tcpip.cpp

// IP, Arp, UDP and TCP functions.
// Author: Guido Socher 
// Copyright: GPL V2
//
// The TCP implementation uses some size optimisations which are valid
// only if all data can be sent in one single packet. This is however
// not a big limitation for a microcontroller as you will anyhow use
// small web-pages. The web server must send the entire web page in one
// packet. The client "web browser" as implemented here can also receive
// large pages.
//
// 2010-05-20 <jc@wippler.nl>

#include "EtherCard.h"
#include "net.h"
#undef word // arduino nonsense

#define gPB ether.buffer

#define PINGPATTERN 0x42

// Avoid spurious pgmspace warnings - http://forum.jeelabs.net/node/327
// See also http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34734
//#undef PROGMEM 
//#define PROGMEM __attribute__(( section(".progmem.data") )) 
//#undef PSTR 
//#define PSTR(s) (__extension__({static prog_char c[] PROGMEM = (s); &c[0];}))

static byte tcpclient_src_port_l=1; 
static byte tcp_fd; // a file descriptor, will be encoded into the port
static byte tcp_client_state;
static byte tcp_client_port_h;
static byte tcp_client_port_l;
static byte (*client_tcp_result_cb)(byte,byte,word,word);
static word (*client_tcp_datafill_cb)(byte);
#define TCPCLIENT_SRC_PORT_H 11
static byte www_fd;
static void (*client_browser_cb)(byte,word,word);
static prog_char *client_additionalheaderline;
static const char *client_postval;
static prog_char *client_urlbuf;
static const char *client_urlbuf_var;
static prog_char *client_hoststr;
static void (*icmp_cb)(byte *ip);
static int16_t delaycnt=1;
static byte gwmacaddr[6];
static byte waitgwmac; // 0=wait, 1=first req no anser, 2=have gwmac, 4=refeshing but have gw mac, 8=accept an arp reply
#define WGW_INITIAL_ARP 1
#define WGW_HAVE_GW_MAC 2
#define WGW_REFRESHING 4
#define WGW_ACCEPT_ARP_REPLY 8
static word info_data_len;
static byte seqnum = 0xa; // my initial tcp sequence number
static byte result_fd = 123; // session id of last reply
static const char* result_ptr;
static unsigned long SEQ; 

#define CLIENTMSS 550
#define TCP_DATA_START ((word)TCP_SRC_PORT_H_P+(gPB[TCP_HEADER_LEN_P]>>4)*4)

const char arpreqhdr[] PROGMEM = { 0,1,8,0,6,4,0,1 };
const char iphdr[] PROGMEM = { 0x45,0,0,0x82,0,0,0x40,0,0x20 };
const char ntpreqhdr[] PROGMEM = { 0xE3,0,4,0xFA,0,1,0,0,0,1 };
const byte allOnes[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
const byte ipBroadcast[] = {255, 255, 255, 255};

static void fill_checksum(byte dest, byte off, word len,byte type) {
  const byte* ptr = gPB + off;
  uint32_t sum = type==1 ? IP_PROTO_UDP_V+len-8 :
                  type==2 ? IP_PROTO_TCP_V+len-8 : 0;
  while(len >1) {
    sum += (word) (((uint32_t)*ptr<<8)|*(ptr+1));
    ptr+=2;
    len-=2;
  }
  if (len)
    sum += ((uint32_t)*ptr)<<8;
  while (sum>>16)
    sum = (word) sum + (sum >> 16);
  word ck = ~ (word) sum;
  gPB[dest] = ck>>8;
  gPB[dest+1] = ck;
}

static void setMACs (const byte *mac) {
  EtherCard::copyMac(gPB + ETH_DST_MAC, mac);
  EtherCard::copyMac(gPB + ETH_SRC_MAC, EtherCard::mymac);
}

static void setMACandIPs (const byte *mac, const byte *dst) {
  setMACs(mac);
  EtherCard::copyIp(gPB + IP_DST_P, dst);
  EtherCard::copyIp(gPB + IP_SRC_P, EtherCard::myip);
}

static byte check_ip_message_is_from(const byte *ip) {
  return memcmp(gPB + IP_SRC_P, ip, 4) == 0;
}

static byte eth_type_is_arp_and_my_ip(word len) {
  return len >= 41 && gPB[ETH_TYPE_H_P] == ETHTYPE_ARP_H_V &&
                      gPB[ETH_TYPE_L_P] == ETHTYPE_ARP_L_V &&
                      memcmp(gPB + ETH_ARP_DST_IP_P, EtherCard::myip, 4) == 0;
}

