init

.gitignore

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+.idea
+cmake-*

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.24)
+project(icmpv6_echo C)
+
+set(CMAKE_C_STANDARD 23)
+
+add_executable(icmpv6_echo main.c)

README.md

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+# Build IPv6 ICMP ECHO packet with Ethernet headers
+
+* https://en.wikipedia.org/wiki/Ethernet_frame
+* https://en.wikipedia.org/wiki/IPv6_packet
+* https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol_for_IPv6
+* https://www.pdbuchan.com/rawsock/icmp6_cooked.c
+* https://stackoverflow.com/a/14937171
+* https://github.com/secdev/scapy/blob/a1f999fb1721a64415af75d575cabde19625a6f5/scapy/utils.py#L493-L501
+* https://github.com/secdev/scapy/blob/master/scapy/layers/inet6.py#L608-L624
+
+## Scapy code samples
+Writen in `scapy` shell
+
+```python
+# import hex as packet
+e = Ether(bytes.fromhex('fc de ad be ef 05 fc de ad be ef 56 86 dd 60 00 00 00 00 08 3a 02 fe 80 00 00 00 00 00 00 00 00 00 00 00 00 00 01 fe 80 00 00 00 00 00 00 50 5d 18 fb 5e 52 ec c0 81 00 4e cd 00 00 00 00 ef be ad de'))
+e.show()
+
+# Write packet as pcap to open in Wireshark
+wrpcap("test.pcap", e)
+
+# Calculate icmpv6 checksum
+i = e[IPv6][ICMPv6EchoReply]
+i.cksum = 0
+r = raw(i)
+print(hex(in6_chksum(socket.IPPROTO_ICMPV6, e[IPv6], r)))
+```

main.c

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+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <netinet/in.h>
+
+struct ethernet_header {
+    uint8_t dest[6];
+    uint8_t src[6];
+    uint16_t ethertype;
+} __attribute__((packed));
+
+struct ipv6_header {
+    uint32_t vtf;
+    /*uint32_t version :4;
+    uint32_t traffic_class :8;
+    uint32_t flow_label :20;*/
+    uint16_t len;
+    uint8_t next_header;
+    uint8_t hop_limit;
+
+    uint8_t src[16];
+    uint8_t dest[16];
+} __attribute__((packed));
+
+struct icmpv6_header {
+    uint8_t type;
+    uint8_t code;
+    uint16_t checksum;
+} __attribute__((packed));
+
+struct ipv6_pseudo {
+    uint8_t src[16];
+    uint8_t dest[16];
+    uint32_t len;
+    uint32_t zeros :24;
+    uint32_t next_header :8;
+} __attribute__((packed));
+
+struct icmpv6_echo {
+    uint16_t identifier;
+    uint16_t sequence;
+} __attribute__((packed));
+
+struct packet {
+    struct ethernet_header eth;
+    struct ipv6_header ip6;
+    struct icmpv6_header icmp;
+    struct icmpv6_echo echo;
+    uint32_t ethernet_frame_check;
+} __attribute__((packed));
+
+uint16_t checksum (uint16_t *addr, size_t bytes) {
+    unsigned int i;
+    uint16_t *p = addr;
+    uint32_t sum = 0;
+
+    /* Sum */
+    for (i=bytes; i > 1; i -= 2)
+        sum += *p++;
+
+    /* If uneven length */
+    if (i > 0)
+        sum += (uint16_t) *((unsigned char *) (p));
+
+    /* Carry */
+    while ((sum & 0xFFFF0000) != 0)
+        sum = (sum >> 16) + (sum & 0xFFFF);
+
+    return ~((uint16_t) sum);
+}
+
+uint16_t calc_icmpv6_checksum(struct ipv6_header *ip6_header, void *data, size_t len) {
+    uint8_t buf[1500] = {};
+    struct ipv6_pseudo pseudo = {};
+
+    memcpy(pseudo.src, ip6_header->src, sizeof(ip6_header->src));
+    memcpy(pseudo.dest, ip6_header->dest, sizeof(ip6_header->dest));
+    pseudo.next_header = ip6_header->next_header;
+    pseudo.len = htonl(len);
+
+    memcpy(buf, &pseudo, sizeof(pseudo));
+    memcpy(buf + sizeof(pseudo), data, len);
+
+    return checksum(&buf, sizeof(pseudo) + len);
+}
+
+int main() {
+    struct packet pkt;
+
+    uint8_t eth_dest[] = {0xfc, 0xde, 0xad, 0xbe, 0xef, 0x05};
+    uint8_t eth_src[] =  {0xfc, 0xde, 0xad, 0xbe, 0xef, 0x56};
+    memcpy(pkt.eth.dest, eth_dest, sizeof(pkt.eth.dest));
+    memcpy(pkt.eth.src, eth_src, sizeof(pkt.eth.src));
+
+    pkt.eth.ethertype = 0xdd86;  // ipv6
+
+    pkt.ip6.vtf = htonl ((6 << 28) | (0 << 20) | 0);
+    /*pkt.ip6.version = 6;
+    pkt.ip6.traffic_class = 0;
+    pkt.ip6.flow_label = 0;*/
+    pkt.ip6.len = htons(sizeof(struct icmpv6_header) + sizeof(struct icmpv6_echo));
+    pkt.ip6.next_header = 0x3a;  // ipv6-icmp
+    pkt.ip6.hop_limit = 2;
+
+    uint8_t ipv6_src[] = {
+            0xfe, 0x80, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x01
+    };
+    uint8_t ipv6_dest[] = {
+            0xfe, 0x80, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+            0x50, 0x5d, 0x18, 0xfb,
+            0x5e, 0x52, 0xec, 0xc0,
+    };
+    memcpy(pkt.ip6.src, ipv6_src, sizeof(pkt.ip6.src));
+    memcpy(pkt.ip6.dest, ipv6_dest, sizeof(pkt.ip6.dest));
+
+    pkt.icmp.type = 129;  // icmp reply
+    pkt.icmp.checksum = 0;
+
+    pkt.echo.identifier = 0;
+    pkt.echo.sequence = 0;
+
+    pkt.icmp.checksum = calc_icmpv6_checksum(&pkt.ip6, &pkt.icmp, sizeof(struct icmpv6_header) + sizeof(struct icmpv6_echo));
+
+    pkt.ethernet_frame_check = 0xdeadbeef;
+
+    printf("sizeof(pkt) = %lu, pointer %p\n", sizeof(pkt), &pkt);
+    printf("checksum %#x\n", pkt.icmp.checksum);
+
+    int i;
+    for (i=0; i < sizeof(pkt); i++) {
+        printf("%02x ", *(((uint8_t *)&pkt) + i));
+    }
+    printf("\n%d", i);
+    return 0;
+}