<commit_before>/*
 * Copyright (c) 2001-2003, <NAME>.
 * 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. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 uIP TCP/IP stack.
 *
 *
 */

/**
 * \file
 * The uIP TCP/IP stack code.
 * \author <NAME> <<EMAIL>>
 */

/**
 * \addtogroup uip
 * @{
 */

#define DEBUG_PRINTF(...) /*printf(__VA_ARGS__)*/

/*
 * uIP is a small implementation of the IP, UDP and TCP protocols (as
 * well as some basic ICMP stuff). The implementation couples the IP,
 * UDP, TCP and the application layers very tightly. To keep the size
 * of the compiled code down, this code frequently uses the goto
 * statement. While it would be possible to break the uip_process()
 * function into many smaller functions, this would increase the code
 * size because of the overhead of parameter passing and the fact that
 * the optimier would not be as efficient.
 *
 * The principle is that we have a small buffer, called the uip_buf,
 * in which the device driver puts an incoming packet. The TCP/IP
 * stack parses the headers in the packet, and calls the
 * application. If the remote host has sent data to the application,
 * this data is present in the uip_buf and the application read the
 * data from there. It is up to the application to put this data into
 * a byte stream if needed. The application will not be fed with data
 * that is out of sequence.
 *
 * If the application whishes to send data to the peer, it should put
 * its data into the uip_buf. The uip_appdata pointer points to the
 * first available byte. The TCP/IP stack will calculate the
 * checksums, and fill in the necessary header fields and finally send
 * the packet back to the peer.
*/

#include "net/ip/uip.h"
#include "net/ip/uipopt.h"
#include "net/ipv4/uip_arp.h"
#include "net/ip/uip_arch.h"

#if !NETSTACK_CONF_WITH_IPV6 /* If NETSTACK_CONF_WITH_IPV6 is defined, we compile the
		      uip6.c file instead of this one. Therefore
		      this #ifndef removes the entire compilation
		      output of the uip.c file */


#if NETSTACK_CONF_WITH_IPV6
#include "net/ipv4/uip-neighbor.h"
#endif /* NETSTACK_CONF_WITH_IPV6 */

#include <string.h>

/*---------------------------------------------------------------------------*/
/* Variable definitions. */


/* The IP address of this host. If it is defined to be fixed (by
   setting UIP_FIXEDADDR to 1 in uipopt.h), the address is set
   here. Otherwise, the address */
#if UIP_FIXEDADDR > 0
const uip_ipaddr_t uip_hostaddr =
  { UIP_IPADDR0, UIP_IPADDR1, UIP_IPADDR2, UIP_IPADDR3 };
const uip_ipaddr_t uip_draddr =
  { UIP_DRIPADDR0, UIP_DRIPADDR1, UIP_DRIPADDR2, UIP_DRIPADDR3 };
const uip_ipaddr_t uip_netmask =
  { UIP_NETMASK0, UIP_NETMASK1, UIP_NETMASK2, UIP_NETMASK3 };
#else
uip_ipaddr_t uip_hostaddr, uip_draddr, uip_netmask;
#endif /* UIP_FIXEDADDR */

const uip_ipaddr_t uip_broadcast_addr =
#if NETSTACK_CONF_WITH_IPV6
  { { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } };
#else /* NETSTACK_CONF_WITH_IPV6 */
  { { 0xff, 0xff, 0xff, 0xff } };
#endif /* NETSTACK_CONF_WITH_IPV6 */
const uip_ipaddr_t uip_all_zeroes_addr = { { 0x0, /* rest is 0 */ } };

#if UIP_FIXEDETHADDR
const uip_lladdr_t uip_lladdr = {{UIP_ETHADDR0,
					  UIP_ETHADDR1,
					  UIP_ETHADDR2,
					  UIP_ETHADDR3,
					  UIP_ETHADDR4,
					  UIP_ETHADDR5}};
#else
uip_lladdr_t uip_lladdr = {{0,0,0,0,0,0}};
#endif

/* The packet buffer that contains incoming packets. */
uip_buf_t uip_aligned_buf;

void *uip_appdata;               /* The uip_appdata pointer points to
				    application data. */
void *uip_sappdata;              /* The uip_appdata pointer points to
				    the application data which is to
				    be sent. */
#if UIP_URGDATA > 0
void *uip_urgdata;               /* The uip_urgdata pointer points to
   				    urgent data (out-of-band data), if
   				    present. */
uint16_t uip_urglen, uip_surglen;
#endif /* UIP_URGDATA > 0 */

uint16_t uip_len, uip_slen;
                             /* The uip_len is either 8 or 16 bits,
				depending on the maximum packet
				size. */

uint8_t uip_flags;     /* The uip_flags variable is used for
				communication between the TCP/IP stack
				and the application program. */
struct uip_conn *uip_conn;   /* uip_conn always points to the current
				connection. */

struct uip_conn uip_conns[UIP_CONNS];
                             /* The uip_conns array holds all TCP
				connections. */
uint16_t uip_listenports[UIP_LISTENPORTS];
                             /* The uip_listenports list all currently
				listning ports. */
#if UIP_UDP
struct uip_udp_conn *uip_udp_conn;
struct uip_udp_conn uip_udp_conns[UIP_UDP_CONNS];
#endif /* UIP_UDP */

static uint16_t ipid;           /* Ths ipid variable is an increasing
				number that is used for the IP ID
				field. */

void uip_setipid(uint16_t id) { ipid = id; }

static uint8_t iss[4];          /* The iss variable is used for the TCP
				initial sequence number. */

#if UIP_ACTIVE_OPEN || UIP_UDP
static uint16_t lastport;       /* Keeps track of the last port used for
				a new connection. */
#endif /* UIP_ACTIVE_OPEN || UIP_UDP */

/* Temporary variables. */
uint8_t uip_acc32[4];
static uint8_t c, opt;
static uint16_t tmp16;

/* Structures and definitions. */
#define TCP_FIN 0x01
#define TCP_SYN 0x02
#define TCP_RST 0x04
#define TCP_PSH 0x08
#define TCP_ACK 0x10
#define TCP_URG 0x20
#define TCP_CTL 0x3f

#define TCP_OPT_END     0   /* End of TCP options list */
#define TCP_OPT_NOOP    1   /* "No-operation" TCP option */
#define TCP_OPT_MSS     2   /* Maximum segment size TCP option */

#define TCP_OPT_MSS_LEN 4   /* Length of TCP MSS option. */

#define ICMP_ECHO_REPLY 0
#define ICMP_ECHO       8

#define ICMP_DEST_UNREACHABLE        3
#define ICMP_PORT_UNREACHABLE        3

#define ICMP6_ECHO_REPLY             129
#define ICMP6_ECHO                   128
#define ICMP6_NEIGHBOR_SOLICITATION  135
#define ICMP6_NEIGHBOR_ADVERTISEMENT 136

#define ICMP6_FLAG_S (1 << 6)

#define ICMP6_OPTION_SOURCE_LINK_ADDRESS 1
#define ICMP6_OPTION_TARGET_LINK_ADDRESS 2


/* Macros. */
#define BUF ((struct uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
#define FBUF ((struct uip_tcpip_hdr *)&uip_reassbuf[0])
#define ICMPBUF ((struct uip_icmpip_hdr *)&uip_buf[UIP_LLH_LEN])
#define UDPBUF ((struct uip_udpip_hdr *)&uip_buf[UIP_LLH_LEN])


#if UIP_STATISTICS == 1
struct uip_stats uip_stat;
#define UIP_STAT(s) s
#else
#define UIP_STAT(s)
#endif /* UIP_STATISTICS == 1 */

#if UIP_LOGGING == 1
#include <stdio.h>
void uip_log(char *msg);
#define UIP_LOG(m) uip_log(m)
#else
#define UIP_LOG(m)
#endif /* UIP_LOGGING == 1 */

#if ! UIP_ARCH_ADD32
void
uip_add32(uint8_t *op32, uint16_t op16)
{
  uip_acc32[3] = op32[3] + (op16 & 0xff);
  uip_acc32[2] = op32[2] + (op16 >> 8);
  uip_acc32[1] = op32[1];
  uip_acc32[0] = op32[0];

  if(uip_acc32[2] < (op16 >> 8)) {
    ++uip_acc32[1];
    if(uip_acc32[1] == 0) {
      ++uip_acc32[0];
    }
  }


  if(uip_acc32[3] < (op16 & 0xff)) {
    ++uip_acc32[2];
    if(uip_acc32[2] == 0) {
      ++uip_acc32[1];
      if(uip_acc32[1] == 0) {
	++uip_acc32[0];
      }
    }
  }
}

#endif /* UIP_ARCH_ADD32 */

#if ! UIP_ARCH_CHKSUM
/*---------------------------------------------------------------------------*/
static uint16_t
chksum(uint16_t sum, const uint8_t *data, uint16_t len)
{
  uint16_t t;
  const uint8_t *dataptr;
  const uint8_t *last_byte;

  dataptr = data;
  last_byte = data + len - 1;

  while(dataptr < last_byte) {	/* At least two more bytes */
    t = (dataptr[0] << 8) + dataptr[1];
    sum += t;
    if(sum < t) {
      sum++;		/* carry */
    }
    dataptr += 2;
  }

  if(dataptr == last_byte) {
    t = (dataptr[0] << 8) + 0;
    sum += t;
    if(sum < t) {
      sum++;		/* carry */
    }
  }

  /* Return sum in host byte order. */
  return sum;
}
/*---------------------------------------------------------------------------*/
uint16_t
uip_chksum(uint16_t *data, uint16_t len)
{
  return uip_htons(chksum(0, (uint8_t *)data, len));
}
/*---------------------------------------------------------------------------*/
#ifndef UIP_ARCH_IPCHKSUM
uint16_t
uip_ipchksum(void)
{
  uint16_t sum;

  sum = chksum(0, &uip_buf[UIP_LLH_LEN], UIP_IPH_LEN);
  DEBUG_PRINTF("uip_ipchksum: sum 0x%04x\n", sum);
  return (sum == 0) ? 0xffff : uip_htons(sum);
}
#endif
/*---------------------------------------------------------------------------*/
static uint16_t
upper_layer_chksum(uint8_t proto)
{
  uint16_t upper_layer_len;
  uint16_t sum;

#if NETSTACK_CONF_WITH_IPV6
  upper_layer_len = (((uint16_t)(BUF->len[0]) << 8) + BUF->len[1]);
#else /* NETSTACK_CONF_WITH_IPV6 */
  upper_layer_len = (((uint16_t)(BUF->len[0]) << 8) + BUF->len[1]) - UIP_IPH_LEN;
#endif /* NETSTACK_CONF_WITH_IPV6 */

  /* First sum pseudoheader. */

  /* IP protocol and length fields. This addition cannot carry. */
  sum = upper_layer_len + proto;
  /* Sum IP source and destination addresses. */
  sum = chksum(sum, (uint8_t *)&BUF->srcipaddr, 2 * sizeof(uip_ipaddr_t));

  /* Sum TCP header and data. */
  sum = chksum(sum, &uip_buf[UIP_IPH_LEN + UIP_LLH_LEN],
	       upper_layer_len);

  return (sum == 0) ? 0xffff : uip_htons(sum);
}
/*---------------------------------------------------------------------------*/
#if NETSTACK_CONF_WITH_IPV6
uint16_t
uip_icmp6chksum(void)
{
  return upper_layer_chksum(UIP_PROTO_ICMP6);

