uip.c

一个小的RTOS具有UIP网络功能

      } else {
	/* All other options have a length field, so that we easily
	   can skip past them. */
	if(uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c] == 0) {
	  /* If the length field is zero, the options are malformed
	     and we don't process them further. */
	  break;
	}
	c += uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c];
      }      
    }
  }
  
  /* Our response will be a SYNACK. */
#if UIP_ACTIVE_OPEN
 tcp_send_synack:
  BUF->flags = TCP_ACK;    
  
 tcp_send_syn:
  BUF->flags |= TCP_SYN;    
#else /* UIP_ACTIVE_OPEN */
 tcp_send_synack:
  BUF->flags = TCP_SYN | TCP_ACK;    
#endif /* UIP_ACTIVE_OPEN */
  
  /* We send out the TCP Maximum Segment Size option with our
     SYNACK. */
  BUF->optdata[0] = 2;
  BUF->optdata[1] = 4;
  BUF->optdata[2] = (UIP_TCP_MSS) / 256;
  BUF->optdata[3] = (UIP_TCP_MSS) & 255;
  uip_len = 44;
  BUF->tcpoffset = 6 << 4;
  goto tcp_send;

  /* This label will be jumped to if we found an active connection. */
 found:
  uip_conn = uip_connr;
  uip_flags = 0;

  /* We do a very naive form of TCP reset processing; we just accept
     any RST and kill our connection. We should in fact check if the
     sequence number of this reset is wihtin our advertised window
     before we accept the reset. */
  if(BUF->flags & TCP_RST) {
    uip_connr->tcpstateflags = CLOSED;
    UIP_LOG("tcp: got reset, aborting connection.");
    uip_flags = UIP_ABORT;
    UIP_APPCALL();
    goto drop;
  }      
  /* Calculated the length of the data, if the application has sent
     any data to us. */
  c = (BUF->tcpoffset >> 4) << 2;
  /* uip_len will contain the length of the actual TCP data. This is
     calculated by subtracing the length of the TCP header (in
     c) and the length of the IP header (20 bytes). */
  uip_len = uip_len - c - 20;

  /* First, check if the sequence number of the incoming packet is
     what we're expecting next. If not, we send out an ACK with the
     correct numbers in. */
  if(uip_len > 0 &&
     (BUF->seqno[0] != uip_connr->rcv_nxt[0] ||
      BUF->seqno[1] != uip_connr->rcv_nxt[1] ||
      BUF->seqno[2] != uip_connr->rcv_nxt[2] ||
      BUF->seqno[3] != uip_connr->rcv_nxt[3])) {
    goto tcp_send_ack;
  }

  /* Next, check if the incoming segment acknowledges any outstanding
     data. If so, we update the sequence number, reset the length of
     the outstanding data, calculate RTT estimations, and reset the
     retransmission timer. */
  if((BUF->flags & TCP_ACK) && uip_outstanding(uip_connr)) {
    uip_add32(uip_connr->snd_nxt, uip_connr->len);
    if(BUF->ackno[0] == uip_acc32[0] &&
       BUF->ackno[1] == uip_acc32[1] &&
       BUF->ackno[2] == uip_acc32[2] &&
       BUF->ackno[3] == uip_acc32[3]) {
      /* Update sequence number. */
      uip_connr->snd_nxt[0] = uip_acc32[0];
      uip_connr->snd_nxt[1] = uip_acc32[1];
      uip_connr->snd_nxt[2] = uip_acc32[2];
      uip_connr->snd_nxt[3] = uip_acc32[3];
	

      /* Do RTT estimation, unless we have done retransmissions. */
      if(uip_connr->nrtx == 0) {
	signed char m;
	m = (UIP_RTO << (uip_connr->nrtx > 4? 4: uip_connr->nrtx)) - uip_connr->timer;
	/* This is taken directly from VJs original code in his paper */
	m = m - (uip_connr->sa >> 3);
	uip_connr->sa += m;
	if(m < 0) {
	  m = -m;
	}
	m = m - (uip_connr->sv >> 2);
	uip_connr->sv += m;
	uip_connr->rto = (uip_connr->sa >> 3) + uip_connr->sv;

      }
      /* Set the acknowledged flag. */
      uip_flags = UIP_ACKDATA;
      /* Reset the length of the outstanding data. */
      uip_connr->len = 0;
      /* Reset the retransmission timer. */
      uip_connr->timer = UIP_RTO;
    }
    
