142 lines
3.2 KiB
C
Executable File
142 lines
3.2 KiB
C
Executable File
#include "dns.h"
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#include "http.h"
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struct dns dns_list[MAX_CONNECTION >> 1]; //一个客户端 + 一个服务端 占用一个dns结构体
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int dnsFd;
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void read_dns_rsp()
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{
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static char rsp_data[512], *ip, *p;
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struct dns *dns;
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conn_t *client;
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int16_t len, dns_id;
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while ((len = read(dnsFd, rsp_data, 512)) > 11)
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{
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memcpy(&dns_id, rsp_data, 2);
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dns = dns_list + dns_id;
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client = cts + (dns_id << 1);
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//判断是否是正常DNS回应，是否已关闭连接
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if (dns_id > MAX_CONNECTION >> 1 || client->fd < 0)
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continue;
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if (dns->request_len + 12 > len || (unsigned char)rsp_data[3] != 128) //char只有7位可用，则正数最高为127
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{
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close_connection(client);
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continue;
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}
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/* get domain ip */
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p = rsp_data + dns->request_len + 11;
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ip = NULL;
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while (p - rsp_data + 4 <= len)
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{
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//type
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if (*(p - 8) != 1)
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{
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p += *p + 12;
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continue;
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}
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ip = p + 1;
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break;
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}
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if (ip == NULL || connectionToServer(*(in_addr_t *)ip, client + 1) != 0)
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{
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close_connection(client);
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continue;
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}
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}
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}
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/* 完全发送返回0，发送部分返回1，出错返回-1 */
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static int8_t send_dns_req(struct dns *dns)
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{
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int write_len;
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write_len = write(dnsFd, dns->request, dns->request_len);
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if (write_len == dns->request_len - dns->sent_len)
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{
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dns->sent_len = dns->request_len;
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return 0;
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}
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else if (write_len > 0)
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{
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return 1;
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}
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else
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{
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return -1;
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}
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}
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void dns_query()
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{
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int16_t i, ret;
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for (i = 0; i < MAX_CONNECTION >> 1; i++)
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{
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if (dns_list[i].request_len != dns_list[i].sent_len)
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{
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ret = send_dns_req(dns_list + i);
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if (ret == 1)
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break;
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else if (ret == -1)
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close_connection(cts + (i << 1));
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}
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}
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//dnsFd的缓冲区以满
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if (i < MAX_CONNECTION >> 1)
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{
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ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
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ev.data.fd = dnsFd;
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epoll_ctl(efd, EPOLL_CTL_MOD, dnsFd, &ev);
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}
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}
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int8_t build_dns_req(struct dns *dns, char *domain)
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{
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char *p, *_p;
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int8_t domain_size;
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domain_size = strlen(domain);
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p = dns->request + 12;
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memcpy(p+1, domain, domain_size + 1);
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while ((_p = strchr(p+1, '.')) != NULL)
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{
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*p = _p - p - 1;
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p = _p;
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}
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*p = strlen(p+1);
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p = dns->request + 14 + domain_size;
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*p++ = 0;
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*p++ = 1;
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*p++ = 0;
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*p++ = 1;
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dns->request_len = p - dns->request;
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switch (send_dns_req(dns))
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{
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case 0:
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return 0;
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case 1:
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ev.data.fd = dnsFd;
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ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
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epoll_ctl(efd, EPOLL_CTL_MOD, dnsFd, &ev);
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return 1;
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default:
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return -1;
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}
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}
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void dns_connect(struct sockaddr_in *dnsAddr)
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{
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dnsFd = socket(AF_INET, SOCK_DGRAM, 0);
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if (dnsFd < 0)
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{
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perror("socket");
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exit(1);
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}
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connect(dnsFd, (struct sockaddr *)dnsAddr, sizeof(struct sockaddr_in));
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fcntl(dnsFd, F_SETFL, O_NONBLOCK);
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}
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