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我正在尝试发出 TCP/SYN 请求。

这是我的代码：

struct tcp_options_mss{
    uint8_t kind;
    uint8_t len;
    uint16_t mss; 
} __attribute__((packed));


struct tcphdr_mss {
    struct tcphdr tcp;
    struct tcp_options_mss mss;
};

struct pseudoHeader{ 
    
    unsigned int sourceAddress;
    unsigned int destinationAddress;
    unsigned char placeHolder; 
    unsigned char protocol;
    unsigned short tcpLength;

    struct tcphdr tcp;
};


unsigned short csum(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;
        *((u_char*)&oddbyte)=*(u_char*)ptr;
        sum+=oddbyte;
    }

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

int main(void)
{
    int s = socket (PF_INET,SOCK_RAW, IPPROTO_TCP);        
    char datagram[4096], sourceIP[32];
    struct iphdr *iph = (struct iphdr *) datagram;
    struct tcphdr_mss *tcp = (struct tcphdr_mss *) (datagram + sizeof(struct ip));
    
    struct pseudoHeader psh; 

    strcpy(sourceIP , "192.168.1.45"); 

    //Propiedades del socket
    sin.sin_family = AF_INET;
    sin.sin_port = htons(80); 
    sin.sin_addr.s_addr = inet_addr ("192.168.0.10"); 
    
    memset (datagram, 0, 4096); 
    
    iph->ihl = 5; 
    iph->version = 4; 
    iph->tos = 0; 
    iph->tot_len = sizeof (struct ip) + sizeof (struct tcphdr); 
    iph->id = htons(54321);
    iph->frag_off |= ntohs(IP_DF); 
    iph->ttl = 128;
    iph->protocol = IPPROTO_TCP; 
    iph->check = 0;
    iph->saddr = inet_addr ( sourceIP );
    iph->daddr = sin.sin_addr.s_addr;

    iph->check = csum ((unsigned short *) datagram, iph->tot_len >> 1);

    tcp->tcp.source = htons (1883); 
    tcp->tcp.dest = htons (80); 
    tcp->tcp.seq = 0;  
    tcp->tcp.ack_seq = 0; 
    tcp->tcp.doff = 5;
    tcp->tcp.urg = 0;
    tcp->tcp.ack = 0;
    tcp->tcp.psh = 0;
    tcp->tcp.rst = 0;
    tcp->tcp.syn = 1;
    tcp->tcp.fin = 0;
    
    tcp->tcp.window = htons (5840);
    tcp->tcp.check = 0;
    tcp->tcp.urg_ptr = 0; 
    
    tcp->mss.kind = 2;
    tcp->mss.len = 2;
    tcp->mss.mss = htons(32000);
     
    psh.sourceAddress = inet_addr( sourceIP );
    psh.destinationAddress = sin.sin_addr.s_addr;
    psh.placeHolder = 0;
    psh.protocol = IPPROTO_TCP;
    psh.tcpLength = htons(20); //
    
    memcpy(&psh.tcp , tcp , sizeof (struct tcphdr));
    
    tcp->tcp.check = csum( (unsigned short*) &psh , sizeof (struct pseudoHeader));

    int one = 1;
    const int *val = &one;
    if (setsockopt (s, IPPROTO_IP, IP_HDRINCL, val, sizeof (one)) < 0)
    {
        printf ("Error setting IP_HDRINCL. Error number : %d . Error message : %s \n" , errno , strerror(errno));
        exit(0);
    }

    //while (1)
    //{
        
        if (sendto (s,      
                    datagram,   
                    iph->tot_len,   
                    0,      
                    (struct sockaddr *) &sin,   
                    sizeof (sin)) < 0)  
        {
            printf ("error\n");
        }
        //Data send successfully
        else
        {
            printf ("Packet Send \n");
        }
    //}
    
    return 0;
}

我正在查看库的源代码#include <netinet/tcp.h>，并且没有 TCP 选项的属性。这就是我为 MSS 添加结构的原因。

当我在 Wireshark 上看到时，没有设置 MSS 选项。但是，如果您看到我的代码，则该选项正在设置中。

另一方面，我应该做同样的设置窗口比例和 SACK 吗？

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0 回答 0