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//! Backend server.
mod builder;
use crate::abi::{self, FastlyStatus};
pub use builder::*;
use fastly_shared::SslVersion;
use http::HeaderValue;
use std::{str::FromStr, time::Duration};
/// The maximum length in characters of a backend name.
pub(crate) const MAX_BACKEND_NAME_LEN: usize = 255;
/// A named backend.
///
/// This represents a backend associated with a service that we can send requests to, potentially
/// caching the responses received.
///
/// Backends come in one of two flavors:
/// * **Static Backends**: These backends are created using the Fastly UI or API,
/// and are predefined by the user. Static backends have short names (see the
/// precise naming rules in [`Backend::from_name`]) that are usable across every
/// session of a service.
/// * **Dynamic Backends**: These backends are created programmatically using the
/// [`Backend::builder`] API. They are defined at runtime, and may or may not be
/// shared across sessions depending on how they are configured.
///
/// To use a backend, pass it to the [`crate::Request::send`] method. Alternatively, the following
/// values can be automatically coerced into a backend for you, without the need to explicitly
/// create a `Backend` object, although they may all induce panics:
///
/// * Any string type ([`&str`][`str`], [`String`, or `&String`][`String`]) will
/// be automatically turned into the static backend of the same name.
///
/// ## Using Static Backends
///
/// As stated at the top level, the following snippet is a minimal program that resends
/// a request to a static backend named "example_backend":
///
/// ```no_run
/// use fastly::{Error, Request, Response};
///
/// #[fastly::main]
/// fn main(ds_req: Request) -> Result<Response, Error> {
/// Ok(ds_req.send("example_backend")?)
/// }
/// ```
///
/// A safer alternative to this example would be the following:
///
/// ```no_run
/// use fastly::{Backend, Error, Request, Response};
///
/// #[fastly::main]
/// fn main(ds_req: Request) -> Result<Response, Error> {
/// match Backend::from_name("example_backend") {
/// Ok(backend) => Ok(ds_req.send(backend)?),
/// Err(_) => {
/// // custom backend failure response
/// unimplemented!()
/// }
/// }
/// }
/// ```
///
/// as this version allows you to handle backend errors more cleanly.
///
/// ## Validating Support for Dynamic Backends
///
/// Since dynamic backends are only enabled for some services, it may be particularly
/// useful to ensure that dynamic backends are supported in your Compute@Edge service.
/// The easiest way to do so is to try to create a dynamic backend, and then explicitly
/// check for the [`crate::backend::BackendCreationError::Disallowed`] code, as follows:
///
/// ```no_run
/// use fastly::{Backend, Error, Request, Response};
/// use fastly::backend::BackendCreationError;
///
/// #[fastly::main]
/// fn main(ds_req: Request) -> Result<Response, Error> {
/// match Backend::builder("custom_backend", "example.org:993").finish() {
/// Ok(backend) => Ok(ds_req.send(backend)?),
/// Err(BackendCreationError::Disallowed) => {
/// // custom code ofr handling when dynamic backends aren't supported
/// unimplemented!()
/// }
/// Err(err) => {
/// // more specific logging/handling for backend misconfigurations
/// unimplemented!()
/// }
/// }
/// }
/// ```
///
///
///
#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct Backend {
name: String,
}
impl Backend {
/// Get a backend by its name.
///
/// This function will return a [`BackendError`] if an invalid name was given.
///
/// Backend names:
/// * cannot be empty
/// * cannot be longer than 255 characters
/// * cannot ASCII control characters such as `'\n'` or `DELETE`.
