Expand SSH identity path tokens

Cargo.lock

@@ -436,7 +436,7 @@ dependencies = [
 
 [[package]]
 name = "dosh"
-version = "1.0.0-rc15"
+version = "1.0.0-rc28"
 dependencies = [
  "anyhow",
  "base64",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dosh"
-version = "1.0.0-rc15"
+version = "1.0.0-rc28"
 edition = "2024"
 license = "MIT"
 

Makefile

@@ -36,7 +36,9 @@ persistence-check:
 package-check:
 	$(MAKE) package-release-linux
 	$(MAKE) package-release-windows
-	sh scripts/verify-release-artifacts.sh
+	sh scripts/verify-release-artifacts.sh \
+		target/dosh-release/dosh-linux-x86_64.tar.gz \
+		target/dosh-release/dosh-windows-x86_64.zip
 
 install:
 	sh install.sh --from-current

README.md

@@ -44,6 +44,7 @@ dosh setup HOST
 dosh HOST
 dosh HOST COMMAND
 dosh update
+dosh update --client|--server|--both
 ```
 
 Useful commands:
@@ -97,6 +98,20 @@ cache_attach_tickets = true
 disconnect_status = true
 ```
 
+Example host entry:
+
+```toml
+[prod]
+ssh = "prod"
+ssh_config = "prod" # OpenSSH alias for IdentityFile, ProxyJump, SendEnv, etc.
+dosh_host = "prod.example.com"
+port = 50000
+```
+
+`ProxyJump` and `ProxyCommand` can be used for SSH setup, but the Dosh UDP
+endpoint still has to be reachable directly from the client. Set `dosh_host` to
+the reachable UDP hostname or IP when it differs from the SSH alias target.
+
 ## Rust Library
 
 Dosh exposes a Rust transport for encrypted, reconnecting application streams.

build.rs

@@ -1,3 +1,4 @@
+use std::env;
 use std::process::Command;
 
 fn git(args: &[&str]) -> Option<String> {
@@ -12,14 +13,29 @@ fn git(args: &[&str]) -> Option<String> {
 fn main() {
     println!("cargo:rerun-if-changed=.git/HEAD");
     println!("cargo:rerun-if-changed=.git/index");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_HASH");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_COMMIT_DATE");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_DIRTY");
 
-    let hash = git(&["rev-parse", "--short=12", "HEAD"]).unwrap_or_else(|| "unknown".into());
+    let hash = env::var("DOSH_BUILD_GIT_HASH")
-    let date = git(&["show", "-s", "--format=%cs", "HEAD"]).unwrap_or_else(|| "unknown".into());
+        .ok()
-    let dirty = Command::new("git")
+        .filter(|value| !value.is_empty())
-        .args(["diff", "--quiet", "--ignore-submodules", "--"])
+        .or_else(|| git(&["rev-parse", "--short=12", "HEAD"]))
-        .status()
+        .unwrap_or_else(|| "unknown".into());
-        .map(|status| if status.success() { "" } else { "+dirty" })
+    let date = env::var("DOSH_BUILD_COMMIT_DATE")
-        .unwrap_or("");
+        .ok()
+        .filter(|value| !value.is_empty())
+        .or_else(|| git(&["show", "-s", "--format=%cs", "HEAD"]))
+        .unwrap_or_else(|| "unknown".into());
+    let dirty = match env::var("DOSH_BUILD_GIT_DIRTY").ok().as_deref() {
+        Some("1" | "true" | "yes" | "+dirty") => "+dirty",
+        Some(_) => "",
+        None => Command::new("git")
+            .args(["diff", "--quiet", "--ignore-submodules", "--"])
+            .status()
+            .map(|status| if status.success() { "" } else { "+dirty" })
+            .unwrap_or(""),
+    };
 
     println!("cargo:rustc-env=DOSH_GIT_HASH={hash}{dirty}");
     println!("cargo:rustc-env=DOSH_COMMIT_DATE={date}");

scripts/package-release.sh

@@ -52,6 +52,22 @@ else
   release_dir="target/release"
 fi
 
+if command -v git >/dev/null 2>&1 && git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+  if [ -z "${DOSH_BUILD_GIT_HASH:-}" ]; then
+    export DOSH_BUILD_GIT_HASH="$(git rev-parse --short=12 HEAD)"
+  fi
+  if [ -z "${DOSH_BUILD_COMMIT_DATE:-}" ]; then
+    export DOSH_BUILD_COMMIT_DATE="$(git show -s --format=%cs HEAD)"
+  fi
+  if [ -z "${DOSH_BUILD_GIT_DIRTY+x}" ]; then
+    if git diff --quiet --ignore-submodules --; then
+      export DOSH_BUILD_GIT_DIRTY=0
+    else
+      export DOSH_BUILD_GIT_DIRTY=1
+    fi
+  fi
+fi
+
 if [ "$os" = "windows" ]; then
   if [ -n "$target" ]; then
     cargo build --release --target "$target" --bin dosh-client --bin dosh-bench

scripts/verify-release-artifacts.sh

@@ -22,11 +22,14 @@ artifact_version() {
   esac
 }
 
+if [ "$#" -gt 0 ]; then
+  artifacts="$*"
+else
+  artifacts="$out_dir/dosh-linux-x86_64.tar.gz $out_dir/dosh-macos-aarch64.tar.gz $out_dir/dosh-windows-x86_64.zip"
+fi
+
 failed=0
-for artifact in \
+for artifact in $artifacts; do
-  "$out_dir/dosh-linux-x86_64.tar.gz" \
-  "$out_dir/dosh-macos-aarch64.tar.gz" \
-  "$out_dir/dosh-windows-x86_64.zip"; do
   if [ ! -f "$artifact" ]; then
     echo "missing release artifact: $artifact" >&2
     failed=1

src/bin/dosh-server.rs

@@ -28,7 +28,7 @@ use dosh::protocol::{
     TicketAttachBody, TicketAttachEnvelope, TicketAttachOkEnvelope,
 };
 use dosh::pty::{PtyHandle, PtyOutput, adopt_pty_from_fd, spawn_pty_session};
-use dosh::udp::is_transient_udp_send_error;
+use dosh::udp::{is_transient_udp_error, is_transient_udp_send_error};
 use sha2::{Digest, Sha256};
 use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};
 use std::fs;
@@ -53,6 +53,7 @@ const STREAM_RETIRED_TOMBSTONES: usize = 16 * 1024;
 /// have accumulated since the last mirror. Keeps the atomic write off the
 /// per-packet hot path while bounding how much fresh output a crash can lose.
 const SCREEN_PERSIST_BYTES: usize = 4096;
+const SCREEN_PERSIST_MAX_AGE: Duration = Duration::from_millis(250);
 const IMPLICIT_EMPTY_SESSION_GRACE_SECS: u64 = 300;
 
