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/*---------------------------------------------------------------
* Copyright (c) 2018
* Broadcom Corporation
* All Rights Reserved.
*---------------------------------------------------------------
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated
* documentation files (the "Software"), to deal in the Software
* without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute,
* sublicense, and/or sell copies of the Software, and to permit
* persons to whom the Software is furnished to do
* so, subject to the following conditions:
*
*
* Redistributions of source code must retain the above
* copyright notice, this list of conditions and
* the following disclaimers.
*
*
* Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimers in the documentation and/or other materials
* provided with the distribution.
*
*
* Neither the name of Broadcom Coporation,
* nor the names of its contributors may be used to endorse
* or promote products derived from this Software without
* specific prior written permission.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE CONTIBUTORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
* ________________________________________________________________
*
* UDP checksums v4 and v6
*
* The checksum calculation is defined in RFC 768
* hints as to how to calculate it efficiently are in RFC 1071
*
* by Robert J. McMahon (rjmcmahon@rjmcmahon.com, bob.mcmahon@broadcom.com)
* -------------------------------------------------------------------
*/
#include "headers.h"
/*
*
* Compute Internet Checksum for UDP packets (assumes 32 bit system)
*
* IPV4 Notes:
*
* User Datagram Header Format
* 0 7 8 15 16 23 24 31
* +--------+--------+--------+--------+
* | Source | Destination |
* | Port | Port |
* +--------+--------+--------+--------+
* | | |
* | Length | Checksum |
* +--------+--------+--------+--------+
* |
* | data octets ...
* +---------------- ...
*
*
* Checksum is the 16-bit one's complement of the one's complement sum of a
* pseudo header of information from the IP header, the UDP header, and the
* data, padded with zero octets at the end (if necessary) to make a
* multiple of two octets.
*
* The ipv4 pseudo header conceptually prefixed to the UDP header contains the
* source address, the destination address, the protocol, and the UDP
* length. This information gives protection against misrouted datagrams.
* This checksum procedure is the same as is used in TCP.
*
* 0 7 8 15 16 23 24 31
* +--------+--------+--------+--------+
* | source address |
* +--------+--------+--------+--------+
* | destination address |
* +--------+--------+--------+--------+
* | zero |protocol| UDP length |
* +--------+--------+--------+--------+
*
* If the computed checksum is zero, it is transmitted as all ones (the
* equivalent in one's complement arithmetic). An all zero transmitted
* checksum value means that the transmitter generated no checksum (for
* debugging or for higher level protocols that don't care).
*
*
* IPV6 Notes:
*
* Any transport or other upper-layer protocol that includes the
* addresses from the IP header in its checksum computation must be
* modified for use over IPv6, to include the 128-bit IPv6 addresses
* instead of 32-bit IPv4 addresses. In particular, the following
* illustration shows the TCP and UDP "pseudo-header" for IPv6:
*
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + +
* | |
* + Source Address +
* | |
* + +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + +
* | |
* + Destination Address +
* | |
* + +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Upper-Layer Packet Length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | zero | Next Header |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* o If the IPv6 packet contains a Routing header, the Destination
* Address used in the pseudo-header is that of the final
* destination. At the originating node, that address will be in
* the last element of the Routing header; at the recipient(s),
* that address will be in the Destination Address field of the
* IPv6 header.
*
* o The Next Header value in the pseudo-header identifies the
* upper-layer protocol (e.g., 6 for TCP, or 17 for UDP). It will
* differ from the Next Header value in the IPv6 header if there
* are extension headers between the IPv6 header and the upper-
* layer header.
*
* o The Upper-Layer Packet Length in the pseudo-header is the
* length of the upper-layer header and data (e.g., TCP header
* plus TCP data). Some upper-layer protocols carry their own
* length information (e.g., the Length field in the UDP header);
* for such protocols, that is the length used in the pseudo-
* header. Other protocols (such as TCP) do not carry their own
* length information, in which case the length used in the
* pseudo-header is the Payload Length from the IPv6 header, minus
* the length of any extension headers present between the IPv6
* header and the upper-layer header.
*
* o Unlike IPv4, when UDP packets are originated by an IPv6 node,
* the UDP checksum is not optional. That is, whenever
* originating a UDP packet, an IPv6 node must compute a UDP
* checksum over the packet and the pseudo-header, and, if that
* computation yields a result of zero, it must be changed to hex
* FFFF for placement in the UDP header. IPv6 receivers must
* discard UDP packets containing a zero checksum, and should log
* the error.
*
*
* Returns zero on checksum success, non zero otherwise
*/
#define IPV4SRCOFFSET 12 // the ipv4 source address offset from the l3 pdu
#define IPV6SRCOFFSET 8 // the ipv6 source address offset
#define IPV6SIZE 8 // units is number of 16 bits, i.e. 128 bits is eight 16 bits
#define IPV4SIZE 2 // v4 is two 16 bits (32 bits)
#define UDPPROTO 17 // UDP protocol value for psuedo header
uint32_t udpchecksum(const void *l3pdu, const void *l4pdu, int udplen, int v6) {
register uint32_t sum = 0;
const uint16_t *data;
int i;
const struct udphdr *udp_hdr = (const struct udphdr *)l4pdu;
if (!udp_hdr->check) {
if (v6)
// v6 requires checksums
return -1;
else
// v4 checksums are optional
return 0;
}
/*
* Build pseudo headers, partially from the packet
* (which are in network byte order) and
* the protocol of UDP (value of 17). Also, the IP dst
* addr immediately follows the src so double the size
* per each loop to cover both addrs
*/
if (v6) {
// skip to the ip header v6 src field, offset 8 (see ipv6 header)
data = (const uint16_t *)((char *)l3pdu + IPV6SRCOFFSET);
for (i = 0; i < (2 * IPV6SIZE); i++) {
sum += *data++;
}
} else {
// skip to the ip header v4 src field, offset 12 (see ipv4 header)
data = (const uint16_t *)((char *)l3pdu + IPV4SRCOFFSET);
for (i = 0; i < (2 * IPV4SIZE); i++) {
sum += *data++;
}
}
// These should work for both v4 and v6 even though
// v6 psuedo header uses 32 bit values because the
// uppers in v6 will be zero
sum += htons(UDPPROTO); // proto of UDP is 17
sum += htons(udplen); // For UDP, the pseudo hdr len equals udp len
/*
* UDP hdr + payload
*/
data = (const uint16_t *) l4pdu;
while( udplen > 1 ) {
sum += *data++;
udplen -= 2;
}
/* Add left-over byte, if any */
if( udplen > 0 )
sum += * (uint8_t *) data;
/* Fold 32-bit sum to 16 bits */
while (sum>>16)
sum = (sum & 0xffff) + (sum >> 16);
/* return ones complement */
sum = (sum ^ 0xffff);
return sum;
}
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