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Possible Duplicate:
C - byte array to structure (dns query)
我有这些结构:
typedef struct dnsQuery {
char header[12];
struct dnsQuerySection *querySection;
} TdnsQuery;
typedef struct dnsQuerySection {
unsigned char *name;
struct dnsQueryQuestion *question;
} TdnsQuerySection;
typedef struct dnsQueryQuestion {
unsigned short qtype;
unsigned short qclass;
} TdnsQueryQuestion;
我在 recvfrom 的字节数组 buf 中有一个 DNS 查询。我正在尝试从这样的字节数组中获取结构:
TdnsQuery* dnsQuery = (TdnsQuery*)buf;
当我尝试像这样访问 qtype 时:
printf("%u", dnsQuery->querySection->question.qtype);
我遇到段错误 11。
有人可以帮我处理这些结构吗？他们怎么了？我试图添加结构:
typedef struct udpPacket {
char header[8];
structr dnsQuery query;
}
并从字节数组映射这个结构，但它没有帮助。有人可以帮我处理这些结构吗？对于使用 UDP 协议(protocol)的 DNS 查询，它们应该是什么样子？
编辑:我的结构现在看起来像这样:
typedef struct {
unsigned short qtype;
unsigned short qclass;
} dnsQueryQuestion;
typedef struct {
dnsQueryQuestion *question;
unsigned char *data[0];
} dnsQuerySection;
typedef struct {
char header[12];
dnsQuerySection querySection[0];
} dnsQuery;
typedef struct udpPacket {
char header[8];
dnsQuery query[0];
} TudpPacket;
我添加了解析函数:
void parse(unsigned char *data, unsigned short *qtype, unsigned short *qclass) {
int i = 0;
while (data[i]) {
int len = data[i];
i += len + 1;
}
*qtype = (unsigned short) data[i+1];
*qclass = (unsigned short) data[i+3];
return;
}
并尝试解析:
TudpPacket udpPack = (TudpPacket)buf;
parse(udpPack.query.querySection.data, &(udpPack.query.querySection.question.qtype), &(udpPack.query.querySection.question.qclass));
printf("%u\n", udpPack.query.querySection.question.qtype);