netdev - [PATCH net-next v2 2/5] selftests/net: add bpf skb forwarding program

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Message-ID: <20251123005108.3694230-3-dw@davidwei.uk>
Date: Sat, 22 Nov 2025 16:51:05 -0800
From: David Wei <dw@...idwei.uk>
To: netdev@...r.kernel.org
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next v2 2/5] selftests/net: add bpf skb forwarding program

Add nk_forward.bpf.c, a bpf program that forwards skbs matching some
IPv6 prefix received on eth0 ifindex to a specified netkit ifindex. This
will be needed by netkit container tests.

Signed-off-by: David Wei <dw@...idwei.uk>
---
 .../selftests/drivers/net/hw/.gitignore       |  2 +
 .../selftests/drivers/net/hw/nk_forward.bpf.c | 49 +++++++++++++++++++
 2 files changed, 51 insertions(+)
 create mode 100644 tools/testing/selftests/drivers/net/hw/nk_forward.bpf.c

diff --git a/tools/testing/selftests/drivers/net/hw/.gitignore b/tools/testing/selftests/drivers/net/hw/.gitignore
index 46540468a775..9ae058dba155 100644
--- a/tools/testing/selftests/drivers/net/hw/.gitignore
+++ b/tools/testing/selftests/drivers/net/hw/.gitignore
@@ -2,3 +2,5 @@
 iou-zcrx
 ncdevmem
 toeplitz
+# bpftool
+tools/
diff --git a/tools/testing/selftests/drivers/net/hw/nk_forward.bpf.c b/tools/testing/selftests/drivers/net/hw/nk_forward.bpf.c
new file mode 100644
index 000000000000..b593cd6c314c
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/hw/nk_forward.bpf.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+#include <linux/if_ether.h>
+#include <linux/ipv6.h>
+#include <linux/in6.h>
+#include <bpf/bpf_endian.h>
+#include <bpf/bpf_helpers.h>
+
+#define TC_ACT_OK 0
+#define ETH_P_IPV6 0x86DD
+
+#define ctx_ptr(field)		(void *)(long)(field)
+
+#define v6_p64_equal(a, b)	(a.s6_addr32[0] == b.s6_addr32[0] && \
+				 a.s6_addr32[1] == b.s6_addr32[1])
+
+volatile __u32 netkit_ifindex;
+volatile __u8 ipv6_prefix[16];
+
+SEC("tc/ingress")
+int tc_redirect_peer(struct __sk_buff *skb)
+{
+	void *data_end = ctx_ptr(skb->data_end);
+	void *data = ctx_ptr(skb->data);
+	struct in6_addr *peer_addr;
+	struct ipv6hdr *ip6h;
+	struct ethhdr *eth;
+
+	peer_addr = (struct in6_addr *)ipv6_prefix;
+
+	if (skb->protocol != bpf_htons(ETH_P_IPV6))
+		return TC_ACT_OK;
+
+	eth = data;
+	if ((void *)(eth + 1) > data_end)
+		return TC_ACT_OK;
+
+	ip6h = data + sizeof(struct ethhdr);
+	if ((void *)(ip6h + 1) > data_end)
+		return TC_ACT_OK;
+
+	if (!v6_p64_equal(ip6h->daddr, (*peer_addr)))
+		return TC_ACT_OK;
+
+	return bpf_redirect_peer(netkit_ifindex, 0);
+}
+
+char __license[] SEC("license") = "GPL";
-- 
2.47.3