Method ForwardToUpstream

src/manager/llm_proxy.cpp:463–754

}

bool LlmProxyService::ForwardToUpstream(uintptr_t client_sock,
                                          const settings::LlmModelMapping& mapping,
                                          const std::string& modified_body,
                                          bool is_streaming, bool keep_alive,
                                          int& out_status, std::string& out_response_body,
                                          StreamEndInfo& out_stream_end) {
    SOCKET client = static_cast<SOCKET>(client_sock);
    const uint64_t t_start = NowMonotonicMs();

    // Default classification: becomes "n/a" for non-streaming, otherwise
    // overwritten by the SSE loop below.
    out_stream_end.reason = is_streaming ? "unknown" : "n/a";

    auto set_handshake_error = [&](const std::string& msg, uint32_t err = 0) {
        out_stream_end.reason = "handshake_error";
        out_stream_end.detail = msg;
        out_stream_end.winhttp_error = err;
        out_stream_end.duration_ms = NowMonotonicMs() - t_start;
    };

    // Build upstream URL: target_url + /chat/completions
    std::string upstream_url = mapping.target_url;
    // Ensure no trailing slash duplication
    if (!upstream_url.empty() && upstream_url.back() == '/')
        upstream_url.pop_back();
    upstream_url += "/chat/completions";

    UrlParts parts;
    if (!ParseUrl(upstream_url, parts)) {
        set_handshake_error("invalid_upstream_url");
        SendErrorResponse(client_sock, 502, "Bad Gateway",
                          "Invalid upstream URL: " + mapping.target_url, keep_alive);
        return false;
    }

    HINTERNET session = WinHttpOpen(L"TenBox-LLM-Proxy/1.0",
                                     WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
                                     WINHTTP_NO_PROXY_NAME,
                                     WINHTTP_NO_PROXY_BYPASS, 0);
    if (!session) {
        set_handshake_error("WinHttpOpen failed", GetLastError());
        SendErrorResponse(client_sock, 502, "Bad Gateway",
                          "WinHttpOpen failed", keep_alive);
        return false;
    }

    // Set explicit WinHTTP timeouts. Default receive timeout (30s) is too short for SSE streams.
    if (!WinHttpSetTimeouts(session, 15000, 60000, 30000, 300000)) {
        DWORD err = GetLastError();
        LOG_ERROR("WinHttpSetTimeouts failed: %lu", err);
    }

    // Enable HTTP/1.1 keep-alive (default in WinHTTP)
    HINTERNET conn = WinHttpConnect(session, parts.host.c_str(), parts.port, 0);
    if (!conn) {
        DWORD err = GetLastError();
        set_handshake_error("WinHttpConnect failed", err);
        WinHttpCloseHandle(session);