// Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).

// All rights reserved.

// This component and the accompanying materials are made available

// under the terms of "Eclipse Public License v1.0"

// which accompanies this distribution, and is available

// at the URL "http://www.eclipse.org/legal/epl-v10.html".

//

// Initial Contributors:

// Nokia Corporation - initial contribution.

//

// Contributors:

//

// Description:

// in_pkt.cpp - packet handling routines

// Mainly the RMBufPacketPeek implementation

// + extension header locations

// + method for adding a destination option

//

#include "in_pkt.h"

#include "ext_hdr.h"

#define OPTIMIZE_PADDING

// RMBufPacketPeek

// ***************

EXPORT_C TUint8 *TInet6PacketBase::Access(RMBufChain &aPacket, TInt aOffset, TInt aSize, TInt aMin)

	/**

	* Accesses a contiguous block of memory within RMBufChain starting

	* at specified offset.

	*

	* Attempts to map aSize amount of contiguous RMBuf space at

	* the specified offset, by rearranging the RMBufs,

	* if necessary.

	*

	* If aSize amount is not available, the returned pointer maps

	* the maximum available space (< aSize).

	*

	* @param	aSize

	*	The size of the requested contiguous mapping (in octets).

	*	The value cannot be larger than KMBufSmallSize. If aSize <= 1,

	*	the method will return availabe contiguous mapping at the

	*	indicated offset without rearranging the RMBuf chain. Values

	*	larger than 1 may require rearrangement to get the requested

	*	area into single RMBuf.

	* @param	aOffset

	*	The offset to the beginning of the area. The value MUST

	*	be in range: 0 <= aOffset <= Length().

	* @param	aMin

	*	The minimum accepted iLength. If iLength is less that aMin,

	*	then returns NULL.

	* @return

	*	A pointer to the data starting at indicated

	*	offset. The iLength is set to the

	*	maximum available contiguous data starting from the

	*	requested offset. iLength is always <= KMBufSmallSize.

	* @note

	*	The length can be either less or

	*	larger than aSize. The caller must verify the returned

	*	length to detect whether Access succeeded.

	*/

	{

	//

	// Can only map at most KMBufSmallSize bytes

	// (truncate aSize to avoid Panics from the Align)

	//

	if (aSize > KMBufSmallSize)

		aSize = KMBufSmallSize;

	for (int already_tried = 0; ;already_tried = 1)

		{

		RMBuf *p;

		TInt offset, len;

		iLength = 0;

		if (aPacket.IsEmpty() || !aPacket.Goto(aOffset, p, offset, len))

			return NULL;

		else if ((aSize <= len && (offset & iAlign) == 0) || already_tried)

			{

			if (len < aMin)

				return NULL;

			iLength = len;

			return p->Buffer() + offset;

			}

		// The requested alignment value is not

		// satisfied!

		//

		// Brute force buffer mangling here: just

		// Split the chain at requested point, apply

		// align to the tail part, and then join the

		// pieces together (assuming this join operation

		// does not undo the align...)

		// (If this is going to occur frequently

		// some optimizations is in order... -- msa)

		//

		//

		// *NOTE*

		//		If aOffset == 0, SplitL works weird (IMHO): it does

		//		nothing (when it logically should move all to the

		//		tail part!). Thus, zero offset needs to be handled

		//		specially (sort of optimizing, so it's not too bad)

		//		-- msa

		//

		if (aOffset > 0)

			{

			RMBufChain tail;

			TInt err = aPacket.Split(aOffset, tail);

			if (err == KErrNone && !tail.IsEmpty())

				{

				tail.Align(aSize);

				aPacket.Append(tail);

				}

			}

		else

			aPacket.Align(aSize);

		// And now just retry the Goto and use that

		// result as is (either we succeeded or not)

		}

	}

EXPORT_C TPtr8 RMBufPacketPeek::Access(TInt aSize, TUint aOffset)

	/**

	* Accesses a contiguous block of memory within RMBufChain starting

	* at specified offset.

	*

	* Attempts to map aSize amount of contiguous RMBuf space at

	* the specified offset into a TPtr8, by rearranging the RMBufs,

	* if necessary.

	*

	* If aSize amount is not available, the returned pointer maps

	* the maximum available space (< aSize).

	*

	* @param	aSize

	*	The size of the requested contiguous mapping (in octets).