static byte eth_type_is_ip_and_my_ip(word len) {
  return len >= 42 && gPB[ETH_TYPE_H_P] == ETHTYPE_IP_H_V &&
                      gPB[ETH_TYPE_L_P] == ETHTYPE_IP_L_V &&
                      gPB[IP_HEADER_LEN_VER_P] == 0x45 &&
                      memcmp(gPB + IP_DST_P, EtherCard::myip, 4) == 0;
}

static void fill_ip_hdr_checksum() {
  gPB[IP_CHECKSUM_P] = 0;
  gPB[IP_CHECKSUM_P+1] = 0;
  gPB[IP_FLAGS_P] = 0x40; // don't fragment
  gPB[IP_FLAGS_P+1] = 0;  // fragement offset
  gPB[IP_TTL_P] = 64; // ttl
  fill_checksum(IP_CHECKSUM_P, IP_P, IP_HEADER_LEN,0);
}

static void make_eth_ip() {
  setMACs(gPB + ETH_SRC_MAC);
  EtherCard::copyIp(gPB + IP_DST_P, gPB + IP_SRC_P);
  EtherCard::copyIp(gPB + IP_SRC_P, EtherCard::myip);
  fill_ip_hdr_checksum();
}

static void step_seq(word rel_ack_num,byte cp_seq) {
  byte i;
  byte tseq;
  i = 4;
  while(i>0) {
    rel_ack_num = gPB[TCP_SEQ_H_P+i-1]+rel_ack_num;
    tseq = gPB[TCP_SEQACK_H_P+i-1];
    gPB[TCP_SEQACK_H_P+i-1] = rel_ack_num;
    if (cp_seq)
      gPB[TCP_SEQ_H_P+i-1] = tseq;
    else
      gPB[TCP_SEQ_H_P+i-1] = 0; // some preset value
    rel_ack_num = rel_ack_num>>8;
    i--;
  }
}

static void make_tcphead(word rel_ack_num,byte cp_seq) {
  byte i = gPB[TCP_DST_PORT_H_P];
  gPB[TCP_DST_PORT_H_P] = gPB[TCP_SRC_PORT_H_P];
  gPB[TCP_SRC_PORT_H_P] = i;
  byte j = gPB[TCP_DST_PORT_L_P];
  gPB[TCP_DST_PORT_L_P] = gPB[TCP_SRC_PORT_L_P];
  gPB[TCP_SRC_PORT_L_P] = j;
  step_seq(rel_ack_num,cp_seq);
  gPB[TCP_CHECKSUM_H_P] = 0;
  gPB[TCP_CHECKSUM_L_P] = 0;
  gPB[TCP_HEADER_LEN_P] = 0x50;
}

static void make_arp_answer_from_request() {
  setMACs(gPB + ETH_SRC_MAC);
  gPB[ETH_ARP_OPCODE_H_P] = ETH_ARP_OPCODE_REPLY_H_V;
  gPB[ETH_ARP_OPCODE_L_P] = ETH_ARP_OPCODE_REPLY_L_V;
  EtherCard::copyMac(gPB + ETH_ARP_DST_MAC_P, gPB + ETH_ARP_SRC_MAC_P);
  EtherCard::copyMac(gPB + ETH_ARP_SRC_MAC_P, EtherCard::mymac);
  EtherCard::copyIp(gPB + ETH_ARP_DST_IP_P, gPB + ETH_ARP_SRC_IP_P);
  EtherCard::copyIp(gPB + ETH_ARP_SRC_IP_P, EtherCard::myip);
  EtherCard::packetSend(42); 
}

static void make_echo_reply_from_request(word len) {
  make_eth_ip();
  gPB[ICMP_TYPE_P] = ICMP_TYPE_ECHOREPLY_V;
  if (gPB[ICMP_CHECKSUM_P] > (0xFF-0x08))
      gPB[ICMP_CHECKSUM_P+1]++;
  gPB[ICMP_CHECKSUM_P] += 0x08;
  EtherCard::packetSend(len);
}

void EtherCard::makeUdpReply (char *data,byte datalen,word port) {
  if (datalen>220)
      datalen = 220;
  gPB[IP_TOTLEN_H_P] = (IP_HEADER_LEN+UDP_HEADER_LEN+datalen) >>8;
  gPB[IP_TOTLEN_L_P] = IP_HEADER_LEN+UDP_HEADER_LEN+datalen;
  make_eth_ip();
  gPB[UDP_DST_PORT_H_P] = gPB[UDP_SRC_PORT_H_P];
  gPB[UDP_DST_PORT_L_P] = gPB[UDP_SRC_PORT_L_P];
  gPB[UDP_SRC_PORT_H_P] = port>>8;
  gPB[UDP_SRC_PORT_L_P] = port;
  gPB[UDP_LEN_H_P] = (UDP_HEADER_LEN+datalen) >> 8;
  gPB[UDP_LEN_L_P] = UDP_HEADER_LEN+datalen;
  gPB[UDP_CHECKSUM_H_P] = 0;
  gPB[UDP_CHECKSUM_L_P] = 0;
  memcpy(gPB + UDP_DATA_P, data, datalen);
  fill_checksum(UDP_CHECKSUM_H_P, IP_SRC_P, 16 + datalen,1);
  packetSend(UDP_HEADER_LEN+IP_HEADER_LEN+ETH_HEADER_LEN+datalen);
}

