* [X-Forwarded-Host](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host)

///

### Habilitar headers reenviados por el Proxy { #enable-proxy-forwarded-headers }

Puedes iniciar FastAPI CLI con la *Opción de CLI* `--forwarded-allow-ips` y pasar las direcciones IP que deberían ser confiables para leer esos headers reenviados.

    response = client.get("/items?token=jessica", headers={"X-Token": "invalid"})
    assert response.status_code == 400
    assert response.json() == {"detail": "X-Token header invalid"}


def test_items_bar_with_invalid_token(client: TestClient):
    response = client.get("/items/bar?token=jessica", headers={"X-Token": "invalid"})
    assert response.status_code == 400

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header(convert_underscores=False)):

    /**
     * Retrieves a specific request header by its ID.
     *
     * @param id the unique identifier of the request header
     * @return an OptionalEntity containing the request header if found, empty otherwise
     */
    public OptionalEntity<RequestHeader> getRequestHeader(final String id) {
        return requestHeaderBhv.selectByPK(id);
    }

    /**
     * Stores a request header configuration to the database.

   */
  public val target: String,
  /** A string like `HTTP/1.1` or `HTTP/2`. */
  public val version: String,
  /** The request URL built using the request line, headers, and local host name. */
  public val url: HttpUrl,
  /** All headers. */
  public val headers: Headers,
  /** The body of this request, or null if it has none. This may be truncated. */
  public val body: ByteString?,

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(
    headers: Annotated[CommonHeaders, Header(convert_underscores=False)],
):

    ]
    filename: Annotated[str | None, Doc("The original file name.")]
    size: Annotated[int | None, Doc("The size of the file in bytes.")]
    headers: Annotated[Headers, Doc("The headers of the request.")]
    content_type: Annotated[
        str | None, Doc("The content type of the request, from the headers.")
    ]

    async def write(
        self,
        data: Annotated[
            bytes,
            Doc(
                """

	// ErrIncompatibleEncryptionMethod indicates that both SSE-C headers and SSE-S3 headers were specified, and are incompatible
	// The client needs to remove the SSE-S3 header or the SSE-C headers
	ErrIncompatibleEncryptionMethod = Errorf("Server side encryption specified with both SSE-C and SSE-S3 headers")

**FastAPI** will use that *temporal* response to extract the cookies (also headers and status code), and will put them in the final response that contains the value you returned, filtered by any `response_model`.

You can also declare the `Response` parameter in dependencies, and set cookies (and headers) in them.

## Return a `Response` directly { #return-a-response-directly }

    public static Iterable<String> iterable(final BufferedReader reader) {
        assertArgumentNotNull("reader", reader);

        return () -> new LineIterator(reader);
    }

    /**
     * Constructs an instance.
     *
     * @param reader
     *            The {@link Reader} to read strings from. Must not be {@literal null}.
     */
    public LineIterator(final Reader reader) {
        assertArgumentNotNull("reader", reader);