/*********************************************************************
* Function: BOOL IPGetHeader( IP_ADDR *localIP,
* NODE_INFO *remote,
* BYTE *Protocol,
* WORD *len)
*
* PreCondition: MACGetHeader() == TRUE
*
* Input: localIP - Local node IP Address as received
* in current IP header.
* If this information is not required
* caller may pass NULL value.
* remote - Remote node info
* Protocol - Current packet protocol
* len - Current packet data length
*
* Output: TRUE, if valid packet was received
* FALSE otherwise
*
* Side Effects: None
*
* Note: Only one IP message can be received.
* Caller may not transmit and receive a message
* at the same time.
*
********************************************************************/
BOOL IPGetHeader(IP_ADDR *localIP,
NODE_INFO *remote,
BYTE *protocol,
WORD *len)
{
WORD_VAL CalcChecksum;
IP_HEADER header;
#if defined(NON_MCHP_MAC)
WORD_VAL ReceivedChecksum;
WORD checksums[2];
BYTE optionsLen;
#define MAX_OPTIONS_LEN (40u) // As per RFC 791.
BYTE options[MAX_OPTIONS_LEN];
#endif
// Read IP header.
MACGetArray((BYTE*)&header, sizeof(header));
// Make sure that this is an IPv4 packet.
if((header.VersionIHL & 0xf0) != IP_VERSION)
return FALSE;
// Throw this packet away if it is a fragment.
// We don't have enough RAM for IP fragment reconstruction.
if(header.FragmentInfo & 0xFF1F)
return FALSE;
IPHeaderLen = (header.VersionIHL & 0x0f) << 2;
#if !defined(NON_MCHP_MAC)
// Validate the IP header. If it is correct, the checksum
// will come out to 0x0000 (because the header contains a
// precomputed checksum). A corrupt header will have a
// nonzero checksum.
CalcChecksum.Val = MACCalcRxChecksum(0, IPHeaderLen);
// Seek to the end of the IP header
MACSetReadPtrInRx(IPHeaderLen);
if(CalcChecksum.Val)
#else
// Calculate options length in this header, if there is any.
// IHL is in terms of numbers of 32-bit DWORDs; i.e. actual
// length is 4 times IHL.
optionsLen = IPHeaderLen - sizeof(header);
// If there is any option(s), read it so that we can include them
// in checksum calculation.
if ( optionsLen > MAX_OPTIONS_LEN )
return FALSE;
if ( optionsLen > 0u )
MACGetArray(options, optionsLen);
// Save header checksum; clear it and recalculate it ourselves.
ReceivedChecksum.Val = header.HeaderChecksum;
header.HeaderChecksum = 0;
// Calculate checksum of header including options bytes.
checksums[0] = ~CalcIPChecksum((BYTE*)&header, sizeof(header));
// Calculate Options checksum too, if they are present.
if ( optionsLen > 0u )
checksums[1] = ~CalcIPChecksum((BYTE*)options, optionsLen);
else
checksums[1] = 0;
CalcChecksum.Val = CalcIPChecksum((BYTE*)checksums,
2 * sizeof(WORD));
// Make sure that checksum is correct
if ( ReceivedChecksum.Val != CalcChecksum.Val )
#endif
{
// Bad packet. The function caller will be notified by means of the FALSE
// return value and it should discard the packet.
return FALSE;
}
// Network to host conversion.
SwapIPHeader(&header);
// If caller is intrested, return destination IP address
// as seen in this IP header.
if ( localIP )
localIP->Val = header.DestAddress.Val;
remote->IPAddr.Val = header.SourceAddress.Val;
*protocol = header.Protocol;
*len = header.TotalLength - IPHeaderLen;
return TRUE;
}
/*********************************************************************
* Function: IPSetRxBuffer(WORD Offset)
*
* PreCondition: IPHeaderLen must have been intialized by
* IPGetHeader() or IPPutHeader()
*
* Input: Offset from beginning of IP data field
*
* Output: Next Read/Write access to receive buffer is
* set to Offset
*
* Side Effects: None
*
* Note: None
*
********************************************************************/
void IPSetRxBuffer(WORD Offset)
{
MACSetReadPtrInRx(Offset+IPHeaderLen);
}
/*********************************************************************
* Function: IPSetRxBuffer(uint16_t Offset)
*
* PreCondition: IPHeaderLen must have been intialized by
* IPGetHeader() or IPPutHeader()
*
* Input: Offset from beginning of IP data field
*
* Output: Next Read/Write access to receive buffer is
* set to Offset
*
* Side Effects: None
*
* Note: None
*
********************************************************************/
void IPSetRxBuffer(uint16_t Offset)
{
MACSetReadPtrInRx(Offset+IPHeaderLen);
}