test: add imitate_tcp_packet test case (TCP over GREv0: GRE enable checksum)

2024-07-15 15:07:38 +08:00
parent d31cfd02fd
commit 07ce636f64
13 changed files with 408 additions and 150 deletions
--- a/src/packet/test/CMakeLists.txt
+++ b/src/packet/test/CMakeLists.txt
@@ -46,8 +46,8 @@ target_link_libraries(gtest_packet_frag packet gtest)
 add_executable(gtest_packet_parse gtest_packet_parse.cpp)
 target_link_libraries(gtest_packet_parse packet gtest)

-add_executable(gtest_packet_build gtest_packet_build.cpp)
-target_link_libraries(gtest_packet_build packet gtest)
+add_executable(gtest_packet_craft gtest_packet_craft.cpp)
+target_link_libraries(gtest_packet_craft packet gtest)

 add_executable(gtest_packet_ldbc gtest_packet_ldbc.cpp)
 target_link_libraries(gtest_packet_ldbc packet gtest)
@@ -69,5 +69,5 @@ gtest_discover_tests(gtest_gtp1_utils)
 gtest_discover_tests(gtest_gtp2_utils)
 gtest_discover_tests(gtest_packet_frag)
 gtest_discover_tests(gtest_packet_parse)
-gtest_discover_tests(gtest_packet_build)
+gtest_discover_tests(gtest_packet_craft)
 gtest_discover_tests(gtest_packet_ldbc)
--- a/src/packet/test/gtest_packet_craft.cpp
+++ b/src/packet/test/gtest_packet_craft.cpp
@@ -6,11 +6,12 @@
 #include "ip4_utils.h"
 #include "ip6_utils.h"
 #include "gtp_utils.h"
+#include "gre_utils.h"
 #include "packet_def.h"
 #include "packet_dump.h"
 #include "packet_layer.h"
 #include "packet_parse.h"
-#include "packet_build.h"
+#include "packet_craft.h"

 #define PRINT_GREEN(fmt, ...) printf("\033[0;32m" fmt "\033[0m\n", ##__VA_ARGS__)
 #define PRINT_RED(fmt, ...) printf("\033[0;31m" fmt "\033[0m\n", ##__VA_ARGS__)
@@ -120,13 +121,13 @@ unsigned char data1[] = {
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

 /*
- * imitate_tcp_packet()
+ * craft_tcp_packet()
 * 	-> ETH->IPv4->TCP
 *	-> with TCP options
 *	-> with TCP payload
 */
 #if 1
-TEST(PACKET_BUILD_TCP, ETH_IP4_TCP)
+TEST(PACKET_CRAFT_TCP, ETH_IP4_TCP)
 {
 	struct packet orig_pkt;
 	memset(&orig_pkt, 0, sizeof(orig_pkt));
@@ -134,13 +135,13 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_TCP)
 	PRINT_GREEN("origin packet:");
 	packet_print(&orig_pkt);

-	struct packet *new_pkt = imitate_tcp_packet(&orig_pkt, 1, 2, TH_ACK, (const char *)&ts_pad_opt, sizeof(ts_pad_opt), "Hello", 5);
+	struct packet *new_pkt = craft_tcp_packet(&orig_pkt, 1, 2, TH_ACK, (const char *)&ts_pad_opt, sizeof(ts_pad_opt), "Hello", 5);
 	EXPECT_TRUE(new_pkt != nullptr);
 	PRINT_GREEN("new packet:");
 	packet_print(new_pkt);

 	packet_dump_hex(new_pkt, STDOUT_FILENO);
-	packet_dump_pcap(new_pkt, "imitate-eth-ipv4-tcp.pcap");
+	packet_dump_pcap(new_pkt, "craft-eth-ipv4-tcp.pcap");