}
#endif /* NETSTACK_CONF_WITH_IPV6 */
/*---------------------------------------------------------------------------*/
uint16_t
uip_tcpchksum(void)
{
  return upper_layer_chksum(UIP_PROTO_TCP);
}
/*---------------------------------------------------------------------------*/
#if UIP_UDP_CHECKSUMS
uint16_t
uip_udpchksum(void)
{
  return upper_layer_chksum(UIP_PROTO_UDP);
}
#endif /* UIP_UDP_CHECKSUMS */
#endif /* UIP_ARCH_CHKSUM */
/*---------------------------------------------------------------------------*/
void
uip_init(void)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    uip_listenports[c] = 0;
  }
  for(c = 0; c < UIP_CONNS; ++c) {
    uip_conns[c].tcpstateflags = UIP_CLOSED;
  }
#if UIP_ACTIVE_OPEN || UIP_UDP
  lastport = 1024;
#endif /* UIP_ACTIVE_OPEN || UIP_UDP */

#if UIP_UDP
  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    uip_udp_conns[c].lport = 0;
  }
#endif /* UIP_UDP */


  /* IPv4 initialization. */
#if UIP_FIXEDADDR == 0
  /*  uip_hostaddr[0] = uip_hostaddr[1] = 0;*/
#endif /* UIP_FIXEDADDR */

}
/*---------------------------------------------------------------------------*/
#if UIP_ACTIVE_OPEN
struct uip_conn *
uip_connect(uip_ipaddr_t *ripaddr, uint16_t rport)
{
  register struct uip_conn *conn, *cconn;

  /* Find an unused local port. */
 again:
  ++lastport;

  if(lastport >= 32000) {
    lastport = 4096;
  }

  /* Check if this port is already in use, and if so try to find
     another one. */
  for(c = 0; c < UIP_CONNS; ++c) {
    conn = &uip_conns[c];
    if(conn->tcpstateflags != UIP_CLOSED &&
       conn->lport == uip_htons(lastport)) {
      goto again;
    }
  }

  conn = 0;
  for(c = 0; c < UIP_CONNS; ++c) {
    cconn = &uip_conns[c];
    if(cconn->tcpstateflags == UIP_CLOSED) {
      conn = cconn;
      break;
    }
    if(cconn->tcpstateflags == UIP_TIME_WAIT) {
      if(conn == 0 ||
	 cconn->timer > conn->timer) {
	conn = cconn;
      }
    }
  }

  if(conn == 0) {
    return 0;
  }

  conn->tcpstateflags = UIP_SYN_SENT;

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

  conn->initialmss = conn->mss = UIP_TCP_MSS;

  conn->len = 1;   /* TCP length of the SYN is one. */
  conn->nrtx = 0;
  conn->timer = 1; /* Send the SYN next time around. */
  conn->rto = UIP_RTO;
  conn->sa = 0;
  conn->sv = 16;   /* Initial value of the RTT variance. */
  conn->lport = uip_htons(lastport);
  conn->rport = rport;
  uip_ipaddr_copy(&conn->ripaddr, ripaddr);

  return conn;
}
#endif /* UIP_ACTIVE_OPEN */
/*---------------------------------------------------------------------------*/
#if UIP_UDP
struct uip_udp_conn *
uip_udp_new(const uip_ipaddr_t *ripaddr, uint16_t rport)
{
  register struct uip_udp_conn *conn;

  /* Find an unused local port. */
 again:
  ++lastport;

  if(lastport >= 32000) {
    lastport = 4096;
  }

  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    if(uip_udp_conns[c].lport == uip_htons(lastport)) {
      goto again;
    }
  }


  conn = 0;
  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    if(uip_udp_conns[c].lport == 0) {
      conn = &uip_udp_conns[c];
      break;
    }
  }

  if(conn == 0) {
    return 0;
  }

  conn->lport = UIP_HTONS(lastport);
  conn->rport = rport;
  if(ripaddr == NULL) {
    memset(&conn->ripaddr, 0, sizeof(uip_ipaddr_t));
  } else {
    uip_ipaddr_copy(&conn->ripaddr, ripaddr);
  }
  conn->ttl = UIP_TTL;

  return conn;
}
#endif /* UIP_UDP */
/*---------------------------------------------------------------------------*/
void
uip_unlisten(uint16_t port)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    if(uip_listenports[c] == port) {
      uip_listenports[c] = 0;
      return;
    }
  }
}
/*---------------------------------------------------------------------------*/
void
uip_listen(uint16_t port)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    if(uip_listenports[c] == 0) {
      uip_listenports[c] = port;
      return;
    }
  }
}
/*---------------------------------------------------------------------------*/
/* XXX: IP fragment reassembly: not well-tested. */

#if UIP_REASSEMBLY && !NETSTACK_CONF_WITH_IPV6
#define UIP_REASS_BUFSIZE (UIP_BUFSIZE - UIP_LLH_LEN)
static uint8_t uip_reassbuf[UIP_REASS_BUFSIZE];
static uint8_t uip_reassbitmap[UIP_REASS_BUFSIZE / (8 * 8)];
static const uint8_t bitmap_bits[8] = {0xff, 0x7f, 0x3f, 0x1f,
				    0x0f, 0x07, 0x03, 0x01};
static uint16_t uip_reasslen;
static uint8_t uip_reassflags;
#define UIP_REASS_FLAG_LASTFRAG 0x01
static uint8_t uip_reasstmr;

#define IP_MF   0x20

static uint8_t
uip_reass(void)
{
  uint16_t offset, len;
  uint16_t i;

  /* If ip_reasstmr is zero, no packet is present in the buffer, so we
     write the IP header of the fragment into the reassembly
     buffer. The timer is updated with the maximum age. */
  if(uip_reasstmr == 0) {
    memcpy(uip_reassbuf, &BUF->vhl, UIP_IPH_LEN);
    uip_reasstmr = UIP_REASS_MAXAGE;
    uip_reassflags = 0;
    /* Clear the bitmap. */
    memset(uip_reassbitmap, 0, sizeof(uip_reassbitmap));
  }

  /* Check if the incoming fragment matches the one currently present
     in the reasembly buffer. If so, we proceed with copying the
     fragment into the buffer. */
  if(BUF->srcipaddr[0] == FBUF->srcipaddr[0] &&
     BUF->srcipaddr[1] == FBUF->srcipaddr[1] &&
     BUF->destipaddr[0] == FBUF->destipaddr[0] &&
     BUF->destipaddr[1] == FBUF->destipaddr[1] &&
     BUF->ipid[0] == FBUF->ipid[0] &&
     BUF->ipid[1] == FBUF->ipid[1]) {

    len = (BUF->len[0] << 8) + BUF->len[1] - (BUF->vhl & 0x0f) * 4;
    offset = (((BUF->ipoffset[0] & 0x3f) << 8) + BUF->ipoffset[1]) * 8;

    /* If the offset or the offset + fragment length overflows the
       reassembly buffer, we discard the entire packet. */
    if(offset > UIP_REASS_BUFSIZE ||
       offset + len > UIP_REASS_BUFSIZE) {
      uip_reasstmr = 0;
      goto nullreturn;
    }

    /* Copy the fragment into the reassembly buffer, at the right
       offset. */
    memcpy(&uip_reassbuf[UIP_IPH_LEN + offset],
	   (char *)BUF + (int)((BUF->vhl & 0x0f) * 4),
	   len);

    /* Update the bitmap. */
    if(offset / (8 * 8) == (offset + len) / (8 * 8)) {
      /* If the two endpoints are in the same byte, we only update
	 that byte. */

      uip_reassbitmap[offset / (8 * 8)] |=
	     bitmap_bits[(offset / 8 ) & 7] &
	     ~bitmap_bits[((offset + len) / 8 ) & 7];
    } else {
      /* If the two endpoints are in different bytes, we update the
	 bytes in the endpoints and fill the stuff inbetween with
	 0xff. */
      uip_reassbitmap[offset / (8 * 8)] |=
	bitmap_bits[(offset / 8 ) & 7];
      for(i = 1 + offset / (8 * 8); i < (offset + len) / (8 * 8); ++i) {
	uip_reassbitmap[i] = 0xff;
      }
      uip_reassbitmap[(offset + len) / (8 * 8)] |=
	~bitmap_bits[((offset + len) / 8 ) & 7];
    }

    /* If this fragment has the More Fragments flag set to zero, we
       know that this is the last fragment, so we can calculate the
       size of the entire packet. We also set the
       IP_REASS_FLAG_LASTFRAG flag to indicate that we have received
       the final fragment. */

    if((BUF->ipoffset[0] & IP_MF) == 0) {
      uip_reassflags |= UIP_REASS_FLAG_LASTFRAG;
      uip_reasslen = offset + len;
    }

    /* Finally, we check if we have a full packet in the buffer. We do
       this by checking if we have the last fragment and if all bits
       in the bitmap are set. */
    if(uip_reassflags & UIP_REASS_FLAG_LASTFRAG) {
      /* Check all bytes up to and including all but the last byte in
	 the bitmap. */
      for(i = 0; i < uip_reasslen / (8 * 8) - 1; ++i) {
	if(uip_reassbitmap[i] != 0xff) {
	  goto nullreturn;
	}
      }
      /* Check the last byte in the bitmap. It should contain just the
	 right amount of bits. */
      if(uip_reassbitmap[uip_reasslen / (8 * 8)] !=
	 (uint8_t)~bitmap_bits[uip_reasslen / 8 & 7]) {
	goto nullreturn;
      }

      /* If we have come this far, we have a full packet in the
	 buffer, so we allocate a pbuf and copy the packet into it. We
	 also reset the timer. */
      uip_reasstmr = 0;
      memcpy(BUF, FBUF, uip_reasslen);

      /* Pretend to be a "normal" (i.e., not fragmented) IP packet
	 from now on. */
      BUF->ipoffset[0] = BUF->ipoffset[1] = 0;
      BUF->len[0] = uip_reasslen >> 8;
      BUF->len[1] = uip_reasslen & 0xff;
      BUF->ipchksum = 0;
      BUF->ipchksum = ~(uip_ipchksum());

      return uip_reasslen;
    }
  }

 nullreturn:
  return 0;
}
#endif /* UIP_REASSEMBLY */
/*---------------------------------------------------------------------------*/
static void
uip_add_rcv_nxt(uint16_t n)
{
  uip_add32(uip_conn->rcv_nxt, n);
  uip_conn->rcv_nxt[0] = uip_acc32[0];
  uip_conn->rcv_nxt[1] = uip_acc32[1];
  uip_conn->rcv_nxt[2] = uip_acc32[2];
  uip_conn->rcv_nxt[3] = uip_acc32[3];
}
/*---------------------------------------------------------------------------*/
void
uip_process(uint8_t flag)
{
  register struct uip_conn *uip_connr = uip_conn;

#if UIP_UDP
  if(flag == UIP_UDP_SEND_CONN) {
    goto udp_send;
  }
#endif /* UIP_UDP */

  uip_sappdata = uip_appdata = &uip_buf[UIP_IPTCPH_LEN + UIP_LLH_LEN];

  /* Check if we were invoked because of a poll request for a
     particular connection. */
  if(flag == UIP_POLL_REQUEST) {
    if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_ESTABLISHED &&
       !uip_outstanding(uip_connr)) {
	uip_flags = UIP_POLL;
	UIP_APPCALL();
	goto appsend;
#if UIP_ACTIVE_OPEN && UIP_TCP
    } else if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_SYN_SENT) {
      /* In the SYN_SENT state, we retransmit out SYN. */
      BUF->flags = 0;
      goto tcp_send_syn;
#endif /* UIP_ACTIVE_OPEN */
    }
    goto drop;