static void make_tcp_synack_from_syn() {
  gPB[IP_TOTLEN_H_P] = 0;
  gPB[IP_TOTLEN_L_P] = IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+4;
  make_eth_ip();
  gPB[TCP_FLAGS_P] = TCP_FLAGS_SYNACK_V;
  make_tcphead(1,0);
  gPB[TCP_SEQ_H_P+0] = 0;
  gPB[TCP_SEQ_H_P+1] = 0;
  gPB[TCP_SEQ_H_P+2] = seqnum; 
  gPB[TCP_SEQ_H_P+3] = 0;
  seqnum += 3;
  gPB[TCP_OPTIONS_P] = 2;
  gPB[TCP_OPTIONS_P+1] = 4;
  gPB[TCP_OPTIONS_P+2] = 0x05;
  gPB[TCP_OPTIONS_P+3] = 0x0;
  gPB[TCP_HEADER_LEN_P] = 0x60;
  gPB[TCP_WIN_SIZE] = 0x5; // 1400=0x578
  gPB[TCP_WIN_SIZE+1] = 0x78;
  fill_checksum(TCP_CHECKSUM_H_P, IP_SRC_P, 8+TCP_HEADER_LEN_PLAIN+4,2);
  EtherCard::packetSend(IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+4+ETH_HEADER_LEN);
}

static word get_tcp_data_len() {
  int16_t i = (((int16_t)gPB[IP_TOTLEN_H_P])<<8)|gPB[IP_TOTLEN_L_P];
  i -= IP_HEADER_LEN;
  i -= (gPB[TCP_HEADER_LEN_P]>>4)*4; // generate len in bytes;
  if (i<=0)
    i = 0;
  return (word)i;
}

static void make_tcp_ack_from_any(int16_t datlentoack,byte addflags) {
  gPB[TCP_FLAGS_P] = TCP_FLAGS_ACK_V|addflags;
  if (addflags!=TCP_FLAGS_RST_V && datlentoack==0)
    datlentoack = 1;
  make_tcphead(datlentoack,1); // no options
  word j = IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN;
  gPB[IP_TOTLEN_H_P] = j>>8;
  gPB[IP_TOTLEN_L_P] = j;
  make_eth_ip();
  gPB[TCP_WIN_SIZE] = 0x4; // 1024=0x400, 1280=0x500 2048=0x800 768=0x300
  gPB[TCP_WIN_SIZE+1] = 0;
  fill_checksum(TCP_CHECKSUM_H_P, IP_SRC_P, 8+TCP_HEADER_LEN_PLAIN,2);
  EtherCard::packetSend(IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+ETH_HEADER_LEN);
}

static void make_tcp_ack_with_data_noflags(word dlen) {
  word j = IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+dlen;
  gPB[IP_TOTLEN_H_P] = j>>8;
  gPB[IP_TOTLEN_L_P] = j;
  fill_ip_hdr_checksum();
  gPB[TCP_CHECKSUM_H_P] = 0;
  gPB[TCP_CHECKSUM_L_P] = 0;
  fill_checksum(TCP_CHECKSUM_H_P, IP_SRC_P, 8+TCP_HEADER_LEN_PLAIN+dlen,2);
  EtherCard::packetSend(IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+dlen+ETH_HEADER_LEN);
}

void EtherCard::httpServerReply (word dlen) {
  make_tcp_ack_from_any(info_data_len,0); // send ack for http get
  gPB[TCP_FLAGS_P] = TCP_FLAGS_ACK_V|TCP_FLAGS_PUSH_V|TCP_FLAGS_FIN_V;
  make_tcp_ack_with_data_noflags(dlen); // send data
}

static void get_seq() { //get the sequence number of packets after an ack from GET
  SEQ =(((unsigned long)gPB[TCP_SEQ_H_P]*256+gPB[TCP_SEQ_H_P+1])*256+gPB[TCP_SEQ_H_P+2])*256+gPB[TCP_SEQ_H_P+3];
} //thanks to mstuetz for the missing (unsigned long)

