// SPDX-License-Identifier: GPL-2.0-only
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/* Kernel module to match Hop-by-Hop and Destination 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 <asm/byteorder.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_opts.h>
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Xtables: IPv6 Hop-By-Hop and Destination Header match");
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MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
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MODULE_ALIAS("ip6t_dst");
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/*
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* (Type & 0xC0) >> 6
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* 0 -> ignorable
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* 1 -> must drop the packet
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* 2 -> send ICMP PARM PROB regardless and drop packet
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* 3 -> Send ICMP if not a multicast address and drop packet
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* (Type & 0x20) >> 5
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* 0 -> invariant
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* 1 -> can change the routing
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* (Type & 0x1F) Type
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* 0 -> Pad1 (only 1 byte!)
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* 1 -> PadN LENGTH info (total length = length + 2)
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* C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k )
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* 5 -> RTALERT 2 x x
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*/
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static struct xt_match hbh_mt6_reg[] __read_mostly;
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static bool
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hbh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
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{
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struct ipv6_opt_hdr _optsh;
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const struct ipv6_opt_hdr *oh;
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const struct ip6t_opts *optinfo = par->matchinfo;
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unsigned int temp;
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unsigned int ptr = 0;
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unsigned int hdrlen = 0;
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bool ret = false;
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u8 _opttype;
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u8 _optlen;
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const u_int8_t *tp = NULL;
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const u_int8_t *lp = NULL;
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unsigned int optlen;
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int err;
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err = ipv6_find_hdr(skb, &ptr,
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(par->match == &hbh_mt6_reg[0]) ?
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NEXTHDR_HOP : NEXTHDR_DEST, 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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oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
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if (oh == NULL) {
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par->hotdrop = true;
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return false;
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}
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hdrlen = ipv6_optlen(oh);
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if (skb->len - ptr < hdrlen) {
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/* Packet smaller than it's length field */
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return false;
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}
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pr_debug("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
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pr_debug("len %02X %04X %02X ",
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optinfo->hdrlen, hdrlen,
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(!(optinfo->flags & IP6T_OPTS_LEN) ||
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((optinfo->hdrlen == hdrlen) ^
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!!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
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ret = (!(optinfo->flags & IP6T_OPTS_LEN) ||
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((optinfo->hdrlen == hdrlen) ^
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!!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
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ptr += 2;
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hdrlen -= 2;
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if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
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return ret;
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} else {
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pr_debug("Strict ");
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pr_debug("#%d ", optinfo->optsnr);
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for (temp = 0; temp < optinfo->optsnr; temp++) {
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/* type field exists ? */
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if (hdrlen < 1)
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break;
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tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
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&_opttype);
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if (tp == NULL)
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break;
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/* Type check */
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if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
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pr_debug("Tbad %02X %02X\n", *tp,
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(optinfo->opts[temp] & 0xFF00) >> 8);
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return false;
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} else {
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pr_debug("Tok ");
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}
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/* Length check */
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if (*tp) {
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u16 spec_len;
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/* length field exists ? */
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if (hdrlen < 2)
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break;
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lp = skb_header_pointer(skb, ptr + 1,
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sizeof(_optlen),
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&_optlen);
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if (lp == NULL)
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break;
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spec_len = optinfo->opts[temp] & 0x00FF;
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if (spec_len != 0x00FF && spec_len != *lp) {
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pr_debug("Lbad %02X %04X\n", *lp,
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spec_len);
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return false;
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}
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pr_debug("Lok ");
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optlen = *lp + 2;
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} else {
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pr_debug("Pad1\n");
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optlen = 1;
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}
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/* Step to the next */
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pr_debug("len%04X\n", optlen);
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if ((ptr > skb->len - optlen || hdrlen < optlen) &&
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temp < optinfo->optsnr - 1) {
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pr_debug("new pointer is too large!\n");
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break;
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}
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ptr += optlen;
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hdrlen -= optlen;
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}
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if (temp == optinfo->optsnr)
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return ret;
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else
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return false;
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}
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return false;
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}
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static int hbh_mt6_check(const struct xt_mtchk_param *par)
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{
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const struct ip6t_opts *optsinfo = par->matchinfo;
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if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
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pr_debug("unknown flags %X\n", optsinfo->invflags);
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return -EINVAL;
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}
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if (optsinfo->flags & IP6T_OPTS_NSTRICT) {
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pr_debug("Not strict - not implemented");
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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 hbh_mt6_reg[] __read_mostly = {
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{
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/* Note, hbh_mt6 relies on the order of hbh_mt6_reg */
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.name = "hbh",
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.family = NFPROTO_IPV6,
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.match = hbh_mt6,
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.matchsize = sizeof(struct ip6t_opts),
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.checkentry = hbh_mt6_check,
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.me = THIS_MODULE,
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},
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{
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.name = "dst",
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.family = NFPROTO_IPV6,
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.match = hbh_mt6,
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.matchsize = sizeof(struct ip6t_opts),
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.checkentry = hbh_mt6_check,
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.me = THIS_MODULE,
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},
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};
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static int __init hbh_mt6_init(void)
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{
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return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
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}
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static void __exit hbh_mt6_exit(void)
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{
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xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
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}
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module_init(hbh_mt6_init);
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module_exit(hbh_mt6_exit);
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