    /* Check if we were invoked because of the perodic timer fireing. */
  } else if(flag == UIP_TIMER) {
#if UIP_REASSEMBLY
    if(uip_reasstmr != 0) {
      --uip_reasstmr;
    }
#endif /* UIP_REASSEMBLY */
    /* Increase the initial sequence number. */
    if(++iss[3] == 0) {
      if(++iss[2] == 0) {
	if(++iss[1] == 0) {
	  ++iss[0];
	}
      }
    }

    /* Reset the length variables. */
    uip_len = 0;
    uip_slen = 0;

#if UIP_TCP
    /* Check if the connection is in a state in which we simply wait
       for the connection to time out. If so, we increase the
       connection's timer and remove the connection if it times
       out. */
    if(uip_connr->tcpstateflags == UIP_TIME_WAIT ||
       uip_connr->tcpstateflags == UIP_FIN_WAIT_2) {
      ++(uip_connr->timer);
      if(uip_connr->timer == UIP_TIME_WAIT_TIMEOUT) {
	uip_connr->tcpstateflags = UIP_CLOSED;
      }
    } else if(uip_connr->tcpstateflags != UIP_CLOSED) {
      /* If the connection has outstanding data, we increase the
	 connection's timer and see if it has reached the RTO value
	 in which case we retransmit. */

      if(uip_outstanding(uip_connr)) {
	if(uip_connr->timer-- == 0) {
	  if(uip_connr->nrtx == UIP_MAXRTX ||
	     ((uip_connr->tcpstateflags == UIP_SYN_SENT ||
	       uip_connr->tcpstateflags == UIP_SYN_RCVD) &&
	      uip_connr->nrtx == UIP_MAXSYNRTX)) {
	    uip_connr->tcpstateflags = UIP_CLOSED;

	    /* We call UIP_APPCALL() with uip_flags set to
	       UIP_TIMEDOUT to inform the application that the
	       connection has timed out. */
	    uip_flags = UIP_TIMEDOUT;
	    UIP_APPCALL();

	    /* We also send a reset packet to the remote host. */
	    BUF->flags = TCP_RST | TCP_ACK;
	    goto tcp_send_nodata;
	  }

	  /* Exponential backoff. */
	  uip_connr->timer = UIP_RTO << (uip_connr->nrtx > 4?
					 4:
					 uip_connr->nrtx);
	  ++(uip_connr->nrtx);

	  /* Ok, so we need to retransmit. We do this differently
	     depending on which state we are in. In ESTABLISHED, we
	     call upon the application so that it may prepare the
	     data for the retransmit. In SYN_RCVD, we resend the
	     SYNACK that we sent earlier and in LAST_ACK we have to
	     retransmit our FINACK. */
	  UIP_STAT(++uip_stat.tcp.rexmit);
	  switch(uip_connr->tcpstateflags & UIP_TS_MASK) {
	  case UIP_SYN_RCVD:
	    /* In the SYN_RCVD state, we should retransmit our
               SYNACK. */
	    goto tcp_send_synack;

#if UIP_ACTIVE_OPEN
	  case UIP_SYN_SENT:
	    /* In the SYN_SENT state, we retransmit out SYN. */
	    BUF->flags = 0;
	    goto tcp_send_syn;
#endif /* UIP_ACTIVE_OPEN */

	  case UIP_ESTABLISHED:
	    /* In the ESTABLISHED state, we call upon the application
               to do the actual retransmit after which we jump into
               the code for sending out the packet (the apprexmit
               label). */
	    uip_flags = UIP_REXMIT;
	    UIP_APPCALL();
	    goto apprexmit;

	  case UIP_FIN_WAIT_1:
	  case UIP_CLOSING:
	  case UIP_LAST_ACK:
	    /* In all these states we should retransmit a FINACK. */
	    goto tcp_send_finack;

	  }
	}
      } else if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_ESTABLISHED) {
	/* If there was no need for a retransmission, we poll the
           application for new data. */
	uip_flags = UIP_POLL;
	UIP_APPCALL();
	goto appsend;
      }
    }
#endif
    goto drop;
  }
#if UIP_UDP
  if(flag == UIP_UDP_TIMER) {
    if(uip_udp_conn->lport != 0) {
      uip_conn = NULL;
      uip_sappdata = uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
      uip_len = uip_slen = 0;
      uip_flags = UIP_POLL;
      UIP_UDP_APPCALL();
      goto udp_send;
    } else {
      goto drop;
    }
  }
#endif

  /* This is where the input processing starts. */
  UIP_STAT(++uip_stat.ip.recv);

  /* Start of IP input header processing code. */

#if NETSTACK_CONF_WITH_IPV6
  /* Check validity of the IP header. */
  if((BUF->vtc & 0xf0) != 0x60)  { /* IP version and header length. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.vhlerr);
    UIP_LOG("ipv6: invalid version.");
    goto drop;
  }
#else /* NETSTACK_CONF_WITH_IPV6 */
  /* Check validity of the IP header. */
  if(BUF->vhl != 0x45)  { /* IP version and header length. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.vhlerr);
    UIP_LOG("ip: invalid version or header length.");
    goto drop;
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

  /* Check the size of the packet. If the size reported to us in
     uip_len is smaller the size reported in the IP header, we assume
     that the packet has been corrupted in transit. If the size of
     uip_len is larger than the size reported in the IP packet header,
     the packet has been padded and we set uip_len to the correct
     value.. */

  if((BUF->len[0] << 8) + BUF->len[1] <= uip_len) {
    uip_len = (BUF->len[0] << 8) + BUF->len[1];
#if NETSTACK_CONF_WITH_IPV6
    uip_len += 40; /* The length reported in the IPv6 header is the
		      length of the payload that follows the
		      header. However, uIP uses the uip_len variable
		      for holding the size of the entire packet,
		      including the IP header. For IPv4 this is not a
		      problem as the length field in the IPv4 header
		      contains the length of the entire packet. But
		      for IPv6 we need to add the size of the IPv6
		      header (40 bytes). */
#endif /* NETSTACK_CONF_WITH_IPV6 */
  } else {
    UIP_LOG("ip: packet shorter than reported in IP header.");
    goto drop;
  }

#if !NETSTACK_CONF_WITH_IPV6
  /* Check the fragment flag. */
  if((BUF->ipoffset[0] & 0x3f) != 0 ||
     BUF->ipoffset[1] != 0) {
#if UIP_REASSEMBLY
    uip_len = uip_reass();
    if(uip_len == 0) {
      goto drop;
    }
#else /* UIP_REASSEMBLY */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.fragerr);
    UIP_LOG("ip: fragment dropped.");
    goto drop;
#endif /* UIP_REASSEMBLY */
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

  if(uip_ipaddr_cmp(&uip_hostaddr, &uip_all_zeroes_addr)) {
    /* 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 && !NETSTACK_CONF_WITH_IPV6
    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 */

  } else {
    /* If IP broadcast support is configured, we check for a broadcast
       UDP packet, which may be destined to us. */
#if UIP_BROADCAST
    DEBUG_PRINTF("UDP IP checksum 0x%04x\n", uip_ipchksum());
    if(BUF->proto == UIP_PROTO_UDP &&
       (uip_ipaddr_cmp(&BUF->destipaddr, &uip_broadcast_addr) ||
	(BUF->destipaddr.u8[0] & 224) == 224)) {  /* XXX this is a
						     hack to be able
						     to receive UDP
						     multicast
						     packets. We check
						     for the bit
						     pattern of the
						     multicast
						     prefix. */
      goto udp_input;
    }
#endif /* UIP_BROADCAST */

    /* Check if the packet is destined for our IP address. */
#if !NETSTACK_CONF_WITH_IPV6
    if(!uip_ipaddr_cmp(&BUF->destipaddr, &uip_hostaddr)) {
      UIP_STAT(++uip_stat.ip.drop);
      goto drop;
    }
#else /* NETSTACK_CONF_WITH_IPV6 */
    /* For IPv6, packet reception is a little trickier as we need to
       make sure that we listen to certain multicast addresses (all
       hosts multicast address, and the solicited-node multicast
       address) as well. However, we will cheat here and accept all
       multicast packets that are sent to the ff02::/16 addresses. */
    if(!uip_ipaddr_cmp(&BUF->destipaddr, &uip_hostaddr) &&
       BUF->destipaddr.u16[0] != UIP_HTONS(0xff02)) {
      UIP_STAT(++uip_stat.ip.drop);
      goto drop;
    }
#endif /* NETSTACK_CONF_WITH_IPV6 */
  }

#if !NETSTACK_CONF_WITH_IPV6
  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;
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

#if UIP_TCP
  if(BUF->proto == UIP_PROTO_TCP) { /* Check for TCP packet. If so,
				       proceed with TCP input
				       processing. */
    goto tcp_input;
  }
#endif

#if UIP_UDP
  if(BUF->proto == UIP_PROTO_UDP) {
    goto udp_input;
  }
#endif /* UIP_UDP */

#if !NETSTACK_CONF_WITH_IPV6
  /* ICMPv4 processing code follows. */
  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) {
    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_ipaddr_cmp(&uip_hostaddr, &uip_all_zeroes_addr)) {
    uip_hostaddr = BUF->destipaddr;
  }
#endif /* UIP_PINGADDRCONF */

  ICMPBUF->type = ICMP_ECHO_REPLY;

  if(ICMPBUF->icmpchksum >= UIP_HTONS(0xffff - (ICMP_ECHO << 8))) {
    ICMPBUF->icmpchksum += UIP_HTONS(ICMP_ECHO << 8) + 1;
  } else {
    ICMPBUF->icmpchksum += UIP_HTONS(ICMP_ECHO << 8);
  }

  /* Swap IP addresses. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  UIP_STAT(++uip_stat.icmp.sent);
  BUF->ttl = UIP_TTL;
  goto ip_send_nolen;

  /* End of IPv4 input header processing code. */
#else /* !NETSTACK_CONF_WITH_IPV6 */

  /* This is IPv6 ICMPv6 processing code. */
  DEBUG_PRINTF("icmp6_input: length %d\n", uip_len);

  if(BUF->proto != UIP_PROTO_ICMP6) { /* We only allow ICMPv6 packets from
					 here. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.protoerr);
    UIP_LOG("ip: neither tcp nor icmp6.");
    goto drop;
  }

  UIP_STAT(++uip_stat.icmp.recv);

  /* If we get a neighbor solicitation for our address we should send
     a neighbor advertisement message back. */
  if(ICMPBUF->type == ICMP6_NEIGHBOR_SOLICITATION) {
    if(uip_ipaddr_cmp(&ICMPBUF->icmp6data, &uip_hostaddr)) {

      if(ICMPBUF->options[0] == ICMP6_OPTION_SOURCE_LINK_ADDRESS) {
	/* Save the sender's address in our neighbor list. */
	uip_neighbor_add(&ICMPBUF->srcipaddr, &(ICMPBUF->options[2]));
      }

      /* We should now send a neighbor advertisement back to where the
	 neighbor solicication came from. */
      ICMPBUF->type = ICMP6_NEIGHBOR_ADVERTISEMENT;
      ICMPBUF->flags = ICMP6_FLAG_S; /* Solicited flag. */

