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/***************************************************************************
* TransportLayerElement.cc -- Class TransportLayerElement is a generic *
* class that represents a transport layer protocol header. Classes like *
* TCPHeader or UDPHeader inherit from it. *
* *
***********************IMPORTANT NMAP LICENSE TERMS************************
*
* The Nmap Security Scanner is (C) 1996-2023 Nmap Software LLC ("The Nmap
* Project"). Nmap is also a registered trademark of the Nmap Project.
*
* This program is distributed under the terms of the Nmap Public Source
* License (NPSL). The exact license text applying to a particular Nmap
* release or source code control revision is contained in the LICENSE
* file distributed with that version of Nmap or source code control
* revision. More Nmap copyright/legal information is available from
* https://nmap.org/book/man-legal.html, and further information on the
* NPSL license itself can be found at https://nmap.org/npsl/ . This
* header summarizes some key points from the Nmap license, but is no
* substitute for the actual license text.
*
* Nmap is generally free for end users to download and use themselves,
* including commercial use. It is available from https://nmap.org.
*
* The Nmap license generally prohibits companies from using and
* redistributing Nmap in commercial products, but we sell a special Nmap
* OEM Edition with a more permissive license and special features for
* this purpose. See https://nmap.org/oem/
*
* If you have received a written Nmap license agreement or contract
* stating terms other than these (such as an Nmap OEM license), you may
* choose to use and redistribute Nmap under those terms instead.
*
* The official Nmap Windows builds include the Npcap software
* (https://npcap.com) for packet capture and transmission. It is under
* separate license terms which forbid redistribution without special
* permission. So the official Nmap Windows builds may not be redistributed
* without special permission (such as an Nmap OEM license).
*
* Source is provided to this software because we believe users have a
* right to know exactly what a program is going to do before they run it.
* This also allows you to audit the software for security holes.
*
* Source code also allows you to port Nmap to new platforms, fix bugs, and add
* new features. You are highly encouraged to submit your changes as a Github PR
* or by email to the dev@nmap.org mailing list for possible incorporation into
* the main distribution. Unless you specify otherwise, it is understood that
* you are offering us very broad rights to use your submissions as described in
* the Nmap Public Source License Contributor Agreement. This is important
* because we fund the project by selling licenses with various terms, and also
* because the inability to relicense code has caused devastating problems for
* other Free Software projects (such as KDE and NASM).
*
* The free version of Nmap is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Warranties,
* indemnification and commercial support are all available through the
* Npcap OEM program--see https://nmap.org/oem/
*
***************************************************************************/
/* This code was originally part of the Nping tool. */
#include "TransportLayerElement.h"
#include "IPv4Header.h"
#include "IPv6Header.h"
/** Computes and returns the Internet checksum.
* @warning This method requires the object to be linked to either an IPv6Header
* object or an IPv4Header one, so the caller must ensure that objects are
* properly linked with calls to setNextElement() like this:
*
* IPv6Header ip6;
* TCPHeader tcp;
* [...] # Set header fields
* ip6.setNextElement(&tcp);
* tcp.setSum();
*
* Note that there can be a number of other headers (like IPv6 extension headers)
* between the transport header and the network one, but all of them need to
* be linked in order for this method to traverse the list of headers and find
* the IP source and destination address, required to compute the checksum. So
* things like the following are OK:
*
* IPv6Header ip6;
* HopByHopHeader hop;
* RoutingHeader rte;
* FragmentHeader frg;
* UDPHeader udp;
* [...] # Set whatever header fields you need
* ip6.setNextElement(&hop);
* hop.setNextElement(&rte);
* rte.setNextElement(&frg);
* frg.setNextElement(&udp);
* udp.setSum(); # setSum() will be able to reach the IPv6Header. */
u16 TransportLayerElement::compute_checksum(){
PacketElement *hdr;
hdr=this->getPrevElement();
u16 final_sum=0;
/* Traverse the list of headers backwards until we find an IP header */
while(hdr!=NULL){
if (hdr->protocol_id()==HEADER_TYPE_IPv6){
IPv6Header *v6hdr=(IPv6Header *)hdr;
struct in6_addr i6src, i6dst;
memcpy(i6src.s6_addr, v6hdr->getSourceAddress(), 16);
memcpy(i6dst.s6_addr, v6hdr->getDestinationAddress(), 16);
u8 *buff=(u8 *)safe_malloc(this->getLen());
this->dumpToBinaryBuffer(buff, this->getLen());
final_sum=ipv6_pseudoheader_cksum(&i6src, &i6dst, this->protocol_id(), this->getLen(), buff);
free(buff);
return final_sum;
}else if(hdr->protocol_id()==HEADER_TYPE_IPv4){
IPv4Header *v4hdr=(IPv4Header *)hdr;
struct in_addr i4src, i4dst;
memcpy(&(i4src.s_addr), v4hdr->getSourceAddress(), 4);
memcpy(&(i4dst.s_addr), v4hdr->getDestinationAddress(), 4);
u8 *buff=(u8 *)safe_malloc(this->getLen());
this->dumpToBinaryBuffer(buff, this->getLen());
final_sum=ipv4_pseudoheader_cksum(&i4src, &i4dst, this->protocol_id(), this->getLen(), buff);
free(buff);
return final_sum;
}else{
hdr=hdr->getPrevElement();
}
}
return 0;
} /* End of setSum() */
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