Add options for specifying the TLS version (#1315)

src/blocking/client.rs

@@ -16,6 +16,8 @@ use super::request::{Request, RequestBuilder};
 use super::response::Response;
 use super::wait;
 #[cfg(feature = "__tls")]
+use crate::tls;
+#[cfg(feature = "__tls")]
 use crate::Certificate;
 #[cfg(any(feature = "native-tls", feature = "__rustls"))]
 use crate::Identity;
@@ -603,6 +605,62 @@ impl ClientBuilder {
         self.with_inner(|inner| inner.danger_accept_invalid_certs(accept_invalid_certs))
     }
 
+    /// Set the minimum required TLS version for connections.
+    ///
+    /// By default the TLS backend's own default is used.
+    ///
+    /// # Errors
+    ///
+    /// A value of `tls::Version::TLS_1_3` will cause an error with the
+    /// `native-tls`/`default-tls` backend. This does not mean the version
+    /// isn't supported, just that it can't be set as a minimum due to
+    /// technical limitations.
+    ///
+    /// # Optional
+    ///
+    /// This requires the optional `default-tls`, `native-tls`, or `rustls-tls(-...)`
+    /// feature to be enabled.
+    #[cfg(feature = "__tls")]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(
+            feature = "default-tls",
+            feature = "native-tls",
+            feature = "rustls-tls"
+        )))
+    )]
+    pub fn min_tls_version(self, version: tls::Version) -> ClientBuilder {
+        self.with_inner(|inner| inner.min_tls_version(version))
+    }
+
+    /// Set the maximum allowed TLS version for connections.
+    ///
+    /// By default there's no maximum.
+    ///
+    /// # Errors
+    ///
+    /// A value of `tls::Version::TLS_1_3` will cause an error with the
+    /// `native-tls`/`default-tls` backend. This does not mean the version
+    /// isn't supported, just that it can't be set as a maximum due to
+    /// technical limitations.
+    ///
+    /// # Optional
+    ///
+    /// This requires the optional `default-tls`, `native-tls`, or `rustls-tls(-...)`
+    /// feature to be enabled.
+    #[cfg(feature = "__tls")]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(
+            feature = "default-tls",
+            feature = "native-tls",
+            feature = "rustls-tls"
+        )))
+    )]
+    pub fn max_tls_version(self, version: tls::Version) -> ClientBuilder {
+        self.with_inner(|inner| inner.max_tls_version(version))
+    }
+
     /// Force using the native TLS backend.
     ///
     /// Since multiple TLS backends can be optionally enabled, this option will