      ICMPBUF->reserved1 = ICMPBUF->reserved2 = ICMPBUF->reserved3 = 0;

      uip_ipaddr_copy(&ICMPBUF->destipaddr, &ICMPBUF->srcipaddr);
      uip_ipaddr_copy(&ICMPBUF->srcipaddr, &uip_hostaddr);
      ICMPBUF->options[0] = ICMP6_OPTION_TARGET_LINK_ADDRESS;
      ICMPBUF->options[1] = 1;  /* Options length, 1 = 8 bytes. */
      memcpy(&(ICMPBUF->options[2]), &uip_lladdr, sizeof(uip_lladdr));
      ICMPBUF->icmpchksum = 0;
      ICMPBUF->icmpchksum = ~uip_icmp6chksum();

      goto send;

    }
    goto drop;
  } else if(ICMPBUF->type == ICMP6_ECHO) {
    /* ICMP echo (i.e., ping) processing. This is simple, we only
       change the ICMP type from ECHO to ECHO_REPLY and update the
       ICMP checksum before we return the packet. */

    ICMPBUF->type = ICMP6_ECHO_REPLY;

    uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
    uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);
    ICMPBUF->icmpchksum = 0;
    ICMPBUF->icmpchksum = ~uip_icmp6chksum();

    UIP_STAT(++uip_stat.icmp.sent);
    goto send;
  } else {
    DEBUG_PRINTF("Unknown icmp6 message type %d\n", ICMPBUF->type);
    UIP_STAT(++uip_stat.icmp.drop);
    UIP_STAT(++uip_stat.icmp.typeerr);
    UIP_LOG("icmp: unknown ICMP message.");
    goto drop;
  }

  /* End of IPv6 ICMP processing. */

#endif /* !NETSTACK_CONF_WITH_IPV6 */

#if UIP_UDP
  /* UDP input processing. */
 udp_input:
  /* UDP processing is really just a hack. We don't do anything to the
     UDP/IP headers, but let the UDP application do all the hard
     work. If the application sets uip_slen, it has a packet to
     send. */
#if UIP_UDP_CHECKSUMS
  uip_len = uip_len - UIP_IPUDPH_LEN;
  uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
  if(UDPBUF->udpchksum != 0 && uip_udpchksum() != 0xffff) {
    UIP_STAT(++uip_stat.udp.drop);
    UIP_STAT(++uip_stat.udp.chkerr);
    UIP_LOG("udp: bad checksum.");
    goto drop;
  }
#else /* UIP_UDP_CHECKSUMS */
  uip_len = uip_len - UIP_IPUDPH_LEN;
#endif /* UIP_UDP_CHECKSUMS */

  /* Make sure that the UDP destination port number is not zero. */
  if(UDPBUF->destport == 0) {
    UIP_LOG("udp: zero port.");
    goto drop;
  }

  /* Demultiplex this UDP packet between the UDP "connections". */
  for(uip_udp_conn = &uip_udp_conns[0];
      uip_udp_conn < &uip_udp_conns[UIP_UDP_CONNS];
      ++uip_udp_conn) {
    /* If the local UDP port is non-zero, the connection is considered
       to be used. If so, the local port number is checked against the
       destination port number in the received packet. If the two port
       numbers match, the remote port number is checked if the
       connection is bound to a remote port. Finally, if the
       connection is bound to a remote IP address, the source IP
       address of the packet is checked. */
    if(uip_udp_conn->lport != 0 &&
       UDPBUF->destport == uip_udp_conn->lport &&
       (uip_udp_conn->rport == 0 ||
        UDPBUF->srcport == uip_udp_conn->rport) &&
       (uip_ipaddr_cmp(&uip_udp_conn->ripaddr, &uip_all_zeroes_addr) ||
	uip_ipaddr_cmp(&uip_udp_conn->ripaddr, &uip_broadcast_addr) ||
	uip_ipaddr_cmp(&BUF->srcipaddr, &uip_udp_conn->ripaddr))) {
      goto udp_found;
    }
  }
  UIP_LOG("udp: no matching connection found");
  UIP_STAT(++uip_stat.udp.drop);
#if UIP_CONF_ICMP_DEST_UNREACH && !NETSTACK_CONF_WITH_IPV6
  /* Copy fields from packet header into payload of this ICMP packet. */
  memcpy(&(ICMPBUF->payload[0]), ICMPBUF, UIP_IPH_LEN + 8);

  /* Set the ICMP type and code. */
  ICMPBUF->type = ICMP_DEST_UNREACHABLE;
  ICMPBUF->icode = ICMP_PORT_UNREACHABLE;

  /* Calculate the ICMP checksum. */
  ICMPBUF->icmpchksum = 0;
  ICMPBUF->icmpchksum = ~uip_chksum((uint16_t *)&(ICMPBUF->type), 36);

  /* Set the IP destination address to be the source address of the
     original packet. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);

  /* Set our IP address as the source address. */
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  /* The size of the ICMP destination unreachable packet is 36 + the
     size of the IP header (20) = 56. */
  uip_len = 36 + UIP_IPH_LEN;
  ICMPBUF->len[0] = 0;
  ICMPBUF->len[1] = (uint8_t)uip_len;
  ICMPBUF->ttl = UIP_TTL;
  ICMPBUF->proto = UIP_PROTO_ICMP;

  goto ip_send_nolen;
#else /* UIP_CONF_ICMP_DEST_UNREACH */
  goto drop;
#endif /* UIP_CONF_ICMP_DEST_UNREACH */

 udp_found:
  UIP_STAT(++uip_stat.udp.recv);
  uip_conn = NULL;
  uip_flags = UIP_NEWDATA;
  uip_sappdata = uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
  uip_slen = 0;
  UIP_UDP_APPCALL();

 udp_send:
  if(uip_slen == 0) {
    goto drop;
  }
  uip_len = uip_slen + UIP_IPUDPH_LEN;

#if NETSTACK_CONF_WITH_IPV6
  /* For IPv6, the IP length field does not include the IPv6 IP header
     length. */
  BUF->len[0] = ((uip_len - UIP_IPH_LEN) >> 8);
  BUF->len[1] = ((uip_len - UIP_IPH_LEN) & 0xff);
#else /* NETSTACK_CONF_WITH_IPV6 */
  BUF->len[0] = (uip_len >> 8);
  BUF->len[1] = (uip_len & 0xff);
#endif /* NETSTACK_CONF_WITH_IPV6 */

  BUF->ttl = uip_udp_conn->ttl;
  BUF->proto = UIP_PROTO_UDP;

  UDPBUF->udplen = UIP_HTONS(uip_slen + UIP_UDPH_LEN);
  UDPBUF->udpchksum = 0;

  BUF->srcport  = uip_udp_conn->lport;
  BUF->destport = uip_udp_conn->rport;

  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);
  uip_ipaddr_copy(&BUF->destipaddr, &uip_udp_conn->ripaddr);

  uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPTCPH_LEN];

#if UIP_UDP_CHECKSUMS
  /* Calculate UDP checksum. */
  UDPBUF->udpchksum = ~(uip_udpchksum());
  if(UDPBUF->udpchksum == 0) {
    UDPBUF->udpchksum = 0xffff;
  }
#endif /* UIP_UDP_CHECKSUMS */

  UIP_STAT(++uip_stat.udp.sent);
  goto ip_send_nolen;
#endif /* UIP_UDP */

  /* TCP input processing. */
#if UIP_TCP
 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;
  }

  /* Make sure that the TCP port number is not zero. */
  if(BUF->destport == 0 || BUF->srcport == 0) {
    UIP_LOG("tcp: zero port.");
    goto drop;
  }

  /* Demultiplex this segment. */
  /* First check any active connections. */
  for(uip_connr = &uip_conns[0]; uip_connr <= &uip_conns[UIP_CONNS - 1];
      ++uip_connr) {
    if(uip_connr->tcpstateflags != UIP_CLOSED &&
       BUF->destport == uip_connr->lport &&
       BUF->srcport == uip_connr->rport &&
       uip_ipaddr_cmp(&BUF->srcipaddr, &uip_connr->ripaddr)) {
      goto found;
    }
  }

  /* If we didn't find and active connection that expected the packet,
     either this packet is an old duplicate, 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:
  /* We do not send resets in response to resets. */
  if(BUF->flags & TCP_RST) {
    goto drop;
  }

  UIP_STAT(++uip_stat.tcp.rst);

  BUF->flags = TCP_RST | TCP_ACK;
  uip_len = UIP_IPTCPH_LEN;
  BUF->tcpoffset = 5 << 4;

  /* Flip 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 port numbers. */
  tmp16 = BUF->srcport;
  BUF->srcport = BUF->destport;
  BUF->destport = tmp16;

  /* Swap IP addresses. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  /* 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:
  /* 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 <NAME> for a very
     nice algorithm for the TIME_WAIT search. */
  uip_connr = 0;
  for(c = 0; c < UIP_CONNS; ++c) {
    if(uip_conns[c].tcpstateflags == UIP_CLOSED) {
      uip_connr = &uip_conns[c];
      break;
    }
    if(uip_conns[c].tcpstateflags == UIP_TIME_WAIT) {
      if(uip_connr == 0 ||
	 uip_conns[c].timer > uip_connr->timer) {
	uip_connr = &uip_conns[c];
      }
    }
  }

  if(uip_connr == 0) {
    /* 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. */
  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_ipaddr_copy(&uip_connr->ripaddr, &BUF->srcipaddr);
  uip_connr->tcpstateflags = UIP_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);

  /* Parse the TCP MSS option, if present. */
  if((BUF->tcpoffset & 0xf0) > 0x50) {
    for(c = 0; c < ((BUF->tcpoffset >> 4) - 5) << 2 ;) {
      opt = uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + c];
      if(opt == TCP_OPT_END) {
	/* End of options. */
	break;
      } else if(opt == TCP_OPT_NOOP) {
	++c;
	/* NOP option. */
      } else if(opt == TCP_OPT_MSS &&
		uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c] == TCP_OPT_MSS_LEN) {
	/* An MSS option with the right option length. */
	tmp16 = ((uint16_t)uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 2 + c] << 8) |
	  (uint16_t)uip_buf[UIP_IPTCPH_LEN + 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
	     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] = TCP_OPT_MSS;
  BUF->optdata[1] = TCP_OPT_MSS_LEN;
  BUF->optdata[2] = (UIP_TCP_MSS) / 256;
  BUF->optdata[3] = (UIP_TCP_MSS) & 255;
  uip_len = UIP_IPTCPH_LEN + TCP_OPT_MSS_LEN;
  BUF->tcpoffset = ((UIP_TCPH_LEN + TCP_OPT_MSS_LEN) / 4) << 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 = UIP_CLOSED;
    UIP_LOG("tcp: got reset, aborting connection.");
    uip_flags = UIP_ABORT;
    UIP_APPCALL();
    goto drop;<commit_msg>Minor typo fixes in comments only<commit_after>/*
 * Copyright (c) 2001-2003, <NAME>.
 * 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. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 uIP TCP/IP stack.
 *
 *
 */

