Test Case: c-instruct-156

  1#include <stdio.h>  2#include <string.h>  3#include <stdint.h>  4​  5#define ETH_ALEN 6  6#define ETH_P_IP 0x0800  7#define IP_HDR_LEN 20  8#define MAX_ETH_DATA_LEN 18  9#define TOTAL_ETH_FRAME_SIZE 60 // Minimum Ethernet frame size 10​ 11// Structure for Ethernet header 12typedef struct { 13    unsigned char dst_mac[ETH_ALEN]; 14    unsigned char src_mac[ETH_ALEN]; 15    unsigned short ethertype; 16} eth_hdr_t; 17​ 18// Structure for IP header 19typedef struct { 20    unsigned char version_ihl; 21    unsigned char tos; 22    unsigned short total_length; 23    unsigned short identification; 24    unsigned short flags_fragment_offset; 25    unsigned char ttl; 26    unsigned char protocol; 27    unsigned short header_checksum; 28    unsigned int src_ip; 29    unsigned int dst_ip; 30} ip_hdr_t; 31​ 32// Placeholder for sending the packet (replace with actual network interface code) 33int send_packet(unsigned char *packet, int packet_len) { 34    // In a real implementation, this would use socket programming 35    // to send the packet over a network interface. 36    printf("Sending packet of length: %d\n", packet_len); 37    // Print the packet content (for debugging) 38    printf("Packet content: "); 39    for (int i = 0; i < packet_len; i++) { 40        printf("%02x ", packet[i]); 41    } 42    printf("\n"); 43    return 0; // Return 0 for success, -1 for failure 44} 45​ 46int send_ethernet_packet(unsigned short type, unsigned char *data, unsigned short dlen) { 47    unsigned char packet[TOTAL_ETH_FRAME_SIZE]; // Allocate space for the entire packet 48    int packet_len = 0; 49​ 50    // 1. Create Ethernet Header 51    eth_hdr_t eth_header; 52    // Set destination and source MAC addresses (replace with actual values) 53    unsigned char dest_mac_addr[ETH_ALEN] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55}; 54    unsigned char src_mac_addr[ETH_ALEN] = {0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF}; 55    memcpy(eth_header.dst_mac, dest_mac_addr, ETH_ALEN); 56    memcpy(eth_header.src_mac, src_mac_addr, ETH_ALEN); 57    eth_header.ethertype = htons(type); // Convert to network byte order 58​ 59    // Copy Ethernet header to the packet buffer 60    memcpy(packet, &eth_header, sizeof(eth_hdr_t)); 61    packet_len += sizeof(eth_hdr_t); 62​ 63    // 2. Copy and Pad Data 64    if (dlen > MAX_ETH_DATA_LEN) { 65        printf("Error: Data length exceeds maximum allowed length.\n"); 66        return -1; // Indicate failure 67    } 68​ 69    memcpy(packet + packet_len, data, dlen); 70    packet_len += dlen; 71​ 72    // Pad with zeros to MAX_ETH_DATA_LEN 73    memset(packet + packet_len, 0, MAX_ETH_DATA_LEN - dlen); 74    packet_len += (MAX_ETH_DATA_LEN - dlen); 75​ 76    // 3. Create IP Header (Example) 77    ip_hdr_t ip_header; 78    ip_header.version_ihl = 0x45; // IPv4, 5 * 4 = 20 bytes header length 79    ip_header.tos = 0; 80    ip_header.total_length = htons(IP_HDR_LEN + MAX_ETH_DATA_LEN); // Total length of IP packet 81    ip_header.identification = htons(12345); // Example ID 82    ip_header.flags_fragment_offset = 0; 83    ip_header.ttl = 64; // Time to live 84    ip_header.protocol = 17; // UDP 85    ip_header.header_checksum = 0; // Initialize checksum to 0 for calculation 86    ip_header.src_ip = htonl(0x0A0A0A01); // 10.10.10.1 87    ip_header.dst_ip = htonl(0x0A0A0A02); // 10.10.10.2 88​ 89    // Calculate IP header checksum (example implementation) 90    unsigned int sum = 0; 91    unsigned short *ip_header_ptr = (unsigned short *)&ip_header; 92    for (int i = 0; i < IP_HDR_LEN / 2; i++) { 93        sum += ip_header_ptr[i]; 94    } 95    while (sum >> 16) { 96        sum = (sum & 0xFFFF) + (sum >> 16); 97    } 98    ip_header.header_checksum = ~sum; 99    ip_header.header_checksum = htons(ip_header.header_checksum);100​101    // Copy IP header into the packet buffer after the Ethernet header and padded data102    memmove(packet + sizeof(eth_hdr_t), &ip_header, sizeof(ip_hdr_t));103    memmove(packet + sizeof(eth_hdr_t) + sizeof(ip_hdr_t), packet + sizeof(eth_hdr_t), MAX_ETH_DATA_LEN);104    memcpy(packet + sizeof(eth_hdr_t), &ip_header, sizeof(ip_hdr_t));105​106    packet_len = sizeof(eth_hdr_t) + sizeof(ip_hdr_t) + MAX_ETH_DATA_LEN;107​108    // Pad the entire Ethernet frame to the minimum size (60 bytes)109    if (packet_len < TOTAL_ETH_FRAME_SIZE) {110        memset(packet + packet_len, 0, TOTAL_ETH_FRAME_SIZE - packet_len);111        packet_len = TOTAL_ETH_FRAME_SIZE;112    }113​114    // 4. Send the Packet115    return send_packet(packet, packet_len);116}

1. WARNINGLine 60

   Calls to memcpy that write to a stack buffer