FRAGMENT.C
资源名称:ertos.rar [点击查看]
上传用户:sunrenlu
上传日期:2022-06-13
资源大小:1419k
文件大小:8k
源码类别:
操作系统开发
开发平台:
DOS
- /*
- * 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_BUFSn" );/*DEBUG STUFF*/
- #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 );/*DEBUG STUFF*/
- #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( " newn" );/*DEBUG STUFF*/
- #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 );/*DEBUG STUFF*/
- #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 );/*DEBUG STUFF*/
- #endif
- }
- else {
- // No, delete current hole
- #ifdef ANIMATE
- printf( " del" );/* DEBUG STUFF*/
- #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 );/*DEBUG STUFF*/
- #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((char *)ip);
- // Now do we have all the parts?
- if (!my_frag->hole_first)
- {
- #ifdef ANIMATE
- printf( " COMPLETEn" );/*DEBUG STUFF*/
- #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_COMEn" );/*DEBUG STUFF*/
- #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 outn" );/*DEBUG STUFF*/
- #endif
- fraglist[i].used = 0;
- active_frags--;
- pkt_buf_release((char *)fraglist[i].ip);
- }
- }