  }

  /* Do different things depending on in what state the connection is. */
  switch(uip_connr->tcpstateflags & TS_MASK) {
    /* CLOSED and LISTEN are not handled here. CLOSE_WAIT is not
	implemented, since we force the application to close when the
	peer sends a FIN (hence the application goes directly from
	ESTABLISHED to LAST_ACK). */
  case SYN_RCVD:
    /* In SYN_RCVD we have sent out a SYNACK in response to a SYN, and
       we are waiting for an ACK that acknowledges the data we sent
       out the last time. Therefore, we want to have the UIP_ACKDATA
       flag set. If so, we enter the ESTABLISHED state. */
    if(uip_flags & UIP_ACKDATA) {
      uip_connr->tcpstateflags = ESTABLISHED;
      uip_flags = UIP_CONNECTED;
      if(uip_len > 0) {
        uip_flags |= UIP_NEWDATA;
        uip_add_rcv_nxt(uip_len);
      }
      uip_slen = 0;
      UIP_APPCALL();
      goto appsend;
    }
    goto drop;
#if UIP_ACTIVE_OPEN
  case SYN_SENT:
    /* In SYN_SENT, we wait for a SYNACK that is sent in response to
       our SYN. The rcv_nxt is set to sequence number in the SYNACK
       plus one, and we send an ACK. We move into the ESTABLISHED
       state. */
    if((uip_flags & UIP_ACKDATA) &&
       BUF->flags == (TCP_SYN | TCP_ACK)) {

      /* Parse the TCP MSS option, if present. */
      if((BUF->tcpoffset & 0xf0) > 0x50) {
	for(c = 0; c < ((BUF->tcpoffset >> 4) - 5) << 2 ;) {
	  opt = uip_buf[40 + UIP_LLH_LEN + c];
	  if(opt == 0x00) {
	    /* End of options. */	
	    break;
	  } else if(opt == 0x01) {
	    ++c;
	    /* NOP option. */
	  } else if(opt == 0x02 &&
		    uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c] == 0x04) {
	    /* An MSS option with the right option length. */
	    tmpport = (uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 2 + c] << 8) |
	      uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 3 + c];
	    uip_connr->mss = tmpport > UIP_TCP_MSS? UIP_TCP_MSS: tmpport;

	    /* And we are done processing options. */
	    break;
	  } else {
	    /* All other options have a length field, so that we easily
	       can skip past them. */
	    if(uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c] == 0) {
	      /* If the length field is zero, the options are malformed
		 and we don't process them further. */
	      break;
	    }
	    c += uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c];
	  }      
	}
      }
      uip_connr->tcpstateflags = ESTABLISHED;      
      uip_connr->rcv_nxt[0] = BUF->seqno[0];
      uip_connr->rcv_nxt[1] = BUF->seqno[1];
      uip_connr->rcv_nxt[2] = BUF->seqno[2];
      uip_connr->rcv_nxt[3] = BUF->seqno[3];
      uip_add_rcv_nxt(1);
      uip_flags = UIP_CONNECTED | UIP_NEWDATA;
      uip_len = 0;
      uip_slen = 0;
      UIP_APPCALL();
      goto appsend;
    }
    goto reset;
#endif /* UIP_ACTIVE_OPEN */
    
  case ESTABLISHED:
    /* In the ESTABLISHED state, we call upon the application to feed
    data into the uip_buf. If the UIP_ACKDATA flag is set, the
    application should put new data into the buffer, otherwise we are
    retransmitting an old segment, and the application should put that
    data into the buffer.

    If the incoming packet is a FIN, we should close the connection on
    this side as well, and we send out a FIN and enter the LAST_ACK
    state. We require that there is no outstanding data; otherwise the
    sequence numbers will be screwed up. */

    if(BUF->flags & TCP_FIN) {
      if(uip_outstanding(uip_connr)) {
	goto drop;
      }
      uip_add_rcv_nxt(1 + uip_len);      
      uip_flags = UIP_CLOSE;
      if(uip_len > 0) {
	uip_flags |= UIP_NEWDATA;
      }
      UIP_APPCALL();
      uip_connr->len = 1;
      uip_connr->tcpstateflags = LAST_ACK;
      uip_connr->nrtx = 0;
    tcp_send_finack:
      BUF->flags = TCP_FIN | TCP_ACK;      
      goto tcp_send_nodata;
    }

