net/netfilter/xt_HMARK.c

   1 /*
   2  * xt_HMARK - Netfilter module to set mark by means of hashing
   3  *
   4  * (C) 2012 by Hans Schillstrom <hans.schillstrom@ericsson.com>
   5  * (C) 2012 by Pablo Neira Ayuso <pablo@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/icmp.h>
  15
  16 #include <linux/netfilter/x_tables.h>
  17 #include <linux/netfilter/xt_HMARK.h>
  18
  19 #include <net/ip.h>
  20 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  21 #include <net/netfilter/nf_conntrack.h>
  22 #endif
  23 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  24 #include <net/ipv6.h>
  25 #include <linux/netfilter_ipv6/ip6_tables.h>
  26 #endif
  27
  28 MODULE_LICENSE("GPL");
  29 MODULE_AUTHOR("Hans Schillstrom <hans.schillstrom@ericsson.com>");
  30 MODULE_DESCRIPTION("Xtables: packet marking using hash calculation");
  31 MODULE_ALIAS("ipt_HMARK");
  32 MODULE_ALIAS("ip6t_HMARK");
  33
  34 struct hmark_tuple {
  35         __be32                  src;
  36         __be32                  dst;
  37         union hmark_ports       uports;
  38         u8                      proto;
  39 };
  40
  41 static inline __be32 hmark_addr6_mask(const __be32 *addr32, const __be32 *mask)
  42 {
  43         return (addr32[0] & mask[0]) ^
  44                (addr32[1] & mask[1]) ^
  45                (addr32[2] & mask[2]) ^
  46                (addr32[3] & mask[3]);
  47 }
  48
  49 static inline __be32
  50 hmark_addr_mask(int l3num, const __be32 *addr32, const __be32 *mask)
  51 {
  52         switch (l3num) {
  53         case AF_INET:
  54                 return *addr32 & *mask;
  55         case AF_INET6:
  56                 return hmark_addr6_mask(addr32, mask);
  57         }
  58         return 0;
  59 }
  60
  61 static inline void hmark_swap_ports(union hmark_ports *uports,
  62                                     const struct xt_hmark_info *info)
  63 {
  64         union hmark_ports hp;
  65         u16 src, dst;
  66
  67         hp.b32 = (uports->b32 & info->port_mask.b32) | info->port_set.b32;
  68         src = ntohs(hp.b16.src);
  69         dst = ntohs(hp.b16.dst);
  70
  71         if (dst > src)
  72                 uports->v32 = (dst << 16) | src;
  73         else
  74                 uports->v32 = (src << 16) | dst;
  75 }
  76
  77 static int
  78 hmark_ct_set_htuple(const struct sk_buff *skb, struct hmark_tuple *t,
  79                     const struct xt_hmark_info *info)
  80 {
  81 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  82         enum ip_conntrack_info ctinfo;
  83         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  84         struct nf_conntrack_tuple *otuple;
  85         struct nf_conntrack_tuple *rtuple;
  86
  87         if (ct == NULL)
  88                 return -1;
  89
  90         otuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  91         rtuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  92
  93         t->src = hmark_addr_mask(otuple->src.l3num, otuple->src.u3.ip6,
  94                                  info->src_mask.ip6);
  95         t->dst = hmark_addr_mask(otuple->src.l3num, rtuple->src.u3.ip6,
  96                                  info->dst_mask.ip6);
  97
  98         if (info->flags & XT_HMARK_FLAG(XT_HMARK_METHOD_L3))
  99                 return 0;
 100
 101         t->proto = nf_ct_protonum(ct);
 102         if (t->proto != IPPROTO_ICMP) {
 103                 t->uports.b16.src = otuple->src.u.all;
 104                 t->uports.b16.dst = rtuple->src.u.all;
 105                 hmark_swap_ports(&t->uports, info);
 106         }
 107
 108         return 0;
 109 #else
 110         return -1;
 111 #endif
 112 }
 113
 114 /* This hash function is endian independent, to ensure consistent hashing if
 115  * the cluster is composed of big and little endian systems. */
 116 static inline u32
 117 hmark_hash(struct hmark_tuple *t, const struct xt_hmark_info *info)
 118 {
 119         u32 hash;
 120         u32 src = ntohl(t->src);
 121         u32 dst = ntohl(t->dst);
 122
 123         if (dst < src)
 124                 swap(src, dst);
 125
 126         hash = jhash_3words(src, dst, t->uports.v32, info->hashrnd);
 127         hash = hash ^ (t->proto & info->proto_mask);
 128
 129         return reciprocal_scale(hash, info->hmodulus) + info->hoffset;
 130 }
 131
 132 static void
 133 hmark_set_tuple_ports(const struct sk_buff *skb, unsigned int nhoff,
