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FRAGMENT.C
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Text File
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1997-03-08
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9KB
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276 lines
/*
* Packet De-Fragmentaion code for WATTCP
* Written by and COPYRIGHT (c)1993 to Quentin Smart
* smart@actrix.gen.nz
* all rights reserved.
*
* This software is distributed in the hope that it will be useful,
* but without any warranty; without even the implied warranty of
* merchantability or fitness for a particular purpose.
*
* You may freely distribute this source code, but if distributed for
* financial gain then only executables derived from the source may be
* sold.
*
* Murf = Murf@perftech.com
* other fragfix = mdurkin@tsoft.net
*
* Based on RFC815
*/
#include <mem.h>
#include <stdlib.h>
#include "wattcp.h"
/* Murf's code structuring macros */ /* add 94.09.16 */
#define LOOP for (;;)
#define LOOPASSERT( c ) if (!(c)) break
/* Murf's macro to get a structure address from a member address */
#define structure(S,m,p) ((S *)( (byte *)(p) - (byte *) &((S *)0)->m ))
/* #define ANIMATE */
#define MAXBUFS 5 /* maximum number of Ethernet buffers */
#define MAXFRAGS MAXBUFS-1
#define FRAGHOLDTIME 15 /* 15 secs to hold before discarding */
#define INFINITY 30000
#define IP_HEADER_SIZE 20
#define IP_MF 0x0020 // More fragment in INTEL form
typedef struct {
longword source;
// longword destination;
byte proto; // use proto now
word identification;
} fragkey;
typedef struct hd {
struct hd * next;
int start;
int end;
} hole_descr;
typedef struct {
byte used; // this position in table in use
fragkey key;
hole_descr *hole_first;
longword timer;
in_Header *ip;
byte *data_offset;
} fraghdr;
static fraghdr fraglist[MAXFRAGS] = {{0,{0,0},NULL,0,NULL},
{0,{0,0},NULL,0,NULL},
{0,{0,0},NULL,0,NULL},
{0,{0,0},NULL,0,NULL}};
int active_frags = 0;
extern word _pktipofs; /* offset from header to start of pkt */
/* Fragment is called if the frag section of the IP header is not zero and DF bit not set */
byte *fragment( in_Header * ip )
{
//int fc;
fraghdr *my_frag;
hole_descr *hole = NULL;
hole_descr *prev_hole = NULL;
fragkey key;
int found = 0;
int got_hole = 0;
int data_start;
int data_end;
int data_length;
int temp,i;
int more_frags; // Set to true if this is the last frag
/*byte * buffer; */
// Should check that the packet is actually valid and do a checksum on it.
// Assemble key
key.proto = ip->proto; // use proto now
key.source=ip->source;
key.identification = ip->identification;
// Check if we have a match
for (i=0;i<MAXFRAGS && !found;i++)
if (fraglist[i].used && !memcmp(&key,&fraglist[i].key,sizeof(fragkey)))
{
found = TRUE;
my_frag = &fraglist[i];
}
if (!found && active_frags == MAXFRAGS) {
#ifdef ANIMATE
printf( "NO_BUFS\n" );
#endif
// Can't handle any new frags, biff packet so that we can continue
// Could do direct!
pkt_buf_release((char*)ip);
return(NULL); // We can't handle any new frags!
}
// Should biff packet?