 	const char *orig_pkt_data = packet_get_raw_data(&orig_pkt);
 	uint16_t orig_pkt_len = packet_get_raw_len(&orig_pkt);
@@ -155,25 +156,25 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_TCP)
 	{
 		if (layer.proto == LAYER_PROTO_IPV4)
 		{
-			const struct ip *ip = (struct ip *)layer.hdr.raw;
+			const struct ip *ip = (const struct ip *)layer.hdr.raw;
 			EXPECT_TRUE(ip4_hdr_get_total_len(ip) == 57);
+			EXPECT_TRUE(ip4_hdr_get_checksum(ip) == 0xb7e1);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_TCP)
 		{
-			const struct tcphdr *tcp = (struct tcphdr *)layer.hdr.raw;
+			const struct tcphdr *tcp = (const struct tcphdr *)layer.hdr.raw;
 			EXPECT_TRUE(tcp_hdr_get_seq(tcp) == 1);
 			EXPECT_TRUE(tcp_hdr_get_ack(tcp) == 2);
 			EXPECT_TRUE(tcp_hdr_get_flags(tcp) == TH_ACK);
 			EXPECT_TRUE(tcp_hdr_get_hdr_len(tcp) == 32);
+			EXPECT_TRUE(tcp_hdr_get_checksum(tcp) == 0xaf73);
 			break;
 		}
 	}
 	for (uint16_t i = 0; i < new_pkt_len - 12 - 5; i++)
 	{
 		if ((16 <= i && i <= 17) || // skip IPv4 total length
-			(18 <= i && i <= 19) || // skip IPv4 identification
-			i == 22 ||				// skip IPv4 TTL
 			(24 <= i && i <= 25))	// skip IPv4 checksum
 		{
 			continue;
@@ -182,7 +183,6 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_TCP)
 			(42 <= i && i <= 45) || // skip TCP ack
 			i == 46 ||				// skip TCP data offset
 			i == 47 ||				// skip TCP flags
-			(48 <= i && i <= 49) || // skip TCP window
 			(50 <= i && i <= 51))	// skip TCP checksum
 		{
 			continue;
@@ -257,12 +257,12 @@ unsigned char data2[] = {
 	0x04, 0x02};

 /*
- * imitate_tcp_packet()
+ * craft_tcp_packet()
 * 	-> ETH->IPv4->IPv6->TCP
 *	-> with TCP payload
 */
 #if 1
-TEST(PACKET_BUILD_TCP, ETH_IP4_IP6_TCP)
+TEST(PACKET_CRAFT_TCP, ETH_IP4_IP6_TCP)
 {
 	struct packet orig_pkt;
 	memset(&orig_pkt, 0, sizeof(orig_pkt));
@@ -270,13 +270,13 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_IP6_TCP)
 	PRINT_GREEN("origin packet:");
 	packet_print(&orig_pkt);

-	struct packet *new_pkt = imitate_tcp_packet(&orig_pkt, 1234, 2345, TH_ACK, NULL, 0, "Hello", 5);
+	struct packet *new_pkt = craft_tcp_packet(&orig_pkt, 1234, 2345, TH_ACK, NULL, 0, "Hello", 5);
 	EXPECT_TRUE(new_pkt != nullptr);
 	PRINT_GREEN("new packet:");
 	packet_print(new_pkt);

 	packet_dump_hex(new_pkt, STDOUT_FILENO);
-	packet_dump_pcap(new_pkt, "imitate-eth-ipv4-ipv6-tcp.pcap");
+	packet_dump_pcap(new_pkt, "craft-eth-ipv4-ipv6-tcp.pcap");

 	const char *orig_pkt_data = packet_get_raw_data(&orig_pkt);
 	uint16_t orig_pkt_len = packet_get_raw_len(&orig_pkt);
@@ -291,37 +291,36 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_IP6_TCP)
 	{
 		if (layer.proto == LAYER_PROTO_IPV4)
 		{
-			const struct ip *ip = (struct ip *)layer.hdr.raw;
+			const struct ip *ip = (const struct ip *)layer.hdr.raw;
 			EXPECT_TRUE(ip4_hdr_get_total_len(ip) == 85);
+			EXPECT_TRUE(ip4_hdr_get_checksum(ip) == 0x09cf);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_IPV6)
 		{
-			const struct ip6_hdr *ip6 = (struct ip6_hdr *)layer.hdr.raw;
+			const struct ip6_hdr *ip6 = (const struct ip6_hdr *)layer.hdr.raw;
 			EXPECT_TRUE(ip6_hdr_get_payload_len(ip6) == 25);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_TCP)
 		{
-			const struct tcphdr *tcp = (struct tcphdr *)layer.hdr.raw;
+			const struct tcphdr *tcp = (const struct tcphdr *)layer.hdr.raw;
 			EXPECT_TRUE(tcp_hdr_get_seq(tcp) == 1234);
 			EXPECT_TRUE(tcp_hdr_get_ack(tcp) == 2345);
 			EXPECT_TRUE(tcp_hdr_get_flags(tcp) == TH_ACK);
 			EXPECT_TRUE(tcp_hdr_get_hdr_len(tcp) == 20);
+			EXPECT_TRUE(tcp_hdr_get_checksum(tcp) == 0xe350);
 			break;
 		}
 	}
 	for (uint16_t i = 0; i < new_pkt_len - 5; i++)
 	{
 		if ((16 <= i && i <= 17) || // skip IPv4 total length
-			(18 <= i && i <= 19) || // skip IPv4 identification
-			i == 22 ||				// skip IPv4 TTL
 			(24 <= i && i <= 25))	// skip IPv4 checksum
 		{
 			continue;
 		}
-		if ((38 <= i && i <= 39) || // skip IPv6 payload length
-			i == 41)				// skip IPv6 hop limit
+		if (38 <= i && i <= 39) // skip IPv6 payload length
 		{
 			continue;
 		}
@@ -329,7 +328,6 @@ TEST(PACKET_BUILD_TCP, ETH_IP4_IP6_TCP)
 			(82 <= i && i <= 85) || // skip TCP ack
 			i == 86 ||				// skip TCP data offset
 			i == 87 ||				// skip TCP flags
-			(88 <= i && i <= 89) || // skip TCP window
 			(90 <= i && i <= 91))	// skip TCP checksum
 		{
 			continue;
@@ -473,12 +471,12 @@ unsigned char data3[] = {
 	0x4f, 0xe9, 0xf5, 0xf0, 0x61, 0x5d, 0x7f, 0xc4, 0xc4, 0xd1, 0x05, 0x54, 0x13, 0xdb};

