uip.c

基于STC单片机与MICROCHIP ENC28J60的TCPIP以太网控制器

    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.fragerr);
    UIP_LOG("ip: fragment dropped.");    
    goto drop;
#endif /* UIP_REASSEMBLY */
  }

  

  /* If we are configured to use ping IP address configuration and
     hasn't been assigned an IP address yet, we accept all ICMP
     packets. */
#if UIP_PINGADDRCONF										//未用到
  if((uip_hostaddr[0] | uip_hostaddr[1]) == 0) {
    if(BUF->proto == UIP_PROTO_ICMP) {
      UIP_LOG("ip: possible ping config packet received.");
      goto icmp_input;
    } else {
      UIP_LOG("ip: packet dropped since no address assigned.");
      goto drop;
    }
  }
#endif /* UIP_PINGADDRCONF */
  
 /***************** Check if the packet is destined for our IP address. *****************************/  
  if(BUF->destipaddr[0] != uip_hostaddr[0]) {			//确认地址是不是发给我的
    UIP_STAT(++uip_stat.ip.drop);
    UIP_LOG("ip: packet not for us.");        
    goto drop;
  }
  if(BUF->destipaddr[1] != uip_hostaddr[1]) {
    UIP_STAT(++uip_stat.ip.drop);
    UIP_LOG("ip: packet not for us.");        
    goto drop;	 	
  }

    

  if(uip_ipchksum() != 0xffff) { /* Compute and check the IP header
				    checksum. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.chkerr);
    UIP_LOG("ip: bad checksum.");    
    goto drop;
  }

  if(BUF->proto == UIP_PROTO_TCP)  /* Check for TCP packet. If so, jump
                                     to the tcp_input label. */
	goto tcp_input;
					

  if(BUF->proto != UIP_PROTO_ICMP) { /* We only allow ICMP packets from
									here. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.protoerr);
    UIP_LOG("ip: neither tcp nor icmp.");        
    goto drop;
  }
  
#if UIP_PINGADDRCONF
  icmp_input:
 #endif /* UIP_PINGADDRCONF */
  UIP_STAT(++uip_stat.icmp.recv);
  
  /* ICMP echo (i.e., ping) processing. This is simple, we only change
     the ICMP type from ECHO to ECHO_REPLY and adjust the ICMP
     checksum before we return the packet. */
  if(ICMPBUF->type != ICMP_ECHO) {						//ICMP_ECHO=8,ICMP_ECHO_replay=0
    UIP_STAT(++uip_stat.icmp.drop);
    UIP_STAT(++uip_stat.icmp.typeerr);
    UIP_LOG("icmp: not icmp echo.");
    goto drop;
  }

  /* If we are configured to use ping IP address assignment, we use
     the destination IP address of this ping packet and assign it to
     ourself.
#if UIP_PINGADDRCONF
  if((uip_hostaddr[0] | uip_hostaddr[1]) == 0) {			//改动
      uip_hostaddr[0] = BUF->destipaddr[0];
      uip_hostaddr[1] = BUF->destipaddr[1];
   }
#endif/* UIP_PINGADDRCONF */

  ICMPBUF->type = ICMP_ECHO_REPLY;
  
  if(ICMPBUF->icmpchksum >= HTONS(0xffff - (ICMP_ECHO << 8))) {		//校验和核实
    ICMPBUF->icmpchksum += HTONS(ICMP_ECHO << 8) + 1;
  } else {
    ICMPBUF->icmpchksum += HTONS(ICMP_ECHO << 8);
  }
  /* Swap IP addresses. */
  tmp16 = BUF->destipaddr[0];			//BUF中的源末地址对调，准备发送
  BUF->destipaddr[0] = BUF->srcipaddr[0];
  BUF->srcipaddr[0] = tmp16;
  tmp16 = BUF->destipaddr[1];
  BUF->destipaddr[1] = BUF->srcipaddr[1];
  BUF->srcipaddr[1] = tmp16;

  UIP_STAT(++uip_stat.icmp.sent);
  goto send;

 /* End of IPv4 input header processing code. */
  
  
/************************************** TCP input processing. *******************************/  
 tcp_input:
  UIP_STAT(++uip_stat.tcp.recv);

