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#include "dns.h"
#include <pthread.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#define DNS_QUERY_COUNT 20
#define DNS_QUERY_NAME_SIZE 256
enum DNSQueryState {
DQS_FREE = 0,
DQS_WAITING = 1,
DQS_COMPLETE = 2,
DQS_ERROR = 3
};
struct DNSQuery {
char name[DNS_QUERY_NAME_SIZE];
in_addr result;
DNSQueryState status;
int version;
};
static DNSQuery dnsQueue[DNS_QUERY_COUNT];
static pthread_t dnsThread;
static pthread_mutex_t dnsQueueMutex;
static pthread_cond_t dnsQueueCond;
static void *dnsThreadProc(void *);
void DNS::start() {
pthread_mutex_init(&dnsQueueMutex, NULL);
pthread_cond_init(&dnsQueueCond, NULL);
pthread_create(&dnsThread, NULL, &dnsThreadProc, NULL);
for (int i = 0; i < DNS_QUERY_COUNT; i++) {
dnsQueue[i].status = DQS_FREE;
dnsQueue[i].version = 0;
}
}
int DNS::makeQuery(const char *name) {
int id = -1;
pthread_mutex_lock(&dnsQueueMutex);
for (int i = 0; i < DNS_QUERY_COUNT; i++) {
if (dnsQueue[i].status == DQS_FREE) {
id = i;
break;
}
}
if (id != -1) {
strncpy(dnsQueue[id].name, name, sizeof(dnsQueue[id].name));
dnsQueue[id].name[sizeof(dnsQueue[id].name) - 1] = 0;
dnsQueue[id].status = DQS_WAITING;
dnsQueue[id].version++;
printf("[DNS::%d] New query: %s\n", id, dnsQueue[id].name);
}
pthread_mutex_unlock(&dnsQueueMutex);
pthread_cond_signal(&dnsQueueCond);
return id;
}
void DNS::closeQuery(int id) {
if (id < 0 || id >= DNS_QUERY_COUNT)
return;
pthread_mutex_lock(&dnsQueueMutex);
printf("[DNS::%d] Closing query\n", id);
dnsQueue[id].status = DQS_FREE;
pthread_mutex_unlock(&dnsQueueMutex);
}
bool DNS::checkQuery(int id, in_addr *pResult, bool *pIsError) {
if (id < 0 || id >= DNS_QUERY_COUNT)
return false;
pthread_mutex_lock(&dnsQueueMutex);
bool finalResult = false;
if (dnsQueue[id].status == DQS_COMPLETE) {
finalResult = true;
*pIsError = false;
memcpy(pResult, &dnsQueue[id].result, sizeof(dnsQueue[id].result));
} else if (dnsQueue[id].status == DQS_ERROR) {
finalResult = true;
*pIsError = true;
}
pthread_mutex_unlock(&dnsQueueMutex);
return finalResult;
}
void *dnsThreadProc(void *) {
pthread_mutex_lock(&dnsQueueMutex);
for (;;) {
for (int i = 0; i < DNS_QUERY_COUNT; i++) {
if (dnsQueue[i].status == DQS_WAITING) {
char nameCopy[DNS_QUERY_NAME_SIZE];
memcpy(nameCopy, dnsQueue[i].name, DNS_QUERY_NAME_SIZE);
int versionCopy = dnsQueue[i].version;
printf("[DNS::%d] Trying %s...\n", i, nameCopy);
pthread_mutex_unlock(&dnsQueueMutex);
addrinfo hints, *res;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_ADDRCONFIG | AI_V4MAPPED;
int s = getaddrinfo(nameCopy, NULL, &hints, &res);
pthread_mutex_lock(&dnsQueueMutex);
// Before we write to the request, check that it hasn't been
// closed (and possibly replaced...!) by another thread
if (dnsQueue[i].status == DQS_WAITING && dnsQueue[i].version == versionCopy) {
if (s == 0) {
// Only try the first one for now...
// Is this safe? Not sure.
dnsQueue[i].status = DQS_COMPLETE;
memcpy(&dnsQueue[i].result, &((sockaddr_in*)res->ai_addr)->sin_addr, sizeof(dnsQueue[i].result));
printf("[DNS::%d] Resolved %s to %x\n", i, dnsQueue[i].name, dnsQueue[i].result.s_addr);
} else {
dnsQueue[i].status = DQS_ERROR;
printf("[DNS::%d] Error condition: %d\n", i, s);
}
} else {
printf("[DNS::%d] Request was cancelled before getaddrinfo completed\n", i);
}
if (s == 0)
freeaddrinfo(res);
}
}
pthread_cond_wait(&dnsQueueCond, &dnsQueueMutex);
}
pthread_mutex_unlock(&dnsQueueMutex);
return NULL;
}
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