Handle hard links in remote builds

Fixes: https://github.com/containers/podman/issues/9893

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

3 files changed, 57 insertions, 12 deletions

diff --git a/pkg/bindings/images/build.go b/pkg/bindings/images/build.go
index f5e7c0c98..b56afbceb 100644
--- a/pkg/bindings/images/build.go
+++ b/pkg/bindings/images/build.go
@@ -28,6 +28,11 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+type devino struct {
+	Dev uint64
+	Ino uint64
+}
+
 var (
 	iidRegex = regexp.MustCompile(`^[0-9a-f]{12}`)
 )
@@ -402,7 +407,7 @@ func nTar(excludes []string, sources ...string) (io.ReadCloser, error) {
 		defer pw.Close()
 		defer gw.Close()
 		defer tw.Close()
-
+		seen := make(map[devino]string)
 		for _, src := range sources {
 			s, err := filepath.Abs(src)
 			if err != nil {
@@ -431,25 +436,40 @@ func nTar(excludes []string, sources ...string) (io.ReadCloser, error) {
 				}
 
 				if info.Mode().IsRegular() { // add file item
-					f, lerr := os.Open(path)
-					if lerr != nil {
-						return lerr
+					di, isHardLink := checkHardLink(info)
+					if err != nil {
+						return err
 					}
 
-					hdr, lerr := tar.FileInfoHeader(info, name)
-					if lerr != nil {
-						f.Close()
-						return lerr
+					hdr, err := tar.FileInfoHeader(info, "")
+					if err != nil {
+						return err
+					}
+					orig, ok := seen[di]
+					if ok {
+						hdr.Typeflag = tar.TypeLink
+						hdr.Linkname = orig
+						hdr.Size = 0
+
+						return tw.WriteHeader(hdr)
+					}
+					f, err := os.Open(path)
+					if err != nil {
+						return err
 					}
+
 					hdr.Name = name
-					if lerr := tw.WriteHeader(hdr); lerr != nil {
+					if err := tw.WriteHeader(hdr); err != nil {
 						f.Close()
-						return lerr
+						return err
 					}
 
-					_, cerr := io.Copy(tw, f)
+					_, err = io.Copy(tw, f)
 					f.Close()
-					return cerr
+					if err == nil && isHardLink {
+						seen[di] = name
+					}
+					return err
 				} else if info.Mode().IsDir() { // add folders
 					hdr, lerr := tar.FileInfoHeader(info, name)
 					if lerr != nil {
diff --git a/pkg/bindings/images/build_unix.go b/pkg/bindings/images/build_unix.go
new file mode 100644
index 000000000..0afb1deb6
--- /dev/null
+++ b/pkg/bindings/images/build_unix.go
@@ -0,0 +1,16 @@
+// +build !windows
+
+package images
+
+import (
+	"os"
+	"syscall"
+)
+
+func checkHardLink(fi os.FileInfo) (devino, bool) {
+	st := fi.Sys().(*syscall.Stat_t)
+	return devino{
+		Dev: uint64(st.Dev),
+		Ino: uint64(st.Ino),
+	}, st.Nlink > 1
+}
diff --git a/pkg/bindings/images/build_windows.go b/pkg/bindings/images/build_windows.go
new file mode 100644
index 000000000..bd71d1bf0
--- /dev/null
+++ b/pkg/bindings/images/build_windows.go
@@ -0,0 +1,9 @@
+package images
+
+import (
+	"os"
+)
+
+func checkHardLink(fi os.FileInfo) (devino, bool) {
+	return devino{}, false
+}