	*	The value cannot be larger than KMBufSmallSize. If aSize <= 1,

	*	the method will return availabe contiguous mapping at the

	*	indicated offset without rearranging the RMBuf chain. Values

	*	larger than 1 may require rearrangement to get the requested

	*	area into single RMBuf.

	* @param	aOffset

	*	The offset to the beginning of the area. The value MUST

	*	be in range: 0 <= aOffset <= Length().

	* @return

	*	A pointer descriptor for the data starting at indicated

	*	offset. The length of the descriptor is set to the

	*	maximum available contiguous data starting from the

	*	requested offset. Length is always <= KMBufSmallSize.

	* @note

	*	The length can be either less or

	*	larger than aSize. The caller must verify the returned

	*	length to detect whether Access succeeded.

	*/

	{

	TInet6PacketBase map(TInet6PacketBase::EAlign1);

	TUint8 *const ptr = map.Access(*this, aOffset, aSize, 1);

	return TPtr8(ptr, map.iLength, map.iLength);

	}

EXPORT_C TIpHeader *RMBufPacketPeek::GetIpHeader()

	/**

	* Access IP header (v4 or v6) from the packet at offset 0.

	*

	* @return IP header (or NULL).

	*	A non-NULL return implies that full header, either IPv4 or

	*	IPv6 is accessible through the pointer. This method is

	*	intended to save code space, and not necessarily for

	*	speed...

	*/

	{

	TInet6Packet<TIpHeader> ip(*this);

	if (ip.iHdr)

		{

		if (ip.iHdr->ip4.Version() == 4)

			{

			// Need to do sanity check on header length (because it can be garbage)

			const TInt hlen = ip.iHdr->ip4.HeaderLength();

			if (hlen >= TInet6HeaderIP4::MinHeaderLength() && ip.iLength >= hlen)

				return (TIpHeader *)ip.iHdr;

			}

		else if (ip.iHdr->ip4.Version() == 6)

			{

			if (ip.iLength >= TInet6HeaderIP::MinHeaderLength())

				return (TIpHeader *)ip.iHdr;

			}

		}

	return NULL;

	}

// TPacketPocker

// *************

EXPORT_C TPacketPoker::TPacketPoker(RMBufChain &aChain) : iCurrent(aChain.First()), iOffset(0), iTail(0)

	/**

	* Constructor.

	*

	* @param aChain	The RMBuf chain to be poked.

	*/

	{

	// Find initial value for iTail.

	while (iCurrent)

		{

		iTail = iCurrent->Length();

		if (iTail > 0)

			break;

		// Ugh. There have been RMBuf's with ZERO length!

		iCurrent = iCurrent->Next();

		}

	}

EXPORT_C void TPacketPoker::OverL(TInt aSize)

	/**

	* Skip over bytes.

	*

	* @param aSize	The number of bytes to skip

	* @leave KErrEof, if skipped past end of chain.

	*/

	{

	for (;;)

		{

		if (aSize < iTail)

			{

			iTail -= aSize;		// Results always: iTail > 0!

			iOffset += aSize;

			return;

			}

		aSize -= iTail;

		if ((iCurrent = iCurrent->Next()) == NULL)

			{

			iTail = 0;			// All scanned, at end of chain

			if (aSize > 0)		// --> Error, if request was more

				User::Leave(KErrEof);	// KErrEof used (for lack of any better)

			return;

			}

		iOffset = 0;

		iTail = iCurrent->Length();

		}

	}

EXPORT_C TUint8 *TPacketPoker::AdjustL(TInt aSize)

	/**

	* Arrange contiguous run of bytes.

	*

	* Arragen content of RMBuf chain so that starting from

	* the current offset, a number of bytes is accessible

	* in contiguous memory.

	*

	* @param aSize The requested length,

	* @return The pointer to be beginning of area.

	* @leave KErrEof, if request cannot be satisfied.

	*/

	{

	RMBufChain chain(iCurrent);

	if (iOffset > 0)

		{

		RMBufChain tail;

		chain.SplitL(iOffset, tail);

		tail.Align(aSize);

		chain.Append(tail);

		}

	else

		chain.Align(aSize);

	ASSERT(iCurrent == chain.First());

	iTail = iCurrent->Length() - iOffset;

	if (iTail < aSize)			// Align failed?

