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我正在尝试创建一个能够创建和发送 tcp 包的程序，但在编译时不断收到这些错误。

error: expected identifier or ‘(’ before ‘,’ token

和

error: ‘sin’ undeclared (first use in this function)
error: ‘din’ undeclared (first use in this function)

现在我确信这些是非常明显的结果，但我对这段代码视而不见，无法理解它。功能如下：

int send_tcp()
        {
            int sock, one = 1;
            char buffer[PCKT_LEN];
            struct sockaddr_in, sin, din;
            const int *val = &one;

            sock = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
            if (sock < 0)
                {
                    printf("\nError: socket()\n\n");
                    exit (-1);
                }
            else
                    printf ("\nsocket() - Using SOCK_RAW and TCP protocol is OK.\n\n");

            /* Size of the headers */           
            struct ipheader *ip = (struct ipheader *) buffer;
            struct tcpheader *tcp = (struct tcpheader *) (buffer + sizeof (struct ipheader));
            memset (buffer, 0, PCKT_LEN);

            /* IP attributes */
            ip->iph_ihl = 5;
            ip->iph_ver = 4;
            ip->iph_tos = 16;
            ip->iph_len = sizeof(struct ipheader) + sizeof(struct tcpheader);
            ip->iph_id = htons(54321);
            ip->iph_offset = 0;
            ip->iph_ttl = 64;
            ip->iph_protocol = 6;
            ip->iph_chksum = 0; 

            ip->iph_sourceip = sip;
            ip->iph_destip = dip;

            /* TCP attributes */
            tcp->tcph_sourceport = sport;
            tcp->tcph_destport = dport;

            tcp->tcph_seqnum = htonl(1);
            tcp->tcph_acknum = 0;
            tcp->tcph_offset = 5;
            tcp->tcph_syn = 1;
            tcp->tcph_ack = 0;
            tcp->tcph_win = htons(32767);
            tcp->tcph_chksum = 0; 
            tcp->tcph_urgptr = 0;

            ip->iph_chksum = checksum ((unsigned short *) buffer, (sizeof (struct ipheader )+ sizeof (struct tcpheader)));

            /* Address family */ 
            sin.sin_family = AF_INET;
            din.sin_family = AF_INET;

            /* Source port */
            sin.sin_port = sport;
            din.sin_port = dport;

            /* Source IP */
            sin.sin_addr.s_addr = sip;
            din.sin_addr.s_addr = dip;      

            /* Tell the Kernel we're building our own packet */
            if ((setsockopt(sock, IPPROTO_IP, IP_HDRINCL, (char *)&one, sizeof (one))) < 0)
                {
                    printf("\nError: Can't set socketoptions\n\n");
                    return (-1);
                }

            /* Send */
            if (sendto(sock, buffer, ip->iph_len, 0, (struct sockaddr *)&sin, sizeof(sin)) < 0)
                {
                    printf("\nError: Can't send packet\n\n");
                    return (-1);
                }

            else
                    printf("Packet sent to %s", dip); 

            close(sock);
        }

我的印象是：

struct sockaddr_in, sin, din;

就足够了，但显然不是。这也是预期标识符错误消息指向的行。我错过了什么？

4

1 回答 1

4

去掉第一个逗号

 struct sockaddr_in, sin, din;
                   ^
                   ^

sockaddr_in是一个结构的名称，所以我假设您在上面的行中尝试声明两个sockadddr_in名为sinand类型的变量din。如果是这样，您需要删除该逗号，因为在struct sockaddr_in. 您所做的与尝试以下操作相同：

 int, a,b;

它也不会在类型名之后立即编译，int编译器需要一个变量名。

删除该逗号，您应该不再收到编译错误。

于 2012-07-19T19:04:22.347 回答