/*
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* Copyright (c) 2005, Swedish Institute of Computer Science
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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*/
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/**
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* \file
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* TCP/IP header compression implementation
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* \author Adam Dunkels <adam@sics.se>
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*
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*/
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#include "net/hc.h"
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#include "net/uip.h"
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#include <string.h>
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#define FLAGS_COMPRESSED 0x8000
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#define FLAGS_BROADCASTDATA 0x4000
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struct hc_hdr {
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uint16_t flagsport;
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uip_ipaddr_t srcipaddr;
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};
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struct udpip_hdr {
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/* IP header. */
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uint8_t vhl,
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tos,
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len[2],
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ipid[2],
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ipoffset[2],
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ttl,
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proto;
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uint16_t ipchksum;
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uip_ipaddr_t srcipaddr, destipaddr;
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/* UDP header. */
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uint16_t srcport,
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destport;
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uint16_t udplen;
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uint16_t udpchksum;
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};
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#include <stdio.h>
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/*---------------------------------------------------------------------------*/
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/**
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* Initialize the header compression module.
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*/
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/*---------------------------------------------------------------------------*/
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void
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hc_init(void)
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{
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Compress a header
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*
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* This function compresses the TCP/IP headers in a buffer and
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* should be called just before sending out data on the network. A
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* pointer to the compressed header is returned, and len is
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* adjusted.
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*
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* If the header could not be compressed, the function does nothing
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* and returns a NULL pointer.
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*
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* \return A pointer to the start of the compressed header or NULL if
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* the header could not be compressed.
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*/
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/*---------------------------------------------------------------------------*/
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int
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hc_compress(uint8_t *buf, int len)
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{
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struct hc_hdr *hdr;
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struct udpip_hdr *uhdr;
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hdr = (struct hc_hdr *)buf;
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uhdr = (struct udpip_hdr *)buf;
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/* Check the original TCP/IP header to see if it matches our
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pattern, and compress if it does. */
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if(uhdr->vhl == 0x45 && /* Only IPv4 without
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options. */
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uhdr->len[0] == 0x00 && /* Only packets < 256
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bytes long. */
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uhdr->ipoffset[0] == 0x00 && /* No fragmented IP
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packets. */
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uhdr->ipoffset[1] == 0x00 && /* No fragmented IP
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packets. */
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uhdr->proto == UIP_PROTO_UDP && /* Only UDP packets. */
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uip_ipaddr_cmp(&uhdr->destipaddr, &uip_broadcast_addr) && /* Only
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link-local broadcast
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packets. */
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uhdr->destport == uhdr->srcport && /* Only packets with
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the same destination
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and source port
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number. */
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(uhdr->destport & UIP_HTONS(0xc000)) == 0) { /* Only packets with the two
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highest bits in the port
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number equal to zero. */
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hdr->flagsport = uip_htons(
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FLAGS_COMPRESSED | /* Compressed header. */
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FLAGS_BROADCASTDATA | /* Broadcast data. */
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(uip_htons(uhdr->destport) & 0x3fff));
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uip_ipaddr_copy(&hdr->srcipaddr, &uhdr->srcipaddr);
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/* Move the packet data to the end of the compressed header. */
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memcpy((char *)hdr + HC_HLEN,
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&buf[UIP_IPUDPH_LEN],
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len - UIP_IPUDPH_LEN);
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/* Return the new packet length. */
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return len - (UIP_IPUDPH_LEN - HC_HLEN);
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}
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/* No compression possible, return NULL pointer. */
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return len;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Inflate (decompress) a header
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*
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* This function should be called to inflate a possibly compressed
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* packet header just after a packet has been received from the
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* network. The function will copy the packet data so that the
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* original header fits and adjusts uip_len.
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*
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*/
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/*---------------------------------------------------------------------------*/
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int
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hc_inflate(uint8_t *buf, int len)
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{
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struct udpip_hdr *uhdr;
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struct hc_hdr *hdr;
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hdr = (struct hc_hdr *)buf;
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/* First, check if the header in buf is compressed or not. */
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if((hdr->flagsport & UIP_HTONS(FLAGS_COMPRESSED)) != 0 &&
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(hdr->flagsport & UIP_HTONS(FLAGS_BROADCASTDATA)) != 0) {
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/* Move packet data in memory to make room for the uncompressed header. */
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memmove(&buf[UIP_IPUDPH_LEN - HC_HLEN],
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buf, len);
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uhdr = (struct udpip_hdr *)buf;
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hdr = (struct hc_hdr *)&buf[UIP_IPUDPH_LEN - HC_HLEN];
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uip_ipaddr_copy(&uhdr->srcipaddr, &hdr->srcipaddr);
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uhdr->srcport = hdr->flagsport & UIP_HTONS(0x3fff);
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uhdr->destport = hdr->flagsport & UIP_HTONS(0x3fff);
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uhdr->udplen = len;
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len += UIP_IPUDPH_LEN - HC_HLEN;
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uhdr->vhl = 0x45;
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uhdr->tos = 0;
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uhdr->len[0] = 0;
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uhdr->len[1] = len;
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uhdr->ipid[0] = uhdr->ipid[1] = 0xAD;
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uhdr->ipoffset[0] = uhdr->ipoffset[1] = 0;
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uhdr->ttl = 2;
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uhdr->proto = UIP_PROTO_UDP;
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uip_ipaddr_copy(&uhdr->destipaddr, &uip_broadcast_addr);
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uhdr->udpchksum = 0;
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uhdr->ipchksum = 0;
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uhdr->ipchksum = ~(uip_ipchksum());
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}
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return len;
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}
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/*---------------------------------------------------------------------------*/
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