net/netfilter/nft_fwd_netdev.c

   1 /*
   2  * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 as published by
   6  * the Free Software Foundation.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/init.h>
  11 #include <linux/module.h>
  12 #include <linux/netlink.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/netfilter/nf_tables.h>
  15 #include <linux/ip.h>
  16 #include <linux/ipv6.h>
  17 #include <net/netfilter/nf_tables.h>
  18 #include <net/netfilter/nf_dup_netdev.h>
  19 #include <net/neighbour.h>
  20 #include <net/ip.h>
  21
  22 struct nft_fwd_netdev {
  23         enum nft_registers      sreg_dev:8;
  24 };
  25
  26 static void nft_fwd_netdev_eval(const struct nft_expr *expr,
  27                                 struct nft_regs *regs,
  28                                 const struct nft_pktinfo *pkt)
  29 {
  30         struct nft_fwd_netdev *priv = nft_expr_priv(expr);
  31         int oif = regs->data[priv->sreg_dev];
  32
  33         nf_fwd_netdev_egress(pkt, oif);
  34         regs->verdict.code = NF_STOLEN;
  35 }
  36
  37 static const struct nla_policy nft_fwd_netdev_policy[NFTA_FWD_MAX + 1] = {
  38         [NFTA_FWD_SREG_DEV]     = { .type = NLA_U32 },
  39         [NFTA_FWD_SREG_ADDR]    = { .type = NLA_U32 },
  40         [NFTA_FWD_NFPROTO]      = { .type = NLA_U32 },
  41 };
  42
  43 static int nft_fwd_netdev_init(const struct nft_ctx *ctx,
  44                                const struct nft_expr *expr,
  45                                const struct nlattr * const tb[])
  46 {
  47         struct nft_fwd_netdev *priv = nft_expr_priv(expr);
  48
  49         if (tb[NFTA_FWD_SREG_DEV] == NULL)
  50                 return -EINVAL;
  51
  52         priv->sreg_dev = nft_parse_register(tb[NFTA_FWD_SREG_DEV]);
  53         return nft_validate_register_load(priv->sreg_dev, sizeof(int));
  54 }
  55
  56 static int nft_fwd_netdev_dump(struct sk_buff *skb, const struct nft_expr *expr)
  57 {
  58         struct nft_fwd_netdev *priv = nft_expr_priv(expr);
  59
  60         if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev))
  61                 goto nla_put_failure;
  62
  63         return 0;
  64
  65 nla_put_failure:
  66         return -1;
  67 }
  68
  69 struct nft_fwd_neigh {
  70         enum nft_registers      sreg_dev:8;
  71         enum nft_registers      sreg_addr:8;
  72         u8                      nfproto;
  73 };
  74
  75 static void nft_fwd_neigh_eval(const struct nft_expr *expr,
  76                               struct nft_regs *regs,
  77                               const struct nft_pktinfo *pkt)
  78 {
  79         struct nft_fwd_neigh *priv = nft_expr_priv(expr);
  80         void *addr = &regs->data[priv->sreg_addr];
  81         int oif = regs->data[priv->sreg_dev];
  82         unsigned int verdict = NF_STOLEN;
  83         struct sk_buff *skb = pkt->skb;
  84         struct net_device *dev;
  85         int neigh_table;
  86
  87         switch (priv->nfproto) {
  88         case NFPROTO_IPV4: {
  89                 struct iphdr *iph;
  90
  91                 if (skb->protocol != htons(ETH_P_IP)) {
  92                         verdict = NFT_BREAK;
  93                         goto out;
  94                 }
  95                 if (skb_try_make_writable(skb, sizeof(*iph))) {
  96                         verdict = NF_DROP;
  97                         goto out;
  98                 }
  99                 iph = ip_hdr(skb);
 100                 ip_decrease_ttl(iph);
 101                 neigh_table = NEIGH_ARP_TABLE;
 102                 break;
 103                 }
 104         case NFPROTO_IPV6: {
 105                 struct ipv6hdr *ip6h;
 106
 107                 if (skb->protocol != htons(ETH_P_IPV6)) {
 108                         verdict = NFT_BREAK;
 109                         goto out;
 110                 }
 111                 if (skb_try_make_writable(skb, sizeof(*ip6h))) {
 112                         verdict = NF_DROP;
 113                         goto out;
 114                 }
 115                 ip6h = ipv6_hdr(skb);
 116                 ip6h->hop_limit--;
 117                 neigh_table = NEIGH_ND_TABLE;
 118                 break;
 119                 }