    /* Check the URG flag. If this is set, the segment carries urgent
       data that we must pass to the application. */
    if(BUF->flags & TCP_URG) {
#if UIP_URGDATA > 0
      uip_urglen = (BUF->urgp[0] << 8) | BUF->urgp[1];
      if(uip_urglen > uip_len) {
	/* There is more urgent data in the next segment to come. */
	uip_urglen = uip_len;
      }
      uip_add_rcv_nxt(uip_urglen);
      uip_len -= uip_urglen;
      uip_urgdata = uip_appdata;
      uip_appdata += uip_urglen;
    } else {
      uip_urglen = 0;
#endif /* UIP_URGDATA > 0 */
      uip_appdata += (BUF->urgp[0] << 8) | BUF->urgp[1];
      uip_len -= (BUF->urgp[0] << 8) | BUF->urgp[1];
    }
    
    
    /* If uip_len > 0 we have TCP data in the packet, and we flag this
       by setting the UIP_NEWDATA flag and update the sequence number
       we acknowledge. If the application has stopped the dataflow
       using uip_stop(), we must not accept any data packets from the
       remote host. */
    if(uip_len > 0 && !(uip_connr->tcpstateflags & UIP_STOPPED)) {
      uip_flags |= UIP_NEWDATA;
      uip_add_rcv_nxt(uip_len);
    }
    

    /* If this packet constitutes an ACK for outstanding data (flagged
       by the UIP_ACKDATA flag, we should call the application since it
       might want to send more data. If the incoming packet had data
       from the peer (as flagged by the UIP_NEWDATA flag), the
       application must also be notified.

       When the application is called, the global variable uip_len
       contains the length of the incoming data. The application can
       access the incoming data through the global pointer
       uip_appdata, which usually points 40 bytes into the uip_buf
       array.

       If the application wishes to send any data, this data should be
       put into the uip_appdata and the length of the data should be
       put into uip_len. If the application don't have any data to
       send, uip_len must be set to 0. */
    if(uip_flags & (UIP_NEWDATA | UIP_ACKDATA)) {
      uip_slen = 0;
      UIP_APPCALL();

    appsend:
      if(uip_flags & UIP_ABORT) {
	uip_slen = 0;
	uip_connr->tcpstateflags = CLOSED;
	BUF->flags = TCP_RST | TCP_ACK;
	goto tcp_send_nodata;
      }

      if(uip_flags & UIP_CLOSE) {
	uip_slen = 0;
	uip_connr->len = 1;
	uip_connr->tcpstateflags = FIN_WAIT_1;
	uip_connr->nrtx = 0;
	BUF->flags = TCP_FIN | TCP_ACK;
	goto tcp_send_nodata;	
      }

      /* If uip_slen > 0, the application has data to be sent. We
         cannot send data if the application already has outstanding
         data. */
      if(uip_slen > 0 &&
	 !uip_outstanding(uip_connr)) {
	uip_connr->nrtx = 0;
	uip_connr->len = uip_slen;
      } else {
	uip_connr->nrtx = 0;
	uip_slen = uip_connr->len;
      }
    apprexmit:
      /* If the application has data to be sent, or if the incoming
         packet had new data in it, we must send out a packet. */
      if(uip_slen > 0 && uip_connr->len > 0) {
	/* Add the length of the IP and TCP headers. */
	uip_len = uip_connr->len + UIP_TCPIP_HLEN;
	/* We always set the ACK flag in response packets. */
	BUF->flags = TCP_ACK | TCP_PSH;
	/* Send the packet. */
	goto tcp_send_noopts;
      }
      /* If there is no data to send, just send out a pure ACK if
	 there is newdata. */
      if(uip_flags & UIP_NEWDATA) {
	uip_len = UIP_TCPIP_HLEN;
	BUF->flags = TCP_ACK;
	goto tcp_send_noopts;
      }
    }
    goto drop;
  case LAST_ACK:
    /* We can close this connection if the peer has acknowledged our
       FIN. This is indicated by the UIP_ACKDATA flag. */     
    if(uip_flags & UIP_ACKDATA) {
      uip_connr->tcpstateflags = CLOSED;
      uip_flags = UIP_CLOSE;
      UIP_APPCALL();
    }
    break;
    
  case FIN_WAIT_1:
    /* The application has closed the connection, but the remote host
       hasn't closed its end yet. Thus we do nothing but wait for a
       FIN from the other side. */
    if(uip_len > 0) {
      uip_add_rcv_nxt(uip_len);
    }
    if(BUF->flags & TCP_FIN) {
      if(uip_flags & UIP_ACKDATA) {
	uip_connr->tcpstateflags = TIME_WAIT;
	uip_connr->timer = 0;
	uip_connr->len = 0;
      } else {
	uip_connr->tcpstateflags = CLOSING;
      }
      uip_add_rcv_nxt(1);
      uip_flags = UIP_CLOSE;
      UIP_APPCALL();
      goto tcp_send_ack;
    } else if(uip_flags & UIP_ACKDATA) {
      uip_connr->tcpstateflags = FIN_WAIT_2;
      uip_connr->len = 0;
      goto drop;
    }
    if(uip_len > 0) {
      goto tcp_send_ack;
    }
    goto drop;
      
