Struct isahc::config::VersionNegotiation

pub struct VersionNegotiation { /* fields omitted */ }

A strategy for selecting what HTTP versions should be used when communicating with a server.

You can set a version negotiation strategy on a given request or on a client with Configurable::version_negotiation.

Attempting to use an HTTP version without client-side support at runtime will result in an error. For example, using the system libcurl on an old machine may not have an HTTP/2 implementation. Using static linking and the http2 crate feature can help guarantee that HTTP/2 will be available to use.

Implementations

impl VersionNegotiation

pub const fn latest_compatible() -> Self

Always prefer the latest supported version announced by the server, falling back to older versions if not explicitly listed as supported. This is the default.

Secure connections will begin with a TLS handshake, after which the highest supported HTTP version listed by the server via ALPN will be used. Once connected, additional upgrades to newer versions may also occur if the server lists support for it. In the future, headers such as Alt-Svc will be used.

Insecure connections always use HTTP/1.x since there is no standard mechanism for a server to declare support for insecure HTTP versions, and only HTTP/1.x and HTTP/2 support insecure transfers.

pub const fn http10() -> Self

Connect via HTTP/1.0 and do not attempt to use a higher version.

pub const fn http11() -> Self

Connect via HTTP/1.1 and do not attempt to use a higher version.

pub const fn http2() -> Self

Connect via HTTP/2. Failure to connect will not fall back to old versions, unless HTTP/1.1 is negotiated via TLS ALPN before the session begins.

If HTTP/2 support is not compiled in, then using this strategy will always result in an error.

This strategy is often referred to as HTTP/2 with Prior Knowledge.

pub const fn http3() -> Self

Connect via HTTP/3. Failure to connect will not fall back to old versions.

Trait Implementations

impl Clone for VersionNegotiation

fn clone(&self) -> VersionNegotiation

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for VersionNegotiation

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for VersionNegotiation

fn default() -> Self

Returns the "default value" for a type.