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Linux/net/bridge/netfilter/ebt_among.c

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  1 /*
  2  *  ebt_among
  3  *
  4  *      Authors:
  5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
  6  *
  7  *  August, 2003
  8  *
  9  */
 10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 11 #include <linux/ip.h>
 12 #include <linux/if_arp.h>
 13 #include <linux/module.h>
 14 #include <linux/netfilter/x_tables.h>
 15 #include <linux/netfilter_bridge/ebtables.h>
 16 #include <linux/netfilter_bridge/ebt_among.h>
 17 
 18 static bool ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
 19                                       const char *mac, __be32 ip)
 20 {
 21         /* You may be puzzled as to how this code works.
 22          * Some tricks were used, refer to
 23          *      include/linux/netfilter_bridge/ebt_among.h
 24          * as there you can find a solution of this mystery.
 25          */
 26         const struct ebt_mac_wormhash_tuple *p;
 27         int start, limit, i;
 28         uint32_t cmp[2] = { 0, 0 };
 29         int key = ((const unsigned char *)mac)[5];
 30 
 31         ether_addr_copy(((char *) cmp) + 2, mac);
 32         start = wh->table[key];
 33         limit = wh->table[key + 1];
 34         if (ip) {
 35                 for (i = start; i < limit; i++) {
 36                         p = &wh->pool[i];
 37                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
 38                                 if (p->ip == 0 || p->ip == ip)
 39                                         return true;
 40                 }
 41         } else {
 42                 for (i = start; i < limit; i++) {
 43                         p = &wh->pool[i];
 44                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
 45                                 if (p->ip == 0)
 46                                         return true;
 47                 }
 48         }
 49         return false;
 50 }
 51 
 52 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
 53                                             *wh)
 54 {
 55         int i;
 56 
 57         for (i = 0; i < 256; i++) {
 58                 if (wh->table[i] > wh->table[i + 1])
 59                         return -0x100 - i;
 60                 if (wh->table[i] < 0)
 61                         return -0x200 - i;
 62                 if (wh->table[i] > wh->poolsize)
 63                         return -0x300 - i;
 64         }
 65         if (wh->table[256] > wh->poolsize)
 66                 return -0xc00;
 67         return 0;
 68 }
 69 
 70 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
 71 {
 72         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
 73                 const struct iphdr *ih;
 74                 struct iphdr _iph;
 75 
 76                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
 77                 if (ih == NULL)
 78                         return -1;
 79                 *addr = ih->daddr;
 80         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
 81                 const struct arphdr *ah;
 82                 struct arphdr _arph;
 83                 const __be32 *bp;
 84                 __be32 buf;
 85 
 86                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
 87                 if (ah == NULL ||
 88                     ah->ar_pln != sizeof(__be32) ||
 89                     ah->ar_hln != ETH_ALEN)
 90                         return -1;
 91                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
 92                                         2 * ETH_ALEN + sizeof(__be32),
 93                                         sizeof(__be32), &buf);
 94                 if (bp == NULL)
 95                         return -1;
 96                 *addr = *bp;
 97         }
 98         return 0;
 99 }
100 
101 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
102 {
103         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
104                 const struct iphdr *ih;
105                 struct iphdr _iph;
106 
107                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
108                 if (ih == NULL)
109                         return -1;
110                 *addr = ih->saddr;
111         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
112                 const struct arphdr *ah;
113                 struct arphdr _arph;
114                 const __be32 *bp;
115                 __be32 buf;
116 
117                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
118                 if (ah == NULL ||
119                     ah->ar_pln != sizeof(__be32) ||
120                     ah->ar_hln != ETH_ALEN)
121                         return -1;
122                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
123                                         ETH_ALEN, sizeof(__be32), &buf);
124                 if (bp == NULL)
125                         return -1;
126                 *addr = *bp;
127         }
128         return 0;
129 }
130 
131 static bool
132 ebt_among_mt(const struct sk_buff *skb, struct xt_action_param *par)
133 {
134         const struct ebt_among_info *info = par->matchinfo;
135         const char *dmac, *smac;
136         const struct ebt_mac_wormhash *wh_dst, *wh_src;
137         __be32 dip = 0, sip = 0;
138 
139         wh_dst = ebt_among_wh_dst(info);
140         wh_src = ebt_among_wh_src(info);
141 
142         if (wh_src) {
143                 smac = eth_hdr(skb)->h_source;
144                 if (get_ip_src(skb, &sip))
145                         return false;
146                 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
147                         /* we match only if it contains */
148                         if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
149                                 return false;
150                 } else {
151                         /* we match only if it DOES NOT contain */
152                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
153                                 return false;
154                 }
155         }
156 
157         if (wh_dst) {
158                 dmac = eth_hdr(skb)->h_dest;
159                 if (get_ip_dst(skb, &dip))
160                         return false;
161                 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
162                         /* we match only if it contains */
163                         if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
164                                 return false;
165                 } else {
166                         /* we match only if it DOES NOT contain */
167                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
168                                 return false;
169                 }
170         }
171 
172         return true;
173 }
174 
175 static int ebt_among_mt_check(const struct xt_mtchk_param *par)
176 {
177         const struct ebt_among_info *info = par->matchinfo;
178         const struct ebt_entry_match *em =
179                 container_of(par->matchinfo, const struct ebt_entry_match, data);
180         int expected_length = sizeof(struct ebt_among_info);
181         const struct ebt_mac_wormhash *wh_dst, *wh_src;
182         int err;
183 
184         wh_dst = ebt_among_wh_dst(info);
185         wh_src = ebt_among_wh_src(info);
186         expected_length += ebt_mac_wormhash_size(wh_dst);
187         expected_length += ebt_mac_wormhash_size(wh_src);
188 
189         if (em->match_size != EBT_ALIGN(expected_length)) {
190                 pr_info("wrong size: %d against expected %d, rounded to %Zd\n",
191                         em->match_size, expected_length,
192                         EBT_ALIGN(expected_length));
193                 return -EINVAL;
194         }
195         if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
196                 pr_info("dst integrity fail: %x\n", -err);
197                 return -EINVAL;
198         }
199         if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
200                 pr_info("src integrity fail: %x\n", -err);
201                 return -EINVAL;
202         }
203         return 0;
204 }
205 
206 static struct xt_match ebt_among_mt_reg __read_mostly = {
207         .name           = "among",
208         .revision       = 0,
209         .family         = NFPROTO_BRIDGE,
210         .match          = ebt_among_mt,
211         .checkentry     = ebt_among_mt_check,
212         .matchsize      = -1, /* special case */
213         .me             = THIS_MODULE,
214 };
215 
216 static int __init ebt_among_init(void)
217 {
218         return xt_register_match(&ebt_among_mt_reg);
219 }
220 
221 static void __exit ebt_among_fini(void)
222 {
223         xt_unregister_match(&ebt_among_mt_reg);
224 }
225 
226 module_init(ebt_among_init);
227 module_exit(ebt_among_fini);
228 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
229 MODULE_LICENSE("GPL");
230 

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