static void set_seq() { //set the correct sequence number and calculate the next with the lenght of current packet
gPB[TCP_SEQ_H_P]= (SEQ & 0xff000000 ) >> 24;
gPB[TCP_SEQ_H_P+1]= (SEQ & 0xff0000 ) >> 16;
gPB[TCP_SEQ_H_P+2]= (SEQ & 0xff00 ) >> 8;
gPB[TCP_SEQ_H_P+3]= (SEQ & 0xff );
}

void EtherCard::httpServerReplyAck () {
make_tcp_ack_from_any(info_data_len,0); // send ack for http get
get_seq(); //get the sequence number of packets after an ack from GET
}

void EtherCard::httpServerReply_with_flags (word dlen , byte flags) {
set_seq();
gPB[TCP_FLAGS_P] = flags; // final packet
make_tcp_ack_with_data_noflags(dlen); // send data
SEQ=SEQ+dlen;
}

void EtherCard::clientIcmpRequest(const byte *destip) {
  setMACandIPs(gwmacaddr, destip);
  gPB[ETH_TYPE_H_P] = ETHTYPE_IP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_IP_L_V;
  memcpy_P(gPB + IP_P,iphdr,9);
  gPB[IP_TOTLEN_L_P] = 0x54;
  gPB[IP_PROTO_P] = IP_PROTO_ICMP_V;
  fill_ip_hdr_checksum();
  gPB[ICMP_TYPE_P] = ICMP_TYPE_ECHOREQUEST_V;
  gPB[ICMP_TYPE_P+1] = 0; // code
  gPB[ICMP_CHECKSUM_H_P] = 0;
  gPB[ICMP_CHECKSUM_L_P] = 0;
  gPB[ICMP_IDENT_H_P] = 5; // some number 
  gPB[ICMP_IDENT_L_P] = EtherCard::myip[3]; // last byte of my IP
  gPB[ICMP_IDENT_L_P+1] = 0; // seq number, high byte
  gPB[ICMP_IDENT_L_P+2] = 1; // seq number, low byte, we send only 1 ping at a time
  memset(gPB + ICMP_DATA_P, PINGPATTERN, 56);
  fill_checksum(ICMP_CHECKSUM_H_P, ICMP_TYPE_P, 56+8,0);
  packetSend(98);
}

void EtherCard::ntpRequest (byte *ntpip,byte srcport) {
  setMACandIPs(gwmacaddr, ntpip);
  gPB[ETH_TYPE_H_P] = ETHTYPE_IP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_IP_L_V;
  memcpy_P(gPB + IP_P,iphdr,9);
  gPB[IP_TOTLEN_L_P] = 0x4c;
  gPB[IP_PROTO_P] = IP_PROTO_UDP_V;
  fill_ip_hdr_checksum();
  gPB[UDP_DST_PORT_H_P] = 0;
  gPB[UDP_DST_PORT_L_P] = 0x7b; // ntp = 123
  gPB[UDP_SRC_PORT_H_P] = 10;
  gPB[UDP_SRC_PORT_L_P] = srcport; // lower 8 bit of src port
  gPB[UDP_LEN_H_P] = 0;
  gPB[UDP_LEN_L_P] = 56; // fixed len
  gPB[UDP_CHECKSUM_H_P] = 0;
  gPB[UDP_CHECKSUM_L_P] = 0;
  memset(gPB + UDP_DATA_P, 0, 48);
  memcpy_P(gPB + UDP_DATA_P,ntpreqhdr,10);
  fill_checksum(UDP_CHECKSUM_H_P, IP_SRC_P, 16 + 48,1);
  packetSend(90);
}

byte EtherCard::ntpProcessAnswer (uint32_t *time,byte dstport_l) {
  if ((dstport_l && gPB[UDP_DST_PORT_L_P]!=dstport_l) || gPB[UDP_LEN_H_P]!=0 ||
      gPB[UDP_LEN_L_P]!=56 || gPB[UDP_SRC_PORT_L_P]!=0x7b)
    return 0;
  ((byte*) time)[3] = gPB[0x52];
  ((byte*) time)[2] = gPB[0x53];
  ((byte*) time)[1] = gPB[0x54];
  ((byte*) time)[0] = gPB[0x55];
  return 1;
}

