Subject: [RFC bpf-next v2 07/14] selftests/bpf: Verify xdp_metadata xdp->skb path

From: Stanislav Fomichev <[email-masked]>
Date: Thu, 3 Nov 2022 20:25:25 -0700

- divert 9081 UDP traffic to the kernel
- call bpf_xdp_metadata_export_to_skb for such packets
- the kernel should fill in hwtstamp
- verify that the received packet has non-zero hwtstamp

Cc: John Fastabend <[email-masked]>
Cc: David Ahern <[email-masked]>
Cc: Martin KaFai Lau <[email-masked]>
Cc: Jakub Kicinski <[email-masked]>
Cc: Willem de Bruijn <[email-masked]>
Cc: Jesper Dangaard Brouer <[email-masked]>
Cc: Anatoly Burakov <[email-masked]>
Cc: Alexander Lobakin <[email-masked]>
Cc: Magnus Karlsson <[email-masked]>
Cc: Maryam Tahhan <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Signed-off-by: Stanislav Fomichev <[email-masked]>
---
 .../selftests/bpf/prog_tests/xdp_metadata.c   | 92 +++++++++++++++++++
 .../selftests/bpf/progs/xdp_metadata.c        | 28 ++++++
 2 files changed, 120 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
index bb06e25fb2bb..96cc6d7697f8 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
@@ -19,6 +19,11 @@
 
 #define AF_XDP_SOURCE_PORT 1234
 #define AF_XDP_CONSUMER_PORT 8080
+#define SOCKET_CONSUMER_PORT 9081
+
+#ifndef SOL_UDP
+#define SOL_UDP		17
+#endif
 
 #define UMEM_NUM 16
 #define UMEM_FRAME_SIZE XSK_UMEM__DEFAULT_FRAME_SIZE
@@ -221,6 +226,71 @@ int verify_xsk_metadata(struct xsk *xsk)
 	return 0;
 }
 
+static void disable_rx_checksum(int fd)
+{
+	int ret, val;
+
+	val = 1;
+	ret = setsockopt(fd, SOL_UDP, UDP_NO_CHECK6_RX, &val, sizeof(val));
+	ASSERT_OK(ret, "setsockopt(UDP_NO_CHECK6_RX)");
+}
+
+static void timestamping_enable(int fd)
+{
+	int ret, val;
+
+	val = SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_RAW_HARDWARE;
+	ret = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val));
+	ASSERT_OK(ret, "setsockopt(SO_TIMESTAMPING)");
+}
+
+int verify_skb_metadata(int fd)
+{
+	char cmsg_buf[1024];
+	char packet_buf[128];
+
+	struct scm_timestamping *ts;
+	struct iovec packet_iov;
+	struct cmsghdr *cmsg;
+	struct msghdr hdr;
+	bool found_hwtstamp = false;
+
+	memset(&hdr, 0, sizeof(hdr));
+	hdr.msg_iov = &packet_iov;
+	hdr.msg_iovlen = 1;
+	packet_iov.iov_base = packet_buf;
+	packet_iov.iov_len = sizeof(packet_buf);
+
+	hdr.msg_control = cmsg_buf;
+	hdr.msg_controllen = sizeof(cmsg_buf);
+
+	if (ASSERT_GE(recvmsg(fd, &hdr, 0), 0, "recvmsg")) {
+		for (cmsg = CMSG_FIRSTHDR(&hdr); cmsg != NULL;
+		     cmsg = CMSG_NXTHDR(&hdr, cmsg)) {
+
+			if (cmsg->cmsg_level != SOL_SOCKET)
+				continue;
+
+			switch (cmsg->cmsg_type) {
+			case SCM_TIMESTAMPING:
+				ts = (struct scm_timestamping *)CMSG_DATA(cmsg);
+				if (ts->ts[2].tv_sec || ts->ts[2].tv_nsec) {
+					found_hwtstamp = true;
+					break;
+				}
+				break;
+			default:
+				break;
+			}
+		}
+	}
+
+	if (!ASSERT_EQ(found_hwtstamp, true, "no hwtstamp!"))
+		return -1;
+
+	return 0;
+}
+
 void test_xdp_metadata(void)
 {
 	struct xdp_metadata *bpf_obj = NULL;
@@ -228,6 +298,7 @@ void test_xdp_metadata(void)
 	struct bpf_program *prog;
 	struct xsk tx_xsk = {};
 	struct xsk rx_xsk = {};
+	int rx_udp_fd = -1;
 	int rx_ifindex;
 	int ret;
 
