contiki/core/net/hc.c

216 lines
6.7 KiB
C

/*
* Copyright (c) 2005, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* @(#)$Id: hc.c,v 1.1 2006/06/17 22:41:18 adamdunkels Exp $
*/
/**
* \file
* TCP/IP header compression implementation
* \author Adam Dunkels <adam@sics.se>
*
*/
#include "net/hc.h"
#include "net/uip.h"
#include <string.h>
#define FLAGS_COMPRESSED 0x8000
#define FLAGS_BROADCASTDATA 0x4000
struct hc_hdr {
u16_t flagsport;
u16_t srcipaddr[2];
};
struct udpip_hdr {
/* IP header. */
u8_t vhl,
tos,
len[2],
ipid[2],
ipoffset[2],
ttl,
proto;
u16_t ipchksum;
u16_t srcipaddr[2],
destipaddr[2];
/* UDP header. */
u16_t srcport,
destport;
u16_t udplen;
u16_t udpchksum;
};
#include <stdio.h>
/*---------------------------------------------------------------------------*/
/**
* Initialize the header compression module.
*/
/*---------------------------------------------------------------------------*/
void
hc_init(void)
{
}
/*---------------------------------------------------------------------------*/
/**
* Compress the header found in the uip_buf.
*
* This function compresses the TCP/IP headers in the uip_buf and
* should be called just before sending out data on the network. A
* pointer to the compressed header is returned, and uip_len is
* adjusted.
*
* If the header could not be compressed, the function does nothing
* and returns a NULL pointer.
*
* \return A pointer to the start of the compressed header or NULL if
* the header could not be compressed.
*/
/*---------------------------------------------------------------------------*/
int
hc_compress(void)
{
struct hc_hdr *hdr;
struct udpip_hdr *uhdr;
hdr = (struct hc_hdr *)&uip_buf[UIP_LLH_LEN];
uhdr = (struct udpip_hdr *)&uip_buf[UIP_LLH_LEN];
/* Check the original TCP/IP header to see if it matches our
pattern, and compress if it does. */
if(uhdr->vhl == 0x45 && /* Only IPv4 without
options. */
uhdr->len[0] == 0x00 && /* Only packets < 256
bytes long. */
uhdr->ipoffset[0] == 0x00 && /* No fragmented IP
packets. */
uhdr->ipoffset[1] == 0x00 && /* No fragmented IP
packets. */
uhdr->proto == UIP_PROTO_UDP && /* Only UDP packets. */
uhdr->destipaddr[0] == 0xffffU && /* Only link-local
broadcast
packets. */
uhdr->destipaddr[1] == 0xffffU && /* Only link-local
broadcast
packets. */
uhdr->destport == uhdr->srcport && /* Only packets with
the same destination
and source port
number. */
(uhdr->destport & HTONS(0xc000)) == 0) { /* Only packets with the two
highest bits in the port
number equal to zero. */
hdr->flagsport = htons(
FLAGS_COMPRESSED | /* Compressed header. */
FLAGS_BROADCASTDATA | /* Broadcast data. */
(htons(uhdr->destport) & 0x3fff));
uip_ipaddr_copy(&hdr->srcipaddr, &uhdr->srcipaddr);
/* Move the packet data to the end of the compressed header. */
memcpy((char *)hdr + HC_HLEN,
&uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN],
uip_len - UIP_IPUDPH_LEN);
/* Return the new packet length. */
return uip_len - (UIP_IPUDPH_LEN - HC_HLEN);
}
/* No compression possible, return NULL pointer. */
return uip_len;
}
/*---------------------------------------------------------------------------*/
/**
* Inflate (decompress) a header in the uip_buf buffer.
*
* This function should be called to inflate a possibly compressed
* packet header just after a packet has been received from the
* network. The function will copy the packet data so that the
* original header fits and adjusts uip_len.
*
*/
/*---------------------------------------------------------------------------*/
int
hc_inflate(void)
{
struct udpip_hdr *uhdr;
struct hc_hdr *hdr;
hdr = (struct hc_hdr *)&uip_buf[UIP_LLH_LEN];
/* First, check if the header in uip_buf is compressed or not. */
if((hdr->flagsport & HTONS(FLAGS_COMPRESSED)) != 0 &&
(hdr->flagsport & HTONS(FLAGS_BROADCASTDATA)) != 0) {
/* Move packet data in memory to make room for the uncompressed header. */
memmove(&uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN - HC_HLEN],
&uip_buf[UIP_LLH_LEN], uip_len);
uhdr = (struct udpip_hdr *)&uip_buf[UIP_LLH_LEN];
hdr = (struct hc_hdr *)&uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN -
HC_HLEN];
uhdr->srcipaddr[0] = hdr->srcipaddr[0];
uhdr->srcipaddr[1] = hdr->srcipaddr[1];
uhdr->srcport = hdr->flagsport & HTONS(0x3fff);
uhdr->destport = hdr->flagsport & HTONS(0x3fff);
uhdr->udplen = uip_len;
uip_len += UIP_IPUDPH_LEN - HC_HLEN;
uhdr->vhl = 0x45;
uhdr->tos = 0;
uhdr->len[0] = 0;
uhdr->len[1] = uip_len;
uhdr->ipid[0] = uhdr->ipid[1] = 0xAD;
uhdr->ipoffset[0] = uhdr->ipoffset[1] = 0;
uhdr->ttl = 2;
uhdr->proto = UIP_PROTO_UDP;
uhdr->destipaddr[0] = uhdr->destipaddr[1] = 0xffff;
uhdr->udpchksum = 0;
uhdr->ipchksum = 0;
uhdr->ipchksum = ~(uip_ipchksum());
}
return uip_len;
}
/*---------------------------------------------------------------------------*/