// 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/bpf_helpers.h> #include <bpf/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";