/// * cannot contain special Unicode characters
/// * should only contain visible ASCII characters or spaces
///
/// Future versions of this function may return an error if your service does not have a backend
/// with this name.
pub fn from_name(s: &str) -> Result<Self, BackendError> {
s.parse()
}
#[doc = include_str!("../docs/snippets/dynamic-backend-builder.md")]
pub fn builder(name: impl ToString, target: impl ToString) -> BackendBuilder {
BackendBuilder::new(name.to_string(), target.to_string())
}
/// Get the name of this backend.
pub fn name(&self) -> &str {
self.name.as_str()
}
/// Turn the backend into its name as a string.
pub fn into_string(self) -> String {
self.name
}
/// Returns true if a backend with this name exists.
pub fn exists(&self) -> bool {
let mut exists = 0;
unsafe { abi::fastly_backend::exists(self.name.as_ptr(), self.name.len(), &mut exists) }
.result()
.map(|_| exists == 1)
.expect("fastly_backend::exists failed")
}
/// Returns true if this is a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn is_dynamic(&self) -> bool {
let mut is = 0;
unsafe { abi::fastly_backend::is_dynamic(self.name.as_ptr(), self.name.len(), &mut is) }
.result()
.map(|_| is == 1)
.expect("fastly_backend::is_dynamic failed")
}
/// Returns the hostname for this backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_host(&self) -> String {
// First, ask the host how long our buffer will need to be. Provide a null pointer, with
// a maximum length of 0. We should get back a `BUFLEN` code, with `nwritten` set to the
// length of the host.
let mut nwritten = 0;
let length = match unsafe {
abi::fastly_backend::get_host(
self.name.as_ptr(),
self.name.len(),
std::ptr::null_mut(),
0,
&mut nwritten,
)
} {
FastlyStatus::BUFLEN => nwritten,
status => panic!(
"fastly_backend::get_host returned an unexpected result: {:?}",
status
),
};
// Now, call once more with a sufficiently long buffer.
let mut buf = Vec::with_capacity(length);
unsafe {
abi::fastly_backend::get_host(
self.name.as_ptr(),
self.name.len(),
buf.as_mut_ptr(),
buf.capacity(),
&mut nwritten,
)
}
.result()
.expect("fastly_backend::get_host returned an unexpected result");
assert!(
nwritten <= buf.capacity(),
"fastly_backend::get_host wrote too many bytes"
);
unsafe {
// Safety:
// - We assert above that `nwritten` is less than or equal to `capacity`.
// - We assume that the host did write to `old_len..new_len`.
buf.set_len(nwritten);
}
String::from_utf8(buf).expect("fastly_backend::get_host returns valid UTF-8 bytes")
}
/// Returns the host header override when contacting this backend.
///
/// This method returns `None` if no host header override is configured for this backend.
///
/// This is used to change the `Host` header sent to the backend. For more information, see
/// the Fastly documentation on host overrides here:
/// <https://docs.fastly.com/en/guides/specifying-an-override-host>
///
/// Use
/// [`BackendBuilder::override_host`][self::builder::BackendBuilder::override_host]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_host_override(&self) -> Option<HeaderValue> {
// First, ask the host how long our buffer will need to be. Provide a null pointer, with
// a maximum length of 0. We should get back a `BUFLEN` code, with `nwritten` set to the
// length of the host.
let mut nwritten = 0;
let length = match unsafe {
abi::fastly_backend::get_override_host(
self.name.as_ptr(),
self.name.len(),
std::ptr::null_mut(),
0,
&mut nwritten,
)
} {
// If a `NONE` code is returned, there is no host override. We are finished!
FastlyStatus::NONE => return None,
FastlyStatus::BUFLEN => nwritten,
status => panic!(
"fastly_backend::get_override_host returned an unexpected result: {:?}",
status
),
};
// Now, call once more with a sufficiently long buffer.
let mut buf = Vec::with_capacity(length);
unsafe {
abi::fastly_backend::get_override_host(
self.name.as_ptr(),
self.name.len(),
buf.as_mut_ptr(),
buf.capacity(),
&mut nwritten,
)
}
.result()
.expect("fastly_backend::get_override_host returned an unexpected result");
assert!(
nwritten <= buf.capacity(),
"fastly_backend::get_override_host wrote too many bytes"
);
unsafe {
// Safety:
// - We assert above that `nwritten` is less than or equal to `capacity`.
// - We assume that the host did write to `old_len..new_len`.
buf.set_len(nwritten);
}
Some(
HeaderValue::try_from(buf)
.expect("fastly_backend::get_override_host returns valid header value bytes"),
)
}
/// Get the port number of the backend's address.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_port(&self) -> u16 {
let mut port = 0;
unsafe { abi::fastly_backend::get_port(self.name.as_ptr(), self.name.len(), &mut port) }
.result()
.map(|_| port)
.expect("fastly_backend::get_port returned an unexpected result")
}
/// Returns the connection timeout for this backend.