 /// Sentinel `target_host` sent to the client on a server-initiated `StreamOpen`
@@ -251,7 +252,7 @@ async fn serve(config_path: Option<std::path::PathBuf>) -> Result<()> {
     if config.persist_sessions {
         let flush_state = Arc::clone(&state);
         tokio::spawn(async move {
-            let mut interval = tokio::time::interval(Duration::from_secs(2));
+            let mut interval = tokio::time::interval(SCREEN_PERSIST_MAX_AGE);
             loop {
                 interval.tick().await;
                 flush_persistent_screens(&flush_state);
@@ -261,7 +262,11 @@ async fn serve(config_path: Option<std::path::PathBuf>) -> Result<()> {
 
     let mut buf = vec![0u8; 65535];
     loop {
-        let (n, peer) = socket.recv_from(&mut buf).await?;
+        let (n, peer) = match socket.recv_from(&mut buf).await {
+            Ok(value) => value,
+            Err(err) if is_transient_udp_error(&err) => continue,
+            Err(err) => return Err(err.into()),
+        };
         if let Err(err) = handle_packet(&state, &socket, peer, &buf[..n]).await {
             eprintln!("packet from {peer}: {err:#}");
         }
@@ -356,6 +361,7 @@ impl NativeAuthRateLimiter {
 struct Session {
     pty: Option<PtyHandle>,
     parser: vt100::Parser,
+    restored_screen: Option<RestoredScreenSnapshot>,
     clients: HashMap<[u8; 16], ClientState>,
     output_seq: u64,
     recent: VecDeque<Vec<u8>>,
@@ -376,6 +382,18 @@ struct Session {
     /// `output_seq` at the last successful screen mirror, so the periodic flush
     /// skips sessions whose screen has not changed.
     last_persisted_seq: u64,
+    /// Last time this session's screen was considered for a mirror. Combined
+    /// with the byte threshold so low-throughput prompt/TUI updates persist
+    /// quickly without writing on every packet in high-throughput bursts.
+    last_screen_persist_at: Instant,
+}
+
+#[derive(Clone)]
+struct RestoredScreenSnapshot {
+    cols: u16,
+    rows: u16,
+    output_seq: u64,
+    snapshot: Vec<u8>,
 }
 
 #[derive(Clone)]
@@ -503,6 +521,7 @@ impl ServerState {
             Session {
                 pty,
                 parser: vt100::Parser::new(rows.max(1), cols.max(1), self.config.scrollback),
+                restored_screen: None,
                 clients: HashMap::new(),
                 output_seq: 0,
                 recent: VecDeque::with_capacity(self.config.scrollback),
@@ -511,6 +530,7 @@ impl ServerState {
                 persistent,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now() - SCREEN_PERSIST_MAX_AGE,
             },
         );
         Ok(())
@@ -631,15 +651,23 @@ impl ServerState {
                 .unwrap_or((80, 24));
             let mut parser = vt100::Parser::new(rows, cols, self.config.scrollback);
             let mut output_seq = 0;
+            let mut restored_screen = None;
             if let Some(saved) = saved {
                 parser.process(&saved.snapshot);
                 output_seq = saved.output_seq;
+                restored_screen = Some(RestoredScreenSnapshot {
+                    cols,
+                    rows,
+                    output_seq,
+                    snapshot: saved.snapshot,
+                });
             }
             self.sessions.insert(
                 name.clone(),
                 Session {
                     pty: Some(pty),
                     parser,
+                    restored_screen,
                     clients: HashMap::new(),
                     output_seq,
                     recent: VecDeque::with_capacity(self.config.scrollback),
@@ -648,6 +676,7 @@ impl ServerState {
                     persistent: true,
                     bytes_since_persist: 0,
                     last_persisted_seq: output_seq,
+                    last_screen_persist_at: Instant::now(),
                 },
             );
             eprintln!(
@@ -751,6 +780,19 @@ fn apply_terminal_size(
     Ok(())
 }
 
+fn attach_snapshot(session: &Session, cols: u16, rows: u16) -> Vec<u8> {
+    let cols = cols.max(1);
+    let rows = rows.max(1);
+    if let Some(restored) = &session.restored_screen
+        && restored.output_seq == session.output_seq
+        && restored.cols == cols
+        && restored.rows == rows
+    {
+        return restored.snapshot.clone();
+    }
+    screen_snapshot(session.parser.screen())
+}
+
 fn mode_allows_terminal_updates(mode: &str) -> bool {
     mode != "view-only" && mode != "forward-only"
 }
@@ -1178,7 +1220,7 @@ async fn handle_native_user_auth(
                 apply_terminal_size(session.pty.as_ref(), &mut session.parser, cols, rows)?;
             }
             let client_id = crypto::random_16();
-            let snapshot = screen_snapshot(session.parser.screen());
+            let snapshot = attach_snapshot(session, cols, rows);
             let output_seq = session.output_seq;
             locked.insert_client(
                 &session_name,
@@ -1326,7 +1368,7 @@ async fn handle_bootstrap_attach(
                 )?;
             }
             let client_id = crypto::random_16();
-            let snapshot = screen_snapshot(session.parser.screen());
+            let snapshot = attach_snapshot(session, req.cols, req.rows);
             let output_seq = session.output_seq;
             let bootstrap_session = req.bootstrap.session.clone();
             locked.insert_client(
@@ -1462,7 +1504,7 @@ async fn handle_ticket_attach(
                 )?;
             }
             let client_id = crypto::random_16();
-            let snapshot = screen_snapshot(session.parser.screen());
+            let snapshot = attach_snapshot(session, req.cols, req.rows);
             let output_seq = session.output_seq;
             let ticket_session = req.session.clone();
             locked.insert_client(
@@ -1575,20 +1617,23 @@ async fn handle_resume(
             .sessions
             .get_mut(&req.session)
             .ok_or_else(|| anyhow!("unknown session"))?;
-        let client = session
+        let (send_seq, allow_terminal_updates) = {
-            .clients
+            let client = session
-            .get_mut(&packet.header.conn_id)
+                .clients
-            .ok_or_else(|| anyhow!("unknown client"))?;
+                .get_mut(&packet.header.conn_id)
-        if !client.replay.accept(packet.header.seq) {
+                .ok_or_else(|| anyhow!("unknown client"))?;
-            return Ok(());
+            if !client.replay.accept(packet.header.seq) {
-        }
+                return Ok(());
-        client.endpoint = peer;
+            }
-        client.last_acked = req.last_rendered_seq;
+            client.endpoint = peer;
-        client.cols = req.cols;
+            client.last_acked = req.last_rendered_seq;
-        client.rows = req.rows;
+            client.cols = req.cols;
-        client.last_seen = Instant::now();
+            client.rows = req.rows;
-        client.send_seq += 1;
+            client.last_seen = Instant::now();
-        if mode_allows_terminal_updates(&client.mode) {
+            client.send_seq += 1;
+            (client.send_seq, mode_allows_terminal_updates(&client.mode))
+        };
+        if allow_terminal_updates {
             apply_terminal_size(
                 session.pty.as_ref(),
                 &mut session.parser,
@@ -1596,8 +1641,8 @@ async fn handle_resume(
                 req.rows,
             )?;
         }
-        let snapshot = screen_snapshot(session.parser.screen());
+        let snapshot = attach_snapshot(session, req.cols, req.rows);
-        (client.send_seq, session.output_seq, snapshot)
+        (send_seq, session.output_seq, snapshot)
     };
     let frame = Frame {
         session: session_name,
@@ -1736,10 +1781,10 @@ async fn handle_detach(state: &Arc<Mutex<ServerState>>, packet: &protocol::Packe
     let (key, _) = find_client_decrypt_key(state, &packet.header)?;
     let _ = protocol::decrypt_body(packet, &key, CLIENT_TO_SERVER)?;
     let mut locked = state.lock().expect("server state poisoned");
-    if let Some(client) = locked.client_mut(&packet.header.conn_id) {
+    if let Some(client) = locked.client_mut(&packet.header.conn_id)
-        if !client.replay.accept(packet.header.seq) {
+        && !client.replay.accept(packet.header.seq)
-            return Ok(());
+    {
-        }
+        return Ok(());
     }
     locked.remove_client_everywhere(&packet.header.conn_id);
     Ok(())
@@ -2521,8 +2566,10 @@ struct UploadState {
     hasher: Sha256,
     written: u64,
     expected_size: u64,
+    mode: Option<u32>,
     modified_secs: Option<u64>,
     atomic: bool,
+    original_len: Option<u64>,
 }
 