 /* Start of TCP input header processing code. */
  
  if(uip_tcpchksum() != 0xffff) {   /* Compute and check the TCP
				       checksum. */
    UIP_STAT(++uip_stat.tcp.drop);
    UIP_STAT(++uip_stat.tcp.chkerr);
    UIP_LOG("tcp: bad checksum.");    
    goto drop;
  }

   
  /* Demultiplex this segment. 多元化段*/
 /* First check any active connections.首先查看是否有任何已有的连接 */ // 怎么产生的连接？
for(uip_connr = &uip_conns[0]; uip_connr < &uip_conns[UIP_CONNS]; ++uip_connr) {
    if(uip_connr->tcpstateflags != CLOSED &&
       BUF->destport == uip_connr->lport &&
       BUF->srcport == uip_connr->rport &&
       BUF->srcipaddr[0] == uip_connr->ripaddr[0] &&
       BUF->srcipaddr[1] == uip_connr->ripaddr[1]) {
      goto found;    
    }
  }

  /* If we didn't find and active connection that expected the packet,
     either this packet is an old duplicate（复制品）, or this is a SYN packet
     destined for a connection in LISTEN. If the SYN flag isn't set,
     it is an old packet and we send a RST. */
  if((BUF->flags & TCP_CTL) != TCP_SYN)
    goto reset;
  
  	tmp16 = BUF->destport;
  /* Next, check listening connections. */  
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    if(tmp16 == uip_listenports[c])
      goto found_listen;
  }
  
  /* No matching connection found, so we send a RST packet. */
  UIP_STAT(++uip_stat.tcp.synrst);
 reset:															//发送重启包
	   
  /* We do not send resets in response to resets. */  //未发过重起包发送一个重起的包
  if(BUF->flags & TCP_RST) 			//TCP_RST=0x04
    goto drop;
   
  UIP_STAT(++uip_stat.tcp.rst);
  
  BUF->flags = TCP_RST | TCP_ACK;		// TCP_ACK 0x10，为什么用或,BUF->flags=0x14
  uip_len = 40;							//tcp长
  BUF->tcpoffset = 5 << 4;				//BUF->tcpoffset=0x50

  /* Flip赋值 the seqno and ackno fields in the TCP header. */
  c = BUF->seqno[3];
  BUF->seqno[3] = BUF->ackno[3];  
  BUF->ackno[3] = c;
  
  c = BUF->seqno[2];
  BUF->seqno[2] = BUF->ackno[2];  
  BUF->ackno[2] = c;
  
  c = BUF->seqno[1];
  BUF->seqno[1] = BUF->ackno[1];
  BUF->ackno[1] = c;
  
  c = BUF->seqno[0];
  BUF->seqno[0] = BUF->ackno[0];  
  BUF->ackno[0] = c;

  /* We also have to increase the sequence number we are
     acknowledging. If the least significant byte overflowed, we need
     to propagate the carry to the other bytes as well. */
  if(++BUF->ackno[3] == 0) {
    if(++BUF->ackno[2] == 0) {
      if(++BUF->ackno[1] == 0) {
	++BUF->ackno[0];
      }
    }
  }
 
  /* Swap交换 port numbers. */
  tmp16 = BUF->srcport;
  BUF->srcport = BUF->destport;
  BUF->destport = tmp16;
  
  /* Swap交换 IP addresses. */
  tmp16 = BUF->destipaddr[0];
  BUF->destipaddr[0] = BUF->srcipaddr[0];
  BUF->srcipaddr[0] = tmp16;
  tmp16 = BUF->destipaddr[1];
  BUF->destipaddr[1] = BUF->srcipaddr[1];
  BUF->srcipaddr[1] = tmp16;

  
  /* And send out the RST packet! */
  goto tcp_send_noconn;

