root/net/bridge/netfilter/ebt_vlan.c

DEFINITIONS

1. ebt_vlan_mt
2. ebt_vlan_mt_check
3. ebt_vlan_init
4. ebt_vlan_fini

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Description: EBTables 802.1Q match extension kernelspace module.
   4  * Authors: Nick Fedchik <nick@fedchik.org.ua>
   5  *          Bart De Schuymer <bdschuym@pandora.be>
   6  */
   7 
   8 #include <linux/if_ether.h>
   9 #include <linux/if_vlan.h>
  10 #include <linux/module.h>
  11 #include <linux/moduleparam.h>
  12 #include <linux/netfilter/x_tables.h>
  13 #include <linux/netfilter_bridge/ebtables.h>
  14 #include <linux/netfilter_bridge/ebt_vlan.h>
  15 
  16 #define MODULE_VERS "0.6"
  17 
  18 MODULE_AUTHOR("Nick Fedchik <nick@fedchik.org.ua>");
  19 MODULE_DESCRIPTION("Ebtables: 802.1Q VLAN tag match");
  20 MODULE_LICENSE("GPL");
  21 
  22 #define GET_BITMASK(_BIT_MASK_) info->bitmask & _BIT_MASK_
  23 #define EXIT_ON_MISMATCH(_MATCH_,_MASK_) {if (!((info->_MATCH_ == _MATCH_)^!!(info->invflags & _MASK_))) return false; }
  24 
  25 static bool
  26 ebt_vlan_mt(const struct sk_buff *skb, struct xt_action_param *par)
  27 {
  28         const struct ebt_vlan_info *info = par->matchinfo;
  29 
  30         unsigned short TCI;     /* Whole TCI, given from parsed frame */
  31         unsigned short id;      /* VLAN ID, given from frame TCI */
  32         unsigned char prio;     /* user_priority, given from frame TCI */
  33         /* VLAN encapsulated Type/Length field, given from orig frame */
  34         __be16 encap;
  35 
  36         if (skb_vlan_tag_present(skb)) {
  37                 TCI = skb_vlan_tag_get(skb);
  38                 encap = skb->protocol;
  39         } else {
  40                 const struct vlan_hdr *fp;
  41                 struct vlan_hdr _frame;
  42 
  43                 fp = skb_header_pointer(skb, 0, sizeof(_frame), &_frame);
  44                 if (fp == NULL)
  45                         return false;
  46 
  47                 TCI = ntohs(fp->h_vlan_TCI);
  48                 encap = fp->h_vlan_encapsulated_proto;
  49         }
  50 
  51         /* Tag Control Information (TCI) consists of the following elements:
  52          * - User_priority. The user_priority field is three bits in length,
  53          * interpreted as a binary number.
  54          * - Canonical Format Indicator (CFI). The Canonical Format Indicator
  55          * (CFI) is a single bit flag value. Currently ignored.
  56          * - VLAN Identifier (VID). The VID is encoded as
  57          * an unsigned binary number.
  58          */
  59         id = TCI & VLAN_VID_MASK;
  60         prio = (TCI >> 13) & 0x7;
  61 
  62         /* Checking VLAN Identifier (VID) */
  63         if (GET_BITMASK(EBT_VLAN_ID))
  64                 EXIT_ON_MISMATCH(id, EBT_VLAN_ID);
  65 
  66         /* Checking user_priority */
  67         if (GET_BITMASK(EBT_VLAN_PRIO))
  68                 EXIT_ON_MISMATCH(prio, EBT_VLAN_PRIO);
  69 
  70         /* Checking Encapsulated Proto (Length/Type) field */
  71         if (GET_BITMASK(EBT_VLAN_ENCAP))
  72                 EXIT_ON_MISMATCH(encap, EBT_VLAN_ENCAP);
  73 
  74         return true;
  75 }
  76 
  77 static int ebt_vlan_mt_check(const struct xt_mtchk_param *par)
  78 {
  79         struct ebt_vlan_info *info = par->matchinfo;
  80         const struct ebt_entry *e = par->entryinfo;
  81 
  82         /* Is it 802.1Q frame checked? */
  83         if (e->ethproto != htons(ETH_P_8021Q)) {
  84                 pr_debug("passed entry proto %2.4X is not 802.1Q (8100)\n",
  85                          ntohs(e->ethproto));
