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, struct xt_action_param *par) 124 { 125 const struct ebt_stp_info *info = par->matchinfo; 126 const struct stp_header *sp; 127 struct stp_header _stph; 128 const uint8_t header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00}; 129 130 sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph); 131 if (sp == NULL) 132 return false; 133 134 /* The stp code only considers these */ 135 if (memcmp(sp, header, sizeof(header))) 136 return false; 137 138 if (info->bitmask & EBT_STP_TYPE && 139 FWINV(info->type != sp->type, EBT_STP_TYPE)) 140 return false; 141 142 if (sp->type == BPDU_TYPE_CONFIG && 143 info->bitmask & EBT_STP_CONFIG_MASK) { 144 const struct stp_config_pdu *st; 145 struct stp_config_pdu _stpc; 146 147 st = skb_header_pointer(skb, sizeof(_stph), 148 sizeof(_stpc), &_stpc); 149 if (st == NULL) 150 return false; 151 return ebt_filter_config(info, st); 152 } 153 return true; 154 } 155 156 static int ebt_stp_mt_check(const struct xt_mtchk_param *par) 157 { 158 const struct ebt_stp_info *info = par->matchinfo; 159 const uint8_t bridge_ula[6] = {0x01, 0x80, 0xc2, 0x00, 0x00, 0x00}; 160 const uint8_t msk[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff}; 161 const struct ebt_entry *e = par->entryinfo; 162 163 if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK || 164 !(info->bitmask & EBT_STP_MASK)) 165 return -EINVAL; 166 /* Make sure the match only receives stp frames */ 167 if (!par->nft_compat && 168 (!ether_addr_equal(e->destmac, bridge_ula) || 169 !ether_addr_equal(e->destmsk, msk) || 170 !(e->bitmask & EBT_DESTMAC))) 171 return -EINVAL; 172 173 return 0; 174 } 175 176 static struct xt_match ebt_stp_mt_reg __read_mostly = { 177 .name = "stp", 178 .revision = 0, 179 .family = NFPROTO_BRIDGE, 180 .match = ebt_stp_mt, 181 .checkentry = ebt_stp_mt_check, 182 .matchsize = sizeof(struct ebt_stp_info), 183 .me = THIS_MODULE, 184 }; 185 186 static int __init ebt_stp_init(void) 187 { 188 return xt_register_match(&ebt_stp_mt_reg); 189 } 190 191 static void __exit ebt_stp_fini(void) 192 { 193 xt_unregister_match(&ebt_stp_mt_reg); 194 } 195 196 module_init(ebt_stp_init); 197 module_exit(ebt_stp_fini); 198 MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match"); 199 MODULE_LICENSE("GPL"); 200