///
/// Use
/// [`BackendBuilder::connect_timeout`][self::builder::BackendBuilder::connect_timeout]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_connect_timeout(&self) -> Duration {
let mut timeout = 0;
unsafe {
abi::fastly_backend::get_connect_timeout_ms(
self.name.as_ptr(),
self.name.len(),
&mut timeout,
)
}
.result()
.map(|_| timeout)
.map(u64::from)
.map(Duration::from_millis)
.expect("fastly_backend::get_connect_timeout_ms returned an unexpected result")
}
/// Returns the "first byte" timeout for this backend.
///
/// This timeout applies between the time of connection and the time we get the first byte back.
///
/// Use
/// [`BackendBuilder::first_byte_timeout`][self::builder::BackendBuilder::first_byte_timeout]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_first_byte_timeout(&self) -> Duration {
let mut timeout = 0;
unsafe {
abi::fastly_backend::get_first_byte_timeout_ms(
self.name.as_ptr(),
self.name.len(),
&mut timeout,
)
}
.result()
.map(|_| timeout)
.map(u64::from)
.map(Duration::from_millis)
.expect("fastly_backend::get_first_byte_timeout returned an unexpected result")
}
/// Returns the "between bytes" timeout for this backend.
///
/// This timeout applies between any two bytes we receive across the wire.
///
/// Use
/// [`BackendBuilder::between_bytes_timeout`][self::builder::BackendBuilder::between_bytes_timeout]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_between_bytes_timeout(&self) -> Duration {
let mut timeout = 0;
unsafe {
abi::fastly_backend::get_between_bytes_timeout_ms(
self.name.as_ptr(),
self.name.len(),
&mut timeout,
)
}
.result()
.map(|_| timeout)
.map(u64::from)
.map(Duration::from_millis)
.expect("fastly_backend::get_between_bytes_timeout returned an unexpected result")
}
/// Returns `true` if SSL/TLS is used to connect to the backend.
///
/// Use
/// [`BackendBuilder::enable_ssl`][self::builder::BackendBuilder::enable_ssl] or
/// [`BackendBuilder::disable_ssl`][self::builder::BackendBuilder::disable_ssl]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn is_ssl(&self) -> bool {
let mut is = 0;
unsafe { abi::fastly_backend::is_ssl(self.name.as_ptr(), self.name.len(), &mut is) }
.result()
.map(|_| is == 1)
.expect("fastly_backend::is_ssl returned an unexpected result")
}
/// Returns the minimum TLS version for connecting to the backend.
///
/// This method returns `None` if SSL/TLS is not enabled for this backend.
///
/// Use
/// [`BackendBuilder::set_min_tls_version`][self::builder::BackendBuilder::set_min_tls_version]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_ssl_min_version(&self) -> Option<SslVersion> {
let mut min = 0;
match unsafe {
abi::fastly_backend::get_ssl_min_version(self.name.as_ptr(), self.name.len(), &mut min)
}
.result()
{
Ok(_) => Some(min.try_into().unwrap()),
Err(FastlyStatus::NONE) => None,
other => panic!(
"fastly_backend::get_ssl_min_version returned an unexpected result: {other:?}"
),
}
}
/// Returns the maximum TLS version for connecting to the backend.
///
/// This method returns `None` if SSL/TLS is not enabled for this backend.
///
/// Use
/// [`BackendBuilder::set_max_tls_version`][self::builder::BackendBuilder::set_max_tls_version]
/// to set this for a dynamic backend.
///
/// # Panics
///
#[doc = include_str!("../docs/snippets/panics-backend-must-exist.md")]
pub fn get_ssl_max_version(&self) -> Option<SslVersion> {
let mut max = 0;
match unsafe {
abi::fastly_backend::get_ssl_max_version(self.name.as_ptr(), self.name.len(), &mut max)
}
.result()
{
Ok(_) => Some(max.try_into().unwrap()),
Err(FastlyStatus::NONE) => None,
other => panic!(
"fastly_backend::get_ssl_max_version returned an unexpected result: {other:?}"
),
}
}
}
/// [`Backend`]-related errors.
