fix: check HTTP status code and fix concurrent fetch race

paramfetch.go

@@ -108,6 +108,12 @@ func (ft *fetch) maybeFetchAsync(ctx context.Context, name string, info paramFil
 		ft.fetchLk.Lock()
 		defer ft.fetchLk.Unlock()
 
+		// Re-check after acquiring the in-process mutex — another goroutine
+		// may have already fetched the file while we waited.
+		if err := ft.checkFile(path, info); err == nil {
+			return
+		}
+
 		var lockfail bool
 		var unlocker io.Closer
 		for {
@@ -275,6 +281,10 @@ func doFetch(ctx context.Context, out string, info paramFile) error {
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
+		return xerrors.Errorf("fetching file from %s: %s", url, resp.Status)
+	}
+
 	bar := pb.New64(fStat.Size() + resp.ContentLength).
 		SetCurrent(fStat.Size()).Start()
 

paramfetch_test.go

@@ -3,8 +3,12 @@ package paramfetch
 import (
 	"context"
 	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	logging "github.com/ipfs/go-log/v2"
@@ -93,3 +97,45 @@ func TestCheckFileIgnoresUntrustableExtension(t *testing.T) {
 	err = ft.checkFile(filepath.Join(".", "also_check_and_fail.srs"), mockParamInfo)
 	assert.Error(t, err)
 }
+
+func TestDoFetchBadStatusCode(t *testing.T) {
+	cases := []struct {
+		name string
+		code int
+	}{
+		{"BadRequest", http.StatusBadRequest},
+		{"Forbidden", http.StatusForbidden},
+		{"NotFound", http.StatusNotFound},
+		{"InternalServerError", http.StatusInternalServerError},
+		{"BadGateway", http.StatusBadGateway},
+		{"ServiceUnavailable", http.StatusServiceUnavailable},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(tc.code)
+			}))
+			defer ts.Close()
+
+			t.Setenv("IPFS_GATEWAY", ts.URL+"/ipfs/")
+
+			tmpDir := t.TempDir()
+			outPath := filepath.Join(tmpDir, "test-param-file")
+
+			info := paramFile{
+				Cid:    "QmFakeCid",
+				Digest: "0000000000000000",
+			}
+
+			err := doFetch(context.Background(), outPath, info)
+			require.Error(t, err)
+
+			errMsg := fmt.Sprintf("%v", err)
+			assert.True(t, strings.Contains(errMsg, fmt.Sprintf("%d", tc.code)),
+				"error should contain HTTP status code %d, got: %s", tc.code, errMsg)
+			assert.False(t, strings.Contains(errMsg, "checksum"),
+				"error should not mention checksum mismatch, got: %s", errMsg)
+		})
+	}
+}