// Calc where data should go
// fragfix - next line replaces... no more bitfields
data_start = intel16(ip->frags) << 3; //* 8
data_length = intel16(ip->length)-in_GetHdrlenBytes(ip);
data_end = data_start + data_length - 1; // Murf 94.09.16
more_frags = ip->frags & IP_MF;
#ifdef ANIMATE
printf( "Data=%d..%d", data_start, data_end );
#endif
if (!found)
{
// Mark as used
*((byte *)ip - (2 + _pktipofs)) = 2;
// Find first empty slot
for (i=0;i < MAXFRAGS && fraglist[i].used;i++);
my_frag = &fraglist[i];
// mark as used
my_frag->used = 1;
// inc active frags counter
active_frags++;
// Setup frag header data, first packet
memcpy(&my_frag->key,&key,sizeof(key));
my_frag->timer = set_timeout(max(FRAGHOLDTIME,ip->ttl));
my_frag->ip = ip;
// Set pointers to beinging of IP packet data
my_frag->data_offset = (byte *)my_frag->ip + in_GetHdrlenBytes(ip);
// Setup initial hole table
if (data_start) // i.e. not Zero
{
memcpy(my_frag->data_offset + data_start,(byte *)ip+in_GetHdrlenBytes(ip),data_length);
// Bracket beginning of data
hole = my_frag->hole_first = (hole_descr *)my_frag->data_offset;
hole->start = 0;
hole->end = data_start-1;
if (more_frags) {
// data_start was missing in next line - Murf 94.09.16
hole->next = (hole_descr *)(my_frag->data_offset + data_start + data_length + 1);
hole = hole->next;
}
else
{
hole = my_frag->hole_first->next = NULL;
// Adjust length
ip->length = intel16(data_end + in_GetHdrlenBytes(ip));
}
}
else
{
// Setup
hole = my_frag->hole_first = (hole_descr*)(my_frag->data_offset + data_length + 1);
}
// Bracket end
if (hole) {
// data_start was missing in next line - Murf 94.09.16
hole->start = data_start + data_length;// + 1;
hole->end = INFINITY;
hole->next = NULL;
}
#ifdef ANIMATE
printf( " new\n" );
#endif
return NULL; // Go back for more!
} // End !found
// Adjust length
if (!more_frags)
my_frag->ip->length = intel16(data_end + 1 + in_GetHdrlenBytes(ip)); // Murf 94.09.16
// Hole handling
hole = structure( hole_descr, next, &my_frag->hole_first ); // Murf 94.09.16
LOOP { // Murf 94.09.16
prev_hole = hole; // Murf 94.09.16
hole = hole->next; // Murf 94.09.16
LOOPASSERT (hole); // Murf 94.09.16
#ifdef ANIMATE
printf( " hole=%d..%d(%d)", hole->start, hole->end, hole->next );
#endif
if (!(data_start > hole->end) && !(data_end < hole->start)) {
// We've found the spot
// Mark as got.
got_hole =1;
// Find where to insert
// Check is there a hole before the new frag
temp = hole->end; // Pick up old hole end for later;
if (data_start > hole->start) {
hole->end = data_start-1;
prev_hole = hole; // We have a new prev
#ifdef ANIMATE
printf( "->%d..%d(%d)", hole->start, hole->end, hole->next );
#endif
}
else {
// No, delete current hole
#ifdef ANIMATE
printf( " del" );
#endif
prev_hole->next = hole->next;
hole = prev_hole; // Leave hole valid - Murf 94.09.16
}
// Is there a hole after the current fragment
// Only if we're not last and more to come
if (data_end < temp && more_frags) { // fragfix - Murf 94.09.14
hole = (hole_descr *)(data_end + 1 + my_frag->data_offset);
hole->start = data_end+1;
hole->end = temp;
hole->next = prev_hole->next;
prev_hole->next = hole;
#ifdef ANIMATE
printf( ",%d..%d(%d)", hole->start, hole->end, hole->next );
#endif
}
}
}
// Thats all setup so copy in the data
if (got_hole)
memcpy(my_frag->data_offset + data_start,(byte *)ip+in_GetHdrlenBytes(ip),data_length);
// And release the buffer;
pkt_buf_release((byte *)ip);
// Now do we have all the parts?
if (!my_frag->hole_first)
{
#ifdef ANIMATE
printf( " COMPLETE\n" );
#endif
my_frag->used = 0;
active_frags--;
// Redo checksum as we've changed the length in the header
my_frag->ip->checksum = 0; // Zero
my_frag->ip->checksum = ~ checksum( my_frag->ip, sizeof( in_Header ));
return((byte *)my_frag->ip - _pktipofs);
}
#ifdef ANIMATE
printf( " MORE_TO_COME\n" );
#endif
return NULL;
}
void timeout_frags( void )
{
int i;
for (i=0;i<MAXFRAGS;i++)
if (fraglist[i].used)
if (chk_timeout(fraglist[i].timer))
{
#ifdef ANIMATE
printf( "BUF timed out\n" );
#endif
fraglist[i].used = 0;
active_frags--;
pkt_buf_release((byte *)fraglist[i].ip);
}
}