 async fn run_file_stream_service(
@@ -2634,6 +2681,46 @@ async fn handle_file_request(
             send_file_response_to_client(state, socket, client_id, stream_id, FileResponse::Ok)
                 .await
         }
+        FileRequest::Readlink { path } => {
+            let path = clean_remote_path(&path, home)?;
+            let target =
+                fs::read_link(&path).with_context(|| format!("readlink {}", path.display()))?;
+            let target = target
+                .to_str()
+                .ok_or_else(|| anyhow!("symlink target is not valid UTF-8"))?
+                .to_string();
+            send_file_response_to_client(
+                state,
+                socket,
+                client_id,
+                stream_id,
+                FileResponse::LinkTarget { target },
+            )
+            .await
+        }
+        FileRequest::Symlink {
+            path,
+            target,
+            overwrite,
+        } => {
+            let path = clean_remote_path(&path, home)?;
+            if let Some(parent) = path.parent() {
+                fs::create_dir_all(parent)
+                    .with_context(|| format!("create {}", parent.display()))?;
+            }
+            if let Ok(metadata) = fs::symlink_metadata(&path) {
+                anyhow::ensure!(overwrite, "destination exists: {}", path.display());
+                anyhow::ensure!(
+                    !metadata.is_dir(),
+                    "destination is a directory: {}",
+                    path.display()
+                );
+                fs::remove_file(&path).with_context(|| format!("remove {}", path.display()))?;
+            }
+            create_symlink(&target, &path)?;
+            send_file_response_to_client(state, socket, client_id, stream_id, FileResponse::Ok)
+                .await
+        }
         FileRequest::Remove { path, recursive } => {
             let path = clean_remote_path(&path, home)?;
             let metadata =
@@ -2671,32 +2758,41 @@ async fn handle_file_request(
                 bail!("destination exists: {}", final_path.display());
             }
             let mut hasher = Sha256::new();
-            let (file, temp_path, written, atomic) = if resume && final_path.exists() {
+            let (file, temp_path, written, atomic, original_len, prefix_sha256) =
-                let mut file = fs::OpenOptions::new()
+                if resume && final_path.exists() {
-                    .read(true)
+                    let original_len = fs::metadata(&final_path)
-                    .write(true)
+                        .with_context(|| format!("stat {}", final_path.display()))?
-                    .append(true)
+                        .len();
-                    .open(&final_path)
+                    let written = original_len.min(size);
-                    .with_context(|| format!("open {}", final_path.display()))?;
+                    if written > 0 {
-                let written = file.metadata()?.len().min(size);
+                        let mut prefix = fs::File::open(&final_path)?;
-                file.set_len(written)
+                        hash_exact_prefix(&mut prefix, written, &mut hasher)?;
-                    .with_context(|| format!("truncate {}", final_path.display()))?;
+                    }
-                if written > 0 {
+                    let prefix_sha256 = (written > 0).then(|| hasher.clone().finalize().into());
-                    let mut prefix = fs::File::open(&final_path)?;
+                    let mut file = fs::OpenOptions::new()
-                    hash_exact_prefix(&mut prefix, written, &mut hasher)?;
+                        .read(true)
-                }
+                        .append(true)
-                file.seek(SeekFrom::Start(written))?;
+                        .open(&final_path)
-                (file, None, written, false)
+                        .with_context(|| format!("open {}", final_path.display()))?;
-            } else {
+                    file.seek(SeekFrom::Start(written))?;
-                let temp_path = upload_temp_path(&final_path, stream_id);
+                    (
-                let file = fs::OpenOptions::new()
+                        file,
-                    .create(true)
+                        None,
-                    .truncate(true)
+                        written,
-                    .write(true)
+                        false,
-                    .open(&temp_path)
+                        Some(original_len),
-                    .with_context(|| format!("create {}", temp_path.display()))?;
+                        prefix_sha256,
-                (file, Some(temp_path), 0, true)
+                    )
-            };
+                } else {
+                    let temp_path = upload_temp_path(&final_path, stream_id);
+                    let file = fs::OpenOptions::new()
+                        .create(true)
+                        .truncate(true)
+                        .write(true)
+                        .open(&temp_path)
+                        .with_context(|| format!("create {}", temp_path.display()))?;
+                    (file, Some(temp_path), 0, true, None, None)
+                };
             *upload = Some(UploadState {
                 final_path,
                 temp_path,
@@ -2704,23 +2800,20 @@ async fn handle_file_request(
                 hasher,
                 written,
                 expected_size: size,
+                mode,
                 modified_secs,
                 atomic,
+                original_len,
             });
-            if let Some(mode) = mode {
-                let target = upload
-                    .as_ref()
-                    .and_then(|state| state.temp_path.as_ref())
-                    .unwrap_or_else(|| &upload.as_ref().unwrap().final_path)
-                    .clone();
-                set_mode(&target, mode)?;
-            }
             send_file_response_to_client(
                 state,
                 socket,
                 client_id,
                 stream_id,
-                FileResponse::Resume { offset: written },
+                FileResponse::Resume {
+                    offset: written,
+                    prefix_sha256,
+                },
             )
             .await
         }
@@ -2742,8 +2835,6 @@ async fn handle_file_request(
             let Some(mut active) = upload.take() else {
                 bail!("no upload in progress");
             };
-            active.file.flush()?;
-            active.file.sync_all()?;
             anyhow::ensure!(
                 active.written == active.expected_size,
                 "upload size mismatch: got {}, expected {}",
@@ -2754,9 +2845,17 @@ async fn handle_file_request(
             if digest != sha256 {
                 if let Some(temp_path) = &active.temp_path {
                     let _ = fs::remove_file(temp_path);
+                } else if let Some(original_len) = active.original_len {
+                    let _ = active.file.set_len(original_len);
                 }
                 bail!("upload checksum mismatch");
             }
+            active
+                .file
+                .set_len(active.expected_size)
+                .with_context(|| format!("truncate {}", active.final_path.display()))?;
+            active.file.flush()?;
+            active.file.sync_all()?;
             drop(active.file);
             if active.atomic
                 && let Some(temp_path) = active.temp_path.take()
@@ -2769,6 +2868,9 @@ async fn handle_file_request(
                     )
                 })?;
             }
+            if let Some(mode) = active.mode {
+                set_mode(&active.final_path, mode)?;
+            }
             if let Some(modified_secs) = active.modified_secs {
                 filetime::set_file_mtime(
                     &active.final_path,
@@ -2796,9 +2898,20 @@ async fn handle_file_request(
                 "remote path is not a file: {}",
                 meta.path
             );
+            anyhow::ensure!(
+                offset <= meta.len,
+                "download offset {offset} is beyond file size {}",
+                meta.len
+            );
             let mut file =
                 fs::File::open(&path).with_context(|| format!("open {}", path.display()))?;
             file.seek(SeekFrom::Start(offset))?;
+            let mut hasher = Sha256::new();
+            if offset > 0 {
+                let mut prefix = fs::File::open(&path)?;
+                hash_exact_prefix(&mut prefix, offset, &mut hasher)?;
+            }
+            let prefix_sha256 = (offset > 0).then(|| hasher.clone().finalize().into());
             send_file_response_to_client(
                 state,
                 socket,
@@ -2807,14 +2920,10 @@ async fn handle_file_request(
                 FileResponse::Start {
                     meta: meta.clone(),
                     offset,
+                    prefix_sha256,
                 },
             )
             .await?;
-            let mut hasher = Sha256::new();
-            if offset > 0 {
-                let mut prefix = fs::File::open(&path)?;
-                hash_exact_prefix(&mut prefix, offset, &mut hasher)?;
-            }
             let mut sent = offset;
             let mut buf = vec![0u8; CHUNK_SIZE];
             loop {
@@ -2996,6 +3105,17 @@ fn set_mode(path: &Path, mode: u32) -> Result<()> {
     fs::set_permissions(path, permissions).with_context(|| format!("chmod {}", path.display()))
 }
 