/**
 * \file
 * The uIP TCP/IP stack code.
 * \author <NAME> <<EMAIL>>
 */

/**
 * \addtogroup uip
 * @{
 */

#define DEBUG_PRINTF(...) /*printf(__VA_ARGS__)*/

/*
 * uIP is a small implementation of the IP, UDP and TCP protocols (as
 * well as some basic ICMP stuff). The implementation couples the IP,
 * UDP, TCP and the application layers very tightly. To keep the size
 * of the compiled code down, this code frequently uses the goto
 * statement. While it would be possible to break the uip_process()
 * function into many smaller functions, this would increase the code
 * size because of the overhead of parameter passing and the fact that
 * the optimier would not be as efficient.
 *
 * The principle is that we have a small buffer, called the uip_buf,
 * in which the device driver puts an incoming packet. The TCP/IP
 * stack parses the headers in the packet, and calls the
 * application. If the remote host has sent data to the application,
 * this data is present in the uip_buf and the application read the
 * data from there. It is up to the application to put this data into
 * a byte stream if needed. The application will not be fed with data
 * that is out of sequence.
 *
 * If the application whishes to send data to the peer, it should put
 * its data into the uip_buf. The uip_appdata pointer points to the
 * first available byte. The TCP/IP stack will calculate the
 * checksums, and fill in the necessary header fields and finally send
 * the packet back to the peer.
*/

#include "net/ip/uip.h"
#include "net/ip/uipopt.h"
#include "net/ipv4/uip_arp.h"
#include "net/ip/uip_arch.h"

#if !NETSTACK_CONF_WITH_IPV6 /* If NETSTACK_CONF_WITH_IPV6 is defined, we compile the
		      uip6.c file instead of this one. Therefore
		      this #ifndef removes the entire compilation
		      output of the uip.c file */


#if NETSTACK_CONF_WITH_IPV6
#include "net/ipv4/uip-neighbor.h"
#endif /* NETSTACK_CONF_WITH_IPV6 */

#include <string.h>

/*---------------------------------------------------------------------------*/
/* Variable definitions. */


/* The IP address of this host. If it is defined to be fixed (by
   setting UIP_FIXEDADDR to 1 in uipopt.h), the address is set
   here. Otherwise, the address */
#if UIP_FIXEDADDR > 0
const uip_ipaddr_t uip_hostaddr =
  { UIP_IPADDR0, UIP_IPADDR1, UIP_IPADDR2, UIP_IPADDR3 };
const uip_ipaddr_t uip_draddr =
  { UIP_DRIPADDR0, UIP_DRIPADDR1, UIP_DRIPADDR2, UIP_DRIPADDR3 };
const uip_ipaddr_t uip_netmask =
  { UIP_NETMASK0, UIP_NETMASK1, UIP_NETMASK2, UIP_NETMASK3 };
#else
uip_ipaddr_t uip_hostaddr, uip_draddr, uip_netmask;
#endif /* UIP_FIXEDADDR */

const uip_ipaddr_t uip_broadcast_addr =
#if NETSTACK_CONF_WITH_IPV6
  { { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } };
#else /* NETSTACK_CONF_WITH_IPV6 */
  { { 0xff, 0xff, 0xff, 0xff } };
#endif /* NETSTACK_CONF_WITH_IPV6 */
const uip_ipaddr_t uip_all_zeroes_addr = { { 0x0, /* rest is 0 */ } };

#if UIP_FIXEDETHADDR
const uip_lladdr_t uip_lladdr = {{UIP_ETHADDR0,
					  UIP_ETHADDR1,
					  UIP_ETHADDR2,
					  UIP_ETHADDR3,
					  UIP_ETHADDR4,
					  UIP_ETHADDR5}};
#else
uip_lladdr_t uip_lladdr = {{0,0,0,0,0,0}};
#endif

/* The packet buffer that contains incoming packets. */
uip_buf_t uip_aligned_buf;

void *uip_appdata;               /* The uip_appdata pointer points to
				    application data. */
void *uip_sappdata;              /* The uip_appdata pointer points to
				    the application data which is to
				    be sent. */
#if UIP_URGDATA > 0
void *uip_urgdata;               /* The uip_urgdata pointer points to
   				    urgent data (out-of-band data), if
   				    present. */
uint16_t uip_urglen, uip_surglen;
#endif /* UIP_URGDATA > 0 */

uint16_t uip_len, uip_slen;
                             /* The uip_len is either 8 or 16 bits,
				depending on the maximum packet
				size. */

uint8_t uip_flags;     /* The uip_flags variable is used for
				communication between the TCP/IP stack
				and the application program. */
struct uip_conn *uip_conn;   /* uip_conn always points to the current
				connection. */

struct uip_conn uip_conns[UIP_CONNS];
                             /* The uip_conns array holds all TCP
				connections. */
uint16_t uip_listenports[UIP_LISTENPORTS];
                             /* The uip_listenports list all currently
				listning ports. */
#if UIP_UDP
struct uip_udp_conn *uip_udp_conn;
struct uip_udp_conn uip_udp_conns[UIP_UDP_CONNS];
#endif /* UIP_UDP */

static uint16_t ipid;           /* Ths ipid variable is an increasing
				number that is used for the IP ID
				field. */

void uip_setipid(uint16_t id) { ipid = id; }

static uint8_t iss[4];          /* The iss variable is used for the TCP
				initial sequence number. */

#if UIP_ACTIVE_OPEN || UIP_UDP
static uint16_t lastport;       /* Keeps track of the last port used for
				a new connection. */
#endif /* UIP_ACTIVE_OPEN || UIP_UDP */

/* Temporary variables. */
uint8_t uip_acc32[4];
static uint8_t c, opt;
static uint16_t tmp16;

/* Structures and definitions. */
#define TCP_FIN 0x01
#define TCP_SYN 0x02
#define TCP_RST 0x04
#define TCP_PSH 0x08
#define TCP_ACK 0x10
#define TCP_URG 0x20
#define TCP_CTL 0x3f

#define TCP_OPT_END     0   /* End of TCP options list */
#define TCP_OPT_NOOP    1   /* "No-operation" TCP option */
#define TCP_OPT_MSS     2   /* Maximum segment size TCP option */

#define TCP_OPT_MSS_LEN 4   /* Length of TCP MSS option. */

#define ICMP_ECHO_REPLY 0
#define ICMP_ECHO       8

#define ICMP_DEST_UNREACHABLE        3
#define ICMP_PORT_UNREACHABLE        3

#define ICMP6_ECHO_REPLY             129
#define ICMP6_ECHO                   128
#define ICMP6_NEIGHBOR_SOLICITATION  135
#define ICMP6_NEIGHBOR_ADVERTISEMENT 136

#define ICMP6_FLAG_S (1 << 6)

#define ICMP6_OPTION_SOURCE_LINK_ADDRESS 1
#define ICMP6_OPTION_TARGET_LINK_ADDRESS 2


/* Macros. */
#define BUF ((struct uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
#define FBUF ((struct uip_tcpip_hdr *)&uip_reassbuf[0])
#define ICMPBUF ((struct uip_icmpip_hdr *)&uip_buf[UIP_LLH_LEN])
#define UDPBUF ((struct uip_udpip_hdr *)&uip_buf[UIP_LLH_LEN])


#if UIP_STATISTICS == 1
struct uip_stats uip_stat;
#define UIP_STAT(s) s
#else
#define UIP_STAT(s)
#endif /* UIP_STATISTICS == 1 */

#if UIP_LOGGING == 1
#include <stdio.h>
void uip_log(char *msg);
#define UIP_LOG(m) uip_log(m)
#else
#define UIP_LOG(m)
#endif /* UIP_LOGGING == 1 */

#if ! UIP_ARCH_ADD32
void
uip_add32(uint8_t *op32, uint16_t op16)
{
  uip_acc32[3] = op32[3] + (op16 & 0xff);
  uip_acc32[2] = op32[2] + (op16 >> 8);
  uip_acc32[1] = op32[1];
  uip_acc32[0] = op32[0];

  if(uip_acc32[2] < (op16 >> 8)) {
    ++uip_acc32[1];
    if(uip_acc32[1] == 0) {
      ++uip_acc32[0];
    }
  }


  if(uip_acc32[3] < (op16 & 0xff)) {
    ++uip_acc32[2];
    if(uip_acc32[2] == 0) {
      ++uip_acc32[1];
      if(uip_acc32[1] == 0) {
	++uip_acc32[0];
      }
    }
  }
}

#endif /* UIP_ARCH_ADD32 */

#if ! UIP_ARCH_CHKSUM
/*---------------------------------------------------------------------------*/
static uint16_t
chksum(uint16_t sum, const uint8_t *data, uint16_t len)
{
  uint16_t t;
  const uint8_t *dataptr;
  const uint8_t *last_byte;

  dataptr = data;
  last_byte = data + len - 1;

  while(dataptr < last_byte) {	/* At least two more bytes */
    t = (dataptr[0] << 8) + dataptr[1];
    sum += t;
    if(sum < t) {
      sum++;		/* carry */
    }
    dataptr += 2;
  }

  if(dataptr == last_byte) {
    t = (dataptr[0] << 8) + 0;
    sum += t;
    if(sum < t) {
      sum++;		/* carry */
    }
  }

  /* Return sum in host byte order. */
  return sum;
}
/*---------------------------------------------------------------------------*/
uint16_t
uip_chksum(uint16_t *data, uint16_t len)
{
  return uip_htons(chksum(0, (uint8_t *)data, len));
}
/*---------------------------------------------------------------------------*/
#ifndef UIP_ARCH_IPCHKSUM
uint16_t
uip_ipchksum(void)
{
  uint16_t sum;

  sum = chksum(0, &uip_buf[UIP_LLH_LEN], UIP_IPH_LEN);
  DEBUG_PRINTF("uip_ipchksum: sum 0x%04x\n", sum);
  return (sum == 0) ? 0xffff : uip_htons(sum);
}
#endif
/*---------------------------------------------------------------------------*/
static uint16_t
upper_layer_chksum(uint8_t proto)
{
  uint16_t upper_layer_len;
  uint16_t sum;

#if NETSTACK_CONF_WITH_IPV6
  upper_layer_len = (((uint16_t)(BUF->len[0]) << 8) + BUF->len[1]);
#else /* NETSTACK_CONF_WITH_IPV6 */
  upper_layer_len = (((uint16_t)(BUF->len[0]) << 8) + BUF->len[1]) - UIP_IPH_LEN;
#endif /* NETSTACK_CONF_WITH_IPV6 */

  /* First sum pseudoheader. */

  /* IP protocol and length fields. This addition cannot carry. */
  sum = upper_layer_len + proto;
  /* Sum IP source and destination addresses. */
  sum = chksum(sum, (uint8_t *)&BUF->srcipaddr, 2 * sizeof(uip_ipaddr_t));

  /* Sum TCP header and data. */
  sum = chksum(sum, &uip_buf[UIP_IPH_LEN + UIP_LLH_LEN],
	       upper_layer_len);

  return (sum == 0) ? 0xffff : uip_htons(sum);
}
/*---------------------------------------------------------------------------*/
#if NETSTACK_CONF_WITH_IPV6
uint16_t
uip_icmp6chksum(void)
{
  return upper_layer_chksum(UIP_PROTO_ICMP6);

}
#endif /* NETSTACK_CONF_WITH_IPV6 */
/*---------------------------------------------------------------------------*/
uint16_t
uip_tcpchksum(void)
{
  return upper_layer_chksum(UIP_PROTO_TCP);
}
/*---------------------------------------------------------------------------*/
#if UIP_UDP_CHECKSUMS
uint16_t
uip_udpchksum(void)
{
  return upper_layer_chksum(UIP_PROTO_UDP);
}
#endif /* UIP_UDP_CHECKSUMS */
#endif /* UIP_ARCH_CHKSUM */
/*---------------------------------------------------------------------------*/
void
uip_init(void)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    uip_listenports[c] = 0;
  }
  for(c = 0; c < UIP_CONNS; ++c) {
    uip_conns[c].tcpstateflags = UIP_CLOSED;
  }
#if UIP_ACTIVE_OPEN || UIP_UDP
  lastport = 1024;
#endif /* UIP_ACTIVE_OPEN || UIP_UDP */