void EtherCard::udpPrepare (word sport, byte *dip, word dport) {
  setMACandIPs(gwmacaddr, dip);
  // see http://tldp.org/HOWTO/Multicast-HOWTO-2.html
  // multicast or broadcast address, https://github.com/jcw/ethercard/issues/59
  if ((dip[0] & 0xF0) == 0xE0 || *((long*) dip) == 0xFFFFFFFF)
    EtherCard::copyMac(gPB + ETH_DST_MAC, allOnes);
  gPB[ETH_TYPE_H_P] = ETHTYPE_IP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_IP_L_V;
  memcpy_P(gPB + IP_P,iphdr,9);
  gPB[IP_TOTLEN_H_P] = 0;
  gPB[IP_PROTO_P] = IP_PROTO_UDP_V;
  gPB[UDP_DST_PORT_H_P] = (dport>>8);
  gPB[UDP_DST_PORT_L_P] = dport; 
  gPB[UDP_SRC_PORT_H_P] = (sport>>8);
  gPB[UDP_SRC_PORT_L_P] = sport; 
  gPB[UDP_LEN_H_P] = 0;
  gPB[UDP_CHECKSUM_H_P] = 0;
  gPB[UDP_CHECKSUM_L_P] = 0;
}

void EtherCard::udpTransmit (word datalen) {
  gPB[IP_TOTLEN_H_P] = (IP_HEADER_LEN+UDP_HEADER_LEN+datalen) >> 8;
  gPB[IP_TOTLEN_L_P] = IP_HEADER_LEN+UDP_HEADER_LEN+datalen;
  fill_ip_hdr_checksum();
  gPB[UDP_LEN_H_P] = (UDP_HEADER_LEN+datalen) >>8;
  gPB[UDP_LEN_L_P] = UDP_HEADER_LEN+datalen;
  fill_checksum(UDP_CHECKSUM_H_P, IP_SRC_P, 16 + datalen,1);
  packetSend(UDP_HEADER_LEN+IP_HEADER_LEN+ETH_HEADER_LEN+datalen);
}

void EtherCard::sendUdp (char *data,byte datalen,word sport, byte *dip, word dport) {
  udpPrepare(sport, dip, dport);
  if (datalen>220)
    datalen = 220;
  memcpy(gPB + UDP_DATA_P, data, datalen);
  udpTransmit(datalen);
}

void EtherCard::sendWol (byte *wolmac) {
  setMACandIPs(allOnes, ipBroadcast);
  gPB[ETH_TYPE_H_P] = ETHTYPE_IP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_IP_L_V;
  memcpy_P(gPB + IP_P,iphdr,9);
  gPB[IP_TOTLEN_L_P] = 0x82;
  gPB[IP_PROTO_P] = IP_PROTO_UDP_V;
  fill_ip_hdr_checksum();
  gPB[UDP_DST_PORT_H_P] = 0;
  gPB[UDP_DST_PORT_L_P] = 0x9; // wol = normally 9
  gPB[UDP_SRC_PORT_H_P] = 10;
  gPB[UDP_SRC_PORT_L_P] = 0x42; // source port does not matter
  gPB[UDP_LEN_H_P] = 0;
  gPB[UDP_LEN_L_P] = 110; // fixed len
  gPB[UDP_CHECKSUM_H_P] = 0;
  gPB[UDP_CHECKSUM_L_P] = 0;
  copyMac(gPB + UDP_DATA_P, allOnes);
  byte pos = UDP_DATA_P;
  for (byte m = 0; m < 16; ++m) {
    pos += 6;
    copyMac(gPB + pos, wolmac);
  }
  fill_checksum(UDP_CHECKSUM_H_P, IP_SRC_P, 16 + 102,1);
  packetSend(pos + 6);
}

// make a arp request
static void client_arp_whohas(byte *ip_we_search) {
  setMACs(allOnes);
  gPB[ETH_TYPE_H_P] = ETHTYPE_ARP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_ARP_L_V;
  memcpy_P(gPB + ETH_ARP_P,arpreqhdr,8);
  memset(gPB + ETH_ARP_DST_MAC_P, 0, 6);
  EtherCard::copyMac(gPB + ETH_ARP_SRC_MAC_P, EtherCard::mymac);
  EtherCard::copyIp(gPB + ETH_ARP_DST_IP_P, ip_we_search);
  EtherCard::copyIp(gPB + ETH_ARP_SRC_IP_P, EtherCard::myip);
  waitgwmac |= WGW_ACCEPT_ARP_REPLY;
  EtherCard::packetSend(42);
}

byte EtherCard::clientWaitingGw () {
  return !(waitgwmac & WGW_HAVE_GW_MAC);
}

static byte client_store_gw_mac() {
  if (memcmp(gPB + ETH_ARP_SRC_IP_P, EtherCard::gwip, 4) != 0)
    return 0;
  EtherCard::copyMac(gwmacaddr, gPB + ETH_ARP_SRC_MAC_P);
  return 1;
}

