rootless: support joining containers that use host ns

pkg/specgen/generate/namespaces.go

@@ -136,7 +136,13 @@ func namespaceOptions(s *specgen.SpecGenerator, rt *libpod.Runtime, pod *libpod.
 		if err != nil {
 			return nil, fmt.Errorf("looking up container to share pid namespace with: %w", err)
 		}
-		toReturn = append(toReturn, libpod.WithPIDNSFrom(pidCtr))
+		if rootless.IsRootless() && pidCtr.NamespaceMode(spec.PIDNamespace, pidCtr.ConfigNoCopy().Spec) == host {
+			// Treat this the same as host, the problem is the runtime tries to do a
+			// setns call and this will fail when it is the host ns as rootless user.
+			s.PidNS.NSMode = specgen.Host
+		} else {
+			toReturn = append(toReturn, libpod.WithPIDNSFrom(pidCtr))
+		}
 	}
 
 	// IPC
@@ -158,9 +164,16 @@ func namespaceOptions(s *specgen.SpecGenerator, rt *libpod.Runtime, pod *libpod.
 		if ipcCtr.ConfigNoCopy().NoShmShare {
 			return nil, fmt.Errorf("joining IPC of container %s is not allowed: non-shareable IPC (hint: use IpcMode:shareable for the donor container)", ipcCtr.ID())
 		}
-		toReturn = append(toReturn, libpod.WithIPCNSFrom(ipcCtr))
-		if !ipcCtr.ConfigNoCopy().NoShm {
-			toReturn = append(toReturn, libpod.WithShmDir(ipcCtr.ShmDir()))
+		if rootless.IsRootless() && ipcCtr.NamespaceMode(spec.IPCNamespace, ipcCtr.ConfigNoCopy().Spec) == host {
+			// Treat this the same as host, the problem is the runtime tries to do a
+			// setns call and this will fail when it is the host ns as rootless user.
+			s.IpcNS.NSMode = specgen.Host
+			toReturn = append(toReturn, libpod.WithShmDir("/dev/shm"))
+		} else {
+			toReturn = append(toReturn, libpod.WithIPCNSFrom(ipcCtr))
+			if !ipcCtr.ConfigNoCopy().NoShm {
+				toReturn = append(toReturn, libpod.WithShmDir(ipcCtr.ShmDir()))
+			}
 		}
 	case specgen.None:
 		toReturn = append(toReturn, libpod.WithNoShm(true))
@@ -187,7 +200,13 @@ func namespaceOptions(s *specgen.SpecGenerator, rt *libpod.Runtime, pod *libpod.
 		if err != nil {
 			return nil, fmt.Errorf("looking up container to share uts namespace with: %w", err)
 		}
-		toReturn = append(toReturn, libpod.WithUTSNSFrom(utsCtr))
+		if rootless.IsRootless() && utsCtr.NamespaceMode(spec.UTSNamespace, utsCtr.ConfigNoCopy().Spec) == host {
+			// Treat this the same as host, the problem is the runtime tries to do a
+			// setns call and this will fail when it is the host ns as rootless user.
+			s.UtsNS.NSMode = specgen.Host
+		} else {
+			toReturn = append(toReturn, libpod.WithUTSNSFrom(utsCtr))
+		}
 	}
 
 	// User
@@ -257,7 +276,13 @@ func namespaceOptions(s *specgen.SpecGenerator, rt *libpod.Runtime, pod *libpod.
 		if err != nil {
 			return nil, fmt.Errorf("looking up container to share cgroup namespace with: %w", err)
 		}
-		toReturn = append(toReturn, libpod.WithCgroupNSFrom(cgroupCtr))
+		if rootless.IsRootless() && cgroupCtr.NamespaceMode(spec.CgroupNamespace, cgroupCtr.ConfigNoCopy().Spec) == host {
+			// Treat this the same as host, the problem is the runtime tries to do a
+			// setns call and this will fail when it is the host ns as rootless user.
+			s.CgroupNS.NSMode = specgen.Host
+		} else {
+			toReturn = append(toReturn, libpod.WithCgroupNSFrom(cgroupCtr))
+		}
 	}
 
 	if s.CgroupParent != "" {
@@ -285,7 +310,13 @@ func namespaceOptions(s *specgen.SpecGenerator, rt *libpod.Runtime, pod *libpod.
 		if err != nil {
 			return nil, fmt.Errorf("looking up container to share net namespace with: %w", err)
 		}
-		toReturn = append(toReturn, libpod.WithNetNSFrom(netCtr))
+		if rootless.IsRootless() && netCtr.NamespaceMode(spec.NetworkNamespace, netCtr.ConfigNoCopy().Spec) == host {
+			// Treat this the same as host, the problem is the runtime tries to do a
+			// setns call and this will fail when it is the host ns as rootless user.
+			s.NetNS.NSMode = specgen.Host
+		} else {
+			toReturn = append(toReturn, libpod.WithNetNSFrom(netCtr))
+		}
 	case specgen.Slirp:
 		portMappings, expose, err := createPortMappings(s, imageData)
 		if err != nil {

test/system/195-run-namesapces.bats

@@ -0,0 +1,52 @@
+#!/usr/bin/env bats   -*- bats -*-
+#
+# Tests for the namespace options
+#
+
+load helpers
+
+@test "podman test all namespaces" {
+    # format is nsname | option name
+    tests="
+cgroup | cgroupns
+ipc    | ipc
+net    | network
+pid    | pid
+uts    | uts
+"
+
+    for nstype in private host; do
+        while read name option; do
+            local cname="c_${name}_$(random_string)"
+            # ipc is special, private does not allow joining from another container.
+            # Instead we must use "shareable".
+            local type=$nstype
+            if [ "$name" = "ipc" ] && [ "$type" = "private" ]; then
+                type="shareable"
+            fi
+
+            run_podman run --name $cname --$option $type -d $IMAGE sh -c \
+                "readlink /proc/self/ns/$name; sleep inf"
+
+            run_podman run --rm --$option container:$cname $IMAGE readlink /proc/self/ns/$name
+            con2_ns="$output"
+
+            run readlink /proc/self/ns/$name
+            host_ns="$output"
+
+            run_podman logs $cname
+            con1_ns="$output"
+
+            assert "$con1_ns" == "$con2_ns" "($name) namespace matches (type: $type)"
+            local matcher="=="
+            if [[ "$type" != "host" ]]; then
+                matcher="!="
+            fi
+            assert "$con1_ns" $matcher "$host_ns" "expected host namespace to ($matcher) (type: $type)"
+
+            run_podman rm -f -t0 $cname
+        done < <(parse_table "$tests")
+    done
+}
+
+# vim: filetype=sh