bridge/netfilter/ebt_stp.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  ebt_stp
0004  *
0005  *  Authors:
0006  *  Bart De Schuymer <bdschuym@pandora.be>
0007  *  Stephen Hemminger <shemminger@osdl.org>
0008  *
0009  *  July, 2003
0010  */
0011 #include <linux/etherdevice.h>
0012 #include <linux/module.h>
0013 #include <linux/netfilter/x_tables.h>
0014 #include <linux/netfilter_bridge/ebtables.h>
0015 #include <linux/netfilter_bridge/ebt_stp.h>
0016
0017 #define BPDU_TYPE_CONFIG 0
0018
0019 struct stp_header {
0020     u8 dsap;
0021     u8 ssap;
0022     u8 ctrl;
0023     u8 pid;
0024     u8 vers;
0025     u8 type;
0026 };
0027
0028 struct stp_config_pdu {
0029     u8 flags;
0030     u8 root[8];
0031     u8 root_cost[4];
0032     u8 sender[8];
0033     u8 port[2];
0034     u8 msg_age[2];
0035     u8 max_age[2];
0036     u8 hello_time[2];
0037     u8 forward_delay[2];
0038 };
0039
0040 #define NR16(p) (p[0] << 8 | p[1])
0041 #define NR32(p) ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3])
0042
0043 static bool ebt_filter_config(const struct ebt_stp_info *info,
0044                   const struct stp_config_pdu *stpc)
0045 {
0046     const struct ebt_stp_config_info *c;
0047     u16 v16;
0048     u32 v32;
0049
0050     c = &info->config;
0051     if ((info->bitmask & EBT_STP_FLAGS) &&
0052         NF_INVF(info, EBT_STP_FLAGS, c->flags != stpc->flags))
0053         return false;
0054     if (info->bitmask & EBT_STP_ROOTPRIO) {
0055         v16 = NR16(stpc->root);
0056         if (NF_INVF(info, EBT_STP_ROOTPRIO,
0057                 v16 < c->root_priol || v16 > c->root_priou))
0058             return false;
0059     }
0060     if (info->bitmask & EBT_STP_ROOTADDR) {
0061         if (NF_INVF(info, EBT_STP_ROOTADDR,
0062                 !ether_addr_equal_masked(&stpc->root[2],
0063                              c->root_addr,
0064                              c->root_addrmsk)))
0065             return false;
0066     }
0067     if (info->bitmask & EBT_STP_ROOTCOST) {
0068         v32 = NR32(stpc->root_cost);
0069         if (NF_INVF(info, EBT_STP_ROOTCOST,
0070                 v32 < c->root_costl || v32 > c->root_costu))
0071             return false;
0072     }
0073     if (info->bitmask & EBT_STP_SENDERPRIO) {
0074         v16 = NR16(stpc->sender);
0075         if (NF_INVF(info, EBT_STP_SENDERPRIO,
0076                 v16 < c->sender_priol || v16 > c->sender_priou))
0077             return false;
0078     }
0079     if (info->bitmask & EBT_STP_SENDERADDR) {
0080         if (NF_INVF(info, EBT_STP_SENDERADDR,
0081                 !ether_addr_equal_masked(&stpc->sender[2],
0082                              c->sender_addr,
0083                              c->sender_addrmsk)))
0084             return false;
0085     }
0086     if (info->bitmask & EBT_STP_PORT) {
0087         v16 = NR16(stpc->port);
0088         if (NF_INVF(info, EBT_STP_PORT,
0089                 v16 < c->portl || v16 > c->portu))
0090             return false;
0091     }
0092     if (info->bitmask & EBT_STP_MSGAGE) {
0093         v16 = NR16(stpc->msg_age);
0094         if (NF_INVF(info, EBT_STP_MSGAGE,
0095                 v16 < c->msg_agel || v16 > c->msg_ageu))
0096             return false;
0097     }
0098     if (info->bitmask & EBT_STP_MAXAGE) {
0099         v16 = NR16(stpc->max_age);
0100         if (NF_INVF(info, EBT_STP_MAXAGE,
0101                 v16 < c->max_agel || v16 > c->max_ageu))
0102             return false;
0103     }
0104     if (info->bitmask & EBT_STP_HELLOTIME) {
0105         v16 = NR16(stpc->hello_time);
0106         if (NF_INVF(info, EBT_STP_HELLOTIME,
0107                 v16 < c->hello_timel || v16 > c->hello_timeu))
0108             return false;
0109     }
0110     if (info->bitmask & EBT_STP_FWDD) {
0111         v16 = NR16(stpc->forward_delay);
0112         if (NF_INVF(info, EBT_STP_FWDD,
0113                 v16 < c->forward_delayl || v16 > c->forward_delayu))
0114             return false;
0115     }
0116     return true;
0117 }
0118
0119 static bool
0120 ebt_stp_mt(const struct sk_buff *skb, struct xt_action_param *par)
0121 {
0122     const struct ebt_stp_info *info = par->matchinfo;
0123     const struct stp_header *sp;
0124     struct stp_header _stph;
0125     const u8 header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
0126
0127     sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
0128     if (sp == NULL)
0129         return false;
0130
0131     /* The stp code only considers these */
0132     if (memcmp(sp, header, sizeof(header)))
0133         return false;
0134
0135     if ((info->bitmask & EBT_STP_TYPE) &&
0136         NF_INVF(info, EBT_STP_TYPE, info->type != sp->type))
0137         return false;
0138
0139     if (sp->type == BPDU_TYPE_CONFIG &&
0140         info->bitmask & EBT_STP_CONFIG_MASK) {
0141         const struct stp_config_pdu *st;
0142         struct stp_config_pdu _stpc;
0143
0144         st = skb_header_pointer(skb, sizeof(_stph),
0145                     sizeof(_stpc), &_stpc);
0146         if (st == NULL)
0147             return false;
0148         return ebt_filter_config(info, st);
0149     }
0150     return true;
0151 }
0152
0153 static int ebt_stp_mt_check(const struct xt_mtchk_param *par)
0154 {
0155     const struct ebt_stp_info *info = par->matchinfo;
0156     const struct ebt_entry *e = par->entryinfo;
0157
0158     if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
0159         !(info->bitmask & EBT_STP_MASK))
0160         return -EINVAL;
0161     /* Make sure the match only receives stp frames */
0162     if (!par->nft_compat &&
0163         (!ether_addr_equal(e->destmac, eth_stp_addr) ||
0164          !(e->bitmask & EBT_DESTMAC) ||
0165          !is_broadcast_ether_addr(e->destmsk)))
0166         return -EINVAL;
0167
0168     return 0;
0169 }
0170
0171 static struct xt_match ebt_stp_mt_reg __read_mostly = {
0172     .name       = "stp",
0173     .revision   = 0,
0174     .family     = NFPROTO_BRIDGE,
0175     .match      = ebt_stp_mt,
0176     .checkentry = ebt_stp_mt_check,
0177     .matchsize  = sizeof(struct ebt_stp_info),
0178     .me     = THIS_MODULE,
0179 };
0180
0181 static int __init ebt_stp_init(void)
0182 {
0183     return xt_register_match(&ebt_stp_mt_reg);
0184 }
0185
0186 static void __exit ebt_stp_fini(void)
0187 {
0188     xt_unregister_match(&ebt_stp_mt_reg);
0189 }
0190
0191 module_init(ebt_stp_init);
0192 module_exit(ebt_stp_fini);
0193 MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
0194 MODULE_LICENSE("GPL");