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Linux/net/bridge/netfilter/ebt_stp.c

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  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 

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