 /*
- * imitate_tcp_packet()
+ * craft_tcp_packet()
 *  -> ETH->IPv6->UDP->GTP->IPv4->TCP
 *  -> with TCP payload
 */
 #if 1
-TEST(PACKET_BUILD_TCP, ETH_IP6_UDP_GTP_IP4_TCP)
+TEST(PACKET_CRAFT_TCP, ETH_IP6_UDP_GTP_IP4_TCP)
 {
 	struct packet orig_pkt;
 	memset(&orig_pkt, 0, sizeof(orig_pkt));
@@ -486,13 +484,13 @@ TEST(PACKET_BUILD_TCP, ETH_IP6_UDP_GTP_IP4_TCP)
 	PRINT_GREEN("origin packet:");
 	packet_print(&orig_pkt);

-	struct packet *new_pkt = imitate_tcp_packet(&orig_pkt, 1, 2, TH_ACK, NULL, 0, "Hello", 5);
+	struct packet *new_pkt = craft_tcp_packet(&orig_pkt, 1, 2, TH_ACK, NULL, 0, "Hello", 5);
 	EXPECT_TRUE(new_pkt != nullptr);
 	PRINT_GREEN("new packet:");
 	packet_print(new_pkt);

 	packet_dump_hex(new_pkt, STDOUT_FILENO);
-	packet_dump_pcap(new_pkt, "imitate-eth-ipv6-udp-gtp-ipv4-tcp.pcap");
+	packet_dump_pcap(new_pkt, "craft-eth-ipv6-udp-gtp-ipv4-tcp.pcap");

 	const char *orig_pkt_data = packet_get_raw_data(&orig_pkt);
 	uint16_t orig_pkt_len = packet_get_raw_len(&orig_pkt);
@@ -507,45 +505,46 @@ TEST(PACKET_BUILD_TCP, ETH_IP6_UDP_GTP_IP4_TCP)
 	{
 		if (layer.proto == LAYER_PROTO_IPV6)
 		{
-			const struct ip6_hdr *ip6 = (struct ip6_hdr *)layer.hdr.raw;
+			const struct ip6_hdr *ip6 = (const struct ip6_hdr *)layer.hdr.raw;
 			EXPECT_TRUE(ip6_hdr_get_payload_len(ip6) == 61);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_UDP)
 		{
-			const struct udphdr *udp = (struct udphdr *)layer.hdr.raw;
+			const struct udphdr *udp = (const struct udphdr *)layer.hdr.raw;
 			EXPECT_TRUE(udp_hdr_get_total_len(udp) == 61);
+			EXPECT_TRUE(udp_hdr_get_checksum(udp) == 0xd375);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_GTP_U)
 		{
 			EXPECT_TRUE(peek_gtp_version(layer.hdr.raw, layer.hdr_len) == 1);
-
-			const struct gtp1_hdr *gtp1 = (struct gtp1_hdr *)layer.hdr.raw;
+			const struct gtp1_hdr *gtp1 = (const struct gtp1_hdr *)layer.hdr.raw;
 			EXPECT_TRUE(gtp1_hdr_get_msg_len(gtp1) == 45);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_IPV4)
 		{
-			const struct ip *ip = (struct ip *)layer.hdr.raw;
+			const struct ip *ip = (const struct ip *)layer.hdr.raw;
 			EXPECT_TRUE(ip4_hdr_get_total_len(ip) == 45);
+			EXPECT_TRUE(ip4_hdr_get_checksum(ip) == 0x4906);
 			break;
 		}
 		if (layer.proto == LAYER_PROTO_TCP)
 		{
-			const struct tcphdr *tcp = (struct tcphdr *)layer.hdr.raw;
+			const struct tcphdr *tcp = (const struct tcphdr *)layer.hdr.raw;
 			EXPECT_TRUE(tcp_hdr_get_seq(tcp) == 1);
 			EXPECT_TRUE(tcp_hdr_get_ack(tcp) == 2);
 			EXPECT_TRUE(tcp_hdr_get_flags(tcp) == TH_ACK);
 			EXPECT_TRUE(tcp_hdr_get_hdr_len(tcp) == 20);
+			EXPECT_TRUE(tcp_hdr_get_checksum(tcp) == 0xcce5);
 			break;
 		}
 	}