  /* This label will be jumped to if we matched the incoming packet
     with a connection in LISTEN. In that case, we should create a new
     connection and send a SYNACK in return. */
 found_listen:					//通过端口建立连接
  /* First we check if there are any connections avaliable. Unused
     connections are kept in the same table as used connections, but
     unused ones have the tcpstate set to CLOSED. Also, connections in
     TIME_WAIT are kept track of and we'll use the oldest one if no
     CLOSED connections are found. Thanks to Eddie C. Dost for a very
     nice algorithm for the TIME_WAIT search. */
  
	 uip_connr = -1;    							// 8051 xdata starts at 0x0000
  for(c = 0; c < UIP_CONNS; ++c) {
    if(uip_conns[c].tcpstateflags == CLOSED) {
      uip_connr = &uip_conns[c];
      break;
  			  }
    if(uip_conns[c].tcpstateflags == TIME_WAIT) {
      if(uip_connr == 0 ||
	 uip_conns[c].timer > uip_connr->timer) {
	uip_connr = &uip_conns[c];	break;			//改加了个break
      }
    }
  }

  if(uip_connr == -1) {  				// 8051 xdata starts at 0x0000
    /* All connections are used already, we drop packet and hope that
       the remote end will retransmit the packet at a time when we
       have more spare connections. */
    UIP_STAT(++uip_stat.tcp.syndrop);
    UIP_LOG("tcp: found no unused connections.");
    goto drop;
  }
  uip_conn = uip_connr; 

  /* Fill in the necessary fields for the new connection. */
  	//在此建立了新的连接，主要是有先建立的端口 
  uip_connr->rto = uip_connr->timer = UIP_RTO;
  uip_connr->sa = 0;
  uip_connr->sv = 4;  
  uip_connr->nrtx = 0;
  uip_connr->lport = BUF->destport;
  uip_connr->rport = BUF->srcport;
  uip_connr->ripaddr[0] = BUF->srcipaddr[0];
  uip_connr->ripaddr[1] = BUF->srcipaddr[1];

  uip_connr->tcpstateflags = SYN_RCVD;

  uip_connr->snd_nxt[0] = iss[0];
  uip_connr->snd_nxt[1] = iss[1];
  uip_connr->snd_nxt[2] = iss[2];
  uip_connr->snd_nxt[3] = iss[3];
  uip_connr->len = 1;

  /* rcv_nxt should be the seqno from the incoming packet + 1. */
  uip_connr->rcv_nxt[3] = BUF->seqno[3];
  uip_connr->rcv_nxt[2] = BUF->seqno[2];
  uip_connr->rcv_nxt[1] = BUF->seqno[1];
  uip_connr->rcv_nxt[0] = BUF->seqno[0];
 
  uip_add_rcv_nxt(1);							//在上面的函数中可知

  /* Parse the TCP MSS option, if present. */
  if((BUF->tcpoffset & 0xf0) > 0x50) {					//对偏移量的处理
    for(c = 0; c < ((BUF->tcpoffset >> 4) - 5) << 2 ;) {
      opt = uip_buf[UIP_TCPIP_HLEN + 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. */	
	tmp16 = ((u16_t)uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 2 + c] << 8) |
	  (u16_t)uip_buf[40 + UIP_LLH_LEN + 3 + c];
		
	  uip_connr->initialmss = uip_connr->mss =
	  tmp16 > UIP_TCP_MSS? UIP_TCP_MSS: tmp16;
	
	/* 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	畸形
	     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:								//发送SYNACK包					
  BUF->flags = TCP_SYN | TCP_ACK;		  		//0x12  
#endif /* UIP_ACTIVE_OPEN */
  
  /* We send out the TCP Maximum Segment Size option with our
     SYNACK. *///将TCP最大段的大小选项作为我们的回应信号
  BUF->optdata[0] = 2;
  BUF->optdata[1] = 4;
  BUF->optdata[2] = (UIP_TCP_MSS) / 256;
  BUF->optdata[3] = (UIP_TCP_MSS) & 255;
  uip_len = 40;
  BUF->tcpoffset = 5 << 4;				//正确,24
  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;				//除去报头的具体数据的长度

  /* 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);
													//无数据ACK包在这里丢失？
    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_connr->rto - 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 retransmission timer. */
      uip_connr->timer = uip_connr->rto;
     }
    
   }

  /* Do different things depending on in what state the connection is. */
  switch(uip_connr->tcpstateflags & TS_MASK) { 							//掩盖上面的4位
    /* 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