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PCARP.C
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C/C++ Source or Header
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1992-02-03
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9KB
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311 lines
/*
* Address Resolution Protocol
*
* Externals:
* _arp_handler( pb ) - returns 1 on handled correctly, 0 on problems
* _arp_resolve - rets 1 on success, 0 on fail
* - does not return hardware address if passed NULL for buffer
*
*/
#include <copyright.h>
#include <wattcp.h>
#include <string.h>
#define MAX_ARP_DATA 40
#define MAX_ARP_ALIVE 300 /* five minutes */
#define MAX_ARP_GRACE 100 /* additional grace upon expiration */
extern word wathndlcbrk;
extern word watcbroke;
extern word multihomes;
typedef struct {
longword ip;
eth_address hardware;
byte flags;
byte bits; /* bits in network */
longword expiry;
} arp_tables;
typedef struct {
longword gate_ip;
longword subnet;
longword mask;
} gate_tables;
#define ARP_FLAG_NEED 0
#define ARP_FLAG_FOUND 1
#define ARP_FLAG_FIXED 255 /* cannot be removed */
/*
* arp resolution cache - we zero fill it to save an initialization routine
*/
static arp_tables arp_data[ MAX_ARP_DATA ] =
{ {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0},
{0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}, {0,{0,0,0},0,0,0}};
gate_tables _arp_gate_data[ MAX_GATE_DATA ];
word _arp_last_gateway;
/*
* _arp_add_gateway - if data is NULL, don't use string
*/
void _arp_add_gateway( char *data , longword ip )
{
int i;
char *subnetp, *maskp;
longword subnet, mask;
subnet = mask = 0;
if ( data ) {
maskp = NULL;
if ( subnetp = strchr( data, ',' ) ) {
*subnetp++ = 0;
if ( maskp = strchr( subnetp, ',' )) {
*maskp++ = 0;
mask = aton( maskp );
subnet = aton( subnetp );
} else {
subnet = aton( subnetp );
switch ( subnet >> 30 ) {
case 0 :
case 1 : mask = 0xff000000L; break;
case 2 : mask = 0xfffffe00L; break; /* minimal class b */
case 3 : mask = 0xffffff00L; break;
}
}
}
ip = aton( data );
}
if ( _arp_last_gateway < MAX_GATE_DATA ) {
for ( i = 0 ; i < _arp_last_gateway ; ++i ) {
if ( _arp_gate_data[i].mask < mask ) {
movmem( &_arp_gate_data[i], &_arp_gate_data[i+1],
(_arp_last_gateway - i) * sizeof( gate_tables ));
break;
}
}
_arp_gate_data[i].gate_ip = ip;
_arp_gate_data[i].subnet = subnet;
_arp_gate_data[i].mask = mask;
++_arp_last_gateway; /* used up another one */
}
}
static void _arp_request( longword ip )
{
arp_Header *op;
op = (arp_Header *)_eth_formatpacket(&_eth_brdcast[0], 0x608);
op->hwType = arp_TypeEther;
op->protType = 0x008; /* IP */
op->hwProtAddrLen = sizeof(eth_address) + (sizeof(longword)<<8);
op->opcode = ARP_REQUEST;
op->srcIPAddr = intel( my_ip_addr );
movmem(_eth_addr, op->srcEthAddr, sizeof(eth_address));
op->dstIPAddr = intel( ip );
/* ...and send the packet */
_eth_send( sizeof(arp_Header) );
}
static word arp_index = 0; /* rotates round-robin */
static arp_tables *_arp_search( longword ip, int create )
{
int i;
arp_tables *arp_ptr;
for ( i = 0; i < MAX_ARP_DATA; ++i ) {
if ( ip == arp_data[i].ip )
return( &arp_data[i] );
}
/* didn't find any */
if ( create ) {
/* pick an old or empty one */
for ( i = 0; i < MAX_ARP_DATA ; ++i ) {
arp_ptr = &arp_data[i];
if ( ! arp_ptr->ip || chk_timeout(arp_ptr->expiry+MAX_ARP_GRACE))
return( arp_ptr );
}
/* pick one at pseudo-random */
return( &arp_data[ arp_index = ( arp_index + 1 ) % MAX_ARP_DATA ] );
}
return( NULL );
}
void _arp_register( longword use, longword instead_of )
{
word i;
arp_tables *arp_ptr;
if ( arp_ptr = _arp_search( instead_of, 0 )) {
/* now insert the address of the new guy */
arp_ptr->flags = ARP_FLAG_NEED;
_arp_resolve( use, &(arp_ptr->hardware));
arp_ptr->expiry = set_timeout( MAX_ARP_ALIVE );