// static void client_gw_arp_refresh() {
//   if (waitgwmac & WGW_HAVE_GW_MAC)
//     waitgwmac |= WGW_REFRESHING;
// }

void EtherCard::setGwIp (const byte *gwipaddr) {
  waitgwmac = WGW_INITIAL_ARP; // causes an arp request in the packet loop
  copyIp(gwip, gwipaddr);
}

static void client_syn(byte srcport,byte dstport_h,byte dstport_l) {
  setMACandIPs(gwmacaddr, EtherCard::hisip);
  gPB[ETH_TYPE_H_P] = ETHTYPE_IP_H_V;
  gPB[ETH_TYPE_L_P] = ETHTYPE_IP_L_V;
  memcpy_P(gPB + IP_P,iphdr,9);
  gPB[IP_TOTLEN_L_P] = 44; // good for syn
  gPB[IP_PROTO_P] = IP_PROTO_TCP_V;
  fill_ip_hdr_checksum();
  gPB[TCP_DST_PORT_H_P] = dstport_h;
  gPB[TCP_DST_PORT_L_P] = dstport_l;
  gPB[TCP_SRC_PORT_H_P] = TCPCLIENT_SRC_PORT_H;
  gPB[TCP_SRC_PORT_L_P] = srcport; // lower 8 bit of src port
  memset(gPB + TCP_SEQ_H_P, 0, 8);
  gPB[TCP_SEQ_H_P+2] = seqnum; 
  seqnum += 3;
  gPB[TCP_HEADER_LEN_P] = 0x60; // 0x60=24 len: (0x60>>4) * 4
  gPB[TCP_FLAGS_P] = TCP_FLAGS_SYN_V;
  gPB[TCP_WIN_SIZE] = 0x3; // 1024 = 0x400 768 = 0x300, initial window
  gPB[TCP_WIN_SIZE+1] = 0x0;
  gPB[TCP_CHECKSUM_H_P] = 0;
  gPB[TCP_CHECKSUM_L_P] = 0;
  gPB[TCP_CHECKSUM_L_P+1] = 0;
  gPB[TCP_CHECKSUM_L_P+2] = 0;
  gPB[TCP_OPTIONS_P] = 2;
  gPB[TCP_OPTIONS_P+1] = 4;
  gPB[TCP_OPTIONS_P+2] = (CLIENTMSS>>8);
  gPB[TCP_OPTIONS_P+3] = (byte) CLIENTMSS;
  fill_checksum(TCP_CHECKSUM_H_P, IP_SRC_P, 8 +TCP_HEADER_LEN_PLAIN+4,2);
  // 4 is the tcp mss option:
  EtherCard::packetSend(IP_HEADER_LEN+TCP_HEADER_LEN_PLAIN+ETH_HEADER_LEN+4);
}

byte EtherCard::clientTcpReq (byte (*result_cb)(byte,byte,word,word),
                              word (*datafill_cb)(byte),word port) {
  client_tcp_result_cb = result_cb;
  client_tcp_datafill_cb = datafill_cb;
  tcp_client_port_h = port>>8;
  tcp_client_port_l = port;
  tcp_client_state = 1; // send a syn
  tcp_fd = (tcp_fd + 1) & 7;
  return tcp_fd;
}

static word www_client_internal_datafill_cb(byte fd) {
  BufferFiller bfill = EtherCard::tcpOffset();
  if (fd==www_fd) {
    if (client_postval == 0) {
      bfill.emit_p(PSTR("GET $F$S HTTP/1.0\r\n"
                        "Host: $F\r\n"
                        "$F\r\n"
                        "\r\n"), client_urlbuf,
                                 client_urlbuf_var,
                                 client_hoststr, client_additionalheaderline);
    } else {
      prog_char* ahl = client_additionalheaderline;
      bfill.emit_p(PSTR("POST $F HTTP/1.0\r\n"
                        "Host: $F\r\n"
                        "$F$S"
                        "Accept: */*\r\n"
                        "Content-Length: $D\r\n"
                        "Content-Type: application/x-www-form-urlencoded\r\n"
                        "\r\n"
                        "$S"), client_urlbuf,
                                 client_hoststr,
                                 ahl != 0 ? ahl : PSTR(""),
                                 ahl != 0 ? "\r\n" : "",
                                 strlen(client_postval),
                                 client_postval);
    }
  }
  return bfill.position();
}

static byte www_client_internal_result_cb(byte fd, byte statuscode, word datapos, word len_of_data) {
  if (fd!=www_fd)
    (*client_browser_cb)(4,0,0);
  else if (statuscode==0 && len_of_data>12 && client_browser_cb) {
    byte f = strncmp("200",(char *)&(gPB[datapos+9]),3) != 0;
    (*client_browser_cb)(f, ((word)TCP_SRC_PORT_H_P+(gPB[TCP_HEADER_LEN_P]>>4)*4),len_of_data);
  }
  return 0;
}