 	for (uint16_t i = 0; i < new_pkt_len - 5; i++)
 	{
-		if ((18 <= i && i <= 19) || // skip IPv6 payload length
-			i == 20)				// skip IPv6 hop limit
+		if (18 <= i && i <= 19) // skip IPv6 payload length
 		{
 			continue;
 		}
@@ -559,18 +558,221 @@ TEST(PACKET_BUILD_TCP, ETH_IP6_UDP_GTP_IP4_TCP)
 			continue;
 		}
 		if ((72 <= i && i <= 73) || // skip IPv4 total length
-			(74 <= i && i <= 75) || // skip IPv4 identification
-			i == 78 ||				// skip IPv4 TTL
 			(80 <= i && i <= 81))	// skip IPv4 checksum
 		{
 			continue;
 		}
-		if ((94 <= i && i <= 98) ||	  // skip TCP seq
-			(99 <= i && i <= 103) ||  // skip TCP ack
-			i == 104 ||				  // skip TCP data offset
-			i == 105 ||				  // skip TCP flags
-			(106 <= i && i <= 107) || // skip TCP window
-			(108 <= i && i <= 109))	  // skip TCP checksum
+		if ((94 <= i && i <= 98) ||	 // skip TCP seq
+			(99 <= i && i <= 103) || // skip TCP ack
+			i == 104 ||				 // skip TCP data offset
+			i == 105 ||				 // skip TCP flags
+			(106 <= i && i <= 107))	 // skip TCP checksum
+		{
+			continue;
+		}
+
+		// printf(("idx: %d, orig: %02x, new: %02x\n"), i, orig_pkt_data[i], new_pkt_data[i]);
+		EXPECT_TRUE(orig_pkt_data[i] == new_pkt_data[i]);
+	}
+}
+#endif
+
+/******************************************************************************
+ * [Protocols in frame: eth:ethertype:ip:gre:ipv6:tcp]
+ ******************************************************************************
+ *
+ * Frame 1: 102 bytes on wire (816 bits), 102 bytes captured (816 bits)
+ * Ethernet II, Src: a0:b1:c2:d3:e4:f5 (a0:b1:c2:d3:e4:f5), Dst: CIMSYS_33:44:55 (00:11:22:33:44:55)
+ * 	Destination: CIMSYS_33:44:55 (00:11:22:33:44:55)
+ * 		Address: CIMSYS_33:44:55 (00:11:22:33:44:55)
+ * 		.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
+ * 		.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
+ * 	Source: a0:b1:c2:d3:e4:f5 (a0:b1:c2:d3:e4:f5)
+ * 		Address: a0:b1:c2:d3:e4:f5 (a0:b1:c2:d3:e4:f5)
+ * 		.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
+ * 		.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
+ * 	Type: IPv4 (0x0800)
+ * Internet Protocol Version 4, Src: 10.0.0.1, Dst: 192.168.1.1
+ * 	0100 .... = Version: 4
+ * 	.... 0101 = Header Length: 20 bytes (5)
+ * 	Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
+ * 		0000 00.. = Differentiated Services Codepoint: Default (0)
+ * 		.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
+ * 	Total Length: 88
+ * 	Identification: 0x0001 (1)
+ * 	000. .... = Flags: 0x0
+ * 		0... .... = Reserved bit: Not set
+ * 		.0.. .... = Don't fragment: Not set
+ * 		..0. .... = More fragments: Not set
+ * 	...0 0000 0000 0000 = Fragment Offset: 0
+ * 	Time to Live: 64
+ * 	Protocol: Generic Routing Encapsulation (47)
+ * 	Header Checksum: 0xaecc [correct]
+ * 	[Header checksum status: Good]
+ * 	[Calculated Checksum: 0xaecc]
+ * 	Source Address: 10.0.0.1
