Test the update-push headers in both directions

crates/client/src/update.rs

@@ -590,20 +590,25 @@ fn runs_at_least(addr: SocketAddr, want: &Version, within: Duration) -> bool {
     }
 }
 
+/// The headers of a host-update push: this version's names and, because a
+/// host older than 4.1 knows only the old ones and is the one this push is
+/// most likely for, the old names too.
+fn push_headers<'a>(version: &'a str, sha: &'a str) -> [(&'static str, &'a str); 5] {
+    [
+        (UPDATE_VERSION_HEADER, version),
+        (UPDATE_SHA256_HEADER, sha),
+        (legacy::UPDATE_VERSION_HEADER, version),
+        (legacy::UPDATE_SHA256_HEADER, sha),
+        ("Content-Type", "application/octet-stream"),
+    ]
+}
+
 fn send_host(ip: Ipv4Addr, version: &str, sha: &str, exe: &[u8]) -> Result<()> {
     let r = http::request_with(
         (ip, CONTROL_PORT),
         "POST",
         UPDATE_PATH,
-        &[
-            (UPDATE_VERSION_HEADER, version),
-            (UPDATE_SHA256_HEADER, sha),
-            // A host older than 4.1 knows only the headers' old names, and
-            // is the one this push is most likely for.
-            (legacy::UPDATE_VERSION_HEADER, version),
-            (legacy::UPDATE_SHA256_HEADER, sha),
-            ("Content-Type", "application/octet-stream"),
-        ],
+        &push_headers(version, sha),
         exe,
         Duration::from_secs(120),
     )?;
@@ -736,6 +741,19 @@ mod tests {
         assert!(!msg.contains("os error"), "{msg}");
     }
 
+    #[test]
+    fn a_push_carries_both_header_names_so_a_4_0_host_accepts_it() {
+        let h = push_headers("4.1.1", "abc");
+        let get = |name: &str| h.iter().find(|(k, _)| *k == name).map(|(_, v)| *v);
+        assert_eq!(get("x-latch-version"), Some("4.1.1"));
+        assert_eq!(get("x-latch-sha256"), Some("abc"));
+        // What a 4.0 host reads, spelled out here so that renaming the
+        // constant in legacy.rs cannot silently break the push.
+        assert_eq!(get("x-brolink-version"), Some("4.1.1"));
+        assert_eq!(get("x-brolink-sha256"), Some("abc"));
+        assert_eq!(get("Content-Type"), Some("application/octet-stream"));
+    }
+
     /// A one-reply HTTP server saying the host runs `version`.
     fn status_server(version: &'static str) -> SocketAddr {
         use std::io::{Read, Write};

crates/host/src/update.rs

@@ -316,6 +316,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn a_push_from_a_4_0_mac_is_accepted_under_the_old_header_names() {
+        let dir = std::env::temp_dir().join(format!("latch-legacy-upd-{}", std::process::id()));
+        std::fs::create_dir_all(&dir).unwrap();
+        let exe = dir.join("brolink-host.exe");
+        let body = fake_exe();
+        let newer = format!("{}.0.0", update::current().major + 1);
+        let request = Request {
+            method: "POST".into(),
+            path: latch_core::api::UPDATE_PATH.into(),
+            headers: vec![
+                ("x-brolink-version".to_string(), newer.clone()),
+                ("x-brolink-sha256".to_string(), update::sha256_hex(&body)),
+            ],
+            body: body.clone(),
+        };
+        let v = stage(&request, &exe).unwrap();
+        assert_eq!(v.to_string(), newer);
+        assert_eq!(std::fs::read(staged(&exe)).unwrap(), body);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
     #[test]
     fn uploads_are_checked_before_anything_is_written() {
         let dir = std::env::temp_dir().join(format!("latch-upd-{}", std::process::id()));