net/bridge/netfilter/ebt_stp.c

   1 /*
   2  *  ebt_stp
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *      Stephen Hemminger <shemminger@osdl.org>
   7  *
   8  *  July, 2003
   9  */
  10 #include <linux/etherdevice.h>
  11 #include <linux/module.h>
  12 #include <linux/netfilter/x_tables.h>
  13 #include <linux/netfilter_bridge/ebtables.h>
  14 #include <linux/netfilter_bridge/ebt_stp.h>
  15
  16 #define BPDU_TYPE_CONFIG 0
  17 #define BPDU_TYPE_TCN 0x80
  18
  19 struct stp_header {
  20         uint8_t dsap;
  21         uint8_t ssap;
  22         uint8_t ctrl;
  23         uint8_t pid;
  24         uint8_t vers;
  25         uint8_t type;
  26 };
  27
  28 struct stp_config_pdu {
  29         uint8_t flags;
  30         uint8_t root[8];
  31         uint8_t root_cost[4];
  32         uint8_t sender[8];
  33         uint8_t port[2];
  34         uint8_t msg_age[2];
  35         uint8_t max_age[2];
  36         uint8_t hello_time[2];
  37         uint8_t forward_delay[2];
  38 };
  39
  40 #define NR16(p) (p[0] << 8 | p[1])
  41 #define NR32(p) ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3])
  42
  43 static bool ebt_filter_config(const struct ebt_stp_info *info,
  44    const struct stp_config_pdu *stpc)
  45 {
  46         const struct ebt_stp_config_info *c;
  47         uint16_t v16;
  48         uint32_t v32;
  49         int verdict, i;
  50
  51         c = &info->config;
  52         if ((info->bitmask & EBT_STP_FLAGS) &&
  53             FWINV(c->flags != stpc->flags, EBT_STP_FLAGS))
  54                 return false;
  55         if (info->bitmask & EBT_STP_ROOTPRIO) {
  56                 v16 = NR16(stpc->root);
  57                 if (FWINV(v16 < c->root_priol ||
  58                     v16 > c->root_priou, EBT_STP_ROOTPRIO))
  59                         return false;
  60         }
  61         if (info->bitmask & EBT_STP_ROOTADDR) {
  62                 verdict = 0;
  63                 for (i = 0; i < 6; i++)
  64                         verdict |= (stpc->root[2+i] ^ c->root_addr[i]) &
  65                                    c->root_addrmsk[i];
  66                 if (FWINV(verdict != 0, EBT_STP_ROOTADDR))
  67                         return false;
  68         }
  69         if (info->bitmask & EBT_STP_ROOTCOST) {
  70                 v32 = NR32(stpc->root_cost);
  71                 if (FWINV(v32 < c->root_costl ||
  72                     v32 > c->root_costu, EBT_STP_ROOTCOST))
  73                         return false;
  74         }
  75         if (info->bitmask & EBT_STP_SENDERPRIO) {
  76                 v16 = NR16(stpc->sender);
  77                 if (FWINV(v16 < c->sender_priol ||
  78                     v16 > c->sender_priou, EBT_STP_SENDERPRIO))
  79                         return false;
  80         }
  81         if (info->bitmask & EBT_STP_SENDERADDR) {
  82                 verdict = 0;
  83                 for (i = 0; i < 6; i++)
  84                         verdict |= (stpc->sender[2+i] ^ c->sender_addr[i]) &
  85                                    c->sender_addrmsk[i];
  86                 if (FWINV(verdict != 0, EBT_STP_SENDERADDR))
  87                         return false;
  88         }
  89         if (info->bitmask & EBT_STP_PORT) {
  90                 v16 = NR16(stpc->port);
  91                 if (FWINV(v16 < c->portl ||
  92                     v16 > c->portu, EBT_STP_PORT))
  93                         return false;
  94         }
  95         if (info->bitmask & EBT_STP_MSGAGE) {
  96                 v16 = NR16(stpc->msg_age);
  97                 if (FWINV(v16 < c->msg_agel ||
  98                     v16 > c->msg_ageu, EBT_STP_MSGAGE))
  99                         return false;
 100         }
 101         if (info->bitmask & EBT_STP_MAXAGE) {
 102                 v16 = NR16(stpc->max_age);
 103                 if (FWINV(v16 < c->max_agel ||