+ * 	Destination Address: 192.168.1.1
+ * Generic Routing Encapsulation (IPv6)
+ * 	Flags and Version: 0x8000
+ * 		1... .... .... .... = Checksum Bit: Yes
+ * 		.0.. .... .... .... = Routing Bit: No
+ * 		..0. .... .... .... = Key Bit: No
+ * 		...0 .... .... .... = Sequence Number Bit: No
+ * 		.... 0... .... .... = Strict Source Route Bit: No
+ * 		.... .000 .... .... = Recursion control: 0
+ * 		.... .... 0000 0... = Flags (Reserved): 0
+ * 		.... .... .... .000 = Version: GRE (0)
+ * 	Protocol Type: IPv6 (0x86dd)
+ * 	Checksum: 0x92e7 [correct]
+ * 	[Checksum Status: Good]
+ * 	Offset: 0
+ * Internet Protocol Version 6, Src: ::, Dst: 2001:db8::1
+ * 	0110 .... = Version: 6
+ * 	.... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
+ * 		.... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
+ * 		.... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
+ * 	.... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
+ * 	Payload Length: 20
+ * 	Next Header: TCP (6)
+ * 	Hop Limit: 64
+ * 	Source Address: ::
+ * 	Destination Address: 2001:db8::1
+ * Transmission Control Protocol, Src Port: 12345, Dst Port: 80, Seq: 0, Len: 0
+ * 	Source Port: 12345
+ * 	Destination Port: 80
+ * 	[Stream index: 0]
+ * 	[Conversation completeness: Incomplete, SYN_SENT (1)]
+ * 		..0. .... = RST: Absent
+ * 		...0 .... = FIN: Absent
+ * 		.... 0... = Data: Absent
+ * 		.... .0.. = ACK: Absent
+ * 		.... ..0. = SYN-ACK: Absent
+ * 		.... ...1 = SYN: Present
+ * 		[Completeness Flags: ·····S]
+ * 	[TCP Segment Len: 0]
+ * 	Sequence Number: 0
+ * 	[Next Sequence Number: 1]
+ * 	Acknowledgment Number: 0
+ * 	Acknowledgment number (raw): 0
+ * 	0101 .... = Header Length: 20 bytes (5)
+ * 	Flags: 0x002 (SYN)
+ * 		000. .... .... = Reserved: Not set
+ * 		...0 .... .... = Accurate ECN: Not set
+ * 		.... 0... .... = Congestion Window Reduced: Not set
+ * 		.... .0.. .... = ECN-Echo: Not set
+ * 		.... ..0. .... = Urgent: Not set
+ * 		.... ...0 .... = Acknowledgment: Not set
+ * 		.... .... 0... = Push: Not set
+ * 		.... .... .0.. = Reset: Not set
+ * 		.... .... ..1. = Syn: Set
+ * 			[Expert Info (Chat/Sequence): Connection establish request (SYN): server port 80]
+ * 				[Connection establish request (SYN): server port 80]
+ * 				[Severity level: Chat]
+ * 				[Group: Sequence]
+ * 		.... .... ...0 = Fin: Not set
+ * 		[TCP Flags: ··········S·]
+ * 	Window: 8192
+ * 	[Calculated window size: 8192]
+ * 	Checksum: 0x31a0 [correct]
+ * 		[Calculated Checksum: 0x31a0]
+ * 	[Checksum Status: Good]
+ * 	Urgent Pointer: 0
+ * 	[Timestamps]
+ * 		[Time since first frame in this TCP stream: 0.000000000 seconds]
+ * 		[Time since previous frame in this TCP stream: 0.000000000 seconds]
+ */
+
+unsigned char data4[] = {
+	0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0xa0, 0xb1, 0xc2, 0xd3, 0xe4, 0xf5, 0x08, 0x00, 0x45, 0x00, 0x00, 0x58, 0x00, 0x01, 0x00, 0x00, 0x40, 0x2f, 0xae, 0xcc,