		User::Leave(KErrEof);	// KErrEof used (for lack of any better)

	return Ptr();

	}

//

EXPORT_C TBool TPacketPoker::IsExtensionHeader(TInt aProtocolId)

	/**

	* Tests whether a protocol is a known IPv6 extension header using the standard format.

	* 

	* @param aProtocolId	Protocol ID to test.

	* @return ETrue,

	* 	if the protocol header follows the generic IPv6 extension

	*	header format (TInet6HeaderExtension).

	*/

	{

	// If more of these are known, could perhaps implement a

	// static boolean table indexed by protocol -- msa

	return

		(

		aProtocolId == STATIC_CAST(TInt, KProtocolInet6HopOptions) ||

		aProtocolId == STATIC_CAST(TInt, KProtocolInet6DestinationOptions) ||

		aProtocolId == STATIC_CAST(TInt, KProtocolInet6RoutingHeader)

		);

	}

// TPacketHead

// ***********

EXPORT_C TBool TPacketHead::ExtHdrGet(TInt aType, TInt& aOfs, TInt& aLen)

	/**

	* Gets the offset and length of an extension header.

	*

	* @param aType Extension header type

	* @retval aOfs On return, the header offset

	* @retval aLen On return, the header length

	* @return ETrue if the header was found, otherwise EFalse 

	*/

	{

	if (iPacket.IsEmpty())

		return EFalse;

	TInt type = ip6.NextHeader();

	TInt ofs = 0;

	while (TPacketPoker::IsExtensionHeader(type) && ofs<iOffset)

		{

		//TInet6Options is about as generic Extension Header class as possible.

		//Thus no need to create another one.

		TInet6Packet<TInet6Options> hdr(iPacket, ofs);

		if (hdr.iHdr == NULL) return EFalse;

		if (type == aType)

			{

			aOfs = ofs;

			aLen = hdr.iHdr->HeaderLength();

			return ETrue;

			}

		type = hdr.iHdr->NextHeader();

		ofs += hdr.iHdr->HeaderLength();

		}

	return EFalse;

	}

EXPORT_C TBool TPacketHead::ExtHdrGetOrPrependL(TInt aType, TInt& aOfs, TInt& aLen)

	/**

	* Gets the offset and length of an extension header, or if it doesn't already 

	* exist, creates the header before all other extension headers.

	*

	* @param aType

	*	Extension header type

	* @retval aOfs

	*	If the header is created, this specifies the header offset. If

	*	the header already exists, on return: the actual header offset.

	* @retval aLen

	*	If the header is created, this specifies the header length. If

	*	the header already exists, on return: the actual header length.

	* @return

	*	ETrue if the header was found, EFalse if the header was created.

	*/

	{

	if (ExtHdrGet(aType, aOfs, aLen))

		return ETrue;

	ASSERT(aLen && ((aLen & 7) == 0));

	if (iPacket.IsEmpty())

		{

		iPacket.AllocL(aLen);

		}

	else

		{

		iPacket.PrependL(aLen);

		}

	//Zero out the header

	iPacket.FillZ(aLen);

	TInet6Packet<TInet6Options> hdr(iPacket, 0);

	if (hdr.iHdr == NULL)

		{

		iPacket.TrimStart(aLen);

		User::Leave(KErrGeneral);

		}

	hdr.iHdr->SetNextHeader(ip6.NextHeader());

	ip6.SetNextHeader(aType);

	hdr.iHdr->SetHdrExtLen((aLen >> 3) - 1);

	aOfs = 0;

	iOffset += aLen;

	return EFalse;

	}

EXPORT_C TBool TPacketHead::ExtHdrGetOrAppendL(TInt aType, TInt& aOfs, TInt& aLen)

	/**

	* Gets the offset and length of an extension header, or if it doesn't already 

	* exist, creates the header after all other extension headers.

	*

	* @param aType	Extension header type

	* @retval aOfs

	*	If the header is created, this specifies the header offset. If

	*	the header already exists, on return, the actual header offset.

	* @retval aLen

	*	If the header is created, this specifies the header length. If

	*	the header already exists, on return, the actual header length.

