selftests/bpf: bpf tunnel encap test

Validate basic tunnel encapsulation using ipip.

Set up two namespaces connected by veth. Connect a client and server.
Do this with and without bpf encap.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 83 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
new file mode 100644
index 000000000000..8223e4347be8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* In-place tunneling */
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <linux/pkt_cls.h>
+#include <linux/types.h>
+
+#include "bpf_endian.h"
+#include "bpf_helpers.h"
+
+static const int cfg_port = 8000;
+
+static __always_inline void set_ipv4_csum(struct iphdr *iph)
+{
+	__u16 *iph16 = (__u16 *)iph;
+	__u32 csum;
+	int i;
+
+	iph->check = 0;
+
+#pragma clang loop unroll(full)
+	for (i = 0, csum = 0; i < sizeof(*iph) >> 1; i++)
+		csum += *iph16++;
+
+	iph->check = ~((csum & 0xffff) + (csum >> 16));
+}
+
+SEC("encap")
+int encap_f(struct __sk_buff *skb)
+{
+	struct iphdr iph_outer, iph_inner;
+	struct tcphdr tcph;
+
+	if (skb->protocol != __bpf_constant_htons(ETH_P_IP))
+		return TC_ACT_OK;
+
+	if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_inner,
+			       sizeof(iph_inner)) < 0)
+		return TC_ACT_OK;
+
+	/* filter only packets we want */
+	if (iph_inner.ihl != 5 || iph_inner.protocol != IPPROTO_TCP)
+		return TC_ACT_OK;
+
+	if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(iph_inner),
+			       &tcph, sizeof(tcph)) < 0)
+		return TC_ACT_OK;
+
+	if (tcph.dest != __bpf_constant_htons(cfg_port))
+		return TC_ACT_OK;
+
+	/* add room between mac and network header */
+	if (bpf_skb_adjust_room(skb, sizeof(iph_outer), BPF_ADJ_ROOM_NET, 0))
+		return TC_ACT_SHOT;
+
+	/* prepare new outer network header */
+	iph_outer = iph_inner;
+	iph_outer.protocol = IPPROTO_IPIP;
+	iph_outer.tot_len = bpf_htons(sizeof(iph_outer) +
+				      bpf_htons(iph_outer.tot_len));
+	set_ipv4_csum(&iph_outer);
+
+	/* store new outer network header */
+	if (bpf_skb_store_bytes(skb, ETH_HLEN, &iph_outer, sizeof(iph_outer),
+				BPF_F_INVALIDATE_HASH) < 0)
+		return TC_ACT_SHOT;
+
+	/* bpf_skb_adjust_room has moved header to start of room: restore */
+	if (bpf_skb_store_bytes(skb, ETH_HLEN + sizeof(iph_outer),
+				&iph_inner, sizeof(iph_inner),
+				BPF_F_INVALIDATE_HASH) < 0)
+		return TC_ACT_SHOT;
+
+	return TC_ACT_OK;
+}
+
+char __license[] SEC("license") = "GPL";