support supplementary groups

Add two new descriptors:
* `groups` for supplementary groups inside the container
* `hgroups` for the counterpart on the host

Example:

```
podman (main) $ ./bin/podman top -l pid,hpid,group,hgroup,groups,hgroups
PID         HPID        GROUP       HGROUP      GROUPS                                                        HGROUPS
1           92536       root        1000        root,bin,daemon,sys,adm,disk,wheel,floppy,dialout,tape,video  1000,100000,100001,100002,100003,100005,100009,100010,100019,100025,100026
```

Closes: #87
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

README.md

@@ -73,8 +73,12 @@ The ps library is compatible with all AIX format descriptors of the ps command-l
   - Set of inheritable capabilities. See capabilities(7) for more information.
 - **capprm**
   - Set of permitted capabilities. See capabilities(7) for more information.
+- **groups**
+  - Supplmentary groups inside the container.
 - **hgroup**
   - The corresponding effective group of a container process on the host.
+- **hgroups**
+  - Supplmentary groups on the host.
 - **hpid**
   - The corresponding host PID of a container process.
 - **huser**

psgo.go

@@ -174,6 +174,11 @@ var (
 			header: "GROUP",
 			procFn: processGROUP,
 		},
+		{
+			normal: "groups",
+			header: "GROUPS",
+			procFn: processGROUPS,
+		},
 		{
 			code:   "%P",
 			normal: "ppid",
@@ -305,6 +310,12 @@ var (
 			onHost: true,
 			procFn: processHGROUP,
 		},
+		{
+			normal: "hgroups",
+			header: "HGROUPS",
+			onHost: true,
+			procFn: processHGROUPS,
+		},
 		{
 			normal: "rss",
 			header: "RSS",
@@ -626,6 +637,21 @@ func processGROUP(p *process.Process, ctx *psContext) (string, error) {
 	return process.LookupGID(p.Status.Gids[1])
 }
 
+// processGROUPS returns the supplementary groups of the process separated by
+// comma. This will be the textual group ID, if it can be obtained, or a
+// decimal representation otherwise.
+func processGROUPS(p *process.Process, ctx *psContext) (string, error) {
+	var err error
+	groups := make([]string, len(p.Status.Groups))
+	for i, g := range p.Status.Groups {
+		groups[i], err = process.LookupGID(g)
+		if err != nil {
+			return "", err
+		}
+	}
+	return strings.Join(groups, ","), nil
+}
+
 // processRGROUP returns the real group ID of the process.  This will be
 // the textual group ID, if it can be obtained, or a decimal representation
 // otherwise.
@@ -867,6 +893,26 @@ func processHGROUP(p *process.Process, ctx *psContext) (string, error) {
 	return "?", nil
 }
 
+// processHGROUPS returns the supplementary groups of the corresponding host
+// process of the (container) or "?" if no corresponding process could be
+// found.
+func processHGROUPS(p *process.Process, ctx *psContext) (string, error) {
+	if hp := findHostProcess(p, ctx); hp != nil {
+		groups := hp.Status.Groups
+		if ctx.opts != nil && len(ctx.opts.GIDMap) > 0 {
+			var err error
+			for i, g := range groups {
+				groups[i], err = findID(g, ctx.opts.GIDMap, process.LookupGID, "/proc/sys/fs/overflowgid")
+				if err != nil {
+					return "", err
+				}
+			}
+		}
+		return strings.Join(groups, ","), nil
+	}
+	return "?", nil
+}
+
 // processRSS returns the resident set size of process p in KiB (1024-byte
 // units).
 func processRSS(p *process.Process, ctx *psContext) (string, error) {

test/format.bats

@@ -33,6 +33,12 @@
 	[[ ${lines[0]} =~ "GROUP" ]]
 }
 
+@test "GROUPS header" {
+	run ./bin/psgo -format "groups"
+	[ "$status" -eq 0 ]
+	[[ ${lines[0]} =~ "GROUPS" ]]
+}
+
 @test "PPID header" {
 	run ./bin/psgo -format "%P"
 	[ "$status" -eq 0 ]
@@ -213,6 +219,15 @@
 	[[ ${lines[1]} =~ "?" ]]
 }
 
+@test "HGROUPS header" {
+	run ./bin/psgo -format "hgroups"
+	[ "$status" -eq 0 ]
+	[[ ${lines[0]} =~ "HGROUPS" ]]
+	# host groups are only extracted with `-pid`
+	[[ ${lines[1]} =~ "?" ]]
+}
+
+
 function is_labeling_enabled() {
 	if [ -e /usr/sbin/selinuxenabled ] && /usr/sbin/selinuxenabled; then
 			echo 1
@@ -250,11 +265,12 @@ function is_labeling_enabled() {
 }
 
 @test "ALL header" {
-	run ./bin/psgo -format "pcpu, group, ppid, user, args, comm, rgroup, nice, pid, pgid, etime, ruser, time, tty, vsz, capamb, capinh, capprm, capeff, capbnd, seccomp, hpid, huser, hgroup, rss, state"
+	run ./bin/psgo -format "pcpu, group, groups, ppid, user, args, comm, rgroup, nice, pid, pgid, etime, ruser, time, tty, vsz, capamb, capinh, capprm, capeff, capbnd, seccomp, hpid, huser, hgroup, hgroups, rss, state"
 	[ "$status" -eq 0 ]
 
 	[[ ${lines[0]} =~ "%CPU" ]]
 	[[ ${lines[0]} =~ "GROUP" ]]
+	[[ ${lines[0]} =~ "GROUPS" ]]
 	[[ ${lines[0]} =~ "PPID" ]]
 	[[ ${lines[0]} =~ "USER" ]]
 	[[ ${lines[0]} =~ "COMMAND" ]]
@@ -276,6 +292,7 @@ function is_labeling_enabled() {
 	[[ ${lines[0]} =~ "HPID" ]]
 	[[ ${lines[0]} =~ "HUSER" ]]
 	[[ ${lines[0]} =~ "HGROUP" ]]
+	[[ ${lines[0]} =~ "HGROUPS" ]]
 	[[ ${lines[0]} =~ "RSS" ]]
 	[[ ${lines[0]} =~ "STATE" ]]
 }

test/list.bats

@@ -3,5 +3,5 @@
 @test "List descriptors" {
 	run ./bin/psgo -list
 	[ "$status" -eq 0 ]
-	[[ ${lines[0]} =~ "args, capamb, capbnd, capeff, capinh, capprm, comm, etime, group, hgroup, hpid, huser, label, nice, pcpu, pgid, pid, ppid, rgroup, rss, ruser, seccomp, state, stime, time, tty, user, vsz" ]]
+	[[ ${lines[0]} =~ "args, capamb, capbnd, capeff, capinh, capprm, comm, etime, group, groups, hgroup, hgroups, hpid, huser, label, nice, pcpu, pgid, pid, ppid, rgroup, rss, ruser, seccomp, state, stime, time, tty, user, vsz" ]]
 }