tools/testing/selftests/bpf/progs/test_lwt_reroute.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/bpf/progs/test_lwt_reroute.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/bpf/progs/test_lwt_reroute.c
Extension
.c
Size
795 bytes
Lines
37
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
#include <inttypes.h>
#include <linux/bpf.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
#include <linux/if_ether.h>
#include <linux/ip.h>

/* This function extracts the last byte of the daddr, and uses it
 * as output dev index.
 */
SEC("lwt_xmit")
int test_lwt_reroute(struct __sk_buff *skb)
{
	struct iphdr *iph = NULL;
	void *start = (void *)(long)skb->data;
	void *end = (void *)(long)skb->data_end;

	/* set mark at most once */
	if (skb->mark != 0)
		return BPF_OK;

	if (start + sizeof(*iph) > end)
		return BPF_DROP;

	iph = (struct iphdr *)start;
	skb->mark = bpf_ntohl(iph->daddr) & 0xff;

	/* do not reroute x.x.x.0 packets */
	if (skb->mark == 0)
		return BPF_OK;

	return BPF_LWT_REROUTE;
}

char _license[] SEC("license") = "GPL";

Annotation

Implementation Notes