使用syscalls在程序集中保存DNS响应

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

typedef struct {
    char *domain;
    char *ip;
    time_t expires;
} DNSCacheEntry;

DNSCacheEntry cache[100];
int cacheSize = 0;

void add_to_cache(const char *domain, const char *ip, time_t ttl) {
    if (cacheSize >= 100) return;
    DNSCacheEntry entry;
    entry.domain = strdup(domain);
    entry.ip = strdup(ip);
    entry.expires = time(NULL) + ttl;
    cache[cacheSize++] = entry;
}

char *lookup_cache(const char *domain) {
    for (int i = 0; i < cacheSize; i++) {
        if (strcmp(cache[i].domain, domain) == 0 && cache[i].expires > time(NULL)) {
            return cache[i].ip;
        }
    }
    return NULL;
}

void clean_cache() {
    for (int i = 0; i < cacheSize; i++) {
        if (cache[i].expires <= time(NULL)) {
            free(cache[i].domain);
            free(cache[i].ip);
            cache[i] = cache[--cacheSize];
        }
    }
}

int main() {
    // Example usage
    add_to_cache("example.com", "93.184.216.34", 3600); // TTL of 1 hour
    char *ip = lookup_cache("example.com");
    if (ip) {
        printf("IP: %s\n", ip);
    } else {
        printf("DNS lookup failed\n");
    }
    clean_cache();
    return 0;
}

#include <pthread.h>

pthread_mutex_t cache_mutex = PTHREAD_MUTEX_INITIALIZER;

void add_to_cache(const char *domain, const char *ip, time_t ttl) {
    pthread_mutex_lock(&cache_mutex);
    // Existing add_to_cache code
    pthread_mutex_unlock(&cache_mutex);
}

char *lookup_cache(const char *domain) {
    pthread_mutex_lock(&cache_mutex);
    // Existing lookup_cache code
    pthread_mutex_unlock(&cache_mutex);
}

void clean_cache() {
    pthread_mutex_lock(&cache_mutex);
    // Existing clean_cache code
    pthread_mutex_unlock(&cache_mutex);
}