void EtherCard::browseUrl (prog_char *urlbuf, const char *urlbuf_varpart, prog_char *hoststr, void (*callback)(byte,word,word)) {
  browseUrl(urlbuf, urlbuf_varpart, hoststr, PSTR("Accept: text/html"), callback);
}

void EtherCard::browseUrl (prog_char *urlbuf, const char *urlbuf_varpart, prog_char *hoststr, prog_char *additionalheaderline, void (*callback)(byte,word,word)) {
  client_urlbuf = urlbuf;
  client_urlbuf_var = urlbuf_varpart;
  client_hoststr = hoststr;
  client_additionalheaderline = additionalheaderline;
  client_postval = 0;
  client_browser_cb = callback;
  www_fd = clientTcpReq(&www_client_internal_result_cb,&www_client_internal_datafill_cb,hisport);
}

void EtherCard::httpPost (prog_char *urlbuf, prog_char *hoststr, prog_char *additionalheaderline,const char *postval,void (*callback)(byte,word,word)) {
  client_urlbuf = urlbuf;
  client_hoststr = hoststr;
  client_additionalheaderline = additionalheaderline;
  client_postval = postval;
  client_browser_cb = callback;
  www_fd = clientTcpReq(&www_client_internal_result_cb,&www_client_internal_datafill_cb,hisport);
}

static word tcp_datafill_cb(byte fd) {
  word len = Stash::length();
  Stash::extract(0, len, EtherCard::tcpOffset());
  Stash::cleanup();
  EtherCard::tcpOffset()[len] = 0;
#if SERIAL
  Serial.print("REQUEST: ");
  Serial.println(len);
  Serial.println((char*) EtherCard::tcpOffset());
#endif
  result_fd = 123; // bogus value
  return len;
}

static byte tcp_result_cb(byte fd, byte status, word datapos, word datalen) {
  if (status == 0) {
    result_fd = fd; // a valid result has been received, remember its session id
    result_ptr = (char*) ether.buffer + datapos;
    // result_ptr[datalen] = 0;
  }
  return 1;
}

byte EtherCard::tcpSend () {
  www_fd = clientTcpReq(&tcp_result_cb, &tcp_datafill_cb, hisport);
  return www_fd;
}

const char* EtherCard::tcpReply (byte fd) {
  if (result_fd != fd)
    return 0;
  result_fd = 123; // set to a bogus value to prevent future match
  return result_ptr;
}

void EtherCard::registerPingCallback (void (*callback)(byte *srcip)) {
  icmp_cb = callback;
}

byte EtherCard::packetLoopIcmpCheckReply (const byte *ip_monitoredhost) {
  return gPB[IP_PROTO_P]==IP_PROTO_ICMP_V &&
          gPB[ICMP_TYPE_P]==ICMP_TYPE_ECHOREPLY_V &&
           gPB[ICMP_DATA_P]== PINGPATTERN &&
            check_ip_message_is_from(ip_monitoredhost);
}

word EtherCard::accept(const word port, word plen) {
  word len;
  len = get_tcp_data_len();
  
  if (gPB[TCP_DST_PORT_H_P] == (port >> 8) &&
      gPB[TCP_DST_PORT_L_P] == ((byte) port)) {
    if (gPB[TCP_FLAGS_P] & TCP_FLAGS_SYN_V)
      make_tcp_synack_from_syn();
    else if (gPB[TCP_FLAGS_P] & TCP_FLAGS_ACK_V) {
      info_data_len = get_tcp_data_len();
      if (info_data_len > 0) {
        len = TCP_DATA_START; // TCP_DATA_START is a formula
        if (len <= plen - 8)
          return len;
      } else if (gPB[TCP_FLAGS_P] & TCP_FLAGS_FIN_V)
        make_tcp_ack_from_any(0,0);
    }
  }
  return 0;
}

word EtherCard::packetLoop (word plen) {
  word len;

  if(using_dhcp){
    ether.DhcpStateMachine(plen);
  }

  if (plen==0) {
    if ((waitgwmac & WGW_INITIAL_ARP || waitgwmac & WGW_REFRESHING) &&
                                          delaycnt==0 && isLinkUp())
      client_arp_whohas(gwip);
    delaycnt++;
    if (tcp_client_state==1 && (waitgwmac & WGW_HAVE_GW_MAC)) { // send a syn
      tcp_client_state = 2;
      tcpclient_src_port_l++; // allocate a new port
      client_syn(((tcp_fd<<5) | (0x1f & tcpclient_src_port_l)),tcp_client_port_h,tcp_client_port_l);
    }
    return 0;
  }
  if ((gPB[30]==239)&&(gPB[31]==255)&&(gPB[32]==255)&&(gPB[33]==250)) { //multicast packets
  	return UDP_DATA_P; //mark as udp structured packet
  }
  
