230 lines
6.7 KiB
C
230 lines
6.7 KiB
C
/* Kernel module to match FRAG parameters. */
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/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ipv6.h>
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#include <linux/types.h>
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#include <net/checksum.h>
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#include <net/ipv6.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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#include <linux/netfilter_ipv6/ip6t_frag.h>
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("IPv6 FRAG match");
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MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(format, args...)
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#endif
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/* Returns 1 if the id is matched by the range, 0 otherwise */
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static inline int
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id_match(u_int32_t min, u_int32_t max, u_int32_t id, int invert)
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{
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int r=0;
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DEBUGP("frag id_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
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min,id,max);
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r=(id >= min && id <= max) ^ invert;
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DEBUGP(" result %s\n",r? "PASS" : "FAILED");
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return r;
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}
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static int
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match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const void *matchinfo,
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int offset,
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unsigned int protoff,
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int *hotdrop)
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{
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struct frag_hdr _frag, *fh = NULL;
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const struct ip6t_frag *fraginfo = matchinfo;
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unsigned int temp;
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int len;
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u8 nexthdr;
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unsigned int ptr;
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unsigned int hdrlen = 0;
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/* type of the 1st exthdr */
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nexthdr = skb->nh.ipv6h->nexthdr;
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/* pointer to the 1st exthdr */
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ptr = sizeof(struct ipv6hdr);
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/* available length */
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len = skb->len - ptr;
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temp = 0;
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while (ip6t_ext_hdr(nexthdr)) {
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struct ipv6_opt_hdr _hdr, *hp;
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DEBUGP("ipv6_frag header iteration \n");
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/* Is there enough space for the next ext header? */
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if (len < (int)sizeof(struct ipv6_opt_hdr))
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return 0;
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/* No more exthdr -> evaluate */
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if (nexthdr == NEXTHDR_NONE) {
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break;
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}
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/* ESP -> evaluate */
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if (nexthdr == NEXTHDR_ESP) {
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break;
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}
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hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
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BUG_ON(hp == NULL);
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/* Calculate the header length */
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if (nexthdr == NEXTHDR_FRAGMENT) {
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hdrlen = 8;
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} else if (nexthdr == NEXTHDR_AUTH)
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hdrlen = (hp->hdrlen+2)<<2;
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else
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hdrlen = ipv6_optlen(hp);
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/* FRAG -> evaluate */
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if (nexthdr == NEXTHDR_FRAGMENT) {
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temp |= MASK_FRAGMENT;
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break;
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}
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/* set the flag */
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switch (nexthdr){
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case NEXTHDR_HOP:
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case NEXTHDR_ROUTING:
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case NEXTHDR_FRAGMENT:
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case NEXTHDR_AUTH:
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case NEXTHDR_DEST:
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break;
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default:
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DEBUGP("ipv6_frag match: unknown nextheader %u\n",nexthdr);
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return 0;
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break;
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}
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nexthdr = hp->nexthdr;
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len -= hdrlen;
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ptr += hdrlen;
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if ( ptr > skb->len ) {
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DEBUGP("ipv6_frag: new pointer too large! \n");
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break;
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}
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}
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/* FRAG header not found */
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if ( temp != MASK_FRAGMENT ) return 0;
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if (len < sizeof(struct frag_hdr)){
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*hotdrop = 1;
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return 0;
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}
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fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
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BUG_ON(fh == NULL);
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DEBUGP("INFO %04X ", fh->frag_off);
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DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
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DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
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DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
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DEBUGP("ID %u %08X\n", ntohl(fh->identification),
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ntohl(fh->identification));
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DEBUGP("IPv6 FRAG id %02X ",
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(id_match(fraginfo->ids[0], fraginfo->ids[1],
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ntohl(fh->identification),
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!!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
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DEBUGP("res %02X %02X%04X %02X ",
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(fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
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ntohs(fh->frag_off) & 0x6,
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!((fraginfo->flags & IP6T_FRAG_RES)
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&& (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
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DEBUGP("first %02X %02X %02X ",
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(fraginfo->flags & IP6T_FRAG_FST),
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ntohs(fh->frag_off) & ~0x7,
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!((fraginfo->flags & IP6T_FRAG_FST)
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&& (ntohs(fh->frag_off) & ~0x7)));
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DEBUGP("mf %02X %02X %02X ",
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(fraginfo->flags & IP6T_FRAG_MF),
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ntohs(fh->frag_off) & IP6_MF,
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!((fraginfo->flags & IP6T_FRAG_MF)
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&& !((ntohs(fh->frag_off) & IP6_MF))));
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DEBUGP("last %02X %02X %02X\n",
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(fraginfo->flags & IP6T_FRAG_NMF),
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ntohs(fh->frag_off) & IP6_MF,
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!((fraginfo->flags & IP6T_FRAG_NMF)
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&& (ntohs(fh->frag_off) & IP6_MF)));
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return (fh != NULL)
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&&
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(id_match(fraginfo->ids[0], fraginfo->ids[1],
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ntohl(fh->identification),
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!!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
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&&
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!((fraginfo->flags & IP6T_FRAG_RES)
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&& (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
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&&
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!((fraginfo->flags & IP6T_FRAG_FST)
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&& (ntohs(fh->frag_off) & ~0x7))
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&&
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!((fraginfo->flags & IP6T_FRAG_MF)
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&& !(ntohs(fh->frag_off) & IP6_MF))
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&&
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!((fraginfo->flags & IP6T_FRAG_NMF)
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&& (ntohs(fh->frag_off) & IP6_MF));
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}
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/* Called when user tries to insert an entry of this type. */
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static int
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checkentry(const char *tablename,
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const struct ip6t_ip6 *ip,
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void *matchinfo,
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unsigned int matchinfosize,
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unsigned int hook_mask)
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{
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const struct ip6t_frag *fraginfo = matchinfo;
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if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_frag))) {
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DEBUGP("ip6t_frag: matchsize %u != %u\n",
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matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_frag)));
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return 0;
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}
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if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
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DEBUGP("ip6t_frag: unknown flags %X\n",
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fraginfo->invflags);
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return 0;
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}
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return 1;
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}
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static struct ip6t_match frag_match = {
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.name = "frag",
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.match = &match,
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.checkentry = &checkentry,
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.me = THIS_MODULE,
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};
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static int __init init(void)
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{
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return ip6t_register_match(&frag_match);
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}
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static void __exit cleanup(void)
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{
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ip6t_unregister_match(&frag_match);
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}
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module_init(init);
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module_exit(cleanup);
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