curl + c-ares CURLE_COULDNT_RESOLVE_HOST Could not resolve hostname

2025-12-05

新版本的c-ares在未设置dns服务器地址的情况下，默认使用127.0.0.1作为dns服务器地址，进而导致无法解析域名。简单的解决方法是，获取默认的系统dns服务器地址并设置，即可。

QString GetSystemDnsServers() {
    ULONG ulOutBufLen = 0;
    FIXED_INFO* pFixedInfo = nullptr;

    DWORD dwRetVal = GetNetworkParams(nullptr, &ulOutBufLen);
    if (dwRetVal != ERROR_BUFFER_OVERFLOW || ulOutBufLen == 0) {
        return QString();
    }

    pFixedInfo = (FIXED_INFO*)malloc(ulOutBufLen);
    if (!pFixedInfo) return QString();

    QStringList dnsList;
    dwRetVal = GetNetworkParams(pFixedInfo, &ulOutBufLen);
    if (dwRetVal == NO_ERROR) {
        IP_ADDR_STRING* pDNS = &pFixedInfo->DnsServerList;
        while (pDNS) {
            if (pDNS->IpAddress.String[0] != '\0') {
                QString ip = QString::fromUtf8(pDNS->IpAddress.String);
                if (!ip.isEmpty() && ip != "0.0.0.0") {
                    dnsList << ip;
                }
            }
            pDNS = pDNS->Next;
        }
    }

    free(pFixedInfo);
    return dnsList.join(',');
}


static std::string GetConfiguredDnsServersUtf8() {
    static std::string s_dns;
    static bool s_inited = false;
    if (!s_inited) {
        s_inited = true;
        QString dns = g_configManager.GetDnsServers();
        if (dns.isEmpty()) {
            dns = GetSystemDnsServers();
        }
        if (!dns.isEmpty()) {
            s_dns = dns.toStdString();
        }
    }
    return s_dns;
}

调用：

std::string dns = GetConfiguredDnsServersUtf8();
if (!dns.empty()) {
    curl_easy_setopt(m_curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
    curl_easy_setopt(m_curl, CURLOPT_DNS_SERVERS, dns.c_str());
}

本文作者： 后知科技

原文链接： curl + c-ares CURLE_COULDNT_RESOLVE_HOST Could not resolve hostname

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curl + c-ares CURLE_COULDNT_RESOLVE_HOST Could not resolve hostname

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