	* @return ETrue if the header was found, EFalse if the header was created 

	*/

	{

	if (ExtHdrGet(aType, aOfs, aLen)) return ETrue;

	if (iPacket.IsEmpty()) return ExtHdrGetOrPrependL(aType, aOfs, aLen);

	ASSERT(aLen && ((aLen & 7) == 0));

	TInt nxt = ip6.NextHeader();

	TInt ofs = 0;

	FOREVER

		{

		TInet6Packet<TInet6Options> hdr(iPacket, ofs);

		if (hdr.iHdr == NULL)

			User::Leave(KErrGeneral);

		nxt = hdr.iHdr->NextHeader();

		ofs += hdr.iHdr->HeaderLength();

		if (ofs >= iOffset)

			{

			hdr.iHdr->SetNextHeader(aType);

			break;

			}

		}

	RMBufChain tail;

	tail.AllocL(aLen);

	tail.FillZ();

	iPacket.Append(tail);

	TInet6Packet<TInet6Options> hdr(iPacket, iOffset);

	if (hdr.iHdr == NULL)

		{

		iPacket.TrimEnd(iOffset);

		User::Leave(KErrGeneral);

		}

	hdr.iHdr->SetNextHeader(nxt);

	hdr.iHdr->SetHdrExtLen((aLen >> 3) - 1);

	aOfs = iOffset;

	iOffset += aLen;

	return EFalse;

	}

//

// TODO: Possibility to replace existing padding with an option which

//       would preserve the alignment. (eg. Home Address is kind of Pad2)

//

EXPORT_C void TPacketHead::AddDestinationOptionL(const TUint8* aOption, TUint8 aLen, TUint8 aAlign/*=0*/, TUint8 aModulo/*=4*/)

	{

	/**

	* Adds a Destination Option extension header option.

	*

	* If no Destination Option extension header already exists, one is created

	* as the first extension header. The option is aligned according to the

	* specified aAlign and aModulo parameters.

	*

	* @param aOption

	*	Option Data

	* @param aLen

	*	Option Data length

	* @param aAlign

	*	Option alignment requirement. The default is no alignment.

	* @param aModulo

	*	Option must start at an octect position which is a multiple 

	*	of the specified value

	*/

	TPtrC8 ptr(aOption, aLen);

	AddDestinationOptionL(ptr, aAlign, aModulo);

	}

EXPORT_C void TPacketHead::AddDestinationOptionL(const TPtrC8& aOption, TUint8 aAlign/*=0*/, TUint8 aModulo/*=4*/)

	/**

	* Adds a Destination Option extension header option.

	*

	* If no Destination Option extension header already exists, one is

	* created as the first extension header. The option is aligned

	* according to the specified aAlign and aModulo parameters.

	*

	* @param aOption

	*	Pointer to the start of the Option Data

	* @param aAlign

	*	Option alignment requirement. The default is no alignment.

	* @param aModulo

	*	Option must start at an octect position which is a multiple

	*	of the specified value

	*/

	{

	TUint padlen = aAlign?(TUint(aAlign - 2) % aModulo):0;  //Leading pad

	TInt len = 2 + padlen + aOption.Length();

	TInt trailpad = (8 - (len & 7)) & 7;

	len += trailpad;

	TInt ofs;

	if (! ExtHdrGetOrAppendL(KProtocolInet6DestinationOptions, ofs, len))

		{

		//Simple case, new header was allocated and initialized with required length.

		//Just put the option in.

		ofs += 2;

#ifdef OPTIMIZE_PADDING

		if (padlen > 1)

			{

			TInet6Packet<TInet6OptionBase> pad(iPacket, ofs);

			if (pad.iHdr == NULL)

				User::Leave(KErrGeneral);

			pad.iHdr->SetType(KDstOptionPadN);

			pad.iHdr->SetDataLen(padlen - 2);

			}

#endif

		ofs += padlen;

		iPacket.CopyIn(aOption, ofs);

#ifdef OPTIMIZE_PADDING

		ofs += aOption.Length();

		if (trailpad > 1)

			{

			TInet6Packet<TInet6OptionBase> pad(iPacket, ofs);

			if (pad.iHdr == NULL)

				User::Leave(KErrGeneral);

			pad.iHdr->SetType(KDstOptionPadN);

			pad.iHdr->SetDataLen(trailpad - 2);

			}

#endif

		return;

		}

	//Now we have the position and size of the header

	TInet6Packet<TInet6Options> opt(iPacket, ofs);

	if (opt.iHdr == NULL)

		User::Leave(KErrGeneral);

	//padlen = leading pad

	ofs += len;

	padlen = aAlign?(TUint(aAlign - ofs) % aModulo):0;

	TInt size = padlen + aOption.Length();

	trailpad = (8 - (size & 7)) & 7;