+#[cfg(unix)]
+fn create_symlink(target: &str, path: &Path) -> Result<()> {
+    std::os::unix::fs::symlink(target, path)
+        .with_context(|| format!("symlink {} -> {}", path.display(), target))
+}
+
+#[cfg(not(unix))]
+fn create_symlink(_target: &str, _path: &Path) -> Result<()> {
+    bail!("symlink creation is not supported on this server platform")
+}
+
 fn upload_temp_path(final_path: &Path, stream_id: u64) -> PathBuf {
     let name = final_path
         .file_name()
@@ -3199,7 +3319,10 @@ async fn flush_stream_pending_data_to_client(
                 if credit < bytes.len() {
                     return Ok(());
                 }
-                let bytes = pending.pop_front().expect("pending front exists");
+                let Some(bytes) = pending.pop_front() else {
+                    client.stream_pending_data.remove(&stream_id);
+                    return Ok(());
+                };
                 if pending.is_empty() {
                     client.stream_pending_data.remove(&stream_id);
                 }
@@ -3444,6 +3567,7 @@ async fn broadcast_output(
             .get_mut(&output.session)
             .ok_or_else(|| anyhow!("unknown session"))?;
         session.parser.process(&output.bytes);
+        session.restored_screen = None;
         session.output_seq += 1;
         let output_seq = session.output_seq;
         session.recent.push_back(output.bytes.clone());
@@ -3451,16 +3575,20 @@ async fn broadcast_output(
             session.recent.pop_front();
         }
         // For a persistent session, mirror the screen to disk periodically so a
-        // post-restart reattach repaints. Throttled by accumulated bytes to keep
+        // post-restart reattach repaints. Throttled by accumulated bytes or a
-        // the (atomic) write off the per-packet hot path. The actual file write
+        // short wall-clock age so low-throughput prompt/TUI changes persist
-        // happens after the lock is dropped.
+        // quickly while large bursts still avoid per-packet disk writes. The
+        // actual file write happens after the lock is dropped.
         if session.persistent {
             session.bytes_since_persist = session
                 .bytes_since_persist
                 .saturating_add(output.bytes.len());
-            if session.bytes_since_persist >= SCREEN_PERSIST_BYTES {
+            let now = Instant::now();
+            if session.bytes_since_persist >= SCREEN_PERSIST_BYTES
+                || now.duration_since(session.last_screen_persist_at) >= SCREEN_PERSIST_MAX_AGE
+            {
                 session.bytes_since_persist = 0;
-                session.last_persisted_seq = output_seq;
+                session.last_screen_persist_at = now;
                 let screen = session.parser.screen();
                 persist_screen = Some((
                     output.session.clone(),
@@ -3519,6 +3647,8 @@ async fn broadcast_output(
             persist::save_screen(&sessions_dir, &name, cols, rows, output_seq, &snapshot)
         {
             eprintln!("screen persist for {name} failed: {err:#}");
+        } else {
+            mark_screen_persisted(state, &name, output_seq);
         }
     }
     for (endpoint, packet) in sends {
@@ -3800,8 +3930,8 @@ fn flush_persistent_screens(state: &Arc<Mutex<ServerState>>) {
             if !session.persistent || session.output_seq == session.last_persisted_seq {
                 continue;
             }
-            session.last_persisted_seq = session.output_seq;
             session.bytes_since_persist = 0;
+            session.last_screen_persist_at = Instant::now();
             let screen = session.parser.screen();
             to_write.push((
                 name.clone(),
@@ -3818,10 +3948,19 @@ fn flush_persistent_screens(state: &Arc<Mutex<ServerState>>) {
             persist::save_screen(&sessions_dir, &name, cols, rows, output_seq, &snapshot)
         {
             eprintln!("screen flush for {name} failed: {err:#}");
+        } else {
+            mark_screen_persisted(state, &name, output_seq);
         }
     }
 }
 
+fn mark_screen_persisted(state: &Arc<Mutex<ServerState>>, name: &str, output_seq: u64) {
+    let mut locked = state.lock().expect("server state poisoned");
+    if let Some(session) = locked.sessions.get_mut(name) {
+        session.last_persisted_seq = session.last_persisted_seq.max(output_seq);
+    }
+}
+
 fn cleanup_disconnected_clients(state: &Arc<Mutex<ServerState>>) {
     // Sessions removed here are dropped after the lock is released so their
     // shells are killed (PtyHandle::drop) without holding up the event loop.
@@ -4024,6 +4163,34 @@ mod tests {
         assert_eq!(ServerConfig::default().client_timeout_secs, 2_592_000);
     }
 
