// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2014 Pablo Neira Ayuso <pablo@netfilter.org>
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*/
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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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#include <linux/ip.h>
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#include <net/ip.h>
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#include <net/ip6_checksum.h>
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#include <linux/netfilter_bridge.h>
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#include <linux/netfilter_ipv6.h>
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#include "../br_private.h"
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static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb,
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struct sk_buff *nskb)
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{
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struct ethhdr *eth;
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eth = skb_push(nskb, ETH_HLEN);
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skb_reset_mac_header(nskb);
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ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest);
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ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source);
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eth->h_proto = eth_hdr(oldskb)->h_proto;
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skb_pull(nskb, ETH_HLEN);
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if (skb_vlan_tag_present(oldskb)) {
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u16 vid = skb_vlan_tag_get(oldskb);
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__vlan_hwaccel_put_tag(nskb, oldskb->vlan_proto, vid);
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}
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}
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static int nft_bridge_iphdr_validate(struct sk_buff *skb)
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{
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struct iphdr *iph;
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u32 len;
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if (!pskb_may_pull(skb, sizeof(struct iphdr)))
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return 0;
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iph = ip_hdr(skb);
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if (iph->ihl < 5 || iph->version != 4)
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return 0;
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len = ntohs(iph->tot_len);
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if (skb->len < len)
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return 0;
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else if (len < (iph->ihl*4))
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return 0;
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if (!pskb_may_pull(skb, iph->ihl*4))
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return 0;
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return 1;
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}
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/* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT)
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* or the bridge port (NF_BRIDGE PREROUTING).
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*/
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static void nft_reject_br_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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struct iphdr *niph;
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const struct tcphdr *oth;
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struct tcphdr _oth;
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if (!nft_bridge_iphdr_validate(oldskb))
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return;
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oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
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if (!oth)
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return;
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nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
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LL_MAX_HEADER, GFP_ATOMIC);
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if (!nskb)
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return;
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skb_reserve(nskb, LL_MAX_HEADER);
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niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
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net->ipv4.sysctl_ip_default_ttl);
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nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
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niph->tot_len = htons(nskb->len);
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ip_send_check(niph);
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nft_reject_br_push_etherhdr(oldskb, nskb);
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br_forward(br_port_get_rcu(dev), nskb, false, true);
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}
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static void nft_reject_br_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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struct iphdr *niph;
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struct icmphdr *icmph;
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unsigned int len;
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__wsum csum;
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u8 proto;
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if (!nft_bridge_iphdr_validate(oldskb))
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return;
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/* IP header checks: fragment. */
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if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
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return;
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/* RFC says return as much as we can without exceeding 576 bytes. */
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len = min_t(unsigned int, 536, oldskb->len);
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if (!pskb_may_pull(oldskb, len))
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return;
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if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len)))
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return;
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proto = ip_hdr(oldskb)->protocol;
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if (!skb_csum_unnecessary(oldskb) &&
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nf_reject_verify_csum(proto) &&
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nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto))
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return;
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nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) +
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LL_MAX_HEADER + len, GFP_ATOMIC);
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if (!nskb)
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return;
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skb_reserve(nskb, LL_MAX_HEADER);
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niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP,
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net->ipv4.sysctl_ip_default_ttl);
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skb_reset_transport_header(nskb);
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icmph = skb_put_zero(nskb, sizeof(struct icmphdr));
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icmph->type = ICMP_DEST_UNREACH;
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icmph->code = code;
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skb_put_data(nskb, skb_network_header(oldskb), len);
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csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0);
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icmph->checksum = csum_fold(csum);
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niph->tot_len = htons(nskb->len);
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ip_send_check(niph);
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nft_reject_br_push_etherhdr(oldskb, nskb);
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br_forward(br_port_get_rcu(dev), nskb, false, true);
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}
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static int nft_bridge_ip6hdr_validate(struct sk_buff *skb)
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{
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struct ipv6hdr *hdr;
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u32 pkt_len;
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if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
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return 0;
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hdr = ipv6_hdr(skb);
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if (hdr->version != 6)
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return 0;
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pkt_len = ntohs(hdr->payload_len);
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if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
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return 0;
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return 1;
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}
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static void nft_reject_br_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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const struct tcphdr *oth;
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struct tcphdr _oth;
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unsigned int otcplen;
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struct ipv6hdr *nip6h;
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if (!nft_bridge_ip6hdr_validate(oldskb))
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return;
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oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
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if (!oth)
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return;
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nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
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LL_MAX_HEADER, GFP_ATOMIC);
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if (!nskb)
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return;
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skb_reserve(nskb, LL_MAX_HEADER);
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nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
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net->ipv6.devconf_all->hop_limit);
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nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
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nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
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nft_reject_br_push_etherhdr(oldskb, nskb);
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br_forward(br_port_get_rcu(dev), nskb, false, true);
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}
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static bool reject6_br_csum_ok(struct sk_buff *skb, int hook)
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{
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const struct ipv6hdr *ip6h = ipv6_hdr(skb);
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int thoff;
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__be16 fo;
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u8 proto = ip6h->nexthdr;
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if (skb_csum_unnecessary(skb))
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return true;
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if (ip6h->payload_len &&
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pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
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return false;
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ip6h = ipv6_hdr(skb);
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thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
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if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
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return false;
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if (!nf_reject_verify_csum(proto))
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return true;
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return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
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}
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static void nft_reject_br_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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struct ipv6hdr *nip6h;
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struct icmp6hdr *icmp6h;
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unsigned int len;
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if (!nft_bridge_ip6hdr_validate(oldskb))
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return;
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/* Include "As much of invoking packet as possible without the ICMPv6
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* packet exceeding the minimum IPv6 MTU" in the ICMP payload.
