[PATCH bpf-next v5 2/2] selftests/bpf: CGROUP_SKB test for skb_store_bytes()

[Tyler Wear <quic_twear@quicinc.com>]

Patch adds a test case to check that the source IP and Port of
packet are correctly changed for BPF_PROG_TYPE_CGROUP_SKB via
skb_store_bytes().

Test creates a client and server and checks that the packet
received on the server has the updated source IP and Port
that the bpf program modifies.

Signed-off-by: Tyler Wear <quic_twear@quicinc.com>
---
 .../bpf/prog_tests/cgroup_store_bytes.c       | 81 +++++++++++++++++++
 .../selftests/bpf/progs/cgroup_store_bytes.c  | 63 +++++++++++++++
 2 files changed, 144 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_store_bytes.c
 create mode 100644 tools/testing/selftests/bpf/progs/cgroup_store_bytes.c

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_store_bytes.c b/tools/testing/selftests/bpf/prog_tests/cgroup_store_bytes.c
new file mode 100644
index 000000000000..f492fdb2f31b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_store_bytes.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "cgroup_store_bytes.skel.h"
+
+static int duration;
+
+void test_cgroup_store_bytes(void)
+{
+	int server_fd, cgroup_fd, client_fd;
+	struct sockaddr server_addr;
+	socklen_t addrlen = sizeof(server_addr);
+	char buf[] = "testing";
+	struct sockaddr_storage ss;
+	char recv_buf[BUFSIZ];
+	socklen_t slen;
+	struct in_addr addr;
+	unsigned short port;
+	struct cgroup_store_bytes *skel;
+
+	cgroup_fd = test__join_cgroup("/cgroup_store_bytes");
+	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
+		return;
+
+	skel = cgroup_store_bytes__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		goto close_cgroup_fd;
+	if (!ASSERT_OK_PTR(skel->bss, "check_bss"))
+		goto close_cgroup_fd;
+
+	skel->links.cgroup_store_bytes = bpf_program__attach_cgroup(
+			skel->progs.cgroup_store_bytes, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel, "cgroup_store_bytes"))
+		goto close_skeleton;
+
+	server_fd = start_server(AF_INET, SOCK_DGRAM, NULL, 0, 0);
+	if (!ASSERT_GE(server_fd, 0, "server_fd"))
+		goto close_cgroup_fd;
+
+	client_fd = start_server(AF_INET, SOCK_DGRAM, NULL, 0, 0);
+	if (!ASSERT_GE(client_fd, 0, "client_fd"))
+		goto close_server_fd;
+
+	if (getsockname(server_fd, &server_addr, &addrlen)) {
+		perror("Failed to get server addr");
+		goto close_client_fd;
+	}
+
+	if (CHECK_FAIL(sendto(client_fd, buf, sizeof(buf), 0, &server_addr,
+			sizeof(server_addr)) != sizeof(buf))) {
+		perror("Can't write on client");
+		goto close_client_fd;
+	}
+
+	if (recvfrom(server_fd, &recv_buf, sizeof(recv_buf), 0,
+			(struct sockaddr *)&ss, &slen) <= 0) {
+		perror("Recvfrom received no packets");
+		goto close_client_fd;
+	}
+
+	addr = ((struct sockaddr_in *)&ss)->sin_addr;
+
+	CHECK(addr.s_addr != 0xac100164, "bpf", "bpf program failed to change saddr");
+
+	port = ((struct sockaddr_in *)&ss)->sin_port;
+
+	CHECK(port != htons(5555), "bpf", "bpf program failed to change port");
+
+	CHECK(skel->bss->test_result != 1, "bpf", "bpf program returned failure");
+
+close_client_fd:
+	close(client_fd);
+close_server_fd:
+	close(server_fd);
+close_skeleton:
+	cgroup_store_bytes__destroy(skel);
+close_cgroup_fd:
+	close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/cgroup_store_bytes.c b/tools/testing/selftests/bpf/progs/cgroup_store_bytes.c
new file mode 100644
index 000000000000..d81d39281526
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cgroup_store_bytes.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <netinet/in.h>
+#include <netinet/udp.h>
+#include <bpf/bpf_helpers.h>
+
+#define IP_SRC_OFF offsetof(struct iphdr, saddr)
+#define UDP_SPORT_OFF (sizeof(struct iphdr) + offsetof(struct udphdr, source))
+
+#define IS_PSEUDO 0x10
+
+#define UDP_CSUM_OFF (sizeof(struct iphdr) + offsetof(struct udphdr, check))
+#define IP_CSUM_OFF offsetof(struct iphdr, check)
+
+int test_result;
+
+SEC("cgroup_skb/egress")
+int cgroup_store_bytes(struct __sk_buff *skb)
+{
+	struct ethhdr eth;
+	struct iphdr iph;
+	struct udphdr udph;
+
+	__u32 map_key = 0;
+	__u32 test_passed = 0;
+
+	if (bpf_skb_load_bytes_relative(skb, 0, &iph, sizeof(iph),
+									BPF_HDR_START_NET))
+		goto fail;
+
+	if (bpf_skb_load_bytes_relative(skb, sizeof(iph), &udph, sizeof(udph),
+									BPF_HDR_START_NET))
+		goto fail;
+
+	__u32 old_ip = htonl(iph.saddr);
+	__u32 new_ip = 0xac100164; //172.16.1.100
+
+	bpf_l4_csum_replace(skb, UDP_CSUM_OFF, old_ip, new_ip,
+						IS_PSEUDO | sizeof(new_ip));
+	bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
+	if (bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0) < 0)
+		goto fail;
+
+	__u16 old_port = udph.source;
+	__u16 new_port = 5555;
+
+	bpf_l4_csum_replace(skb, UDP_CSUM_OFF, old_port, new_port,
+						IS_PSEUDO | sizeof(new_port));
+	if (bpf_skb_store_bytes(skb, UDP_SPORT_OFF, &new_port, sizeof(new_port),
+							0) < 0)
+		goto fail;
+
+	test_passed = 1;
+
+fail:
+	test_result = test_passed;
+
+	return 1;
+}
-- 
2.25.1