+    #[test]
+    fn attach_snapshot_prefers_restored_screen_for_same_size_reattach() {
+        let restored = b"\x1b[?1049lRESTORED_SCREEN_MARKER".to_vec();
+        let mut session = Session {
+            pty: None,
+            parser: vt100::Parser::new(24, 80, 100),
+            restored_screen: Some(RestoredScreenSnapshot {
+                cols: 80,
+                rows: 24,
+                output_seq: 7,
+                snapshot: restored.clone(),
+            }),
+            clients: HashMap::new(),
+            output_seq: 7,
+            recent: VecDeque::new(),
+            empty_since: Some(Instant::now()),
+            holder_control: None,
+            persistent: true,
+            bytes_since_persist: 0,
+            last_persisted_seq: 7,
+            last_screen_persist_at: Instant::now(),
+        };
+
+        session.parser.set_size(24, 80);
+        assert_eq!(attach_snapshot(&session, 80, 24), restored);
+        assert_ne!(attach_snapshot(&session, 100, 30), restored);
+    }
+
     #[tokio::test]
     async fn unknown_resume_reject_keeps_client_id() {
         let (pty_tx, _rx) = mpsc::unbounded_channel();
@@ -4374,6 +4541,7 @@ mod tests {
             Session {
                 pty: None,
                 parser: vt100::Parser::new(24, 80, 100),
+                restored_screen: None,
                 clients: HashMap::from([(client_id, client)]),
                 output_seq: 0,
                 recent: VecDeque::new(),
@@ -4382,6 +4550,7 @@ mod tests {
                 persistent: false,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now(),
             },
         );
         state.client_index.insert(client_id, "test".to_string());
@@ -4437,6 +4606,7 @@ mod tests {
             Session {
                 pty: None,
                 parser: vt100::Parser::new(24, 80, 100),
+                restored_screen: None,
                 clients: HashMap::from([(client_id, client)]),
                 output_seq: 0,
                 recent: VecDeque::new(),
@@ -4445,6 +4615,7 @@ mod tests {
                 persistent: false,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now(),
             },
         );
         state.client_index.insert(client_id, "test".to_string());
@@ -4512,6 +4683,7 @@ mod tests {
             Session {
                 pty: None,
                 parser: vt100::Parser::new(24, 80, 100),
+                restored_screen: None,
                 clients: HashMap::from([(client_id, client)]),
                 output_seq: 0,
                 recent: VecDeque::new(),
@@ -4520,6 +4692,7 @@ mod tests {
                 persistent: false,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now(),
             },
         );
         state.client_index.insert(client_id, "test".to_string());
@@ -4651,6 +4824,7 @@ mod tests {
             Session {
                 pty: None,
                 parser: vt100::Parser::new(24, 80, 100),
+                restored_screen: None,
                 clients: HashMap::from([(
                     client_id,
                     ClientState {
@@ -4689,6 +4863,7 @@ mod tests {
                 persistent: false,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now(),
             },
         );
         // Keep the O(1) conn_id index in sync, matching `insert_client`.
@@ -4747,6 +4922,7 @@ mod tests {
             Session {
                 pty: None,
                 parser: vt100::Parser::new(24, 80, 100),
+                restored_screen: None,
                 clients: HashMap::from([(
                     client_id,
                     ClientState {
@@ -4785,6 +4961,7 @@ mod tests {
                 persistent: false,
                 bytes_since_persist: 0,
                 last_persisted_seq: 0,
+                last_screen_persist_at: Instant::now(),
             },
         );
         state.client_index.insert(client_id, "test".to_string());

src/client.rs

@@ -13,6 +13,7 @@ use crate::protocol::{
 };
 use crate::ssh_agent;
 use crate::transport::{DoshTransport, SessionRole, SessionTransportConfig, TransportConfig};
+use crate::udp::{recv_udp_retrying_transient, send_udp_retrying_transient};
 use anyhow::{Context, Result, anyhow, bail};
 use std::net::{SocketAddr, ToSocketAddrs};
 use std::path::PathBuf;
@@ -214,10 +215,10 @@ impl DoshClientBuilder {
                 hello: hello.clone(),
             })?,
         )?;
-        socket.send_to(&packet, peer_addr).await?;
+        send_udp_retrying_transient(&socket, &packet, peer_addr, timeout).await?;
 
         let mut buf = vec![0u8; 65535];
-        let (n, _) = tokio::time::timeout(timeout, socket.recv_from(&mut buf)).await??;
+        let (n, _) = recv_udp_retrying_transient(&socket, &mut buf, timeout).await?;
         let packet = protocol::decode(&buf[..n])?;
         if packet.header.kind != PacketKind::NativeServerHello {
             if packet.header.kind == PacketKind::AttachReject {
@@ -261,8 +262,8 @@ impl DoshClientBuilder {
             CLIENT_TO_SERVER,
             &protocol::to_body(&NativeUserAuthBody { auth })?,
         )?;
-        socket.send_to(&auth_packet, peer_addr).await?;
+        send_udp_retrying_transient(&socket, &auth_packet, peer_addr, timeout).await?;
-        let (n, _) = tokio::time::timeout(timeout, socket.recv_from(&mut buf)).await??;
+        let (n, _) = recv_udp_retrying_transient(&socket, &mut buf, timeout).await?;
         let packet = protocol::decode(&buf[..n])?;
         if packet.header.kind != PacketKind::NativeAuthOk {
             if packet.header.kind == PacketKind::AttachReject {

src/config.rs

@@ -150,6 +150,12 @@ pub struct ClientConfig {
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub struct HostConfig {
     pub ssh: Option<String>,
+    /// Optional OpenSSH config host name to use for SSH-backed bootstrap,
+    /// trust/setup/doctor checks, and native-auth identity selection. This lets
+    /// a Dosh host keep a separate UDP endpoint while still inheriting
+    /// alias-scoped OpenSSH settings like IdentityFile, ProxyJump, and SendEnv.
+    #[serde(default)]
+    pub ssh_config: Option<String>,
     pub user: Option<String>,
     pub dosh_host: Option<String>,
     pub port: Option<u16>,

src/file_transfer.rs

@@ -18,6 +18,14 @@ pub enum FileRequest {
         path: String,
         mode: Option<u32>,
     },
+    Readlink {
+        path: String,
+    },
+    Symlink {
+        path: String,
+        target: String,
+        overwrite: bool,
+    },
     Remove {
         path: String,
         recursive: bool,
@@ -46,13 +54,35 @@ pub enum FileRequest {
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub enum FileResponse {
     Ok,
-    Resume { offset: u64 },
+    Resume {
-    Stat { meta: FileMeta },
+        offset: u64,
-    List { entries: Vec<FileEntry> },
+        prefix_sha256: Option<[u8; 32]>,
-    Start { meta: FileMeta, offset: u64 },
+    },
-    Chunk { offset: u64, bytes: Vec<u8> },
+    Stat {
-    Done { sha256: [u8; 32], bytes: u64 },
+        meta: FileMeta,
-    Error { message: String },
+    },
+    List {
+        entries: Vec<FileEntry>,
+    },
+    LinkTarget {
+        target: String,
+    },
+    Start {
+        meta: FileMeta,
+        offset: u64,
+        prefix_sha256: Option<[u8; 32]>,
+    },
+    Chunk {
+        offset: u64,
+        bytes: Vec<u8>,
+    },
+    Done {
+        sha256: [u8; 32],
+        bytes: u64,
+    },
+    Error {
+        message: String,
+    },
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]

src/persist.rs

@@ -23,12 +23,14 @@ use std::io::{Read, Write};
 use std::os::fd::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::path::{Path, PathBuf};
+use std::sync::Mutex;
 use std::time::Duration;
 
 /// One-byte commands a server sends to a holder over its control socket after
 /// the holder has handed back the master fd.
 const HOLDER_CMD_SHUTDOWN: u8 = b'X';
 const HOLDER_STARTUP_TIMEOUT: Duration = Duration::from_millis(750);
+static SCREEN_WRITE_LOCK: Mutex<()> = Mutex::new(());
 
