fix

internal/client/client.go

@@ -134,9 +134,11 @@ func (c *Client) streamToS3(snapshot *zfs.Dataset, uploadURL, storageKey string)
 		gzWriter := gzip.NewWriter(pw)
 
 		go func() {
-			defer pw.Close()
-			defer gzWriter.Close()
+			// Copy zfs output to gzip writer
 			io.Copy(gzWriter, zfsOut)
+			// Close gzip writer first to flush footer, then close pipe
+			gzWriter.Close()
+			pw.Close()
 		}()
 
 		reader = pr

internal/client/snapshot.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 	"os/exec"
 	"sort"
 	"strings"
@@ -186,7 +187,11 @@ func (c *Client) SendIncremental(snapshot *zfs.Dataset, base string) error {
 	fmt.Printf("  Type: %s\n", uploadMethod)
 	fmt.Printf("  Storage key: %s\n", uploadResp.StorageKey)
 
-	return c.streamIncrementalToS3(snapshot, base, uploadResp.UploadURL, uploadResp.StorageKey)
+	// Choose upload method based on server response
+	if uploadResp.UploadMethod == "s3" {
+		return c.streamIncrementalToS3(snapshot, base, uploadResp.UploadURL, uploadResp.StorageKey)
+	}
+	return c.sendIncrementalViaZFS(snapshot, base, uploadResp.StorageKey)
 }
 
 // streamIncrementalToS3 streams an incremental ZFS snapshot to S3.
@@ -222,9 +227,11 @@ func (c *Client) streamIncrementalToS3(snapshot *zfs.Dataset, base, uploadURL, s
 		gzWriter := gzip.NewWriter(pw)
 
 		go func() {
-			defer pw.Close()
-			defer gzWriter.Close()
+			// Copy zfs output to gzip writer
 			io.Copy(gzWriter, zfsOut)
+			// Close gzip writer first to flush footer, then close pipe
+			gzWriter.Close()
+			pw.Close()
 		}()
 
 		reader = pr
@@ -289,6 +296,50 @@ func (c *Client) streamIncrementalToS3(snapshot *zfs.Dataset, base, uploadURL, s
 	return nil
 }
 
+// sendIncrementalViaZFS sends an incremental snapshot via ZFS send/receive over SSH.
+// This method is used when the server uses local ZFS storage.
+func (c *Client) sendIncrementalViaZFS(snapshot *zfs.Dataset, base, receivePath string) error {
+	fmt.Printf("-> Sending via ZFS send/receive...\n")
+
+	// Extract server host from URL
+	serverHost := c.config.ServerURL
+	if len(serverHost) > 7 && strings.HasPrefix(serverHost, "http://") {
+		serverHost = serverHost[7:]
+	} else if len(serverHost) > 8 && strings.HasPrefix(serverHost, "https://") {
+		serverHost = serverHost[8:]
+	}
+
+	// Remove port if present
+	if idx := strings.LastIndex(serverHost, ":"); idx > 0 {
+		serverHost = serverHost[:idx]
+	}
+
+	// Build zfs send command
+	var zfsSendCmd string
+	if base != "" {
+		// Incremental send
+		fmt.Printf("  Base: %s\n", base)
+		zfsSendCmd = fmt.Sprintf("zfs send -i %s %s", base, snapshot.Name)
+	} else {
+		// Full send
+		zfsSendCmd = fmt.Sprintf("zfs send %s", snapshot.Name)
+	}
+
+	// Execute ZFS send over SSH
+	cmd := exec.Command("sh", "-c",
+		fmt.Sprintf("%s | ssh %s 'zfs recv -F %s'", zfsSendCmd, serverHost, receivePath))
+
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("failed to send snapshot: %v", err)
+	}
+
+	fmt.Printf("Snapshot sent successfully!\n")
+	return nil
+}
+
 // RotateLocalSnapshots removes old snapshots based on the retention policy.
 // This is similar to zfs-auto-snapshot's rotation behavior.
 func (c *Client) RotateLocalSnapshots(policy *SnapshotPolicy) error {

internal/server/server.go

@@ -289,7 +289,8 @@ func (s *Server) HandleUpload(w http.ResponseWriter, r *http.Request) {
 
 	timestamp := time.Now().Format("2006-01-02_15:04:05")
 
-	if client.StorageType == "s3" {
+	// Check if S3 backend is available for S3 storage type
+	if client.StorageType == "s3" && s.s3Backend != nil {
 		// S3 upload
 		storageKey := fmt.Sprintf("%s/%s_%s.zfs", req.ClientID, req.DatasetName, timestamp)
 		if req.Compressed {
@@ -303,6 +304,12 @@ func (s *Server) HandleUpload(w http.ResponseWriter, r *http.Request) {
 			StorageKey:   storageKey,
 			UploadURL:    fmt.Sprintf("/upload-stream/%s", req.ClientID),
 		})
+	} else if client.StorageType == "s3" && s.s3Backend == nil {
+		// S3 requested but not configured
+		respondJSON(w, http.StatusInternalServerError, UploadResponse{
+			Success: false,
+			Message: "S3 storage requested but S3 backend is not configured on server",
+		})
 	} else {
 		// Local ZFS receive
 		snapshotName := fmt.Sprintf("%s@%s_%s", client.Dataset, req.ClientID, timestamp)
@@ -346,9 +353,17 @@ func (s *Server) HandleUploadStream(w http.ResponseWriter, r *http.Request) {
 	ctx := context.Background()
 
 	// Upload to S3
+	// When using chunked transfer (io.Pipe), ContentLength is -1
+	// MinIO requires -1 for unknown size to use streaming upload
 	size := r.ContentLength
 	if size < 0 {
-		size = 0
+		size = -1 // Use streaming upload for unknown size
+	}
+
+	if s.s3Backend == nil {
+		log.Printf("Error: S3 backend not initialized")
+		http.Error(w, "S3 backend not configured", http.StatusInternalServerError)
+		return
 	}
 
 	if err := s.s3Backend.Upload(ctx, storageKey, r.Body, size); err != nil {