  if (eth_type_is_arp_and_my_ip(plen)) {
    if (gPB[ETH_ARP_OPCODE_L_P]==ETH_ARP_OPCODE_REQ_L_V)
        make_arp_answer_from_request();
    if (waitgwmac & WGW_ACCEPT_ARP_REPLY && (gPB[ETH_ARP_OPCODE_L_P]==ETH_ARP_OPCODE_REPLY_L_V) && client_store_gw_mac())
      waitgwmac = WGW_HAVE_GW_MAC;
    return 0;
  }
  if (eth_type_is_ip_and_my_ip(plen)==0) {
    return 0;
  }
  if (gPB[IP_PROTO_P]==IP_PROTO_ICMP_V && gPB[ICMP_TYPE_P]==ICMP_TYPE_ECHOREQUEST_V) {
    if (icmp_cb)
      (*icmp_cb)(&(gPB[IP_SRC_P]));
    make_echo_reply_from_request(plen);
    return 0;
  }
  if (ether.udpServerListening() && gPB[IP_PROTO_P]==IP_PROTO_UDP_V) {
  	if(ether.udpServerHasProcessedPacket(plen))
	  	return 0;
  }
  if (plen<54 && gPB[IP_PROTO_P]!=IP_PROTO_TCP_V )
    return 0;
  if ( gPB[TCP_DST_PORT_H_P]==TCPCLIENT_SRC_PORT_H) {
    if (check_ip_message_is_from(hisip)==0)
      return 0;
    if (gPB[TCP_FLAGS_P] & TCP_FLAGS_RST_V) {
      if (client_tcp_result_cb)
        (*client_tcp_result_cb)((gPB[TCP_DST_PORT_L_P]>>5)&0x7,3,0,0);
	  tcp_client_state = 5;
      return 0;
    }
    len = get_tcp_data_len();
    if (tcp_client_state==2) {
      if ((gPB[TCP_FLAGS_P] & TCP_FLAGS_SYN_V) && (gPB[TCP_FLAGS_P] &TCP_FLAGS_ACK_V)) {
        make_tcp_ack_from_any(0,0);
        gPB[TCP_FLAGS_P] = TCP_FLAGS_ACK_V|TCP_FLAGS_PUSH_V;
        if (client_tcp_datafill_cb)
          len = (*client_tcp_datafill_cb)((gPB[TCP_SRC_PORT_L_P]>>5)&0x7);
        else
          len = 0;
        tcp_client_state = 3;
        make_tcp_ack_with_data_noflags(len);
      }else{
        tcp_client_state = 1; // retry
        len++;
        if (gPB[TCP_FLAGS_P] & TCP_FLAGS_ACK_V)
          len = 0;
        make_tcp_ack_from_any(len,TCP_FLAGS_RST_V);
      }
      return 0;
    }
    if (tcp_client_state==3 && len>0) { 
	  if (client_tcp_result_cb) {
        word tcpstart = TCP_DATA_START; // TCP_DATA_START is a formula
        if (tcpstart>plen-8)
          tcpstart = plen-8; // dummy but save
        word save_len = len;
        if (tcpstart+len>plen)
          save_len = plen-tcpstart;
        (*client_tcp_result_cb)((gPB[TCP_DST_PORT_L_P]>>5)&0x7,0,tcpstart,save_len);

        if(persist_tcp_connection){
            make_tcp_ack_from_any(len,TCP_FLAGS_PUSH_V);
        }
        else{
		    make_tcp_ack_from_any(len,TCP_FLAGS_PUSH_V|TCP_FLAGS_FIN_V);
            tcp_client_state = 6;
        }
        return 0;
      }
    }
    if (tcp_client_state != 5) {
      if (gPB[TCP_FLAGS_P] & TCP_FLAGS_FIN_V) {
	    if(tcp_client_state == 3) {
			return 0; // In some instances FIN is received *before* DATA.  If that is the case, we just return here and keep looking for the data packet
		}
        make_tcp_ack_from_any(len+1,TCP_FLAGS_PUSH_V|TCP_FLAGS_FIN_V);
        tcp_client_state = 6; // connection terminated
      } else if (len>0) {
        make_tcp_ack_from_any(len,0);
	  }
    }
    return 0;
  }

  return accept(hisport, plen);
}

void EtherCard::persistTcpConnection(bool persist){
  persist_tcp_connection = persist;
}