+	0x0a, 0x00, 0x00, 0x01, 0xc0, 0xa8, 0x01, 0x01, 0x80, 0x00, 0x86, 0xdd, 0x92, 0xe7, 0x00, 0x00, 0x60, 0x00, 0x00, 0x00, 0x00, 0x14, 0x06, 0x40, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x01, 0x30, 0x39, 0x00, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x50, 0x02, 0x20, 0x00, 0x31, 0xa0, 0x00, 0x00};
+
+/*
+ * craft_tcp_packet()
+ * 	-> ETH->IPv4->GRE->IPv6->TCP
+ *	-> with TCP payload
+ *  -> with GRE checksum
+ */
+#if 1
+TEST(PACKET_CRAFT_TCP, ETH_IP4_GRE_IP6_TCP)
+{
+	struct packet orig_pkt;
+	memset(&orig_pkt, 0, sizeof(orig_pkt));
+	packet_parse(&orig_pkt, (const char *)data4, sizeof(data4));
+	PRINT_GREEN("origin packet:");
+	packet_print(&orig_pkt);
+
+	struct packet *new_pkt = craft_tcp_packet(&orig_pkt, 1, 2, TH_ACK, NULL, 0, "Hello", 5);
+	EXPECT_TRUE(new_pkt != nullptr);
+	PRINT_GREEN("new packet:");
+	packet_print(new_pkt);
+
+	packet_dump_hex(new_pkt, STDOUT_FILENO);
+	packet_dump_pcap(new_pkt, "craft-eth-ipv4-gre-ipv6-tcp.pcap");
+
+	const char *orig_pkt_data = packet_get_raw_data(&orig_pkt);
+	uint16_t orig_pkt_len = packet_get_raw_len(&orig_pkt);
+
+	const char *new_pkt_data = packet_get_raw_data(new_pkt);
+	uint16_t new_pkt_len = packet_get_raw_len(new_pkt);
+
+	EXPECT_TRUE(orig_pkt_len ==
+				new_pkt_len - 5); // trim TCP payload
+	struct layer layer;
+	PACKET_FOREACH_LAYER_INORDER(new_pkt, layer)
+	{
+		if (layer.proto == LAYER_PROTO_IPV4)
+		{
+			const struct ip *ip = (const struct ip *)layer.hdr.raw;
+			EXPECT_TRUE(ip4_hdr_get_total_len(ip) == 93);
+			EXPECT_TRUE(ip4_hdr_get_checksum(ip) == 0xaec7);
+			break;
+		}
+		if (layer.proto == LAYER_PROTO_GRE)
+		{
+			const struct gre0_hdr *gre = (const struct gre0_hdr *)layer.hdr.raw;
+			EXPECT_TRUE(gre0_hdr_get_version(gre) == 0);
+			EXPECT_TRUE(gre0_hdr_get_checksum(gre) == 0x92e7);
+			break;
+		}
+		if (layer.proto == LAYER_PROTO_IPV6)
+		{
+			const struct ip6_hdr *ip6 = (const struct ip6_hdr *)layer.hdr.raw;
+			EXPECT_TRUE(ip6_hdr_get_payload_len(ip6) == 25);
+			break;
+		}
+		if (layer.proto == LAYER_PROTO_TCP)
+		{
+			const struct tcphdr *tcp = (const struct tcphdr *)layer.hdr.raw;
+			EXPECT_TRUE(tcp_hdr_get_seq(tcp) == 1);
+			EXPECT_TRUE(tcp_hdr_get_ack(tcp) == 2);
+			EXPECT_TRUE(tcp_hdr_get_flags(tcp) == TH_ACK);
+			EXPECT_TRUE(tcp_hdr_get_hdr_len(tcp) == 20);
+			EXPECT_TRUE(tcp_hdr_get_checksum(tcp) == 0x0db8);
+			break;
+		}
+	}
+
+	for (uint16_t i = 0; i < new_pkt_len - 5; i++)
+	{
+		if ((16 <= i && i <= 17) || // skip IP total length
+			(24 <= i && i <= 25))	// skip IP checksum
+		{
+			continue;
+		}
+		if (38 <= i && i <= 39) // skip GRE checksum
+		{
+			continue;
+		}
+		if (47 <= i && i <= 48) // skip IPv6 payload length
+		{
+			continue;
+		}
+		if ((86 <= i && i <= 89) || // skip TCP seq
+			(90 <= i && i <= 93) || // skip TCP ack
+			i == 95 ||				// skip TCP flags
+			(98 <= i && i <= 99))	// skip TCP checksum
 		{
 			continue;
 		}