vj.c

lm3s下lwip的udp

  case SPECIAL_I:
  case SPECIAL_D:
    /*
     * actual changes match one of our special case encodings --
     * send packet uncompressed.
     */
    goto uncompressed;

  case NEW_S|NEW_A:
    if (deltaS == deltaA && deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
      /* special case for echoed terminal traffic */
      changes = SPECIAL_I;
      cp = new_seq;
    }
    break;

  case NEW_S:
    if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
      /* special case for data xfer */
      changes = SPECIAL_D;
      cp = new_seq;
    }
    break;
  }

  deltaS = (u_short)(ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id));
  if (deltaS != 1) {
    ENCODEZ(deltaS);
    changes |= NEW_I;
  }
  if (th->th_flags & TCP_PSH) {
    changes |= TCP_PUSH_BIT;
  }
  /*
   * Grab the cksum before we overwrite it below.  Then update our
   * state with this packet's header.
   */
  deltaA = ntohs(th->th_sum);
  BCOPY(ip, &cs->cs_ip, hlen);

  /*
   * We want to use the original packet as our compressed packet.
   * (cp - new_seq) is the number of bytes we need for compressed
   * sequence numbers.  In addition we need one byte for the change
   * mask, one for the connection id and two for the tcp checksum.
   * So, (cp - new_seq) + 4 bytes of header are needed.  hlen is how
   * many bytes of the original packet to toss so subtract the two to
   * get the new packet size.
   */
  deltaS = (u_short)(cp - new_seq);
  if (!comp->compressSlot || comp->last_xmit != cs->cs_id) {
    comp->last_xmit = cs->cs_id;
    hlen -= deltaS + 4;
    if(pbuf_header(pb, -hlen)){
      /* Can we cope with this failing?  Just assert for now */
      LWIP_ASSERT("pbuf_header failed\n", 0);
    }
    cp = (u_char *)pb->payload;
    *cp++ = changes | NEW_C;
    *cp++ = cs->cs_id;
  } else {
    hlen -= deltaS + 3;
    if(pbuf_header(pb, -hlen)) {
      /* Can we cope with this failing?  Just assert for now */
      LWIP_ASSERT("pbuf_header failed\n", 0);
    }
    cp = (u_char *)pb->payload;
    *cp++ = changes;
  }
  *cp++ = deltaA >> 8;
  *cp++ = deltaA;
  BCOPY(new_seq, cp, deltaS);
  INCR(vjs_compressed);
  return (TYPE_COMPRESSED_TCP);

  /*
   * Update connection state cs & send uncompressed packet (that is,
   * a regular ip/tcp packet but with the 'conversation id' we hope
   * to use on future compressed packets in the protocol field).
   */
uncompressed:
  BCOPY(ip, &cs->cs_ip, hlen);
  ip->ip_p = cs->cs_id;
  comp->last_xmit = cs->cs_id;
  return (TYPE_UNCOMPRESSED_TCP);
}

/*
 * Called when we may have missed a packet.
 */
void
vj_uncompress_err(struct vjcompress *comp)
{
  comp->flags |= VJF_TOSS;
  INCR(vjs_errorin);
}

/*
 * "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP.
 * Return 0 on success, -1 on failure.
 */
int
vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp)
{
  register u_int hlen;
  register struct cstate *cs;
  register struct ip *ip;
  
  ip = (struct ip *)nb->payload;
  hlen = getip_hl(*ip) << 2;
  if (ip->ip_p >= MAX_SLOTS
      || hlen + sizeof(struct tcphdr) > nb->len
      || (hlen += getth_off(*((struct tcphdr *)&((char *)ip)[hlen])) << 2)
          > nb->len
      || hlen > MAX_HDR) {
    PPPDEBUG((LOG_INFO, "vj_uncompress_uncomp: bad cid=%d, hlen=%d buflen=%d\n", 
          ip->ip_p, hlen, nb->len));
    comp->flags |= VJF_TOSS;
    INCR(vjs_errorin);
    return -1;
  }
  cs = &comp->rstate[comp->last_recv = ip->ip_p];
  comp->flags &=~ VJF_TOSS;
  ip->ip_p = IPPROTO_TCP;
  BCOPY(ip, &cs->cs_ip, hlen);
  cs->cs_hlen = hlen;
  INCR(vjs_uncompressedin);
  return 0;
}

/*
 * Uncompress a packet of type TYPE_COMPRESSED_TCP.
 * The packet is composed of a buffer chain and the first buffer
 * must contain an accurate chain length.
 * The first buffer must include the entire compressed TCP/IP header. 
 * This procedure replaces the compressed header with the uncompressed
 * header and returns the length of the VJ header.
 */
int
vj_uncompress_tcp(struct pbuf **nb, struct vjcompress *comp)
{
  u_char *cp;
  struct tcphdr *th;
  struct cstate *cs;
  u_short *bp;
  struct pbuf *n0 = *nb;
  u32_t tmp;
  u_int vjlen, hlen, changes;