 /// Magic written into a holder's `meta` file, bumped if the on-disk layout
 /// changes so a stale holder from an incompatible build is ignored.
@@ -140,13 +142,28 @@ pub fn save_screen(
         // No holder runtime for this session (non-persistent): nothing to do.
         return Ok(());
     }
+    let _guard = SCREEN_WRITE_LOCK
+        .lock()
+        .map_err(|_| anyhow!("screen persistence lock poisoned"))?;
+    let path = screen_path(&dir);
+    if existing_screen_output_seq(&path).is_some_and(|existing| existing >= output_seq) {
+        return Ok(());
+    }
     let mut buf = Vec::with_capacity(snapshot.len() + 32);
     buf.extend_from_slice(&cols.to_be_bytes());
     buf.extend_from_slice(&rows.to_be_bytes());
     buf.extend_from_slice(&output_seq.to_be_bytes());
     buf.extend_from_slice(&(snapshot.len() as u32).to_be_bytes());
     buf.extend_from_slice(snapshot);
-    atomic_write(&screen_path(&dir), &buf)
+    atomic_write(&path, &buf)
+}
+
+fn existing_screen_output_seq(path: &Path) -> Option<u64> {
+    let data = std::fs::read(path).ok()?;
+    if data.len() < 12 {
+        return None;
+    }
+    Some(u64::from_be_bytes(data[4..12].try_into().ok()?))
 }
 
 /// A restored screen for a re-adopted session.
@@ -619,6 +636,20 @@ mod tests {
         assert_eq!(loaded.snapshot, snap);
     }
 
+    #[test]
+    fn save_screen_never_overwrites_newer_snapshot_with_older_seq() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sessions_dir = tmp.path();
+        ensure_runtime_dir(sessions_dir, "work").unwrap();
+
+        save_screen(sessions_dir, "work", 80, 24, 10, b"new-screen").unwrap();
+        save_screen(sessions_dir, "work", 80, 24, 9, b"old-screen").unwrap();
+
+        let loaded = load_screen(sessions_dir, "work").expect("screen restored");
+        assert_eq!(loaded.output_seq, 10);
+        assert_eq!(loaded.snapshot, b"new-screen");
+    }
+
     #[test]
     fn load_screen_absent_is_none() {
         let tmp = tempfile::tempdir().unwrap();

src/server.rs

@@ -13,7 +13,7 @@ use crate::transport::{
     DoshTransport, SessionEvent, SessionRole, SessionTransportConfig, TransportConfig,
     service_name_from_target,
 };
-use crate::udp::is_transient_udp_send_error;
+use crate::udp::{is_transient_udp_error, is_transient_udp_send_error};
 use anyhow::{Context, Result, anyhow, bail};
 use ed25519_dalek::SigningKey;
 use std::collections::{HashMap, HashSet};
@@ -169,7 +169,11 @@ impl DoshServer {
         let mut buf = vec![0u8; 65535];
         loop {
             self.expire_pending();
-            let (n, peer) = self.socket.recv_from(&mut buf).await?;
+            let (n, peer) = match self.socket.recv_from(&mut buf).await {
+                Ok(value) => value,
+                Err(err) if is_transient_udp_error(&err) => continue,
+                Err(err) => return Err(err.into()),
+            };
             let packet = match protocol::decode(&buf[..n]) {
                 Ok(packet) => packet,
                 Err(_) => continue,

src/transport.rs

@@ -19,7 +19,7 @@ use crate::protocol::{
     self, CLIENT_TO_SERVER, PacketKind, ReplayWindow, SERVER_TO_CLIENT, StreamClose, StreamData,
     StreamOpen, StreamOpenOk, StreamOpenReject, StreamWindowAdjust,
 };
-use crate::udp::is_transient_udp_send_error;
+use crate::udp::{is_transient_udp_error, is_transient_udp_send_error};
 use anyhow::{Result, anyhow, bail};
 use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};
 use std::net::SocketAddr;
@@ -596,11 +596,13 @@ impl StreamMux {
             if self.send_credit.get(&stream_id).copied().unwrap_or(0) < front_len {
                 break;
             }
-            let bytes = self
+            let Some(bytes) = self
                 .pending_data
                 .get_mut(&stream_id)
                 .and_then(VecDeque::pop_front)
-                .expect("pending front exists");
+            else {
+                break;
+            };
             if self
                 .pending_data
                 .get(&stream_id)
@@ -852,7 +854,11 @@ impl DoshTransport {
     pub async fn recv(&mut self) -> Result<SessionEvent> {
         let mut buf = vec![0u8; 65535];
         loop {
-            let (n, peer) = self.socket.recv_from(&mut buf).await?;
+            let (n, peer) = match self.socket.recv_from(&mut buf).await {
+                Ok(value) => value,
+                Err(err) if transport_recv_error_is_retryable(&err) => continue,
+                Err(err) => return Err(err.into()),
+            };
             let packet = match protocol::decode(&buf[..n]) {
                 Ok(packet) => packet,
                 Err(_) => continue,
@@ -984,6 +990,10 @@ impl DoshTransport {
     }
 }
 
+fn transport_recv_error_is_retryable(err: &std::io::Error) -> bool {
+    is_transient_udp_error(err)
+}
+
 fn initial_stream_id(role: SessionRole) -> u64 {
     match role {
         SessionRole::Client => 1,
@@ -1033,6 +1043,35 @@ mod tests {
         assert!(service_target("../bad").is_err());
     }
 
+    #[test]
+    fn transport_recv_retries_network_churn_errors() {
+        for kind in [
+            std::io::ErrorKind::Interrupted,
+            std::io::ErrorKind::TimedOut,
+            std::io::ErrorKind::WouldBlock,
+        ] {
+            let err = std::io::Error::from(kind);
+            assert!(transport_recv_error_is_retryable(&err));
+        }
+        assert!(!transport_recv_error_is_retryable(&std::io::Error::from(
+            std::io::ErrorKind::PermissionDenied,
+        )));
+
+        #[cfg(unix)]
+        for code in [libc::ENETUNREACH, libc::EHOSTUNREACH, libc::ECONNRESET] {
+            assert!(transport_recv_error_is_retryable(
+                &std::io::Error::from_raw_os_error(code)
+            ));
+        }
+
+        #[cfg(windows)]
+        for code in [10051, 10054, 10065] {
+            assert!(transport_recv_error_is_retryable(
+                &std::io::Error::from_raw_os_error(code)
+            ));
+        }
+    }
+
     #[test]
     fn service_registry_matches_registered_service_opens() {
         let mut registry = ServiceRegistry::new();

src/udp.rs

@@ -1,6 +1,10 @@
 //! UDP error classification shared by Dosh clients, servers, and embedders.
 
