrFieldSize(uint16_t aFcf)
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{
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uint8_t size = kFcfSize + kDsnSize;
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// This static method calculates the size (number of bytes) of
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// Address header field for a given Frame Control `aFcf` value.
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// The size includes the Frame Control and Sequence Number fields
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// along with Destination and Source PAN ID and Short/Extended
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// Addresses. If the `aFcf` is not valid, this method returns
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// `kInvalidSize`.
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if (IsDstPanIdPresent(aFcf))
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{
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size += sizeof(PanId);
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}
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switch (aFcf & kFcfDstAddrMask)
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{
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case kFcfDstAddrNone:
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break;
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case kFcfDstAddrShort:
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index += sizeof(ShortAddress);
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size += sizeof(ShortAddress);
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break;
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case kFcfDstAddrExt:
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index += sizeof(ExtAddress);
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size += sizeof(ExtAddress);
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break;
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default:
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ExitNow(index = kInvalidIndex);
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ExitNow(size = kInvalidSize);
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break;
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}
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// Source PAN
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if (IsSrcPanIdPresent(fcf))
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if (IsSrcPanIdPresent(aFcf))
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{
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index += sizeof(PanId);
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size += sizeof(PanId);
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}
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// Source Address
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switch (fcf & kFcfSrcAddrMask)
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switch (aFcf & kFcfSrcAddrMask)
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{
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case kFcfSrcAddrNone:
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break;
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case kFcfSrcAddrShort:
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index += sizeof(ShortAddress);
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size += sizeof(ShortAddress);
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break;
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case kFcfSrcAddrExt:
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index += sizeof(ExtAddress);
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size += sizeof(ExtAddress);
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break;
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default:
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ExitNow(index = kInvalidIndex);
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ExitNow(size = kInvalidSize);
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break;
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}
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exit:
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return index;
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return size;
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}
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uint8_t Frame::FindPayloadIndex(void) const
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@@ -522,14 +522,6 @@ public:
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*/
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void SetDstAddr(const Address &aAddress);
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/**
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* This method indicates whether or not the Src PanId is present.
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*
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* @returns TRUE if the Src PanId is present, FALSE otherwise.
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*
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*/
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bool IsSrcPanIdPresent(uint16_t aFcf) const;
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/**
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* This method gets the Source PAN Identifier.
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*
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@@ -945,6 +937,7 @@ private:
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enum
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{
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kInvalidIndex = 0xff,
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kInvalidSize = kInvalidIndex,
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kSequenceIndex = kFcfSize,
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};
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@@ -966,7 +959,12 @@ private:
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static bool IsDstAddrPresent(uint16_t aFcf) { return (aFcf & kFcfDstAddrMask) != kFcfDstAddrNone; }
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static bool IsDstPanIdPresent(uint16_t aFcf);
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static bool IsSrcAddrPresent(uint16_t aFcf) { return (aFcf & kFcfSrcAddrMask) != kFcfSrcAddrNone; }
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static bool IsSrcPanIdPresent(uint16_t aFcf);
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static bool IsVersion2015(uint16_t aFcf) { return (aFcf & kFcfFrameVersionMask) == kFcfFrameVersion2015; }
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static uint8_t CalculateAddrFieldSize(uint16_t aFcf);
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static uint8_t CalculateSecurityHeaderSize(uint8_t aSecurityControl);
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static uint8_t CalculateMicSize(uint8_t aSecurityControl);
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};
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/**
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