  case FIN_WAIT_2:
    if(uip_len > 0) {
      uip_add_rcv_nxt(uip_len);
    }
    if(BUF->flags & TCP_FIN) {
      uip_connr->tcpstateflags = TIME_WAIT;
      uip_connr->timer = 0;
      uip_add_rcv_nxt(1);
      uip_flags = UIP_CLOSE;
      UIP_APPCALL();
      goto tcp_send_ack;
    }
    if(uip_len > 0) {
      goto tcp_send_ack;
    }
    goto drop;

  case TIME_WAIT:
    goto tcp_send_ack;
    
  case CLOSING:
    if(uip_flags & UIP_ACKDATA) {
      uip_connr->tcpstateflags = TIME_WAIT;
      uip_connr->timer = 0;
    }
  }  
  goto drop;
  

  /* We jump here when we are ready to send the packet, and just want
     to set the appropriate TCP sequence numbers in the TCP header. */
 tcp_send_ack:
  BUF->flags = TCP_ACK;
 tcp_send_nodata:
  uip_len = 40;
 tcp_send_noopts:
  BUF->tcpoffset = 5 << 4;
 tcp_send:
  /* We're done with the input processing. We are now ready to send a
     reply. Our job is to fill in all the fields of the TCP and IP
     headers before calculating the checksum and finally send the
     packet. */
  BUF->ackno[0] = uip_connr->rcv_nxt[0];
  BUF->ackno[1] = uip_connr->rcv_nxt[1];
  BUF->ackno[2] = uip_connr->rcv_nxt[2];
  BUF->ackno[3] = uip_connr->rcv_nxt[3];
  
  BUF->seqno[0] = uip_connr->snd_nxt[0];
  BUF->seqno[1] = uip_connr->snd_nxt[1];
  BUF->seqno[2] = uip_connr->snd_nxt[2];
  BUF->seqno[3] = uip_connr->snd_nxt[3];

  BUF->proto = UIP_PROTO_TCP;
  
  BUF->srcport  = uip_connr->lport;
  BUF->destport = uip_connr->rport;

  BUF->srcipaddr[0] = uip_hostaddr[0];
  BUF->srcipaddr[1] = uip_hostaddr[1];
  BUF->destipaddr[0] = uip_connr->ripaddr[0];
  BUF->destipaddr[1] = uip_connr->ripaddr[1];
 

  if(uip_connr->tcpstateflags & UIP_STOPPED) {
    /* If the connection has issued uip_stop(), we advertise a zero
       window so that the remote host will stop sending data. */
    BUF->wnd[0] = BUF->wnd[1] = 0;
  } else {
#if (UIP_TCP_MSS) > 255
    BUF->wnd[0] = (uip_connr->mss >> 8);
#else
    BUF->wnd[0] = 0;
#endif /* UIP_MSS */
    BUF->wnd[1] = (uip_connr->mss & 0xff); 
  }

 tcp_send_noconn:

#if UIP_BUFSIZE > 255
  BUF->len[0] = (uip_len >> 8);
  BUF->len[1] = (uip_len & 0xff);
#else
  BUF->len[0] = 0;
  BUF->len[1] = uip_len;
#endif /* UIP_BUFSIZE > 255 */

  /* Calculate TCP checksum. */
  BUF->tcpchksum = 0;
  BUF->tcpchksum = ~(uip_tcpchksum());
  
 ip_send_nolen:

  BUF->vhl = 0x45;
  BUF->tos = 0;
  BUF->ipoffset[0] = BUF->ipoffset[1] = 0;
  BUF->ttl  = UIP_TTL;
  ++ipid;
  BUF->ipid[0] = ipid >> 8;
  BUF->ipid[1] = ipid & 0xff;
  
  /* Calculate IP checksum. */
  BUF->ipchksum = 0;
  BUF->ipchksum = ~(uip_ipchksum());

  UIP_STAT(++uip_stat.tcp.sent);
 send:
  UIP_STAT(++uip_stat.ip.sent);
  /* Return and let the caller do the actual transmission. */
  return;
 drop:
  uip_len = 0;
  return;
}
/*-----------------------------------------------------------------------------------*/
u16_t
htons(u16_t val)
{
  return HTONS(val);
}
/*-----------------------------------------------------------------------------------*/