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