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