-pub fn is_transient_udp_send_error(err: &std::io::Error) -> bool {
+use std::net::SocketAddr;
+use std::time::{Duration, Instant};
+use tokio::net::UdpSocket;
+
+pub fn is_transient_udp_error(err: &std::io::Error) -> bool {
     matches!(
         err.kind(),
         std::io::ErrorKind::Interrupted
@@ -9,6 +13,58 @@ pub fn is_transient_udp_send_error(err: &std::io::Error) -> bool {
     ) || err.raw_os_error().is_some_and(is_transient_udp_os_error)
 }
 
+pub fn is_transient_udp_send_error(err: &std::io::Error) -> bool {
+    is_transient_udp_error(err)
+}
+
+pub async fn send_udp_retrying_transient(
+    socket: &UdpSocket,
+    packet: &[u8],
+    peer: SocketAddr,
+    wait: Duration,
+) -> std::io::Result<()> {
+    let deadline = Instant::now() + wait.max(Duration::from_millis(1));
+    loop {
+        match socket.send_to(packet, peer).await {
+            Ok(_) => return Ok(()),
+            Err(err) if is_transient_udp_send_error(&err) && Instant::now() < deadline => {
+                sleep_until_retry(deadline).await;
+            }
+            Err(err) => return Err(err),
+        }
+    }
+}
+
+pub async fn recv_udp_retrying_transient(
+    socket: &UdpSocket,
+    buf: &mut [u8],
+    wait: Duration,
+) -> std::io::Result<(usize, SocketAddr)> {
+    let deadline = Instant::now() + wait.max(Duration::from_millis(1));
+    loop {
+        let now = Instant::now();
+        if now >= deadline {
+            return Err(std::io::Error::from(std::io::ErrorKind::TimedOut));
+        }
+        match tokio::time::timeout(deadline - now, socket.recv_from(buf)).await {
+            Ok(Ok(value)) => return Ok(value),
+            Ok(Err(err)) if is_transient_udp_error(&err) && Instant::now() < deadline => {
+                sleep_until_retry(deadline).await;
+            }
+            Ok(Err(err)) => return Err(err),
+            Err(_) => return Err(std::io::Error::from(std::io::ErrorKind::TimedOut)),
+        }
+    }
+}
+
+async fn sleep_until_retry(deadline: Instant) {
+    let now = Instant::now();
+    if now >= deadline {
+        return;
+    }
+    tokio::time::sleep((deadline - now).min(Duration::from_millis(20))).await;
+}
+
 #[cfg(unix)]
 fn is_transient_udp_os_error(code: i32) -> bool {
     matches!(
@@ -48,20 +104,56 @@ fn is_transient_udp_os_error(_code: i32) -> bool {
 
 #[cfg(test)]
 mod tests {
-    use super::is_transient_udp_send_error;
+    use super::{
+        is_transient_udp_error, is_transient_udp_send_error, recv_udp_retrying_transient,
+        send_udp_retrying_transient,
+    };
+    use std::time::Duration;
+    use tokio::net::UdpSocket;
 
     #[test]
-    fn classifies_portable_transient_send_errors() {
+    fn classifies_portable_transient_udp_errors() {
         for kind in [
             std::io::ErrorKind::Interrupted,
             std::io::ErrorKind::TimedOut,
             std::io::ErrorKind::WouldBlock,
         ] {
-            assert!(is_transient_udp_send_error(&std::io::Error::from(kind)));
+            let err = std::io::Error::from(kind);
+            assert!(is_transient_udp_error(&err));
+            assert!(is_transient_udp_send_error(&err));
         }
-        assert!(!is_transient_udp_send_error(&std::io::Error::from(
+        let fatal = std::io::Error::from(std::io::ErrorKind::PermissionDenied);
-            std::io::ErrorKind::PermissionDenied,
+        assert!(!is_transient_udp_error(&fatal));
-        )));
+        assert!(!is_transient_udp_send_error(&fatal));
+    }
+
+    #[tokio::test]
+    async fn retrying_udp_send_and_receive_round_trip() {
+        let receiver = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let sender = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let addr = receiver.local_addr().unwrap();
+
+        send_udp_retrying_transient(&sender, b"hello", addr, Duration::from_millis(50))
+            .await
+            .unwrap();
+        let mut buf = [0u8; 16];
+        let (n, peer) = recv_udp_retrying_transient(&receiver, &mut buf, Duration::from_millis(50))
+            .await
+            .unwrap();
+
+        assert_eq!(&buf[..n], b"hello");
+        assert_eq!(peer, sender.local_addr().unwrap());
+    }
+
+    #[tokio::test]
+    async fn retrying_udp_receive_times_out_cleanly() {
+        let receiver = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let mut buf = [0u8; 16];
+        let err = recv_udp_retrying_transient(&receiver, &mut buf, Duration::from_millis(1))
+            .await
+            .unwrap_err();
+
+        assert_eq!(err.kind(), std::io::ErrorKind::TimedOut);
     }
 
     #[cfg(unix)]
@@ -78,9 +170,9 @@ mod tests {
             libc::ENETUNREACH,
             libc::ETIMEDOUT,
         ] {
-            assert!(is_transient_udp_send_error(
+            let err = std::io::Error::from_raw_os_error(code);
-                &std::io::Error::from_raw_os_error(code)
+            assert!(is_transient_udp_error(&err));
-            ));
+            assert!(is_transient_udp_send_error(&err));
         }
     }
 
@@ -90,9 +182,9 @@ mod tests {
         for code in [
             10049, 10050, 10051, 10052, 10054, 10060, 10061, 10064, 10065,
         ] {
-            assert!(is_transient_udp_send_error(
+            let err = std::io::Error::from_raw_os_error(code);
-                &std::io::Error::from_raw_os_error(code)
+            assert!(is_transient_udp_error(&err));
-            ));
+            assert!(is_transient_udp_send_error(&err));
         }
     }
 }

tests/hostile_network.rs

@@ -29,7 +29,7 @@ use std::io::{Read, Write};
 use std::net::{SocketAddr, TcpListener, UdpSocket};
 use std::process::{Child, Command, Stdio};
 use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU32, AtomicU64, Ordering};
 use std::sync::mpsc::{Receiver, Sender, channel};
 use std::thread;
 use std::time::{Duration, Instant};
@@ -49,9 +49,20 @@ use ed25519_dalek::{SigningKey, VerifyingKey};
 use rand::rngs::StdRng;
 use rand::{Rng, SeedableRng};
 
+const TEST_UDP_PORT_START: u16 = 31_000;
+const TEST_UDP_PORT_END: u16 = 60_999;
+static NEXT_UDP_PORT: AtomicU32 = AtomicU32::new(TEST_UDP_PORT_START as u32);
+
 fn free_udp_port() -> u16 {
-    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    let span = u32::from(TEST_UDP_PORT_END - TEST_UDP_PORT_START) + 1;
-    socket.local_addr().unwrap().port()
+    for _ in TEST_UDP_PORT_START..=TEST_UDP_PORT_END {
+        let offset = NEXT_UDP_PORT.fetch_add(1, Ordering::SeqCst) % span;
+        let port = TEST_UDP_PORT_START + offset as u16;
+        if UdpSocket::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free UDP test port in {TEST_UDP_PORT_START}-{TEST_UDP_PORT_END}");
 }
 
 fn write_server_config(dir: &tempfile::TempDir, port: u16) -> std::path::PathBuf {

tests/integration_smoke.rs

@@ -3,9 +3,11 @@
 use std::fs;
 use std::io::{Read, Write};
 use std::net::{TcpListener, TcpStream, UdpSocket};
+use std::os::unix::fs::PermissionsExt;
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::path::{Path, PathBuf};
 use std::process::{Child, Command, Stdio};
+use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::mpsc;
 use std::thread;
 use std::time::Duration;
@@ -23,14 +25,35 @@ use dosh::protocol::{
 };
 use ed25519_dalek::{Signer, SigningKey, VerifyingKey};
 
