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
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