  86                 return -EINVAL;
  87         }
  88 
  89         /* Check for bitmask range
  90          * True if even one bit is out of mask
  91          */
  92         if (info->bitmask & ~EBT_VLAN_MASK) {
  93                 pr_debug("bitmask %2X is out of mask (%2X)\n",
  94                          info->bitmask, EBT_VLAN_MASK);
  95                 return -EINVAL;
  96         }
  97 
  98         /* Check for inversion flags range */
  99         if (info->invflags & ~EBT_VLAN_MASK) {
 100                 pr_debug("inversion flags %2X is out of mask (%2X)\n",
 101                          info->invflags, EBT_VLAN_MASK);
 102                 return -EINVAL;
 103         }
 104 
 105         /* Reserved VLAN ID (VID) values
 106          * -----------------------------
 107          * 0 - The null VLAN ID.
 108          * 1 - The default Port VID (PVID)
 109          * 0x0FFF - Reserved for implementation use.
 110          * if_vlan.h: VLAN_N_VID 4096.
 111          */
 112         if (GET_BITMASK(EBT_VLAN_ID)) {
 113                 if (!!info->id) { /* if id!=0 => check vid range */
 114                         if (info->id > VLAN_N_VID) {
 115                                 pr_debug("id %d is out of range (1-4096)\n",
 116                                          info->id);
 117                                 return -EINVAL;
 118                         }
 119                         /* Note: This is valid VLAN-tagged frame point.
 120                          * Any value of user_priority are acceptable,
 121                          * but should be ignored according to 802.1Q Std.
 122                          * So we just drop the prio flag.
 123                          */
 124                         info->bitmask &= ~EBT_VLAN_PRIO;
 125                 }
 126                 /* Else, id=0 (null VLAN ID)  => user_priority range (any?) */
 127         }
 128 
 129         if (GET_BITMASK(EBT_VLAN_PRIO)) {
 130                 if ((unsigned char) info->prio > 7) {
 131                         pr_debug("prio %d is out of range (0-7)\n",
 132                                  info->prio);
 133                         return -EINVAL;
 134                 }
 135         }
 136         /* Check for encapsulated proto range - it is possible to be
 137          * any value for u_short range.
 138          * if_ether.h:  ETH_ZLEN        60   -  Min. octets in frame sans FCS
 139          */
 140         if (GET_BITMASK(EBT_VLAN_ENCAP)) {
 141                 if ((unsigned short) ntohs(info->encap) < ETH_ZLEN) {
 142                         pr_debug("encap frame length %d is less than "
 143                                  "minimal\n", ntohs(info->encap));
 144                         return -EINVAL;
 145                 }
 146         }
 147 
 148         return 0;
 149 }
 150 
 151 static struct xt_match ebt_vlan_mt_reg __read_mostly = {
 152         .name           = "vlan",
 153         .revision       = 0,
 154         .family         = NFPROTO_BRIDGE,
 155         .match          = ebt_vlan_mt,
 156         .checkentry     = ebt_vlan_mt_check,
 157         .matchsize      = sizeof(struct ebt_vlan_info),
 158         .me             = THIS_MODULE,
 159 };
 160 
 161 static int __init ebt_vlan_init(void)
 162 {
 163         pr_debug("ebtables 802.1Q extension module v" MODULE_VERS "\n");
 164         return xt_register_match(&ebt_vlan_mt_reg);
 165 }
 166 
 167 static void __exit ebt_vlan_fini(void)
 168 {
 169         xt_unregister_match(&ebt_vlan_mt_reg);
 170 }
 171 
 172 module_init(ebt_vlan_init);
 173 module_exit(ebt_vlan_fini);