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*/
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len = min_t(unsigned int, 1220, oldskb->len);
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if (!pskb_may_pull(oldskb, len))
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return;
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if (!reject6_br_csum_ok(oldskb, hook))
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return;
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nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) +
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LL_MAX_HEADER + len, GFP_ATOMIC);
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if (!nskb)
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return;
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skb_reserve(nskb, LL_MAX_HEADER);
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nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
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net->ipv6.devconf_all->hop_limit);
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skb_reset_transport_header(nskb);
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icmp6h = skb_put_zero(nskb, sizeof(struct icmp6hdr));
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icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
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icmp6h->icmp6_code = code;
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skb_put_data(nskb, skb_network_header(oldskb), len);
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nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
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icmp6h->icmp6_cksum =
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csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
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nskb->len - sizeof(struct ipv6hdr),
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IPPROTO_ICMPV6,
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csum_partial(icmp6h,
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nskb->len - sizeof(struct ipv6hdr),
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0));
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nft_reject_br_push_etherhdr(oldskb, nskb);
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br_forward(br_port_get_rcu(dev), nskb, false, true);
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}
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static void nft_reject_bridge_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 nft_reject *priv = nft_expr_priv(expr);
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const unsigned char *dest = eth_hdr(pkt->skb)->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_hdr(pkt->skb)->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_br_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_br_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_br_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_br_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_br_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_br_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_bridge_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_BR_PRE_ROUTING) |
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(1 << NF_BR_LOCAL_IN));
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}
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static int nft_reject_bridge_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_reject *priv = nft_expr_priv(expr);
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int icmp_code;
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if (tb[NFTA_REJECT_TYPE] == NULL)
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return -EINVAL;
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priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE]));
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switch (priv->type) {
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case NFT_REJECT_ICMP_UNREACH:
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case NFT_REJECT_ICMPX_UNREACH:
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if (tb[NFTA_REJECT_ICMP_CODE] == NULL)
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return -EINVAL;
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icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]);
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if (priv->type == NFT_REJECT_ICMPX_UNREACH &&
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icmp_code > NFT_REJECT_ICMPX_MAX)
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return -EINVAL;
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priv->icmp_code = icmp_code;
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break;
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case NFT_REJECT_TCP_RST:
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break;
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default:
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return -EINVAL;
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}
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return 0;
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}
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static int nft_reject_bridge_dump(struct sk_buff *skb,
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const struct nft_expr *expr)
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{
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const struct nft_reject *priv = nft_expr_priv(expr);
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if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type)))
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goto nla_put_failure;
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switch (priv->type) {
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case NFT_REJECT_ICMP_UNREACH:
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case NFT_REJECT_ICMPX_UNREACH:
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if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code))
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goto nla_put_failure;
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break;
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default:
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break;
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}
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return 0;
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nla_put_failure:
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return -1;
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}
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static struct nft_expr_type nft_reject_bridge_type;
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static const struct nft_expr_ops nft_reject_bridge_ops = {
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.type = &nft_reject_bridge_type,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
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.eval = nft_reject_bridge_eval,
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.init = nft_reject_bridge_init,
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.dump = nft_reject_bridge_dump,
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.validate = nft_reject_bridge_validate,
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};
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static struct nft_expr_type nft_reject_bridge_type __read_mostly = {
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.family = NFPROTO_BRIDGE,
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.name = "reject",
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.ops = &nft_reject_bridge_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_bridge_module_init(void)
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{
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return nft_register_expr(&nft_reject_bridge_type);
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}
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static void __exit nft_reject_bridge_module_exit(void)
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{
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nft_unregister_expr(&nft_reject_bridge_type);
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}
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module_init(nft_reject_bridge_module_init);
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module_exit(nft_reject_bridge_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
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MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject");
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MODULE_DESCRIPTION("Reject packets from bridge via nftables");
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