TCP/IP学习--udp row socket实作

最新推荐文章于 2025-04-28 17:21:23 发布

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最新推荐文章于 2025-04-28 17:21:23 发布

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分类专栏： TCP/IP 文章标签： socket struct buffer header parameters centos

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本文介绍如何利用原始套接口实现UDP数据包的直接构造与发送，包括设置套接口选项、构建IP及UDP头部，并提供了一个在CentOS 4上运行的示例程序。

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对原始套接口感兴趣还在于它是构建端口扫描，泛洪攻击，会话拦截等一系列网络行为的基础。

原始套接口提供普通的TCP和UDP套接口不提供的以下3个能力：

1.进程可以读与写ICMP,IGMP等分组。

2.进程可以读与写内核不处理其协议字段的IPv4数据报。

3.进程可以使用IP_HDRINCL 套接口选项自行构造IPv4头部。

下面的简单的tcp row socket 实现，在centos 4 中编译通过

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/udp.h>

#define PCKT_LEN 8192

//can create separate header file
//ip header's structs
struct ipheader{
    unsigned char      iph_ihl:5,iph_ver:4;
    unsigned char       iph_tos;
    unsigned short int iph_len;
    unsigned short int iph_ident;
    unsigned char       iph_flag;
    unsigned short int iph_offset;
    unsigned char       iph_ttl;
    unsigned char       iph_protocol;
    unsigned short int iph_chksum;
    unsigned int        iph_sourceip;
    unsigned int        iph_destip;
};
//udp header's structure
struct udpheader{
    unsigned short int udph_srcport;
    unsigned short int udph_destport;
    unsigned short int udph_len;
    unsigned short int udph_chksum;
};
//check sum function
unsigned short check_sum(unsigned short *buf,int nwords){
    unsigned long sum;
    for(sum = 0; nwords > 0; nwords--)
        sum += *buf++;
    sum = (sum >> 16) + (sum &0xffff);
    sum += (sum >>16);
    return (unsigned short)(~sum);
}

int main(int argc,char *argv[]) {
    int sockfd;
    char buffer[PCKT_LEN];
    struct ipheader *ip = (struct ipheader *)buffer;
    struct udpheader *udp = (struct udpheader *)(buffer+sizeof(struct ipheader));
    struct sockaddr_in sin,din;
    int one = 1;
    const int *val = &one;
    memset(buffer,0,PCKT_LEN);
    if(argc != 5){
        printf("- Invalid parameters!!!/n");
        printf("- Usage %s <source hostname/ip><source port> <target hostname/ip><target port>/n",argv[0]);
        exit(-1);
    }
    sockfd = socket(PF_INET,SOCK_RAW,IPPROTO_UDP);
    if(sockfd < 0) {
        perror("socket() error");
        exit(-1);
    } else
        printf("socket() - Using sock_raw socket and udp protocol is OK./n");
    sin.sin_family = AF_INET;
    din.sin_family = AF_INET;
    sin.sin_port = htons(atoi(argv[2]));
    din.sin_port = htons(atoi(argv[4]));
    sin.sin_addr.s_addr = inet_addr(argv[1]);
    sin.sin_addr.s_addr = inet_addr(argv[3]);

    ip->iph_ihl = 5;
    ip->iph_ver = 4;
    ip->iph_tos = 16;
    ip->iph_len = sizeof(struct ipheader) + sizeof(struct udpheader);
    ip->iph_ident = htons(54321);
    ip->iph_ttl = 64;
    ip->iph_protocol = 17; //udp
    ip->iph_sourceip = inet_addr(argv[1]);
    ip->iph_destip = inet_addr(argv[3]);

    udp->udph_srcport = htons(atoi(argv[2]));
    udp->udph_destport = htons(atoi(argv[4]));
    udp->udph_len = htons(sizeof(struct udpheader));
    ip->iph_chksum = check_sum((unsigned short *)buffer,sizeof(struct ipheader) + sizeof(struct udpheader));
    if(setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one)) < 0) {
        perror("setsockopt() error");
        exit(-1);
    } else
        printf("setsockopt() is ok./n");
    printf("Trying ..../n");
    printf("Using raw socket and udp protocol/n");
    printf("Using source ip: %s port: %u,Target ip: %s port: %u./n",argv[1],atoi(argv[2]),argv[3],atoi(argv[4]));
    int count;
    for(count = 1;count <= 20; count++){
        if(sendto(sockfd,buffer,ip->iph_len,0,(struct sockaddr *)&sin,sizeof(sin)) < 0) {
            perror("sendto() error");
            exit(-1);
        } else {
            printf("Count #%u - sendto() is OK./n",count);
            sleep(2);
        }
    }
    close(sockfd);
    return 0;
}