// SPDX-License-Identifier: GPL-2.0
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#include <stddef.h>
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#include <string.h>
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#include <linux/bpf.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_endian.h>
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struct grehdr {
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__be16 flags;
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__be16 protocol;
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};
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SEC("encap_gre")
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int bpf_lwt_encap_gre(struct __sk_buff *skb)
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{
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struct encap_hdr {
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struct iphdr iph;
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struct grehdr greh;
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} hdr;
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int err;
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memset(&hdr, 0, sizeof(struct encap_hdr));
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hdr.iph.ihl = 5;
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hdr.iph.version = 4;
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hdr.iph.ttl = 0x40;
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hdr.iph.protocol = 47; /* IPPROTO_GRE */
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#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
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hdr.iph.saddr = 0x640110ac; /* 172.16.1.100 */
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hdr.iph.daddr = 0x641010ac; /* 172.16.16.100 */
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#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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hdr.iph.saddr = 0xac100164; /* 172.16.1.100 */
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hdr.iph.daddr = 0xac101064; /* 172.16.16.100 */
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#else
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#error "Fix your compiler's __BYTE_ORDER__?!"
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#endif
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hdr.iph.tot_len = bpf_htons(skb->len + sizeof(struct encap_hdr));
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hdr.greh.protocol = skb->protocol;
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err = bpf_lwt_push_encap(skb, BPF_LWT_ENCAP_IP, &hdr,
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sizeof(struct encap_hdr));
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if (err)
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return BPF_DROP;
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return BPF_LWT_REROUTE;
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}
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SEC("encap_gre6")
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int bpf_lwt_encap_gre6(struct __sk_buff *skb)
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{
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struct encap_hdr {
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struct ipv6hdr ip6hdr;
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struct grehdr greh;
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} hdr;
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int err;
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memset(&hdr, 0, sizeof(struct encap_hdr));
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hdr.ip6hdr.version = 6;
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hdr.ip6hdr.payload_len = bpf_htons(skb->len + sizeof(struct grehdr));
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hdr.ip6hdr.nexthdr = 47; /* IPPROTO_GRE */
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hdr.ip6hdr.hop_limit = 0x40;
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/* fb01::1 */
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hdr.ip6hdr.saddr.s6_addr[0] = 0xfb;
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hdr.ip6hdr.saddr.s6_addr[1] = 1;
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hdr.ip6hdr.saddr.s6_addr[15] = 1;
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/* fb10::1 */
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hdr.ip6hdr.daddr.s6_addr[0] = 0xfb;
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hdr.ip6hdr.daddr.s6_addr[1] = 0x10;
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hdr.ip6hdr.daddr.s6_addr[15] = 1;
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hdr.greh.protocol = skb->protocol;
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err = bpf_lwt_push_encap(skb, BPF_LWT_ENCAP_IP, &hdr,
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sizeof(struct encap_hdr));
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if (err)
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return BPF_DROP;
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return BPF_LWT_REROUTE;
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}
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char _license[] SEC("license") = "GPL";
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