/*********************************************************************
* Function: void ICMPProcess(void)
*
* PreCondition: MAC buffer contains ICMP type packet.
*
* Input: *remote: Pointer to a NODE_INFO structure of the
* ping requester
* len: Count of how many bytes the ping header and
* payload are in this IP packet
*
* Output: Generates an echo reply, if requested
* Validates and sets ICMPFlags.bReplyValid if a
* correct ping response to one of ours is received.
*
* Side Effects: None
*
* Overview: None
*
* Note: None
********************************************************************/
void ICMPProcess(NODE_INFO *remote, uint16_t len)
{
TCPIP_UINT32_VAL dwVal;
// Obtain the ICMP header Type, Code, and Checksum fields
MACGetArray((uint8_t*)&dwVal, sizeof(dwVal));
// See if this is an ICMP echo (ping) request
if(dwVal.w[0] == 0x0008u)
{
// Validate the checksum using the Microchip MAC's DMA module
// The checksum data includes the precomputed checksum in the
// header, so a valid packet will always have a checksum of
// 0x0000 if the packet is not disturbed.
if(MACCalcRxChecksum(0+sizeof(IP_HEADER), len))
return;
// Calculate new Type, Code, and Checksum values
dwVal.v[0] = 0x00; // Type: 0 (ICMP echo/ping reply)
dwVal.v[2] += 8; // Subtract 0x0800 from the checksum
if(dwVal.v[2] < 8u)
{
dwVal.v[3]++;
if(dwVal.v[3] == 0u)
dwVal.v[2]++;
}
// Wait for TX hardware to become available (finish transmitting
// any previous packet)
while(!IPIsTxReady());
// Position the write pointer for the next IPPutHeader operation
// NOTE: do not put this before the IPIsTxReady() call for WF compatbility
MACSetWritePtr(BASE_TX_ADDR + sizeof(ETHER_HEADER));
// Create IP header in TX memory
IPPutHeader(remote, IP_PROT_ICMP, len);
// Copy ICMP response into the TX memory
MACPutArray((uint8_t*)&dwVal, sizeof(dwVal));
MACMemCopyAsync(-1, -1, len-4);
while(!MACIsMemCopyDone());
// Transmit the echo reply packet
MACFlush();
}
#if defined(STACK_USE_ICMP_CLIENT)
else if(dwVal.w[0] == 0x0000u) // See if this an ICMP Echo reply to our request
{
// Get the sequence number and identifier fields
MACGetArray((uint8_t*)&dwVal, sizeof(dwVal));
// See if the identifier matches the one we sent
if(dwVal.w[0] != 0xEFBE)
return;
if(dwVal.w[1] != wICMPSequenceNumber)
return;
// Validate the ICMP checksum field
IPSetRxBuffer(0);
if(CalcIPBufferChecksum(sizeof(ICMP_PACKET))) // Two bytes of payload were sent in the echo request
return;
// Flag that we received the response and stop the timer ticking
ICMPFlags.bReplyValid = 1;
ICMPTimer = TickGet() - ICMPTimer;
}
#endif
}
/*********************************************************************
* 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;
}