@@ -243,6 +314,8 @@ void test_xdp_metadata(void)
 	SYS("ip link set dev " RX_NAME " up");
 	SYS("ip addr add " TX_ADDR "/" PREFIX_LEN " dev " TX_NAME);
 	SYS("ip addr add " RX_ADDR "/" PREFIX_LEN " dev " RX_NAME);
+	SYS("sysctl -q net.ipv4.ip_forward=1");
+	SYS("sysctl -q net.ipv4.conf.all.accept_local=1");
 
 	rx_ifindex = if_nametoindex(RX_NAME);
 
@@ -256,6 +329,14 @@ void test_xdp_metadata(void)
 	if (!ASSERT_OK(ret, "open_xsk(RX_NAME)"))
 		goto out;
 
+	/* Setup UPD listener for RX interface. */
+
+	rx_udp_fd = start_server(FAMILY, SOCK_DGRAM, NULL, SOCKET_CONSUMER_PORT, 1000);
+	if (!ASSERT_GE(rx_udp_fd, 0, "start_server"))
+		goto out;
+	disable_rx_checksum(rx_udp_fd);
+	timestamping_enable(rx_udp_fd);
+
 	/* Attach BPF program to RX interface. */
 
 	bpf_obj = xdp_metadata__open();
@@ -291,9 +372,20 @@ void test_xdp_metadata(void)
 		       "verify_xsk_metadata"))
 	    goto out;
 
+	/* Send packet destined to RX UDP socket. */
+	if (!ASSERT_GE(generate_packet(&tx_xsk, SOCKET_CONSUMER_PORT), 0,
+		       "generate SOCKET_CONSUMER_PORT"))
+	    goto out;
+
+	/* Verify SKB RX packet has proper metadata. */
+	if (!ASSERT_GE(verify_skb_metadata(rx_udp_fd), 0,
+		       "verify_skb_metadata"))
+	    goto out;
+
 out:
 	close_xsk(&rx_xsk);
 	close_xsk(&tx_xsk);
+	close(rx_udp_fd);
 	if (bpf_obj)
 		xdp_metadata__destroy(bpf_obj);
 	system("ip netns del xdp_metadata");
diff --git a/tools/testing/selftests/bpf/progs/xdp_metadata.c b/tools/testing/selftests/bpf/progs/xdp_metadata.c
index bdde17961ab6..6e7292c58b86 100644
--- a/tools/testing/selftests/bpf/progs/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/progs/xdp_metadata.c
@@ -17,6 +17,7 @@ struct {
 	__type(value, __u32);
 } xsk SEC(".maps");
 
+extern void bpf_xdp_metadata_export_to_skb(const struct xdp_md *ctx) __ksym;
 extern int bpf_xdp_metadata_rx_timestamp_supported(const struct xdp_md *ctx) __ksym;
 extern const __u64 bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx) __ksym;
 
@@ -24,8 +25,35 @@ SEC("xdp")
 int rx(struct xdp_md *ctx)
 {
 	void *data, *data_meta;
+	struct ethhdr *eth = NULL;
+	struct udphdr *udp = NULL;
+	struct iphdr *iph = NULL;
+	void *data_end;
 	int ret;
 
+	/* Exercise xdp -> skb metadata path by diverting some traffic
+	 * into the kernel (UDP destination port 9081).
+	 */
+
+	data = (void *)(long)ctx->data;
+	data_end = (void *)(long)ctx->data_end;
+	eth = data;
+	if (eth + 1 < data_end) {
+		if (eth->h_proto == bpf_htons(ETH_P_IP)) {
+			iph = (void *)(eth + 1);
+			if (iph + 1 < data_end && iph->protocol == IPPROTO_UDP)
+				udp = (void *)(iph + 1);
+		}
+		if (udp && udp + 1 > data_end)
+			udp = NULL;
+	}
+	if (udp && udp->dest == bpf_htons(9081)) {
+		bpf_xdp_metadata_export_to_skb(ctx);
+		bpf_printk("exporting metadata to skb for UDP port 9081");
+		/*return bpf_redirect(ifindex, BPF_F_INGRESS);*/
+		return XDP_PASS;
+	}
+
 	if (bpf_xdp_metadata_rx_timestamp_supported(ctx)) {
 		__u64 rx_timestamp = bpf_xdp_metadata_rx_timestamp(ctx);
 
-- 
2.38.1.431.g37b22c650d-goog