/* * 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 1.5 2010/10/19 18:29:04 adamdunkels Exp $ */ /** * \file * TCP/IP header compression implementation * \author Adam Dunkels * */ #include "net/hc.h" #include "net/uip.h" #include #define FLAGS_COMPRESSED 0x8000 #define FLAGS_BROADCASTDATA 0x4000 struct hc_hdr { u16_t flagsport; uip_ipaddr_t srcipaddr; }; struct udpip_hdr { /* IP header. */ u8_t vhl, tos, len[2], ipid[2], ipoffset[2], ttl, proto; u16_t ipchksum; uip_ipaddr_t srcipaddr, destipaddr; /* UDP header. */ u16_t srcport, destport; u16_t udplen; u16_t udpchksum; }; #include /*---------------------------------------------------------------------------*/ /** * Initialize the header compression module. */ /*---------------------------------------------------------------------------*/ void hc_init(void) { } /*---------------------------------------------------------------------------*/ /** * Compress a header * * This function compresses the TCP/IP headers in a buffer and * should be called just before sending out data on the network. A * pointer to the compressed header is returned, and 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(u8_t *buf, int len) { struct hc_hdr *hdr; struct udpip_hdr *uhdr; hdr = (struct hc_hdr *)buf; uhdr = (struct udpip_hdr *)buf; /* 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. */ uip_ipaddr_cmp(&uhdr->destipaddr, &uip_broadcast_addr) && /* Only link-local broadcast packets. */ uhdr->destport == uhdr->srcport && /* Only packets with the same destination and source port number. */ (uhdr->destport & UIP_HTONS(0xc000)) == 0) { /* Only packets with the two highest bits in the port number equal to zero. */ hdr->flagsport = uip_htons( FLAGS_COMPRESSED | /* Compressed header. */ FLAGS_BROADCASTDATA | /* Broadcast data. */ (uip_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, &buf[UIP_IPUDPH_LEN], len - UIP_IPUDPH_LEN); /* Return the new packet length. */ return len - (UIP_IPUDPH_LEN - HC_HLEN); } /* No compression possible, return NULL pointer. */ return len; } /*---------------------------------------------------------------------------*/ /** * Inflate (decompress) a header * * 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(u8_t *buf, int len) { struct udpip_hdr *uhdr; struct hc_hdr *hdr; hdr = (struct hc_hdr *)buf; /* First, check if the header in buf is compressed or not. */ if((hdr->flagsport & UIP_HTONS(FLAGS_COMPRESSED)) != 0 && (hdr->flagsport & UIP_HTONS(FLAGS_BROADCASTDATA)) != 0) { /* Move packet data in memory to make room for the uncompressed header. */ memmove(&buf[UIP_IPUDPH_LEN - HC_HLEN], buf, len); uhdr = (struct udpip_hdr *)buf; hdr = (struct hc_hdr *)&buf[UIP_IPUDPH_LEN - HC_HLEN]; uip_ipaddr_copy(&uhdr->srcipaddr, &hdr->srcipaddr); uhdr->srcport = hdr->flagsport & UIP_HTONS(0x3fff); uhdr->destport = hdr->flagsport & UIP_HTONS(0x3fff); uhdr->udplen = len; len += UIP_IPUDPH_LEN - HC_HLEN; uhdr->vhl = 0x45; uhdr->tos = 0; uhdr->len[0] = 0; uhdr->len[1] = len; uhdr->ipid[0] = uhdr->ipid[1] = 0xAD; uhdr->ipoffset[0] = uhdr->ipoffset[1] = 0; uhdr->ttl = 2; uhdr->proto = UIP_PROTO_UDP; uip_ipaddr_copy(&uhdr->destipaddr, &uip_broadcast_addr); uhdr->udpchksum = 0; uhdr->ipchksum = 0; uhdr->ipchksum = ~(uip_ipchksum()); } return len; } /*---------------------------------------------------------------------------*/