+const TEST_PORT_START: u16 = 30_000;
+const TEST_PORT_END: u16 = 60_999;
+static NEXT_UDP_PORT: AtomicU32 = AtomicU32::new(TEST_PORT_START as u32);
+static NEXT_TCP_PORT: AtomicU32 = AtomicU32::new(TEST_PORT_START as u32);
+
+fn next_test_port(counter: &AtomicU32) -> u16 {
+    let span = u32::from(TEST_PORT_END - TEST_PORT_START) + 1;
+    let offset = counter.fetch_add(1, Ordering::SeqCst) % span;
+    TEST_PORT_START + offset as u16
+}
+
 fn free_udp_port() -> u16 {
-    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    for _ in TEST_PORT_START..=TEST_PORT_END {
-    socket.local_addr().unwrap().port()
+        let port = next_test_port(&NEXT_UDP_PORT);
+        if UdpSocket::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free UDP test port in {TEST_PORT_START}-{TEST_PORT_END}");
 }
 
 fn free_tcp_port() -> u16 {
-    let listener = TcpListener::bind("127.0.0.1:0").unwrap();
+    for _ in TEST_PORT_START..=TEST_PORT_END {
-    listener.local_addr().unwrap().port()
+        let port = next_test_port(&NEXT_TCP_PORT);
+        if TcpListener::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free TCP test port in {TEST_PORT_START}-{TEST_PORT_END}");
 }
 
 fn write_server_config(dir: &tempfile::TempDir, port: u16) -> std::path::PathBuf {
@@ -980,6 +1003,8 @@ fn native_file_copy_recursive_round_trip() {
     fs::create_dir_all(src.join("nested")).unwrap();
     fs::write(src.join("root.txt"), b"root file\n").unwrap();
     fs::write(src.join("nested/child.txt"), b"child file\n").unwrap();
+    std::os::unix::fs::symlink("root.txt", src.join("root-link")).unwrap();
+    std::os::unix::fs::symlink("nested/child.txt", src.join("child-link")).unwrap();
 
     let client_bin = env!("CARGO_BIN_EXE_dosh-client");
     let upload = Command::new(client_bin)
@@ -1085,6 +1110,14 @@ fn native_file_copy_recursive_round_trip() {
         fs::read_to_string(downloaded.join("nested/child.txt")).unwrap(),
         "child file\n"
     );
+    assert_eq!(
+        fs::read_link(downloaded.join("root-link")).unwrap(),
+        PathBuf::from("root.txt")
+    );
+    assert_eq!(
+        fs::read_link(downloaded.join("child-link")).unwrap(),
+        PathBuf::from("nested/child.txt")
+    );
 
     let remove = Command::new(client_bin)
         .arg("--dosh-host")
@@ -1219,6 +1252,80 @@ fn native_file_copy_resume_truncates_oversized_destinations() {
     let _ = server.wait();
 }
 
+#[test]
+fn native_file_copy_resume_prefix_mismatch_preserves_destinations() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config(&dir, port);
+    write_native_client_auth(&dir, &config);
+    let mut server = start_server(&dir, &config);
+    let client_bin = env!("CARGO_BIN_EXE_dosh-client");
+
+    let local_upload = dir.path().join("upload-prefix.txt");
+    let remote_upload = dir.path().join("remote-upload.txt");
+    fs::write(&local_upload, b"local-prefix\n").unwrap();
+    fs::write(&remote_upload, b"remote-prefix-with-tail\n").unwrap();
+    fs::set_permissions(&local_upload, fs::Permissions::from_mode(0o755)).unwrap();
+    fs::set_permissions(&remote_upload, fs::Permissions::from_mode(0o600)).unwrap();
+
+    let bad_upload_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg(&local_upload)
+        .arg("local:remote-upload.txt")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_upload_resume.status.success(),
+        "bad upload resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_upload_resume.stdout),
+        String::from_utf8_lossy(&bad_upload_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&remote_upload).unwrap(),
+        "remote-prefix-with-tail\n"
+    );
+    assert_eq!(
+        fs::metadata(&remote_upload).unwrap().permissions().mode() & 0o777,
+        0o600
+    );
+
+    fs::write(dir.path().join("remote-download.txt"), b"remote-download\n").unwrap();
+    let local_download = dir.path().join("download-prefix.txt");
+    fs::write(&local_download, b"local-download-with-tail\n").unwrap();
+
+    let bad_download_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg("local:remote-download.txt")
+        .arg(&local_download)
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_download_resume.status.success(),
+        "bad download resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_download_resume.stdout),
+        String::from_utf8_lossy(&bad_download_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&local_download).unwrap(),
+        "local-download-with-tail\n"
+    );
+
+    let _ = server.kill();
+    let _ = server.wait();
+}
+
 #[test]
 fn native_exec_command_smoke() {
     let dir = tempfile::tempdir().unwrap();

tests/release_scripts.rs

@@ -19,6 +19,46 @@ fn release_scripts_skip_stale_artifacts_when_auto_discovering() {
     assert!(publish.contains("actual=\"$(artifact_version \"$artifact\" || true)\""));
 }
 
+#[test]
+fn package_check_verifies_only_artifacts_it_builds() {
+    let makefile = include_str!("../Makefile");
+    let verify = include_str!("../scripts/verify-release-artifacts.sh");
+    assert!(
+        verify.contains("if [ \"$#\" -gt 0 ]; then"),
+        "release verifier must accept an explicit artifact list"
+    );
+    let package_check = makefile
+        .split("package-check:")
+        .nth(1)
+        .and_then(|tail| tail.split("\ninstall:").next())
+        .expect("package-check target");
+    assert!(package_check.contains("package-release-linux"));
+    assert!(package_check.contains("package-release-windows"));
+    assert!(package_check.contains("dosh-linux-x86_64.tar.gz"));
+    assert!(package_check.contains("dosh-windows-x86_64.zip"));
+    assert!(
+        !package_check.contains("dosh-macos-aarch64.tar.gz"),
+        "Linux package-check does not build macOS artifacts, so it must not depend on one"
+    );
+}
+
+#[test]
+fn package_release_stamps_git_build_info() {
+    let package = include_str!("../scripts/package-release.sh");
+    let build = include_str!("../build.rs");
+    for name in [
+        "DOSH_BUILD_GIT_HASH",
+        "DOSH_BUILD_COMMIT_DATE",
+        "DOSH_BUILD_GIT_DIRTY",
+    ] {
+        assert!(package.contains(name), "package script must export {name}");
+        assert!(build.contains(name), "build.rs must consume {name}");
+    }
+    assert!(package.contains("git rev-parse --short=12 HEAD"));
+    assert!(package.contains("git show -s --format=%cs HEAD"));
+    assert!(build.contains("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_HASH"));
+}
+
 #[test]
 fn systemd_service_does_not_sandbox_remote_shells() {
     let service = include_str!("../packaging/systemd/dosh-server.service");