 104                     v16 > c->max_ageu, EBT_STP_MAXAGE))
 105                         return false;
 106         }
 107         if (info->bitmask & EBT_STP_HELLOTIME) {
 108                 v16 = NR16(stpc->hello_time);
 109                 if (FWINV(v16 < c->hello_timel ||
 110                     v16 > c->hello_timeu, EBT_STP_HELLOTIME))
 111                         return false;
 112         }
 113         if (info->bitmask & EBT_STP_FWDD) {
 114                 v16 = NR16(stpc->forward_delay);
 115                 if (FWINV(v16 < c->forward_delayl ||
 116                     v16 > c->forward_delayu, EBT_STP_FWDD))
 117                         return false;
 118         }
 119         return true;
 120 }
 121
 122 static bool
 123 ebt_stp_mt(const struct sk_buff *skb, const struct net_device *in,
 124            const struct net_device *out, const struct xt_match *match,
 125            const void *data, int offset, unsigned int protoff, bool *hotdrop)
 126 {
 127         const struct ebt_stp_info *info = data;
 128         const struct stp_header *sp;
 129         struct stp_header _stph;
 130         const uint8_t header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
 131
 132         sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
 133         if (sp == NULL)
 134                 return false;
 135
 136         /* The stp code only considers these */
 137         if (memcmp(sp, header, sizeof(header)))
 138                 return false;
 139
 140         if (info->bitmask & EBT_STP_TYPE
 141             && FWINV(info->type != sp->type, EBT_STP_TYPE))
 142                 return false;
 143
 144         if (sp->type == BPDU_TYPE_CONFIG &&
 145             info->bitmask & EBT_STP_CONFIG_MASK) {
 146                 const struct stp_config_pdu *st;
 147                 struct stp_config_pdu _stpc;
 148
 149                 st = skb_header_pointer(skb, sizeof(_stph),
 150                                         sizeof(_stpc), &_stpc);
 151                 if (st == NULL)
 152                         return false;
 153                 return ebt_filter_config(info, st);
 154         }
 155         return true;
 156 }
 157
 158 static bool
 159 ebt_stp_mt_check(const char *table, const void *entry,
 160                  const struct xt_match *match, void *data,
 161                  unsigned int hook_mask)
 162 {
 163         const struct ebt_stp_info *info = data;
 164         const uint8_t bridge_ula[6] = {0x01, 0x80, 0xc2, 0x00, 0x00, 0x00};
 165         const uint8_t msk[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
 166         const struct ebt_entry *e = entry;
 167
 168         if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
 169             !(info->bitmask & EBT_STP_MASK))
 170                 return false;
 171         /* Make sure the match only receives stp frames */
 172         if (compare_ether_addr(e->destmac, bridge_ula) ||
 173             compare_ether_addr(e->destmsk, msk) || !(e->bitmask & EBT_DESTMAC))
 174                 return false;
 175
 176         return true;
 177 }
 178
 179 static struct xt_match ebt_stp_mt_reg __read_mostly = {
 180         .name           = "stp",
 181         .revision       = 0,
 182         .family         = NFPROTO_BRIDGE,
 183         .match          = ebt_stp_mt,
 184         .checkentry     = ebt_stp_mt_check,
 185         .matchsize      = XT_ALIGN(sizeof(struct ebt_stp_info)),
 186         .me             = THIS_MODULE,
 187 };
 188
 189 static int __init ebt_stp_init(void)
 190 {
 191         return xt_register_match(&ebt_stp_mt_reg);
 192 }
 193
 194 static void __exit ebt_stp_fini(void)
 195 {
 196         xt_unregister_match(&ebt_stp_mt_reg);
 197 }
 198
 199 module_init(ebt_stp_init);
 200 module_exit(ebt_stp_fini);
 201 MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
 202 MODULE_LICENSE("GPL");