return;
}
arp_ptr = _arp_search( use , 1 ); /* create a new one */
arp_ptr->flags = ARP_FLAG_NEED;
arp_ptr->ip = instead_of;
_arp_resolve( use, &(arp_ptr->hardware));
arp_ptr->expiry = set_timeout( MAX_ARP_ALIVE );
}
_arp_tick( longword ip )
{
arp_tables *arp_ptr;
if ( arp_ptr = _arp_search( ip , 0))
arp_ptr->expiry = set_timeout( MAX_ARP_ALIVE );
}
/*
* _arp_handler - handle incomming ARP packets
*/
_arp_handler( arp_Header *in)
{
arp_Header *op;
longword his_ip;
arp_tables *arp_ptr;
if ( in->hwType != arp_TypeEther || /* have ethernet hardware, */
in->protType != 8 ) /* and internet software, */
return( 0 );
/* continuously accept data - but only for people we talk to */
his_ip = intel( in->srcIPAddr );
if ( arp_ptr = _arp_search( his_ip, 0)) {
arp_ptr->expiry = set_timeout( MAX_ARP_ALIVE );
movmem( in->srcEthAddr, arp_ptr->hardware, sizeof( eth_address ));
arp_ptr->flags = ARP_FLAG_FOUND;
}
/* does someone else want our Ethernet address ? */
if ( in->opcode == ARP_REQUEST && /* and be a resolution req. */
((longword)(intel(in->dstIPAddr) - my_ip_addr ) <= multihomes )
) {
op = (arp_Header *)_eth_formatpacket(in->srcEthAddr, 0x0608);
op->hwType = arp_TypeEther;
op->protType = 0x008; /* intel for ip */
op->hwProtAddrLen = sizeof(eth_address) + (sizeof(longword) << 8 );
op->opcode = ARP_REPLY;
op->dstIPAddr = in->srcIPAddr;
op->srcIPAddr = in->dstIPAddr;
movmem(_eth_addr, op->srcEthAddr, sizeof(eth_address));
movmem(in->srcEthAddr, op->dstEthAddr, sizeof(eth_address));
_eth_send(sizeof(arp_Header));
return ( 1 );
}
}
/*
* _arp_resolve - resolve IP address to hardware address
*/
_arp_resolve( longword ina, eth_address *ethap)
{
static arp_tables *arp_ptr;
int i, oldhndlcbrk;
longword timeout, resend;
int packettype;
if ( _pktdevclass == PD_SLIP ) {
/* we are running slip or somthing which does not use addresses */
return( 1 );
}
if ( (longword)(ina - my_ip_addr) < multihomes) {
if (ethap)
movmem( _eth_addr, ethap, sizeof( eth_address ));
return( 1 );
}
/* attempt to solve with ARP cache */
/* fake while loop */
while ( arp_ptr = _arp_search( ina, 0)) {
if ( arp_ptr->flags != ARP_FLAG_NEED ) {
/* has been resolved */
#ifdef NEW_EXPIRY
if ( chk_timeout( arp_ptr->timeout ) {
if ( ! chk_timeout( arp_ptr->timeout + MAX_ARP_GRACE ) {
/* we wish to refresh it asynchronously */
_arp_request( ina );
else
break; /* must do full fledged arp */
#endif NEW_EXPIRY
if (ethap)
movmem( arp_ptr->hardware, ethap, sizeof(eth_address));
return( 1 );
}
break;
}
/* make a new one if necessary */
if (! arp_ptr )
arp_ptr = _arp_search( ina, 1 );
/* we must look elsewhere - but is it on our subnet??? */
if (( ina ^ my_ip_addr ) & sin_mask ) {
/* not of this network */
for ( i = 0; i < _arp_last_gateway ; ++i ) {
/* is the gateway on our subnet */
if ( ((_arp_gate_data[i].gate_ip ^ my_ip_addr ) & sin_mask ) == 0) {
/* compare the various subnet bits */
if ( (_arp_gate_data[i].mask & ina ) == _arp_gate_data[i].subnet ) {
if ( _arp_resolve( _arp_gate_data[i].gate_ip , ethap ))
return( 1 );
}
}
}
return( 0 );
}
/* return if no host, or no gateway */
if (! ina )
return( 0 );
/* is on our subnet, we must resolve */
timeout = set_timeout( 5 ); /* five seconds is long for ARP */
oldhndlcbrk = wathndlcbrk;
wathndlcbrk = 1;
watcbroke = 0;
while ( !chk_timeout( timeout )) {
/* do the request */
_arp_request( arp_ptr->ip = ina );
resend = set_timeout( 1 ) - 14L; /* 250 ms */
while (!chk_timeout( resend )) {
if (watcbroke) goto fail;
tcp_tick( NULL );
if ( arp_ptr->flags) {
if (ethap)
movmem( arp_ptr->hardware, ethap, sizeof(eth_address));
arp_ptr->expiry = set_timeout( MAX_ARP_ALIVE );
watcbroke = 0;
wathndlcbrk = oldhndlcbrk;
return ( 1 );
}
}
}
fail:
watcbroke = 0;
wathndlcbrk = oldhndlcbrk;
return ( 0 );
}