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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2020 Laura Garcia Liebana <nevola@gmail.com>
* Copyright (c) 2020 Jose M. Guisado <guigom@riseup.net>
*/
#include <linux/etherdevice.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nft_reject.h>
#include <net/netfilter/ipv4/nf_reject.h>
#include <net/netfilter/ipv6/nf_reject.h>
static void nft_reject_queue_xmit(struct sk_buff *nskb, struct sk_buff *oldskb)
{
dev_hard_header(nskb, nskb->dev, ntohs(oldskb->protocol),
eth_hdr(oldskb)->h_source, eth_hdr(oldskb)->h_dest,
nskb->len);
dev_queue_xmit(nskb);
}
static void nft_reject_netdev_send_v4_tcp_reset(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook)
{
struct sk_buff *nskb;
nskb = nf_reject_skb_v4_tcp_reset(net, oldskb, dev, hook);
if (!nskb)
return;
nft_reject_queue_xmit(nskb, oldskb);
}
static void nft_reject_netdev_send_v4_unreach(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook, u8 code)
{
struct sk_buff *nskb;
nskb = nf_reject_skb_v4_unreach(net, oldskb, dev, hook, code);
if (!nskb)
return;
nft_reject_queue_xmit(nskb, oldskb);
}
static void nft_reject_netdev_send_v6_tcp_reset(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook)
{
struct sk_buff *nskb;
nskb = nf_reject_skb_v6_tcp_reset(net, oldskb, dev, hook);
if (!nskb)
return;
nft_reject_queue_xmit(nskb, oldskb);
}
static void nft_reject_netdev_send_v6_unreach(struct net *net,
struct sk_buff *oldskb,
const struct net_device *dev,
int hook, u8 code)
{
struct sk_buff *nskb;
nskb = nf_reject_skb_v6_unreach(net, oldskb, dev, hook, code);
if (!nskb)
return;
nft_reject_queue_xmit(nskb, oldskb);
}
static void nft_reject_netdev_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct ethhdr *eth = eth_hdr(pkt->skb);
struct nft_reject *priv = nft_expr_priv(expr);
const unsigned char *dest = eth->h_dest;
if (is_broadcast_ether_addr(dest) ||
is_multicast_ether_addr(dest))
goto out;
switch (eth->h_proto) {
case htons(ETH_P_IP):
switch (priv->type) {
case NFT_REJECT_ICMP_UNREACH:
nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt),
priv->icmp_code);
break;
case NFT_REJECT_TCP_RST:
nft_reject_netdev_send_v4_tcp_reset(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt));
break;
case NFT_REJECT_ICMPX_UNREACH:
nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt),
nft_reject_icmp_code(priv->icmp_code));
break;
}
break;
case htons(ETH_P_IPV6):
switch (priv->type) {
case NFT_REJECT_ICMP_UNREACH:
nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt),
priv->icmp_code);
break;
case NFT_REJECT_TCP_RST:
nft_reject_netdev_send_v6_tcp_reset(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt));
break;
case NFT_REJECT_ICMPX_UNREACH:
nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb,
nft_in(pkt),
nft_hook(pkt),
nft_reject_icmpv6_code(priv->icmp_code));
break;
}
break;
default:
/* No explicit way to reject this protocol, drop it. */
break;
}
out:
regs->verdict.code = NF_DROP;
}
static int nft_reject_netdev_validate(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nft_data **data)
{
return nft_chain_validate_hooks(ctx->chain, (1 << NF_NETDEV_INGRESS));
}
static struct nft_expr_type nft_reject_netdev_type;
static const struct nft_expr_ops nft_reject_netdev_ops = {
.type = &nft_reject_netdev_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
.eval = nft_reject_netdev_eval,
.init = nft_reject_init,
.dump = nft_reject_dump,
.validate = nft_reject_netdev_validate,
};
static struct nft_expr_type nft_reject_netdev_type __read_mostly = {
.family = NFPROTO_NETDEV,
.name = "reject",
.ops = &nft_reject_netdev_ops,
.policy = nft_reject_policy,
.maxattr = NFTA_REJECT_MAX,
.owner = THIS_MODULE,
};
static int __init nft_reject_netdev_module_init(void)
{
return nft_register_expr(&nft_reject_netdev_type);
}
static void __exit nft_reject_netdev_module_exit(void)
{
nft_unregister_expr(&nft_reject_netdev_type);
}
module_init(nft_reject_netdev_module_init);
module_exit(nft_reject_netdev_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Laura Garcia Liebana <nevola@gmail.com>");
MODULE_AUTHOR("Jose M. Guisado <guigom@riseup.net>");
MODULE_DESCRIPTION("Reject packets from netdev via nftables");
MODULE_ALIAS_NFT_AF_EXPR(5, "reject");
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