#if UIP_UDP
  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    uip_udp_conns[c].lport = 0;
  }
#endif /* UIP_UDP */


  /* IPv4 initialization. */
#if UIP_FIXEDADDR == 0
  /*  uip_hostaddr[0] = uip_hostaddr[1] = 0;*/
#endif /* UIP_FIXEDADDR */

}
/*---------------------------------------------------------------------------*/
#if UIP_ACTIVE_OPEN
struct uip_conn *
uip_connect(uip_ipaddr_t *ripaddr, uint16_t rport)
{
  register struct uip_conn *conn, *cconn;

  /* Find an unused local port. */
 again:
  ++lastport;

  if(lastport >= 32000) {
    lastport = 4096;
  }

  /* Check if this port is already in use, and if so try to find
     another one. */
  for(c = 0; c < UIP_CONNS; ++c) {
    conn = &uip_conns[c];
    if(conn->tcpstateflags != UIP_CLOSED &&
       conn->lport == uip_htons(lastport)) {
      goto again;
    }
  }

  conn = 0;
  for(c = 0; c < UIP_CONNS; ++c) {
    cconn = &uip_conns[c];
    if(cconn->tcpstateflags == UIP_CLOSED) {
      conn = cconn;
      break;
    }
    if(cconn->tcpstateflags == UIP_TIME_WAIT) {
      if(conn == 0 ||
	 cconn->timer > conn->timer) {
	conn = cconn;
      }
    }
  }

  if(conn == 0) {
    return 0;
  }

  conn->tcpstateflags = UIP_SYN_SENT;

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

  conn->initialmss = conn->mss = UIP_TCP_MSS;

  conn->len = 1;   /* TCP length of the SYN is one. */
  conn->nrtx = 0;
  conn->timer = 1; /* Send the SYN next time around. */
  conn->rto = UIP_RTO;
  conn->sa = 0;
  conn->sv = 16;   /* Initial value of the RTT variance. */
  conn->lport = uip_htons(lastport);
  conn->rport = rport;
  uip_ipaddr_copy(&conn->ripaddr, ripaddr);

  return conn;
}
#endif /* UIP_ACTIVE_OPEN */
/*---------------------------------------------------------------------------*/
#if UIP_UDP
struct uip_udp_conn *
uip_udp_new(const uip_ipaddr_t *ripaddr, uint16_t rport)
{
  register struct uip_udp_conn *conn;

  /* Find an unused local port. */
 again:
  ++lastport;

  if(lastport >= 32000) {
    lastport = 4096;
  }

  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    if(uip_udp_conns[c].lport == uip_htons(lastport)) {
      goto again;
    }
  }


  conn = 0;
  for(c = 0; c < UIP_UDP_CONNS; ++c) {
    if(uip_udp_conns[c].lport == 0) {
      conn = &uip_udp_conns[c];
      break;
    }
  }

  if(conn == 0) {
    return 0;
  }

  conn->lport = UIP_HTONS(lastport);
  conn->rport = rport;
  if(ripaddr == NULL) {
    memset(&conn->ripaddr, 0, sizeof(uip_ipaddr_t));
  } else {
    uip_ipaddr_copy(&conn->ripaddr, ripaddr);
  }
  conn->ttl = UIP_TTL;

  return conn;
}
#endif /* UIP_UDP */
/*---------------------------------------------------------------------------*/
void
uip_unlisten(uint16_t port)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    if(uip_listenports[c] == port) {
      uip_listenports[c] = 0;
      return;
    }
  }
}
/*---------------------------------------------------------------------------*/
void
uip_listen(uint16_t port)
{
  for(c = 0; c < UIP_LISTENPORTS; ++c) {
    if(uip_listenports[c] == 0) {
      uip_listenports[c] = port;
      return;
    }
  }
}
/*---------------------------------------------------------------------------*/
/* XXX: IP fragment reassembly: not well-tested. */

#if UIP_REASSEMBLY && !NETSTACK_CONF_WITH_IPV6
#define UIP_REASS_BUFSIZE (UIP_BUFSIZE - UIP_LLH_LEN)
static uint8_t uip_reassbuf[UIP_REASS_BUFSIZE];
static uint8_t uip_reassbitmap[UIP_REASS_BUFSIZE / (8 * 8)];
static const uint8_t bitmap_bits[8] = {0xff, 0x7f, 0x3f, 0x1f,
				    0x0f, 0x07, 0x03, 0x01};
static uint16_t uip_reasslen;
static uint8_t uip_reassflags;
#define UIP_REASS_FLAG_LASTFRAG 0x01
static uint8_t uip_reasstmr;

#define IP_MF   0x20

static uint8_t
uip_reass(void)
{
  uint16_t offset, len;
  uint16_t i;

  /* If ip_reasstmr is zero, no packet is present in the buffer, so we
     write the IP header of the fragment into the reassembly
     buffer. The timer is updated with the maximum age. */
  if(uip_reasstmr == 0) {
    memcpy(uip_reassbuf, &BUF->vhl, UIP_IPH_LEN);
    uip_reasstmr = UIP_REASS_MAXAGE;
    uip_reassflags = 0;
    /* Clear the bitmap. */
    memset(uip_reassbitmap, 0, sizeof(uip_reassbitmap));
  }

  /* Check if the incoming fragment matches the one currently present
     in the reasembly buffer. If so, we proceed with copying the
     fragment into the buffer. */
  if(BUF->srcipaddr[0] == FBUF->srcipaddr[0] &&
     BUF->srcipaddr[1] == FBUF->srcipaddr[1] &&
     BUF->destipaddr[0] == FBUF->destipaddr[0] &&
     BUF->destipaddr[1] == FBUF->destipaddr[1] &&
     BUF->ipid[0] == FBUF->ipid[0] &&
     BUF->ipid[1] == FBUF->ipid[1]) {

    len = (BUF->len[0] << 8) + BUF->len[1] - (BUF->vhl & 0x0f) * 4;
    offset = (((BUF->ipoffset[0] & 0x3f) << 8) + BUF->ipoffset[1]) * 8;

    /* If the offset or the offset + fragment length overflows the
       reassembly buffer, we discard the entire packet. */
    if(offset > UIP_REASS_BUFSIZE ||
       offset + len > UIP_REASS_BUFSIZE) {
      uip_reasstmr = 0;
      goto nullreturn;
    }

    /* Copy the fragment into the reassembly buffer, at the right
       offset. */
    memcpy(&uip_reassbuf[UIP_IPH_LEN + offset],
	   (char *)BUF + (int)((BUF->vhl & 0x0f) * 4),
	   len);

    /* Update the bitmap. */
    if(offset / (8 * 8) == (offset + len) / (8 * 8)) {
      /* If the two endpoints are in the same byte, we only update
	 that byte. */

      uip_reassbitmap[offset / (8 * 8)] |=
	     bitmap_bits[(offset / 8 ) & 7] &
	     ~bitmap_bits[((offset + len) / 8 ) & 7];
    } else {
      /* If the two endpoints are in different bytes, we update the
	 bytes in the endpoints and fill the stuff inbetween with
	 0xff. */
      uip_reassbitmap[offset / (8 * 8)] |=
	bitmap_bits[(offset / 8 ) & 7];
      for(i = 1 + offset / (8 * 8); i < (offset + len) / (8 * 8); ++i) {
	uip_reassbitmap[i] = 0xff;
      }
      uip_reassbitmap[(offset + len) / (8 * 8)] |=
	~bitmap_bits[((offset + len) / 8 ) & 7];
    }

    /* If this fragment has the More Fragments flag set to zero, we
       know that this is the last fragment, so we can calculate the
       size of the entire packet. We also set the
       IP_REASS_FLAG_LASTFRAG flag to indicate that we have received
       the final fragment. */

    if((BUF->ipoffset[0] & IP_MF) == 0) {
      uip_reassflags |= UIP_REASS_FLAG_LASTFRAG;
      uip_reasslen = offset + len;
    }

    /* Finally, we check if we have a full packet in the buffer. We do
       this by checking if we have the last fragment and if all bits
       in the bitmap are set. */
    if(uip_reassflags & UIP_REASS_FLAG_LASTFRAG) {
      /* Check all bytes up to and including all but the last byte in
	 the bitmap. */
      for(i = 0; i < uip_reasslen / (8 * 8) - 1; ++i) {
	if(uip_reassbitmap[i] != 0xff) {
	  goto nullreturn;
	}
      }
      /* Check the last byte in the bitmap. It should contain just the
	 right amount of bits. */
      if(uip_reassbitmap[uip_reasslen / (8 * 8)] !=
	 (uint8_t)~bitmap_bits[uip_reasslen / 8 & 7]) {
	goto nullreturn;
      }

      /* If we have come this far, we have a full packet in the
	 buffer, so we allocate a pbuf and copy the packet into it. We
	 also reset the timer. */
      uip_reasstmr = 0;
      memcpy(BUF, FBUF, uip_reasslen);

      /* Pretend to be a "normal" (i.e., not fragmented) IP packet
	 from now on. */
      BUF->ipoffset[0] = BUF->ipoffset[1] = 0;
      BUF->len[0] = uip_reasslen >> 8;
      BUF->len[1] = uip_reasslen & 0xff;
      BUF->ipchksum = 0;
      BUF->ipchksum = ~(uip_ipchksum());

      return uip_reasslen;
    }
  }

 nullreturn:
  return 0;
}
#endif /* UIP_REASSEMBLY */
/*---------------------------------------------------------------------------*/
static void
uip_add_rcv_nxt(uint16_t n)
{
  uip_add32(uip_conn->rcv_nxt, n);
  uip_conn->rcv_nxt[0] = uip_acc32[0];
  uip_conn->rcv_nxt[1] = uip_acc32[1];
  uip_conn->rcv_nxt[2] = uip_acc32[2];
  uip_conn->rcv_nxt[3] = uip_acc32[3];
}
/*---------------------------------------------------------------------------*/
void
uip_process(uint8_t flag)
{
  register struct uip_conn *uip_connr = uip_conn;

#if UIP_UDP
  if(flag == UIP_UDP_SEND_CONN) {
    goto udp_send;
  }
#endif /* UIP_UDP */

  uip_sappdata = uip_appdata = &uip_buf[UIP_IPTCPH_LEN + UIP_LLH_LEN];

  /* Check if we were invoked because of a poll request for a
     particular connection. */
  if(flag == UIP_POLL_REQUEST) {
    if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_ESTABLISHED &&
       !uip_outstanding(uip_connr)) {
	uip_flags = UIP_POLL;
	UIP_APPCALL();
	goto appsend;
#if UIP_ACTIVE_OPEN && UIP_TCP
    } else if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_SYN_SENT) {
      /* In the SYN_SENT state, we retransmit out SYN. */
      BUF->flags = 0;
      goto tcp_send_syn;
#endif /* UIP_ACTIVE_OPEN */
    }
    goto drop;

    /* Check if we were invoked because of the periodic timer firing. */
  } else if(flag == UIP_TIMER) {
#if UIP_REASSEMBLY
    if(uip_reasstmr != 0) {
      --uip_reasstmr;
    }
#endif /* UIP_REASSEMBLY */
    /* Increase the initial sequence number. */
    if(++iss[3] == 0) {
      if(++iss[2] == 0) {
	if(++iss[1] == 0) {
	  ++iss[0];
	}
      }
    }

