Add --preservefds to podman run

Add --preservefds to podman run. close https://github.com/containers/libpod/issues/6458

Signed-off-by: Qi Wang <qiwan@redhat.com>

3 files changed, 40 insertions, 1 deletions

diff --git a/libpod/container.go b/libpod/container.go
index 20702903e..c85249676 100644
--- a/libpod/container.go
+++ b/libpod/container.go
@@ -418,6 +418,11 @@ type ContainerConfig struct {
 
 	// HealthCheckConfig has the health check command and related timings
 	HealthCheckConfig *manifest.Schema2HealthConfig `json:"healthcheck"`
+
+	// PreserveFDs is a number of additional file descriptors (in addition
+	// to 0, 1, 2) that will be passed to the executed process. The total FDs
+	// passed will be 3 + PreserveFDs.
+	PreserveFDs uint `json:"preserveFds,omitempty"`
 }
 
 // ContainerNamedVolume is a named volume that will be mounted into the
diff --git a/libpod/oci_conmon_linux.go b/libpod/oci_conmon_linux.go
index 625a5bf70..d8a89047e 100644
--- a/libpod/oci_conmon_linux.go
+++ b/libpod/oci_conmon_linux.go
@@ -904,6 +904,10 @@ func (r *ConmonOCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Co
 		}
 	}
 
+	if ctr.config.PreserveFDs > 0 {
+		args = append(args, formatRuntimeOpts("--preserve-fds", fmt.Sprintf("%d", ctr.config.PreserveFDs))...)
+	}
+
 	if restoreOptions != nil {
 		args = append(args, "--restore", ctr.CheckpointPath())
 		if restoreOptions.TCPEstablished {
@@ -935,8 +939,16 @@ func (r *ConmonOCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Co
 		return err
 	}
 
+	if ctr.config.PreserveFDs > 0 {
+		for fd := 3; fd < int(3+ctr.config.PreserveFDs); fd++ {
+			cmd.ExtraFiles = append(cmd.ExtraFiles, os.NewFile(uintptr(fd), fmt.Sprintf("fd-%d", fd)))
+		}
+	}
+
 	cmd.Env = r.conmonEnv
-	cmd.Env = append(cmd.Env, fmt.Sprintf("_OCI_SYNCPIPE=%d", 3), fmt.Sprintf("_OCI_STARTPIPE=%d", 4))
+	// we don't want to step on users fds they asked to preserve
+	// Since 0-2 are used for stdio, start the fds we pass in at preserveFDs+3
+	cmd.Env = append(cmd.Env, fmt.Sprintf("_OCI_SYNCPIPE=%d", ctr.config.PreserveFDs+3), fmt.Sprintf("_OCI_STARTPIPE=%d", ctr.config.PreserveFDs+4))
 	cmd.Env = append(cmd.Env, conmonEnv...)
 	cmd.ExtraFiles = append(cmd.ExtraFiles, childSyncPipe, childStartPipe)
 	cmd.ExtraFiles = append(cmd.ExtraFiles, envFiles...)
@@ -1018,6 +1030,16 @@ func (r *ConmonOCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Co
 		ctr.state.ConmonPID = conmonPID
 	}
 
+	if ctr.config.PreserveFDs > 0 {
+		for fd := 3; fd < int(3+ctr.config.PreserveFDs); fd++ {
+			// These fds were passed down to the runtime.  Close them
+			// and not interfere
+			if err := os.NewFile(uintptr(fd), fmt.Sprintf("fd-%d", fd)).Close(); err != nil {
+				logrus.Debugf("unable to close file fd-%d", fd)
+			}
+		}
+	}
+
 	return nil
 }
 
diff --git a/libpod/options.go b/libpod/options.go
index ffc9c1018..7a60870a0 100644
--- a/libpod/options.go
+++ b/libpod/options.go
@@ -1369,6 +1369,18 @@ func WithHealthCheck(healthCheck *manifest.Schema2HealthConfig) CtrCreateOption
 	}
 }
 
+// WithPreserveFDs forwards from the process running Libpod into the container
+// the given number of extra FDs (starting after the standard streams) to the created container
+func WithPreserveFDs(fd uint) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return define.ErrCtrFinalized
+		}
+		ctr.config.PreserveFDs = fd
+		return nil
+	}
+}
+
 // WithCreateCommand adds the full command plus arguments of the current
 // process to the container config.
 func WithCreateCommand() CtrCreateOption {