#[derive(Copy, Clone, Debug, thiserror::Error, PartialEq, Eq)]
pub enum BackendError {
/// The backend name was empty.
#[error("an empty string is not a valid backend")]
EmptyName,
/// The backend name was too long.
#[error("backend names must be <= 255 characters")]
TooLong,
/// The backend name contained invalid characters.
#[error("backend names must only contain visible ASCII characters or spaces")]
InvalidName,
}
impl FromStr for Backend {
type Err = BackendError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
validate_backend(s)?;
Ok(Self { name: s.to_owned() })
}
}
impl std::fmt::Display for Backend {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str(self.name.as_str())
}
}
/// Validate that a string looks like an acceptable [`Backend`] value.
///
/// Note that this is *not* meant to be a filter for things that could cause security issues, it is
/// only meant to catch errors before the hostcalls do in order to yield friendlier error messages.
///
/// This function will return a [`BackendError`] if an invalid name was given.
///
/// Backend names:
/// * cannot be empty
/// * cannot be longer than 255 characters
/// * cannot ASCII control characters such as `'\n'` or `DELETE`.
/// * cannot contain special Unicode characters
/// * should only contain visible ASCII characters or spaces
//
// TODO KTM 2020-03-10: We should not allow VCL keywords like `if`, `now`, `true`, `urldecode`, and
// so on. Once we have better errors, let's make sure that these are caught in a pleasant manner.
pub fn validate_backend(backend: &str) -> Result<(), BackendError> {
if backend.is_empty() {
Err(BackendError::EmptyName)
} else if backend.len() > MAX_BACKEND_NAME_LEN {
Err(BackendError::TooLong)
} else if backend.chars().any(is_invalid_char) {
Err(BackendError::InvalidName)
} else {
Ok(())
}
}
/// Return true if a character is not allowed in a [`Backend`] name.
///
/// This is used to enforce the rules described in the documentation of [`Backend::from_name()`]. A
/// backend name should only contain visible ASCII characters, or spaces.
#[inline]
fn is_invalid_char(c: char) -> bool {
c != ' ' && !c.is_ascii_graphic()
}
#[cfg(test)]
mod validate_backend_tests {
use super::*;
#[test]
fn valid_backend_names_are_accepted() {
let valid_backend_names = [
"valid_backend_1",
"1_backend_with_leading_integer",
"backend-with-kebab-case",
"backend with spaces",
"backend.with.periods",
"123_456_789_000",
"123.456.789.000",
"tilde~backend",
"(parens-backend)",
];
for backend in valid_backend_names.iter() {
match validate_backend(backend) {
Ok(_) => {}
x => panic!(
"backend string \"{}\" yielded unexpected result: {:?}",
backend, x
),
}
}
}
#[test]
fn empty_str_is_not_accepted() {
let invalid_backend = "";
match validate_backend(invalid_backend) {
Err(BackendError::EmptyName) => {}
x => panic!("unexpected result: {:?}", x),
}
}
#[test]
fn name_equal_to_character_limit_is_accepted() {
use std::iter::FromIterator;
let invalid_backend: String = String::from_iter(vec!['a'; 255]);
match validate_backend(&invalid_backend) {
Ok(_) => {}
x => panic!("unexpected result: {:?}", x),
}
}
#[test]
fn name_longer_than_character_limit_are_not_accepted() {
use std::iter::FromIterator;
let invalid_backend: String = String::from_iter(vec!['a'; 256]);
match validate_backend(&invalid_backend) {
Err(BackendError::TooLong) => {}
x => panic!("unexpected result: {:?}", x),
}
}
#[test]
fn unprintable_characters_are_not_accepted() {
let invalid_backend = "\n";
match validate_backend(invalid_backend) {
Err(BackendError::InvalidName) => {}
x => panic!("unexpected result: {:?}", x),
}
}
#[test]
fn unicode_is_not_accepted() {
let invalid_backend = "♓";
match validate_backend(invalid_backend) {
Err(BackendError::InvalidName) => {}
x => panic!("unexpected result: {:?}", x),
}
}
}