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Linux/net/ipv6/netfilter/ip6t_frag.c

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  1 /* Kernel module to match FRAG parameters. */
  2 
  3 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License version 2 as
  7  * published by the Free Software Foundation.
  8  */
  9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 10 #include <linux/module.h>
 11 #include <linux/skbuff.h>
 12 #include <linux/ipv6.h>
 13 #include <linux/types.h>
 14 #include <net/checksum.h>
 15 #include <net/ipv6.h>
 16 
 17 #include <linux/netfilter/x_tables.h>
 18 #include <linux/netfilter_ipv6/ip6_tables.h>
 19 #include <linux/netfilter_ipv6/ip6t_frag.h>
 20 
 21 MODULE_LICENSE("GPL");
 22 MODULE_DESCRIPTION("Xtables: IPv6 fragment match");
 23 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
 24 
 25 /* Returns 1 if the id is matched by the range, 0 otherwise */
 26 static inline bool
 27 id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
 28 {
 29         bool r;
 30         pr_debug("id_match:%c 0x%x <= 0x%x <= 0x%x\n", invert ? '!' : ' ',
 31                  min, id, max);
 32         r = (id >= min && id <= max) ^ invert;
 33         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
 34         return r;
 35 }
 36 
 37 static bool
 38 frag_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 39 {
 40         struct frag_hdr _frag;
 41         const struct frag_hdr *fh;
 42         const struct ip6t_frag *fraginfo = par->matchinfo;
 43         unsigned int ptr = 0;
 44         int err;
 45 
 46         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL, NULL);
 47         if (err < 0) {
 48                 if (err != -ENOENT)
 49                         par->hotdrop = true;
 50                 return false;
 51         }
 52 
 53         fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
 54         if (fh == NULL) {
 55                 par->hotdrop = true;
 56                 return false;
 57         }
 58 
 59         pr_debug("INFO %04X ", fh->frag_off);
 60         pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
 61         pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
 62         pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
 63         pr_debug("ID %u %08X\n", ntohl(fh->identification),
 64                  ntohl(fh->identification));
 65 
 66         pr_debug("IPv6 FRAG id %02X ",
 67                  id_match(fraginfo->ids[0], fraginfo->ids[1],
 68                           ntohl(fh->identification),
 69                           !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
 70         pr_debug("res %02X %02X%04X %02X ",
 71                  fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
 72                  ntohs(fh->frag_off) & 0x6,
 73                  !((fraginfo->flags & IP6T_FRAG_RES) &&
 74                    (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
 75         pr_debug("first %02X %02X %02X ",
 76                  fraginfo->flags & IP6T_FRAG_FST,
 77                  ntohs(fh->frag_off) & ~0x7,
 78                  !((fraginfo->flags & IP6T_FRAG_FST) &&
 79                    (ntohs(fh->frag_off) & ~0x7)));
 80         pr_debug("mf %02X %02X %02X ",
 81                  fraginfo->flags & IP6T_FRAG_MF,
 82                  ntohs(fh->frag_off) & IP6_MF,
 83                  !((fraginfo->flags & IP6T_FRAG_MF) &&
 84                    !((ntohs(fh->frag_off) & IP6_MF))));
 85         pr_debug("last %02X %02X %02X\n",
 86                  fraginfo->flags & IP6T_FRAG_NMF,
 87                  ntohs(fh->frag_off) & IP6_MF,
 88                  !((fraginfo->flags & IP6T_FRAG_NMF) &&
 89                    (ntohs(fh->frag_off) & IP6_MF)));
 90 
 91         return (fh != NULL) &&
 92                 id_match(fraginfo->ids[0], fraginfo->ids[1],
 93                          ntohl(fh->identification),
 94                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)) &&
 95                 !((fraginfo->flags & IP6T_FRAG_RES) &&
 96                   (fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
 97                 !((fraginfo->flags & IP6T_FRAG_FST) &&
 98                   (ntohs(fh->frag_off) & ~0x7)) &&
 99                 !((fraginfo->flags & IP6T_FRAG_MF) &&
100                   !(ntohs(fh->frag_off) & IP6_MF)) &&
101                 !((fraginfo->flags & IP6T_FRAG_NMF) &&
102                   (ntohs(fh->frag_off) & IP6_MF));
103 }
104 
105 static int frag_mt6_check(const struct xt_mtchk_param *par)
106 {
107         const struct ip6t_frag *fraginfo = par->matchinfo;
108 
109         if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
110                 pr_debug("unknown flags %X\n", fraginfo->invflags);
111                 return -EINVAL;
112         }
113         return 0;
114 }
115 
116 static struct xt_match frag_mt6_reg __read_mostly = {
117         .name           = "frag",
118         .family         = NFPROTO_IPV6,
119         .match          = frag_mt6,
120         .matchsize      = sizeof(struct ip6t_frag),
121         .checkentry     = frag_mt6_check,
122         .me             = THIS_MODULE,
123 };
124 
125 static int __init frag_mt6_init(void)
126 {
127         return xt_register_match(&frag_mt6_reg);
128 }
129 
130 static void __exit frag_mt6_exit(void)
131 {
132         xt_unregister_match(&frag_mt6_reg);
133 }
134 
135 module_init(frag_mt6_init);
136 module_exit(frag_mt6_exit);
137 

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