 134                       struct hmark_tuple *t, const struct xt_hmark_info *info)
 135 {
 136         int protoff;
 137
 138         protoff = proto_ports_offset(t->proto);
 139         if (protoff < 0)
 140                 return;
 141
 142         nhoff += protoff;
 143         if (skb_copy_bits(skb, nhoff, &t->uports, sizeof(t->uports)) < 0)
 144                 return;
 145
 146         hmark_swap_ports(&t->uports, info);
 147 }
 148
 149 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 150 static int get_inner6_hdr(const struct sk_buff *skb, int *offset)
 151 {
 152         struct icmp6hdr *icmp6h, _ih6;
 153
 154         icmp6h = skb_header_pointer(skb, *offset, sizeof(_ih6), &_ih6);
 155         if (icmp6h == NULL)
 156                 return 0;
 157
 158         if (icmp6h->icmp6_type && icmp6h->icmp6_type < 128) {
 159                 *offset += sizeof(struct icmp6hdr);
 160                 return 1;
 161         }
 162         return 0;
 163 }
 164
 165 static int
 166 hmark_pkt_set_htuple_ipv6(const struct sk_buff *skb, struct hmark_tuple *t,
 167                           const struct xt_hmark_info *info)
 168 {
 169         struct ipv6hdr *ip6, _ip6;
 170         int flag = IP6_FH_F_AUTH;
 171         unsigned int nhoff = 0;
 172         u16 fragoff = 0;
 173         int nexthdr;
 174
 175         ip6 = (struct ipv6hdr *) (skb->data + skb_network_offset(skb));
 176         nexthdr = ipv6_find_hdr(skb, &nhoff, -1, &fragoff, &flag);
 177         if (nexthdr < 0)
 178                 return 0;
 179         /* No need to check for icmp errors on fragments */
 180         if ((flag & IP6_FH_F_FRAG) || (nexthdr != IPPROTO_ICMPV6))
 181                 goto noicmp;
 182         /* Use inner header in case of ICMP errors */
 183         if (get_inner6_hdr(skb, &nhoff)) {
 184                 ip6 = skb_header_pointer(skb, nhoff, sizeof(_ip6), &_ip6);
 185                 if (ip6 == NULL)
 186                         return -1;
 187                 /* If AH present, use SPI like in ESP. */
 188                 flag = IP6_FH_F_AUTH;
 189                 nexthdr = ipv6_find_hdr(skb, &nhoff, -1, &fragoff, &flag);
 190                 if (nexthdr < 0)
 191                         return -1;
 192         }
 193 noicmp:
 194         t->src = hmark_addr6_mask(ip6->saddr.s6_addr32, info->src_mask.ip6);
 195         t->dst = hmark_addr6_mask(ip6->daddr.s6_addr32, info->dst_mask.ip6);
 196
 197         if (info->flags & XT_HMARK_FLAG(XT_HMARK_METHOD_L3))
 198                 return 0;
 199
 200         t->proto = nexthdr;
 201         if (t->proto == IPPROTO_ICMPV6)
 202                 return 0;
 203
 204         if (flag & IP6_FH_F_FRAG)
 205                 return 0;
 206
 207         hmark_set_tuple_ports(skb, nhoff, t, info);
 208         return 0;
 209 }
 210
 211 static unsigned int
 212 hmark_tg_v6(struct sk_buff *skb, const struct xt_action_param *par)
 213 {
 214         const struct xt_hmark_info *info = par->targinfo;
 215         struct hmark_tuple t;
 216
 217         memset(&t, 0, sizeof(struct hmark_tuple));
 218
 219         if (info->flags & XT_HMARK_FLAG(XT_HMARK_CT)) {
 220                 if (hmark_ct_set_htuple(skb, &t, info) < 0)
 221                         return XT_CONTINUE;
 222         } else {
 223                 if (hmark_pkt_set_htuple_ipv6(skb, &t, info) < 0)
 224                         return XT_CONTINUE;
 225         }
 226
 227         skb->mark = hmark_hash(&t, info);
 228         return XT_CONTINUE;
 229 }
 230 #endif
 231
 232 static int get_inner_hdr(const struct sk_buff *skb, int iphsz, int *nhoff)
 233 {
 234         const struct icmphdr *icmph;
 235         struct icmphdr _ih;
 236
 237         /* Not enough header? */
 238         icmph = skb_header_pointer(skb, *nhoff + iphsz, sizeof(_ih), &_ih);
 239         if (icmph == NULL || icmph->type > NR_ICMP_TYPES)
 240                 return 0;
 241
 242         /* Error message? */
 243         if (icmph->type != ICMP_DEST_UNREACH &&
 244             icmph->type != ICMP_SOURCE_QUENCH &&
 245             icmph->type != ICMP_TIME_EXCEEDED &&
 246             icmph->type != ICMP_PARAMETERPROB &&
 247             icmph->type != ICMP_REDIRECT)
 248                 return 0;
 249
 250         *nhoff += iphsz + sizeof(_ih);
 251         return 1;
 252 }
 253
 254 static int
 255 hmark_pkt_set_htuple_ipv4(const struct sk_buff *skb, struct hmark_tuple *t,
