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   1 /*
   2  *  ebt_ip
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *
   7  *  April, 2002
   8  *
   9  *  Changes:
  10  *    added ip-sport and ip-dport
  11  *    Innominate Security Technologies AG <mhopf@innominate.com>
  12  *    September, 2002
  13  */
  14 #include <linux/ip.h>
  15 #include <net/ip.h>
  16 #include <linux/in.h>
  17 #include <linux/module.h>
  18 #include <linux/netfilter/x_tables.h>
  19 #include <linux/netfilter_bridge/ebtables.h>
  20 #include <linux/netfilter_bridge/ebt_ip.h>
  21
  22 struct tcpudphdr {
  23         __be16 src;
  24         __be16 dst;
  25 };
  26
  27 static bool
  28 ebt_ip_mt(const struct sk_buff *skb, const struct net_device *in,
  29           const struct net_device *out, const struct xt_match *match,
  30           const void *data, int offset, unsigned int protoff, bool *hotdrop)
  31 {
  32         const struct ebt_ip_info *info = data;
  33         const struct iphdr *ih;
  34         struct iphdr _iph;
  35         const struct tcpudphdr *pptr;
  36         struct tcpudphdr _ports;
  37
  38         ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
  39         if (ih == NULL)
  40                 return false;
  41         if (info->bitmask & EBT_IP_TOS &&
  42            FWINV(info->tos != ih->tos, EBT_IP_TOS))
  43                 return false;
  44         if (info->bitmask & EBT_IP_SOURCE &&
  45            FWINV((ih->saddr & info->smsk) !=
  46            info->saddr, EBT_IP_SOURCE))
  47                 return false;
  48         if ((info->bitmask & EBT_IP_DEST) &&
  49            FWINV((ih->daddr & info->dmsk) !=
  50            info->daddr, EBT_IP_DEST))
  51                 return false;
  52         if (info->bitmask & EBT_IP_PROTO) {
  53                 if (FWINV(info->protocol != ih->protocol, EBT_IP_PROTO))
  54                         return false;
  55                 if (!(info->bitmask & EBT_IP_DPORT) &&
  56                     !(info->bitmask & EBT_IP_SPORT))
  57                         return true;
  58                 if (ntohs(ih->frag_off) & IP_OFFSET)
  59                         return false;
  60                 pptr = skb_header_pointer(skb, ih->ihl*4,
  61                                           sizeof(_ports), &_ports);
  62                 if (pptr == NULL)
  63                         return false;
  64                 if (info->bitmask & EBT_IP_DPORT) {
  65                         u32 dst = ntohs(pptr->dst);
  66                         if (FWINV(dst < info->dport[0] ||
  67                                   dst > info->dport[1],
  68                                   EBT_IP_DPORT))
  69                         return false;
  70                 }
  71                 if (info->bitmask & EBT_IP_SPORT) {
  72                         u32 src = ntohs(pptr->src);
  73                         if (FWINV(src < info->sport[0] ||
  74                                   src > info->sport[1],
  75                                   EBT_IP_SPORT))
  76                         return false;
  77                 }
  78         }
  79         return true;
  80 }
  81
  82 static bool
  83 ebt_ip_mt_check(const char *table, const void *entry,
  84                 const struct xt_match *match, void *data,
  85                 unsigned int hook_mask)
  86 {
  87         const struct ebt_ip_info *info = data;
  88         const struct ebt_entry *e = entry;
  89
  90         if (e->ethproto != htons(ETH_P_IP) ||
  91            e->invflags & EBT_IPROTO)
  92                 return false;
  93         if (info->bitmask & ~EBT_IP_MASK || info->invflags & ~EBT_IP_MASK)
  94                 return false;
  95         if (info->bitmask & (EBT_IP_DPORT | EBT_IP_SPORT)) {
  96                 if (info->invflags & EBT_IP_PROTO)
  97                         return false;
  98                 if (info->protocol != IPPROTO_TCP &&
  99                     info->protocol != IPPROTO_UDP &&
 100                     info->protocol != IPPROTO_UDPLITE &&
 101                     info->protocol != IPPROTO_SCTP &&
 102                     info->protocol != IPPROTO_DCCP)
 103                          return false;
 104         }
 105         if (info->bitmask & EBT_IP_DPORT && info->dport[0] > info->dport[1])
 106                 return false;
 107         if (info->bitmask & EBT_IP_SPORT && info->sport[0] > info->sport[1])
 108                 return false;
 109         return true;
 110 }
 111
 112 static struct xt_match ebt_ip_mt_reg __read_mostly = {
 113         .name           = "ip",
 114         .revision       = 0,
 115         .family         = NFPROTO_BRIDGE,
 116         .match          = ebt_ip_mt,
 117         .checkentry     = ebt_ip_mt_check,
 118         .matchsize      = XT_ALIGN(sizeof(struct ebt_ip_info)),
 119         .me             = THIS_MODULE,
 120 };
 121
 122 static int __init ebt_ip_init(void)
 123 {
 124         return xt_register_match(&ebt_ip_mt_reg);
 125 }
 126
 127 static void __exit ebt_ip_fini(void)
 128 {
 129         xt_unregister_match(&ebt_ip_mt_reg);
 130 }
 131
 132 module_init(ebt_ip_init);
 133 module_exit(ebt_ip_fini);
 134 MODULE_DESCRIPTION("Ebtables: IPv4 protocol packet match");
 135 MODULE_LICENSE("GPL");