| 1 | // SPDX-License-Identifier: GPL-2.0 |
|---|---|
| 2 | #include <inttypes.h> |
| 3 | #include <linux/bpf.h> |
| 4 | #include <bpf/bpf_endian.h> |
| 5 | #include <bpf/bpf_helpers.h> |
| 6 | #include <linux/if_ether.h> |
| 7 | #include <linux/ip.h> |
| 8 | |
| 9 | /* This function extracts the last byte of the daddr, and uses it |
| 10 | * as output dev index. |
| 11 | */ |
| 12 | SEC("lwt_xmit") |
| 13 | int test_lwt_reroute(struct __sk_buff *skb) |
| 14 | { |
| 15 | struct iphdr *iph = NULL; |
| 16 | void *start = (void *)(long)skb->data; |
| 17 | void *end = (void *)(long)skb->data_end; |
| 18 | |
| 19 | /* set mark at most once */ |
| 20 | if (skb->mark != 0) |
| 21 | return BPF_OK; |
| 22 | |
| 23 | if (start + sizeof(*iph) > end) |
| 24 | return BPF_DROP; |
| 25 | |
| 26 | iph = (struct iphdr *)start; |
| 27 | skb->mark = bpf_ntohl(iph->daddr) & 0xff; |
| 28 | |
| 29 | /* do not reroute x.x.x.0 packets */ |
| 30 | if (skb->mark == 0) |
| 31 | return BPF_OK; |
| 32 | |
| 33 | return BPF_LWT_REROUTE; |
| 34 | } |
| 35 | |
| 36 | char _license[] SEC("license") = "GPL"; |
| 37 |