tcp/udp/icmp校验和计算c代码

以下是一个计算TCP/UDP/ICMP校验和的C代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

uint16_t checksum(uint16_t *buf, int len) {
    uint32_t sum = 0;
    while (len > 1) {
        sum += *buf++;
        len -= 2;
    }
    if (len == 1) {
        sum += *(uint8_t*)buf;
    }
    while (sum >> 16) {
        sum = (sum & 0xffff) + (sum >> 16);
    }
    return ~sum;
}

int main() {
    char data[] = "hello world";
    int len = strlen(data);
    uint16_t *buf = (uint16_t*)data;
    uint16_t cksum = checksum(buf, len);
    printf("Checksum: 0x%04x\n", cksum);
    return 0;
}

这个代码示例可以计算任意数据的校验和，包括TCP、UDP和ICMP协议中的数据。

相关问题

tcp/udp/icmp校验和计算的代码

这是一个编程类的问题，我可以回答。以下是一个计算TCP校验和的代码示例：

import struct

def checksum(data):
    if len(data) % 2 != 0:
        data += b'\x00'
    s = sum(struct.unpack('!H', data[i:i+2])[0] for i in range(0, len(data), 2))
    s = (s >> 16) + (s & 0xffff)
    s += s >> 16
    return ~s & 0xffff

# Example usage
src_ip = b'\x7f\x00\x00\x01'
dst_ip = b'\x7f\x00\x00\x01'
protocol = 6  # TCP
tcp_length = 20  # TCP header length
tcp_header = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x50\x02\x00\x00\x00\x00\x00\x00'
pseudo_header = src_ip + dst_ip + struct.pack('!BBH', 0, protocol, tcp_length)
checksum_data = pseudo_header + tcp_header
tcp_checksum = checksum(checksum_data)
print(hex(tcp_checksum))

如果您需要计算UDP或ICMP校验和，可以根据相应的协议头格式和伪头格式修改代码。

读取文件tcp/udp/icmp校验和计算的c代码

以下是一个简单的C代码，用于读取文件并计算TCP/UDP/ICMP校验和：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <netinet/ip_icmp.h>

unsigned short calculate_checksum(unsigned short *ptr, int nbytes);

int main(int argc, char *argv[]) {
if (argc != 2) {
printf("Usage: %s <filename>\n", argv[0]);
return 1;
}

FILE *fp = fopen(argv[1], "rb");
if (fp == NULL) {
printf("Error: cannot open file %s\n", argv[1]);
return 1;
}

unsigned char buffer[65536];
int total_size = 0;

while (!feof(fp)) {
int read_size = fread(buffer + total_size, 1, sizeof(buffer) - total_size, fp);
if (read_size <= 0) {
break;
}
total_size += read_size;
}

fclose(fp);

struct iphdr *ip_header = (struct iphdr *) buffer;
int ip_header_size = ip_header->ihl * 4;

if (ip_header->protocol == IPPROTO_TCP) {
struct tcphdr *tcp_header = (struct tcphdr *) (buffer + ip_header_size);
tcp_header->check = 0;
tcp_header->check = calculate_checksum((unsigned short *) tcp_header, ntohs(ip_header->tot_len) - ip_header_size);
printf("TCP checksum: 0x%04x\n", tcp_header->check);
} else if (ip_header->protocol == IPPROTO_UDP) {
struct udphdr *udp_header = (struct udphdr *) (buffer + ip_header_size);
udp_header->check = 0;
udp_header->check = calculate_checksum((unsigned short *) udp_header, ntohs(ip_header->tot_len) - ip_header_size);
printf("UDP checksum: 0x%04x\n", udp_header->check);
} else if (ip_header->protocol == IPPROTO_ICMP) {
struct icmphdr *icmp_header = (struct icmphdr *) (buffer + ip_header_size);
icmp_header->checksum = 0;
icmp_header->checksum = calculate_checksum((unsigned short *) icmp_header, ntohs(ip_header->tot_len) - ip_header_size);
printf("ICMP checksum: 0x%04x\n", icmp_header->checksum);
} else {
printf("Error: unsupported protocol %d\n", ip_header->protocol);
return 1;
}

return 0;
}

unsigned short calculate_checksum(unsigned short *ptr, int nbytes) {
unsigned long sum = 0;
while (nbytes > 1) {
sum += *ptr++;
nbytes -= 2;
}
if (nbytes == 1) {
sum += *(unsigned char *) ptr;
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return (unsigned short) ~sum;
}