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/*
* $Id: frag.c,v 1.1 1997/08/12 16:37:50 begemot Exp begemot $
* $Log: frag.c,v $
* Revision 1.1 1997/08/12 16:37:50 begemot
* Initial revision
*
*/
/*
* Copyright (C) 1994-1996 D.Gorodchanin. See COPYING for more info.
*/
#include "trafshow.h"
#define HASH_BITS 8
#define HASH_SIZE (1 << HASH_BITS)
#define HASH(x) ((x ^ (x >> 8)) & (HASH_SIZE - 1))
#define TABLE_SIZE (FRAGS_COUNT + 1)
struct hash_entry {
unsigned long next;
unsigned long saddr;
unsigned long daddr;
unsigned long type;
unsigned long len;
unsigned long seq;
unsigned short id;
char resolved;
char protocol;
};
static struct hash_entry table[TABLE_SIZE];
static unsigned int hash_table[HASH_SIZE];
static unsigned long lookup_no = 1;
static struct hash_entry * lookup(const struct iphdr * iph)
{
int h;
h = hash_table[HASH(iph->id)];
#ifdef FRAG_DEBUG
fprintf(stderr, "Lookup id %x h %d ", iph->id, h);
#endif
while ( h ) {
if (iph->id == table[h].id &&
iph->saddr == table[h].saddr &&
iph->daddr == table[h].daddr &&
iph->protocol == table[h].protocol) {
table[h].seq = ++lookup_no;
#ifdef FRAG_DEBUG
fprintf(stderr, "returns %p (%d)\n", table+h, h);
#endif
return table + h;
}
h = table[h].next;
}
#ifdef FRAG_DEBUG
fprintf(stderr, "returns NULL\n");
#endif
return NULL;
}
static struct hash_entry * insert(const struct iphdr * iph)
{
unsigned int i;
unsigned long minseq = lookup_no;
unsigned int minno = 0;
for (i = 1; i < TABLE_SIZE; i++) {
if (table[i].seq < minseq) {
minno = i;
if (!(minseq = table[i].seq)) {
break;
}
}
}
#ifdef FRAG_DEBUG
fprintf(stderr, "Insert id = %x, minno = %d, minseq = %d ",
iph->id, minno, minseq);
#endif
if (minseq) {
i = hash_table[HASH(table[minno].id)];
if (i == minno) {
hash_table[HASH(table[minno].id)] = table[i].next;
} else {
while (table[i].next != minno) {
if (!table[i].next) {
#ifdef FRAG_DEBUG
fprintf (stderr,"frag: Internal logic error in hash management!!!!\n");
#endif
exit(1);
}
i = table[i].next;
}
table[i].next = table[minno].next;
}
}
table[minno].seq = ++lookup_no;
table[minno].saddr = iph->saddr;
table[minno].daddr = iph->daddr;
table[minno].protocol = iph->protocol;
table[minno].id = iph->id;
table[minno].len = 0;
table[minno].resolved = 0;
table[minno].next = hash_table[HASH(iph->id)];
hash_table[HASH(iph->id)] = minno;
#ifdef FRAG_DEBUG
fprintf(stderr, "returns %p (%d)\n", table + minno, minno);
#endif
return table + minno;
}
int handle_fragment(struct iphdr * iph, int len)
{
struct hash_entry * h;
#ifdef FRAG_DEBUG
fprintf(stderr, "packet : src %x dst %x id %x frag %x proto %x len %x\n",
iph->saddr, iph->daddr, iph->id, iph->frag_off, iph->protocol, len);
#endif
if (!(h = lookup(iph))) {
#ifdef FRAG_DEBUG
fprintf(stderr, "Lookup failed !\n");
#endif
h = insert(iph);
}
#ifdef FRAG_DEBUG
fprintf(stderr,"entry: %p src %x dst %x id %x proto %x len %d h->len %d resolved %d\n",
h, h->saddr, h->daddr, h->id, h->protocol, len, h->len, h->resolved);
#endif
if (!(iph->frag_off & 0xff1f)) {
/* First fragment */
len += h->len;
h->len = 0;
h->resolved = 1;
memcpy(&h->type, (unsigned long *)iph + iph->ihl, 4);
#ifdef FRAG_DEBUG
fprintf(stderr, "first fragment, return %d\n", len);
#endif
return len;
}
if (h->resolved) {
memcpy((unsigned long *)iph + iph->ihl, &h->type, 4);
#ifdef FRAG_DEBUG
fprintf(stderr, "header copied, return %d\n", len);
#endif
return len;
}
h->len += len;
#ifdef FRAG_DEBUG
fprintf(stderr, "no first, h->len %d\n", h->len);
#endif
return 0;
}
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