fix(download_timeout): introduce RUSTUP_DOWNLOAD_TIMEOUT for overriding download timeout

As some (corporate) firewalls take too much time to verify the
downloads, the timeout is reached and the user cannot complete its
installation.

Besides changing the timeout from 30 secs to 3 mins, a new environment
variable is introduced to allow users to override the timeout value to
their taste.

Author: FranciscoTGouveia

doc/user-guide/src/environment-variables.md

@@ -66,6 +66,9 @@
 
 - `RUSTUP_TERM_WIDTH` (default: none). Allows to override the terminal width for progress bars.
 
+- `RUSTUP_DOWNLOAD_TIMEOUT` (default: 180). Allows to override the default
+  timeout for downloading components.
+
 [directive syntax]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#directives
 [dc]: https://docs.docker.com/storage/storagedriver/overlayfs-driver/#modifying-files-or-directories
 [override]: overrides.md

src/download/mod.rs

@@ -1,7 +1,9 @@
 //! Easy file downloading
 
 use std::fs::remove_file;
+use std::num::NonZeroU64;
 use std::path::Path;
+use std::time::Duration;
 
 use anyhow::Context;
 #[cfg(any(
@@ -202,7 +204,7 @@ async fn download_file_(
     });
 
     let res = backend
-        .download_to_path(url, path, resume_from_partial, Some(callback))
+        .download_to_path(url, path, resume_from_partial, Some(callback), process)
         .await;
 
     notify_handler(Notification::DownloadFinished);
@@ -241,9 +243,10 @@ impl Backend {
         path: &Path,
         resume_from_partial: bool,
         callback: Option<DownloadCallback<'_>>,
+        process: &Process,
     ) -> anyhow::Result<()> {
         let Err(err) = self
-            .download_impl(url, path, resume_from_partial, callback)
+            .download_impl(url, path, resume_from_partial, callback, process)
             .await
         else {
             return Ok(());
@@ -265,6 +268,7 @@ impl Backend {
         path: &Path,
         resume_from_partial: bool,
         callback: Option<DownloadCallback<'_>>,
+        process: &Process,
     ) -> anyhow::Result<()> {
         use std::cell::RefCell;
         use std::fs::OpenOptions;
@@ -322,9 +326,15 @@ impl Backend {
         };
 
         let file = RefCell::new(file);
+        let timeout = Duration::from_secs(match process.var("RUSTUP_DOWNLOAD_TIMEOUT") {
+            Ok(s) => s.parse::<NonZeroU64>().context(
+                "invalid value in RUSTUP_DOWNLOAD_TIMEOUT -- must be a natural number greater than zero",
+            ).unwrap().get(),
+            Err(_) => 180,
+        });
 
         // TODO: the sync callback will stall the async runtime if IO calls block, which is OS dependent. Rearrange.
-        self.download(url, resume_from, &|event| {
+        self.download(url, resume_from, &timeout, &|event| {
             if let Event::DownloadDataReceived(data) = event {
                 file.borrow_mut()
                     .write_all(data)
@@ -356,13 +366,14 @@ impl Backend {
         self,
         url: &Url,
         resume_from: u64,
+        timeout: &Duration,
         callback: DownloadCallback<'_>,
     ) -> anyhow::Result<()> {
         match self {
             #[cfg(feature = "curl-backend")]
-            Self::Curl => curl::download(url, resume_from, callback),
+            Self::Curl => curl::download(url, resume_from, callback, timeout),
             #[cfg(any(feature = "reqwest-rustls-tls", feature = "reqwest-native-tls"))]
-            Self::Reqwest(tls) => tls.download(url, resume_from, callback).await,
+            Self::Reqwest(tls) => tls.download(url, resume_from, callback, timeout).await,
         }
     }
 }
@@ -383,10 +394,11 @@ impl TlsBackend {
         url: &Url,
         resume_from: u64,
         callback: DownloadCallback<'_>,
+        timeout: &Duration,
     ) -> anyhow::Result<()> {
         let client = match self {
             #[cfg(feature = "reqwest-rustls-tls")]
-            Self::Rustls => reqwest_be::rustls_client()?,
+            Self::Rustls => reqwest_be::rustls_client(timeout)?,
             #[cfg(feature = "reqwest-native-tls")]
             Self::NativeTls => &reqwest_be::CLIENT_NATIVE_TLS,
         };
@@ -424,6 +436,7 @@ mod curl {
         url: &Url,
         resume_from: u64,
         callback: &dyn Fn(Event<'_>) -> Result<()>,
+        timeout: &Duration,
     ) -> Result<()> {
         // Fetch either a cached libcurl handle (which will preserve open
         // connections) or create a new one if it isn't listed.
@@ -446,8 +459,8 @@ mod curl {
                 let _ = handle.resume_from(0);
             }
 
-            // Take at most 30s to connect
-            handle.connect_timeout(Duration::new(30, 0))?;
+            // Take at most 3m to connect if the `RUSTUP_DOWNLOAD_TIMEOUT` env var is not set.`
+            handle.connect_timeout(*timeout)?;
 
             {
                 let cberr = RefCell::new(None);
@@ -586,11 +599,10 @@ mod reqwest_be {
             .pool_max_idle_per_host(0)
             .gzip(false)
             .proxy(Proxy::custom(env_proxy))
-            .read_timeout(Duration::from_secs(30))
     }
 
     #[cfg(feature = "reqwest-rustls-tls")]
-    pub(super) fn rustls_client() -> Result<&'static Client, DownloadError> {
+    pub(super) fn rustls_client(timeout: &Duration) -> Result<&'static Client, DownloadError> {
         if let Some(client) = CLIENT_RUSTLS_TLS.get() {
             return Ok(client);
         }
@@ -607,6 +619,7 @@ mod reqwest_be {
         tls_config.alpn_protocols = vec![b"h2".to_vec(), b"http/1.1".to_vec()];
 
         let client = client_generic()
+            .read_timeout(*timeout)
             .use_preconfigured_tls(tls_config)
             .user_agent(super::REQWEST_RUSTLS_TLS_USER_AGENT)
             .build()