    /* Reset the length variables. */
    uip_len = 0;
    uip_slen = 0;

#if UIP_TCP
    /* Check if the connection is in a state in which we simply wait
       for the connection to time out. If so, we increase the
       connection's timer and remove the connection if it times
       out. */
    if(uip_connr->tcpstateflags == UIP_TIME_WAIT ||
       uip_connr->tcpstateflags == UIP_FIN_WAIT_2) {
      ++(uip_connr->timer);
      if(uip_connr->timer == UIP_TIME_WAIT_TIMEOUT) {
	uip_connr->tcpstateflags = UIP_CLOSED;
      }
    } else if(uip_connr->tcpstateflags != UIP_CLOSED) {
      /* If the connection has outstanding data, we increase the
	 connection's timer and see if it has reached the RTO value
	 in which case we retransmit. */

      if(uip_outstanding(uip_connr)) {
	if(uip_connr->timer-- == 0) {
	  if(uip_connr->nrtx == UIP_MAXRTX ||
	     ((uip_connr->tcpstateflags == UIP_SYN_SENT ||
	       uip_connr->tcpstateflags == UIP_SYN_RCVD) &&
	      uip_connr->nrtx == UIP_MAXSYNRTX)) {
	    uip_connr->tcpstateflags = UIP_CLOSED;

	    /* We call UIP_APPCALL() with uip_flags set to
	       UIP_TIMEDOUT to inform the application that the
	       connection has timed out. */
	    uip_flags = UIP_TIMEDOUT;
	    UIP_APPCALL();

	    /* We also send a reset packet to the remote host. */
	    BUF->flags = TCP_RST | TCP_ACK;
	    goto tcp_send_nodata;
	  }

	  /* Exponential backoff. */
	  uip_connr->timer = UIP_RTO << (uip_connr->nrtx > 4?
					 4:
					 uip_connr->nrtx);
	  ++(uip_connr->nrtx);

	  /* Ok, so we need to retransmit. We do this differently
	     depending on which state we are in. In ESTABLISHED, we
	     call upon the application so that it may prepare the
	     data for the retransmit. In SYN_RCVD, we resend the
	     SYNACK that we sent earlier and in LAST_ACK we have to
	     retransmit our FINACK. */
	  UIP_STAT(++uip_stat.tcp.rexmit);
	  switch(uip_connr->tcpstateflags & UIP_TS_MASK) {
	  case UIP_SYN_RCVD:
	    /* In the SYN_RCVD state, we should retransmit our
               SYNACK. */
	    goto tcp_send_synack;

#if UIP_ACTIVE_OPEN
	  case UIP_SYN_SENT:
	    /* In the SYN_SENT state, we retransmit out SYN. */
	    BUF->flags = 0;
	    goto tcp_send_syn;
#endif /* UIP_ACTIVE_OPEN */

	  case UIP_ESTABLISHED:
	    /* In the ESTABLISHED state, we call upon the application
               to do the actual retransmit after which we jump into
               the code for sending out the packet (the apprexmit
               label). */
	    uip_flags = UIP_REXMIT;
	    UIP_APPCALL();
	    goto apprexmit;

	  case UIP_FIN_WAIT_1:
	  case UIP_CLOSING:
	  case UIP_LAST_ACK:
	    /* In all these states we should retransmit a FINACK. */
	    goto tcp_send_finack;

	  }
	}
      } else if((uip_connr->tcpstateflags & UIP_TS_MASK) == UIP_ESTABLISHED) {
	/* If there was no need for a retransmission, we poll the
           application for new data. */
	uip_flags = UIP_POLL;
	UIP_APPCALL();
	goto appsend;
      }
    }
#endif
    goto drop;
  }
#if UIP_UDP
  if(flag == UIP_UDP_TIMER) {
    if(uip_udp_conn->lport != 0) {
      uip_conn = NULL;
      uip_sappdata = uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
      uip_len = uip_slen = 0;
      uip_flags = UIP_POLL;
      UIP_UDP_APPCALL();
      goto udp_send;
    } else {
      goto drop;
    }
  }
#endif

  /* This is where the input processing starts. */
  UIP_STAT(++uip_stat.ip.recv);

  /* Start of IP input header processing code. */

#if NETSTACK_CONF_WITH_IPV6
  /* Check validity of the IP header. */
  if((BUF->vtc & 0xf0) != 0x60)  { /* IP version and header length. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.vhlerr);
    UIP_LOG("ipv6: invalid version.");
    goto drop;
  }
#else /* NETSTACK_CONF_WITH_IPV6 */
  /* Check validity of the IP header. */
  if(BUF->vhl != 0x45)  { /* IP version and header length. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.vhlerr);
    UIP_LOG("ip: invalid version or header length.");
    goto drop;
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

  /* Check the size of the packet. If the size reported to us in
     uip_len is smaller the size reported in the IP header, we assume
     that the packet has been corrupted in transit. If the size of
     uip_len is larger than the size reported in the IP packet header,
     the packet has been padded and we set uip_len to the correct
     value. */

  if((BUF->len[0] << 8) + BUF->len[1] <= uip_len) {
    uip_len = (BUF->len[0] << 8) + BUF->len[1];
#if NETSTACK_CONF_WITH_IPV6
    uip_len += 40; /* The length reported in the IPv6 header is the
		      length of the payload that follows the
		      header. However, uIP uses the uip_len variable
		      for holding the size of the entire packet,
		      including the IP header. For IPv4 this is not a
		      problem as the length field in the IPv4 header
		      contains the length of the entire packet. But
		      for IPv6 we need to add the size of the IPv6
		      header (40 bytes). */
#endif /* NETSTACK_CONF_WITH_IPV6 */
  } else {
    UIP_LOG("ip: packet shorter than reported in IP header.");
    goto drop;
  }

#if !NETSTACK_CONF_WITH_IPV6
  /* Check the fragment flag. */
  if((BUF->ipoffset[0] & 0x3f) != 0 ||
     BUF->ipoffset[1] != 0) {
#if UIP_REASSEMBLY
    uip_len = uip_reass();
    if(uip_len == 0) {
      goto drop;
    }
#else /* UIP_REASSEMBLY */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.fragerr);
    UIP_LOG("ip: fragment dropped.");
    goto drop;
#endif /* UIP_REASSEMBLY */
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

  if(uip_ipaddr_cmp(&uip_hostaddr, &uip_all_zeroes_addr)) {
    /* If we are configured to use ping IP address configuration and
       haven't been assigned an IP address yet, we accept all ICMP
       packets. */
#if UIP_PINGADDRCONF && !NETSTACK_CONF_WITH_IPV6
    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 */

  } else {
    /* If IP broadcast support is configured, we check for a broadcast
       UDP packet, which may be destined to us. */
#if UIP_BROADCAST
    DEBUG_PRINTF("UDP IP checksum 0x%04x\n", uip_ipchksum());
    if(BUF->proto == UIP_PROTO_UDP &&
       (uip_ipaddr_cmp(&BUF->destipaddr, &uip_broadcast_addr) ||
	(BUF->destipaddr.u8[0] & 224) == 224)) {  /* XXX this is a
						     hack to be able
						     to receive UDP
						     multicast
						     packets. We check
						     for the bit
						     pattern of the
						     multicast
						     prefix. */
      goto udp_input;
    }
#endif /* UIP_BROADCAST */

    /* Check if the packet is destined for our IP address. */
#if !NETSTACK_CONF_WITH_IPV6
    if(!uip_ipaddr_cmp(&BUF->destipaddr, &uip_hostaddr)) {
      UIP_STAT(++uip_stat.ip.drop);
      goto drop;
    }
#else /* NETSTACK_CONF_WITH_IPV6 */
    /* For IPv6, packet reception is a little trickier as we need to
       make sure that we listen to certain multicast addresses (all
       hosts multicast address, and the solicited-node multicast
       address) as well. However, we will cheat here and accept all
       multicast packets that are sent to the ff02::/16 addresses. */
    if(!uip_ipaddr_cmp(&BUF->destipaddr, &uip_hostaddr) &&
       BUF->destipaddr.u16[0] != UIP_HTONS(0xff02)) {
      UIP_STAT(++uip_stat.ip.drop);
      goto drop;
    }
#endif /* NETSTACK_CONF_WITH_IPV6 */
  }

#if !NETSTACK_CONF_WITH_IPV6
  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;
  }
#endif /* NETSTACK_CONF_WITH_IPV6 */

#if UIP_TCP
  if(BUF->proto == UIP_PROTO_TCP) { /* Check for TCP packet. If so,
				       proceed with TCP input
				       processing. */
    goto tcp_input;
  }
#endif

#if UIP_UDP
  if(BUF->proto == UIP_PROTO_UDP) {
    goto udp_input;
  }
#endif /* UIP_UDP */

#if !NETSTACK_CONF_WITH_IPV6
  /* ICMPv4 processing code follows. */
  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) {
    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_ipaddr_cmp(&uip_hostaddr, &uip_all_zeroes_addr)) {
    uip_hostaddr = BUF->destipaddr;
  }
#endif /* UIP_PINGADDRCONF */

  ICMPBUF->type = ICMP_ECHO_REPLY;

  if(ICMPBUF->icmpchksum >= UIP_HTONS(0xffff - (ICMP_ECHO << 8))) {
    ICMPBUF->icmpchksum += UIP_HTONS(ICMP_ECHO << 8) + 1;
  } else {
    ICMPBUF->icmpchksum += UIP_HTONS(ICMP_ECHO << 8);
  }

  /* Swap IP addresses. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  UIP_STAT(++uip_stat.icmp.sent);
  BUF->ttl = UIP_TTL;
  goto ip_send_nolen;

  /* End of IPv4 input header processing code. */
#else /* !NETSTACK_CONF_WITH_IPV6 */

  /* This is IPv6 ICMPv6 processing code. */
  DEBUG_PRINTF("icmp6_input: length %d\n", uip_len);

  if(BUF->proto != UIP_PROTO_ICMP6) { /* We only allow ICMPv6 packets from
					 here. */
    UIP_STAT(++uip_stat.ip.drop);
    UIP_STAT(++uip_stat.ip.protoerr);
    UIP_LOG("ip: neither tcp nor icmp6.");
    goto drop;
  }

  UIP_STAT(++uip_stat.icmp.recv);

  /* If we get a neighbor solicitation for our address we should send
     a neighbor advertisement message back. */
  if(ICMPBUF->type == ICMP6_NEIGHBOR_SOLICITATION) {
    if(uip_ipaddr_cmp(&ICMPBUF->icmp6data, &uip_hostaddr)) {

      if(ICMPBUF->options[0] == ICMP6_OPTION_SOURCE_LINK_ADDRESS) {
	/* Save the sender's address in our neighbor list. */
	uip_neighbor_add(&ICMPBUF->srcipaddr, &(ICMPBUF->options[2]));
      }

      /* We should now send a neighbor advertisement back to where the
	 neighbor solicication came from. */
      ICMPBUF->type = ICMP6_NEIGHBOR_ADVERTISEMENT;
      ICMPBUF->flags = ICMP6_FLAG_S; /* Solicited flag. */