  INCR(vjs_compressedin);
  cp = (u_char *)n0->payload;
  changes = *cp++;
  if (changes & NEW_C) {
    /* 
     * Make sure the state index is in range, then grab the state.
     * If we have a good state index, clear the 'discard' flag. 
     */
    if (*cp >= MAX_SLOTS) {
      PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: bad cid=%d\n", *cp));
      goto bad;
    }

    comp->flags &=~ VJF_TOSS;
    comp->last_recv = *cp++;
  } else {
    /* 
     * this packet has an implicit state index.  If we've
     * had a line error since the last time we got an
     * explicit state index, we have to toss the packet. 
     */
    if (comp->flags & VJF_TOSS) {
      PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: tossing\n"));
      INCR(vjs_tossed);
      return (-1);
    }
  }
  cs = &comp->rstate[comp->last_recv];
  hlen = getip_hl(cs->cs_ip) << 2;
  th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
  th->th_sum = htons((*cp << 8) | cp[1]);
  cp += 2;
  if (changes & TCP_PUSH_BIT) {
    th->th_flags |= TCP_PSH;
  } else {
    th->th_flags &=~ TCP_PSH;
  }

  switch (changes & SPECIALS_MASK) {
  case SPECIAL_I:
    {
      register u32_t i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
      /* some compilers can't nest inline assembler.. */
      tmp = ntohl(th->th_ack) + i;
      th->th_ack = htonl(tmp);
      tmp = ntohl(th->th_seq) + i;
      th->th_seq = htonl(tmp);
    }
    break;

  case SPECIAL_D:
    /* some compilers can't nest inline assembler.. */
    tmp = ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
    th->th_seq = htonl(tmp);
    break;

  default:
    if (changes & NEW_U) {
      th->th_flags |= TCP_URG;
      DECODEU(th->th_urp);
    } else {
      th->th_flags &=~ TCP_URG;
    }
    if (changes & NEW_W) {
      DECODES(th->th_win);
    }
    if (changes & NEW_A) {
      DECODEL(th->th_ack);
    }
    if (changes & NEW_S) {
      DECODEL(th->th_seq);
    }
    break;
  }
  if (changes & NEW_I) {
    DECODES(cs->cs_ip.ip_id);
  } else {
    cs->cs_ip.ip_id = ntohs(cs->cs_ip.ip_id) + 1;
    cs->cs_ip.ip_id = htons(cs->cs_ip.ip_id);
  }

  /*
   * At this point, cp points to the first byte of data in the
   * packet.  Fill in the IP total length and update the IP
   * header checksum.
   */
  vjlen = (u_short)(cp - (u_char*)n0->payload);
  if (n0->len < vjlen) {
    /* 
     * We must have dropped some characters (crc should detect
     * this but the old slip framing won't) 
     */
    PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: head buffer %d too short %d\n", 
          n0->len, vjlen));
    goto bad;
  }

#if BYTE_ORDER == LITTLE_ENDIAN
  tmp = n0->tot_len - vjlen + cs->cs_hlen;
  cs->cs_ip.ip_len = htons(tmp);
#else
  cs->cs_ip.ip_len = htons(n0->tot_len - vjlen + cs->cs_hlen);
#endif

  /* recompute the ip header checksum */
  bp = (u_short *) &cs->cs_ip;
  cs->cs_ip.ip_sum = 0;
  for (tmp = 0; hlen > 0; hlen -= 2) {
    tmp += *bp++;
  }
  tmp = (tmp & 0xffff) + (tmp >> 16);
  tmp = (tmp & 0xffff) + (tmp >> 16);
  cs->cs_ip.ip_sum = (u_short)(~tmp);
  
  /* Remove the compressed header and prepend the uncompressed header. */
  if(pbuf_header(n0, -((s16_t)(vjlen)))) {
    /* Can we cope with this failing?  Just assert for now */
    LWIP_ASSERT("pbuf_header failed\n", 0);
    goto bad;
  }

  if(LWIP_MEM_ALIGN(n0->payload) != n0->payload) {
    struct pbuf *np, *q;
    u8_t *bufptr;

    np = pbuf_alloc(PBUF_RAW, n0->len + cs->cs_hlen, PBUF_POOL);
    if(!np) {
      PPPDEBUG((LOG_WARNING, "vj_uncompress_tcp: realign failed\n"));
      goto bad;
    }

    if(pbuf_header(np, -cs->cs_hlen)) {
      /* Can we cope with this failing?  Just assert for now */
      LWIP_ASSERT("pbuf_header failed\n", 0);
      goto bad;
    }

    bufptr = n0->payload;
    for(q = np; q != NULL; q = q->next) {
      MEMCPY(q->payload, bufptr, q->len);
      bufptr += q->len;
    }

    if(n0->next) {
      pbuf_chain(np, n0->next);
      pbuf_dechain(n0);
    }
    pbuf_free(n0);
    n0 = np;
  }

  if(pbuf_header(n0, cs->cs_hlen)) {
    struct pbuf *np;

    LWIP_ASSERT("vj_uncompress_tcp: cs->cs_hlen <= PBUF_POOL_BUFSIZE", cs->cs_hlen <= PBUF_POOL_BUFSIZE);
    np = pbuf_alloc(PBUF_RAW, cs->cs_hlen, PBUF_POOL);
    if(!np) {
      PPPDEBUG((LOG_WARNING, "vj_uncompress_tcp: prepend failed\n"));
      goto bad;
    }
    pbuf_cat(np, n0);
    n0 = np;
  }
  LWIP_ASSERT("n0->len >= cs->cs_hlen", n0->len >= cs->cs_hlen);
  MEMCPY(n0->payload, &cs->cs_ip, cs->cs_hlen);

  *nb = n0;

  return vjlen;

bad:
  comp->flags |= VJF_TOSS;
  INCR(vjs_errorin);
  return (-1);
}

#endif /* VJ_SUPPORT */

#endif /* PPP_SUPPORT */