 256                           const struct xt_hmark_info *info)
 257 {
 258         struct iphdr *ip, _ip;
 259         int nhoff = skb_network_offset(skb);
 260
 261         ip = (struct iphdr *) (skb->data + nhoff);
 262         if (ip->protocol == IPPROTO_ICMP) {
 263                 /* Use inner header in case of ICMP errors */
 264                 if (get_inner_hdr(skb, ip->ihl * 4, &nhoff)) {
 265                         ip = skb_header_pointer(skb, nhoff, sizeof(_ip), &_ip);
 266                         if (ip == NULL)
 267                                 return -1;
 268                 }
 269         }
 270
 271         t->src = ip->saddr & info->src_mask.ip;
 272         t->dst = ip->daddr & info->dst_mask.ip;
 273
 274         if (info->flags & XT_HMARK_FLAG(XT_HMARK_METHOD_L3))
 275                 return 0;
 276
 277         t->proto = ip->protocol;
 278
 279         /* ICMP has no ports, skip */
 280         if (t->proto == IPPROTO_ICMP)
 281                 return 0;
 282
 283         /* follow-up fragments don't contain ports, skip all fragments */
 284         if (ip->frag_off & htons(IP_MF | IP_OFFSET))
 285                 return 0;
 286
 287         hmark_set_tuple_ports(skb, (ip->ihl * 4) + nhoff, t, info);
 288
 289         return 0;
 290 }
 291
 292 static unsigned int
 293 hmark_tg_v4(struct sk_buff *skb, const struct xt_action_param *par)
 294 {
 295         const struct xt_hmark_info *info = par->targinfo;
 296         struct hmark_tuple t;
 297
 298         memset(&t, 0, sizeof(struct hmark_tuple));
 299
 300         if (info->flags & XT_HMARK_FLAG(XT_HMARK_CT)) {
 301                 if (hmark_ct_set_htuple(skb, &t, info) < 0)
 302                         return XT_CONTINUE;
 303         } else {
 304                 if (hmark_pkt_set_htuple_ipv4(skb, &t, info) < 0)
 305                         return XT_CONTINUE;
 306         }
 307
 308         skb->mark = hmark_hash(&t, info);
 309         return XT_CONTINUE;
 310 }
 311
 312 static int hmark_tg_check(const struct xt_tgchk_param *par)
 313 {
 314         const struct xt_hmark_info *info = par->targinfo;
 315
 316         if (!info->hmodulus) {
 317                 pr_info("xt_HMARK: hash modulus can't be zero\n");
 318                 return -EINVAL;
 319         }
 320         if (info->proto_mask &&
 321             (info->flags & XT_HMARK_FLAG(XT_HMARK_METHOD_L3))) {
 322                 pr_info("xt_HMARK: proto mask must be zero with L3 mode\n");
 323                 return -EINVAL;
 324         }
 325         if (info->flags & XT_HMARK_FLAG(XT_HMARK_SPI_MASK) &&
 326             (info->flags & (XT_HMARK_FLAG(XT_HMARK_SPORT_MASK) |
 327                              XT_HMARK_FLAG(XT_HMARK_DPORT_MASK)))) {
 328                 pr_info("xt_HMARK: spi-mask and port-mask can't be combined\n");
 329                 return -EINVAL;
 330         }
 331         if (info->flags & XT_HMARK_FLAG(XT_HMARK_SPI) &&
 332             (info->flags & (XT_HMARK_FLAG(XT_HMARK_SPORT) |
 333                              XT_HMARK_FLAG(XT_HMARK_DPORT)))) {
 334                 pr_info("xt_HMARK: spi-set and port-set can't be combined\n");
 335                 return -EINVAL;
 336         }
 337         return 0;
 338 }
 339
 340 static struct xt_target hmark_tg_reg[] __read_mostly = {
 341         {
 342                 .name           = "HMARK",
 343                 .family         = NFPROTO_IPV4,
 344                 .target         = hmark_tg_v4,
 345                 .targetsize     = sizeof(struct xt_hmark_info),
 346                 .checkentry     = hmark_tg_check,
 347                 .me             = THIS_MODULE,
 348         },
 349 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 350         {
 351                 .name           = "HMARK",
 352                 .family         = NFPROTO_IPV6,
 353                 .target         = hmark_tg_v6,
 354                 .targetsize     = sizeof(struct xt_hmark_info),
 355                 .checkentry     = hmark_tg_check,
 356                 .me             = THIS_MODULE,
 357         },
 358 #endif
 359 };
 360
 361 static int __init hmark_tg_init(void)
 362 {
 363         return xt_register_targets(hmark_tg_reg, ARRAY_SIZE(hmark_tg_reg));
 364 }
 365
 366 static void __exit hmark_tg_exit(void)
 367 {
 368         xt_unregister_targets(hmark_tg_reg, ARRAY_SIZE(hmark_tg_reg));
 369 }
 370
 371 module_init(hmark_tg_init);
 372 module_exit(hmark_tg_exit);