用C语言和python分别生成抓取ip报文的代码

C语言代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>

int main(int argc, char const *argv[])
{
    int sockfd;
    struct sockaddr_in addr;
    char buffer[1024];
    struct iphdr *ip;
    struct tcphdr *tcp;

    // 创建原始套接字
    sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
    if (sockfd < 0)
    {
        perror("socket");
        exit(1);
    }

    // 设置目标IP地址
    addr.sin_family = AF_INET;
    addr.sin_port = htons(80);
    addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    // 构造IP头部
    ip = (struct iphdr *)buffer;
    ip->ihl = 5;
    ip->version = 4;
    ip->tos = 0;
    ip->tot_len = sizeof(struct iphdr) + sizeof(struct tcphdr);
    ip->id = htons(54321);
    ip->frag_off = 0;
    ip->ttl = 255;
    ip->protocol = IPPROTO_TCP;
    ip->check = 0;
    ip->saddr = inet_addr("192.168.1.100");
    ip->daddr = addr.sin_addr.s_addr;

    // 构造TCP头部
    tcp = (struct tcphdr *)(buffer + sizeof(struct iphdr));
    tcp->source = htons(8888);
    tcp->dest = addr.sin_port;
    tcp->seq = htonl(1105024978);
    tcp->ack_seq = 0;
    tcp->doff = 5;
    tcp->syn = 1;
    tcp->window = htons(14600);
    tcp->check = 0;
    tcp->urg_ptr = 0;

    // 计算IP校验和
    ip->check = htons((unsigned short)checksum((unsigned short *)ip, sizeof(struct iphdr)));

    // 发送报文
    if (sendto(sockfd, buffer, ip->tot_len, 0, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
        perror("sendto");
        exit(1);
    }

    printf("Packet sent successfully!\n");

    // 关闭套接字
    close(sockfd);

    return 0;
}

// 计算校验和
unsigned short checksum(unsigned short *ptr, int nbytes)
{
    register long sum;
    unsigned short oddbyte;
    register short answer;

    sum = 0;
    while (nbytes > 1)
    {
        sum += *ptr++;
        nbytes -= 2;
    }

    if (nbytes == 1)
    {
        oddbyte = 0;
        *((unsigned char *)&oddbyte) = *(unsigned char *)ptr;
        sum += oddbyte;
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum = sum + (sum >> 16);
    answer = (short)~sum;

    return answer;
}

Python代码：

import socket
import struct

# 构造IP头部
def make_ip_header(src_ip, dst_ip):
    version = 4                          # 版本号
    ihl = 5                              # IP头部长度
    tos = 0                              # 服务类型
    tot_len = 20 + 20                     # 总长度
    id = 54321                           # 标识符
    frag_off = 0                         # 分段标识和偏移量
    ttl = 255                            # 生存时间
    protocol = socket.IPPROTO_TCP        # 协议类型
    check = 0                            # 校验和
    saddr = socket.inet_aton(src_ip)      # 源IP地址
    daddr = socket.inet_aton(dst_ip)      # 目标IP地址

    ip_header = struct.pack('!BBHHHBBH4s4s', (version << 4) + ihl, tos, tot_len, id, frag_off, ttl, protocol, check, saddr, daddr)

    return ip_header

# 构造TCP头部
def make_tcp_header(src_port, dst_port, seq, ack_seq, syn, window):
    doff = 5                             # TCP头部长度
    res1 = 0                             # 保留位
    res2 = 0                             # 保留位
    urg_ptr = 0                          # 紧急指针
    offset_res = (doff << 4) + res1      # 偏移量和保留位
    flags = syn                           # 标志位
    window_size = window                 # 窗口大小
    check = 0                            # 校验和

    tcp_header = struct.pack('!HHLLBBHHH', src_port, dst_port, seq, ack_seq, offset_res, flags, window_size, check, urg_ptr)

    return tcp_header

# 计算校验和
def checksum(msg):
    s = 0
    for i in range(0, len(msg), 2):
        w = (msg[i] << 8) + (msg[i+1])
        s += w
    s = (s >> 16) + (s & 0xffff)
    s = ~s & 0xffff

    return s

# 发送报文
def send_packet(src_ip, dst_ip, src_port, dst_port, seq, syn, window):
    # 创建原始套接字
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)

    # 构造IP头部和TCP头部
    ip_header = make_ip_header(src_ip, dst_ip)
    tcp_header = make_tcp_header(src_port, dst_port, seq, 0, syn, window)

    # 计算校验和
    pseudo_header = struct.pack('!4s4sBBH', socket.inet_aton(src_ip), socket.inet_aton(dst_ip), 0, socket.IPPROTO_TCP, len(tcp_header))
    checksum_tcp = checksum(pseudo_header + tcp_header)
    tcp_header = struct.pack('!HHLLBBHHH', src_port, dst_port, seq, 0, (5 << 4), syn, window, checksum_tcp, 0)

    # 构造最终报文
    packet = ip_header + tcp_header

    # 发送报文
    s.sendto(packet, (dst_ip, 0))

    print('Packet sent successfully!')

    # 关闭套接字
    s.close()

# 测试代码
if __name__ == '__main__':
    src_ip = '192.168.1.100'
    dst_ip = '127.0.0.1'
    src_port = 8888
    dst_port = 80
    seq = 1105024978
    syn = 1
    window = 14600

    send_packet(src_ip, dst_ip, src_port, dst_port, seq, syn, window)