 120         default:
 121                 verdict = NFT_BREAK;
 122                 goto out;
 123         }
 124
 125         dev = dev_get_by_index_rcu(nft_net(pkt), oif);
 126         if (dev == NULL)
 127                 return;
 128
 129         skb->dev = dev;
 130         neigh_xmit(neigh_table, dev, addr, skb);
 131 out:
 132         regs->verdict.code = verdict;
 133 }
 134
 135 static int nft_fwd_neigh_init(const struct nft_ctx *ctx,
 136                               const struct nft_expr *expr,
 137                               const struct nlattr * const tb[])
 138 {
 139         struct nft_fwd_neigh *priv = nft_expr_priv(expr);
 140         unsigned int addr_len;
 141         int err;
 142
 143         if (!tb[NFTA_FWD_SREG_DEV] ||
 144             !tb[NFTA_FWD_SREG_ADDR] ||
 145             !tb[NFTA_FWD_NFPROTO])
 146                 return -EINVAL;
 147
 148         priv->sreg_dev = nft_parse_register(tb[NFTA_FWD_SREG_DEV]);
 149         priv->sreg_addr = nft_parse_register(tb[NFTA_FWD_SREG_ADDR]);
 150         priv->nfproto = ntohl(nla_get_be32(tb[NFTA_FWD_NFPROTO]));
 151
 152         switch (priv->nfproto) {
 153         case NFPROTO_IPV4:
 154                 addr_len = sizeof(struct in_addr);
 155                 break;
 156         case NFPROTO_IPV6:
 157                 addr_len = sizeof(struct in6_addr);
 158                 break;
 159         default:
 160                 return -EOPNOTSUPP;
 161         }
 162
 163         err = nft_validate_register_load(priv->sreg_dev, sizeof(int));
 164         if (err < 0)
 165                 return err;
 166
 167         return nft_validate_register_load(priv->sreg_addr, addr_len);
 168 }
 169
 170 static int nft_fwd_neigh_dump(struct sk_buff *skb, const struct nft_expr *expr)
 171 {
 172         struct nft_fwd_neigh *priv = nft_expr_priv(expr);
 173
 174         if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev) ||
 175             nft_dump_register(skb, NFTA_FWD_SREG_ADDR, priv->sreg_addr) ||
 176             nla_put_be32(skb, NFTA_FWD_NFPROTO, htonl(priv->nfproto)))
 177                 goto nla_put_failure;
 178
 179         return 0;
 180
 181 nla_put_failure:
 182         return -1;
 183 }
 184
 185 static struct nft_expr_type nft_fwd_netdev_type;
 186 static const struct nft_expr_ops nft_fwd_neigh_netdev_ops = {
 187         .type           = &nft_fwd_netdev_type,
 188         .size           = NFT_EXPR_SIZE(sizeof(struct nft_fwd_neigh)),
 189         .eval           = nft_fwd_neigh_eval,
 190         .init           = nft_fwd_neigh_init,
 191         .dump           = nft_fwd_neigh_dump,
 192 };
 193
 194 static const struct nft_expr_ops nft_fwd_netdev_ops = {
 195         .type           = &nft_fwd_netdev_type,
 196         .size           = NFT_EXPR_SIZE(sizeof(struct nft_fwd_netdev)),
 197         .eval           = nft_fwd_netdev_eval,
 198         .init           = nft_fwd_netdev_init,
 199         .dump           = nft_fwd_netdev_dump,
 200 };
 201
 202 static const struct nft_expr_ops *
 203 nft_fwd_select_ops(const struct nft_ctx *ctx,
 204                    const struct nlattr * const tb[])
 205 {
 206         if (tb[NFTA_FWD_SREG_ADDR])
 207                 return &nft_fwd_neigh_netdev_ops;
 208         if (tb[NFTA_FWD_SREG_DEV])
 209                 return &nft_fwd_netdev_ops;
 210
 211         return ERR_PTR(-EOPNOTSUPP);
 212 }
 213
 214 static struct nft_expr_type nft_fwd_netdev_type __read_mostly = {
 215         .family         = NFPROTO_NETDEV,
 216         .name           = "fwd",
 217         .select_ops     = nft_fwd_select_ops,
 218         .policy         = nft_fwd_netdev_policy,
 219         .maxattr        = NFTA_FWD_MAX,
 220         .owner          = THIS_MODULE,
 221 };
 222
 223 static int __init nft_fwd_netdev_module_init(void)
 224 {
 225         return nft_register_expr(&nft_fwd_netdev_type);
 226 }
 227
 228 static void __exit nft_fwd_netdev_module_exit(void)
 229 {
 230         nft_unregister_expr(&nft_fwd_netdev_type);
 231 }
 232
 233 module_init(nft_fwd_netdev_module_init);
 234 module_exit(nft_fwd_netdev_module_exit);
 235
 236 MODULE_LICENSE("GPL");
 237 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 238 MODULE_ALIAS_NFT_AF_EXPR(5, "fwd");