      ICMPBUF->reserved1 = ICMPBUF->reserved2 = ICMPBUF->reserved3 = 0;

      uip_ipaddr_copy(&ICMPBUF->destipaddr, &ICMPBUF->srcipaddr);
      uip_ipaddr_copy(&ICMPBUF->srcipaddr, &uip_hostaddr);
      ICMPBUF->options[0] = ICMP6_OPTION_TARGET_LINK_ADDRESS;
      ICMPBUF->options[1] = 1;  /* Options length, 1 = 8 bytes. */
      memcpy(&(ICMPBUF->options[2]), &uip_lladdr, sizeof(uip_lladdr));
      ICMPBUF->icmpchksum = 0;
      ICMPBUF->icmpchksum = ~uip_icmp6chksum();

      goto send;

    }
    goto drop;
  } else if(ICMPBUF->type == ICMP6_ECHO) {
    /* ICMP echo (i.e., ping) processing. This is simple, we only
       change the ICMP type from ECHO to ECHO_REPLY and update the
       ICMP checksum before we return the packet. */

    ICMPBUF->type = ICMP6_ECHO_REPLY;

    uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
    uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);
    ICMPBUF->icmpchksum = 0;
    ICMPBUF->icmpchksum = ~uip_icmp6chksum();

    UIP_STAT(++uip_stat.icmp.sent);
    goto send;
  } else {
    DEBUG_PRINTF("Unknown icmp6 message type %d\n", ICMPBUF->type);
    UIP_STAT(++uip_stat.icmp.drop);
    UIP_STAT(++uip_stat.icmp.typeerr);
    UIP_LOG("icmp: unknown ICMP message.");
    goto drop;
  }

  /* End of IPv6 ICMP processing. */

#endif /* !NETSTACK_CONF_WITH_IPV6 */

#if UIP_UDP
  /* UDP input processing. */
 udp_input:
  /* UDP processing is really just a hack. We don't do anything to the
     UDP/IP headers, but let the UDP application do all the hard
     work. If the application sets uip_slen, it has a packet to
     send. */
#if UIP_UDP_CHECKSUMS
  uip_len = uip_len - UIP_IPUDPH_LEN;
  uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
  if(UDPBUF->udpchksum != 0 && uip_udpchksum() != 0xffff) {
    UIP_STAT(++uip_stat.udp.drop);
    UIP_STAT(++uip_stat.udp.chkerr);
    UIP_LOG("udp: bad checksum.");
    goto drop;
  }
#else /* UIP_UDP_CHECKSUMS */
  uip_len = uip_len - UIP_IPUDPH_LEN;
#endif /* UIP_UDP_CHECKSUMS */

  /* Make sure that the UDP destination port number is not zero. */
  if(UDPBUF->destport == 0) {
    UIP_LOG("udp: zero port.");
    goto drop;
  }

  /* Demultiplex this UDP packet between the UDP "connections". */
  for(uip_udp_conn = &uip_udp_conns[0];
      uip_udp_conn < &uip_udp_conns[UIP_UDP_CONNS];
      ++uip_udp_conn) {
    /* If the local UDP port is non-zero, the connection is considered
       to be used. If so, the local port number is checked against the
       destination port number in the received packet. If the two port
       numbers match, the remote port number is checked if the
       connection is bound to a remote port. Finally, if the
       connection is bound to a remote IP address, the source IP
       address of the packet is checked. */
    if(uip_udp_conn->lport != 0 &&
       UDPBUF->destport == uip_udp_conn->lport &&
       (uip_udp_conn->rport == 0 ||
        UDPBUF->srcport == uip_udp_conn->rport) &&
       (uip_ipaddr_cmp(&uip_udp_conn->ripaddr, &uip_all_zeroes_addr) ||
	uip_ipaddr_cmp(&uip_udp_conn->ripaddr, &uip_broadcast_addr) ||
	uip_ipaddr_cmp(&BUF->srcipaddr, &uip_udp_conn->ripaddr))) {
      goto udp_found;
    }
  }
  UIP_LOG("udp: no matching connection found");
  UIP_STAT(++uip_stat.udp.drop);
#if UIP_CONF_ICMP_DEST_UNREACH && !NETSTACK_CONF_WITH_IPV6
  /* Copy fields from packet header into payload of this ICMP packet. */
  memcpy(&(ICMPBUF->payload[0]), ICMPBUF, UIP_IPH_LEN + 8);

  /* Set the ICMP type and code. */
  ICMPBUF->type = ICMP_DEST_UNREACHABLE;
  ICMPBUF->icode = ICMP_PORT_UNREACHABLE;

  /* Calculate the ICMP checksum. */
  ICMPBUF->icmpchksum = 0;
  ICMPBUF->icmpchksum = ~uip_chksum((uint16_t *)&(ICMPBUF->type), 36);

  /* Set the IP destination address to be the source address of the
     original packet. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);

  /* Set our IP address as the source address. */
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  /* The size of the ICMP destination unreachable packet is 36 + the
     size of the IP header (20) = 56. */
  uip_len = 36 + UIP_IPH_LEN;
  ICMPBUF->len[0] = 0;
  ICMPBUF->len[1] = (uint8_t)uip_len;
  ICMPBUF->ttl = UIP_TTL;
  ICMPBUF->proto = UIP_PROTO_ICMP;

  goto ip_send_nolen;
#else /* UIP_CONF_ICMP_DEST_UNREACH */
  goto drop;
#endif /* UIP_CONF_ICMP_DEST_UNREACH */

 udp_found:
  UIP_STAT(++uip_stat.udp.recv);
  uip_conn = NULL;
  uip_flags = UIP_NEWDATA;
  uip_sappdata = uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPUDPH_LEN];
  uip_slen = 0;
  UIP_UDP_APPCALL();

 udp_send:
  if(uip_slen == 0) {
    goto drop;
  }
  uip_len = uip_slen + UIP_IPUDPH_LEN;

#if NETSTACK_CONF_WITH_IPV6
  /* For IPv6, the IP length field does not include the IPv6 IP header
     length. */
  BUF->len[0] = ((uip_len - UIP_IPH_LEN) >> 8);
  BUF->len[1] = ((uip_len - UIP_IPH_LEN) & 0xff);
#else /* NETSTACK_CONF_WITH_IPV6 */
  BUF->len[0] = (uip_len >> 8);
  BUF->len[1] = (uip_len & 0xff);
#endif /* NETSTACK_CONF_WITH_IPV6 */

  BUF->ttl = uip_udp_conn->ttl;
  BUF->proto = UIP_PROTO_UDP;

  UDPBUF->udplen = UIP_HTONS(uip_slen + UIP_UDPH_LEN);
  UDPBUF->udpchksum = 0;

  BUF->srcport  = uip_udp_conn->lport;
  BUF->destport = uip_udp_conn->rport;

  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);
  uip_ipaddr_copy(&BUF->destipaddr, &uip_udp_conn->ripaddr);

  uip_appdata = &uip_buf[UIP_LLH_LEN + UIP_IPTCPH_LEN];

#if UIP_UDP_CHECKSUMS
  /* Calculate UDP checksum. */
  UDPBUF->udpchksum = ~(uip_udpchksum());
  if(UDPBUF->udpchksum == 0) {
    UDPBUF->udpchksum = 0xffff;
  }
#endif /* UIP_UDP_CHECKSUMS */

  UIP_STAT(++uip_stat.udp.sent);
  goto ip_send_nolen;
#endif /* UIP_UDP */

  /* TCP input processing. */
#if UIP_TCP
 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;
  }

  /* Make sure that the TCP port number is not zero. */
  if(BUF->destport == 0 || BUF->srcport == 0) {
    UIP_LOG("tcp: zero port.");
    goto drop;
  }

  /* Demultiplex this segment. */
  /* First check any active connections. */
  for(uip_connr = &uip_conns[0]; uip_connr <= &uip_conns[UIP_CONNS - 1];
      ++uip_connr) {
    if(uip_connr->tcpstateflags != UIP_CLOSED &&
       BUF->destport == uip_connr->lport &&
       BUF->srcport == uip_connr->rport &&
       uip_ipaddr_cmp(&BUF->srcipaddr, &uip_connr->ripaddr)) {
      goto found;
    }
  }

  /* If we didn't find an active connection that expected the packet,
     either this packet is an old duplicate, 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:
  /* We do not send resets in response to resets. */
  if(BUF->flags & TCP_RST) {
    goto drop;
  }

  UIP_STAT(++uip_stat.tcp.rst);

  BUF->flags = TCP_RST | TCP_ACK;
  uip_len = UIP_IPTCPH_LEN;
  BUF->tcpoffset = 5 << 4;

  /* Flip 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 port numbers. */
  tmp16 = BUF->srcport;
  BUF->srcport = BUF->destport;
  BUF->destport = tmp16;

  /* Swap IP addresses. */
  uip_ipaddr_copy(&BUF->destipaddr, &BUF->srcipaddr);
  uip_ipaddr_copy(&BUF->srcipaddr, &uip_hostaddr);

  /* 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:
  /* 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 <NAME> for a very
     nice algorithm for the TIME_WAIT search. */
  uip_connr = 0;
  for(c = 0; c < UIP_CONNS; ++c) {
    if(uip_conns[c].tcpstateflags == UIP_CLOSED) {
      uip_connr = &uip_conns[c];
      break;
    }
    if(uip_conns[c].tcpstateflags == UIP_TIME_WAIT) {
      if(uip_connr == 0 ||
	 uip_conns[c].timer > uip_connr->timer) {
	uip_connr = &uip_conns[c];
      }
    }
  }

  if(uip_connr == 0) {
    /* 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. */
  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_ipaddr_copy(&uip_connr->ripaddr, &BUF->srcipaddr);
  uip_connr->tcpstateflags = UIP_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);

  /* Parse the TCP MSS option, if present. */
  if((BUF->tcpoffset & 0xf0) > 0x50) {
    for(c = 0; c < ((BUF->tcpoffset >> 4) - 5) << 2 ;) {
      opt = uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + c];
      if(opt == TCP_OPT_END) {
	/* End of options. */
	break;
      } else if(opt == TCP_OPT_NOOP) {
	++c;
	/* NOP option. */
      } else if(opt == TCP_OPT_MSS &&
		uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 1 + c] == TCP_OPT_MSS_LEN) {
	/* An MSS option with the right option length. */
	tmp16 = ((uint16_t)uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN + 2 + c] << 8) |
	  (uint16_t)uip_buf[UIP_IPTCPH_LEN + 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
	     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] = TCP_OPT_MSS;
  BUF->optdata[1] = TCP_OPT_MSS_LEN;
  BUF->optdata[2] = (UIP_TCP_MSS) / 256;
  BUF->optdata[3] = (UIP_TCP_MSS) & 255;
  uip_len = UIP_IPTCPH_LEN + TCP_OPT_MSS_LEN;
  BUF->tcpoffset = ((UIP_TCPH_LEN + TCP_OPT_MSS_LEN) / 4) << 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 within our advertised window
     before we accept the reset. */
  if(BUF->flags & TCP_RST) {
    uip_connr->tcpstateflags = UIP_CLOSED;
    UIP_LOG("tcp: got reset, aborting connection.");
    uip_flags = UIP_ABORT;
    UIP_APPCALL();
    goto drop;
{'fraction_non_alphanumeric': 0.14608171847474002, 'fraction_numerical': 0.018048530999602203, 'mean_word_length': 2.71798013944644, 'pattern_counts': {'":': 0, '<': 129, '<?xml version=': 0, '>': 601, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 6, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '467034', 'n_tokens_mistral': 35113, 'n_tokens_neox': 33217, 'n_words': 8562}