// SPDX-License-Identifier: GPL-2.0-only
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/* 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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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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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/x_tables.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("Xtables: IPv6 fragment match");
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MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
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/* Returns 1 if the id is matched by the range, 0 otherwise */
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static inline bool
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id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
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{
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bool r;
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pr_debug("id_match:%c 0x%x <= 0x%x <= 0x%x\n", invert ? '!' : ' ',
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min, id, max);
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r = (id >= min && id <= max) ^ invert;
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pr_debug(" result %s\n", r ? "PASS" : "FAILED");
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return r;
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}
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static bool
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frag_mt6(const struct sk_buff *skb, struct xt_action_param *par)
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{
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struct frag_hdr _frag;
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const struct frag_hdr *fh;
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const struct ip6t_frag *fraginfo = par->matchinfo;
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unsigned int ptr = 0;
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int err;
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err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL, NULL);
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if (err < 0) {
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if (err != -ENOENT)
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par->hotdrop = true;
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return false;
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}
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fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
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if (fh == NULL) {
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par->hotdrop = true;
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return false;
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}
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pr_debug("INFO %04X ", fh->frag_off);
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pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
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pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
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pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
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pr_debug("ID %u %08X\n", ntohl(fh->identification),
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ntohl(fh->identification));
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pr_debug("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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pr_debug("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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pr_debug("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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pr_debug("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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pr_debug("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 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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!((fraginfo->flags & IP6T_FRAG_RES) &&
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(fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
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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_MF) &&
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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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}
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static int frag_mt6_check(const struct xt_mtchk_param *par)
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{
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const struct ip6t_frag *fraginfo = par->matchinfo;
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if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
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pr_debug("unknown flags %X\n", fraginfo->invflags);
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return -EINVAL;
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}
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return 0;
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}
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static struct xt_match frag_mt6_reg __read_mostly = {
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.name = "frag",
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.family = NFPROTO_IPV6,
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.match = frag_mt6,
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.matchsize = sizeof(struct ip6t_frag),
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.checkentry = frag_mt6_check,
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.me = THIS_MODULE,
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};
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static int __init frag_mt6_init(void)
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{
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return xt_register_match(&frag_mt6_reg);
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}
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static void __exit frag_mt6_exit(void)
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{
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xt_unregister_match(&frag_mt6_reg);
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}
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module_init(frag_mt6_init);
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module_exit(frag_mt6_exit);
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