deps: switch to moby/sys/capability

github.com/moby/sys/capability is a fork of the (no longer maintained)
github.com/syndtr/gocapability package.

For changes since the fork took place, see
https://github.com/moby/sys/blob/main/capability/CHANGELOG.md

Note that the "workaround for RHEL6" is removed for a number of reasons.
Feel free to choose the one you like the most, either is sufficient:

1. /proc/sys/kernel/cap_last_cap is available since RHEL 6.7
   (kernel 2.6.32-573.el6), released 9 years ago (2015-07-22).

2. It incorrectly returns CAP_BLOCK_SUSPEND (36), which was only added
   in kernel v3.5 and was never backported to RHEL6 kernels. The
   correct value for RHEL6 would be CAP_MAC_ADMIN (33).

3. As far as upstream kernels go, /proc/sys/kernel/cap_last_cap was
   added in kernel v3.2, and a correct value depends on the kernel
   version. It could be CAP_WAKE_ALARM (35), added to kernel v3.0, or
   CAP_SYSLOG (34), added to kernel v2.6.38, or possibly a lesser value
   for even older kernels.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

drivers/shared/capabilities/defaults.go

@@ -7,7 +7,7 @@ import (
 	"fmt"
 	"regexp"
 
-	"github.com/syndtr/gocapability/capability"
+	"github.com/moby/sys/capability"
 )
 
 const (
@@ -40,18 +40,9 @@ func NomadDefaults() *Set {
 func Supported() *Set {
 	s := New(nil)
 
-	last := capability.CAP_LAST_CAP
-
-	// workaround for RHEL6 which has no /proc/sys/kernel/cap_last_cap
-	if last == capability.Cap(63) {
-		last = capability.CAP_BLOCK_SUSPEND
-	}
-
+	list, _ := capability.ListSupported()
 	// accumulate every capability supported by this system
-	for _, c := range capability.List() {
-		if c > last {
-			continue
-		}
+	for _, c := range list {
 		s.Add(c.String())
 	}
 

drivers/shared/executor/executor.go

@@ -27,7 +27,7 @@ import (
 	cstructs "github.com/hashicorp/nomad/client/structs"
 	"github.com/hashicorp/nomad/drivers/shared/executor/procstats"
 	"github.com/hashicorp/nomad/plugins/drivers"
-	"github.com/syndtr/gocapability/capability"
+	"github.com/moby/sys/capability"
 )
 
 const (
@@ -778,15 +778,8 @@ func makeExecutable(binPath string) error {
 // SupportedCaps returns a list of all supported capabilities in kernel.
 func SupportedCaps(allowNetRaw bool) []string {
 	var allCaps []string
-	last := capability.CAP_LAST_CAP
-	// workaround for RHEL6 which has no /proc/sys/kernel/cap_last_cap
-	if last == capability.Cap(63) {
-		last = capability.CAP_BLOCK_SUSPEND
-	}
-	for _, cap := range capability.List() {
-		if cap > last {
-			continue
-		}
+	list, _ := capability.ListSupported()
+	for _, cap := range list {
 		if !allowNetRaw && cap == capability.CAP_NET_RAW {
 			continue
 		}

go.mod

@@ -105,6 +105,7 @@ require (
 	github.com/mitchellh/mapstructure v1.5.0
 	github.com/mitchellh/pointerstructure v1.2.1
 	github.com/mitchellh/reflectwalk v1.0.2
+	github.com/moby/sys/capability v0.3.0
 	github.com/moby/sys/mount v0.3.3
 	github.com/moby/sys/mountinfo v0.7.1
 	github.com/moby/term v0.5.0
@@ -123,7 +124,6 @@ require (
 	github.com/shoenig/go-m1cpu v0.1.6
 	github.com/shoenig/test v1.11.0
 	github.com/stretchr/testify v1.9.0
-	github.com/syndtr/gocapability v0.0.0-20200815063812-42c35b437635
 	github.com/zclconf/go-cty v1.13.0
 	github.com/zclconf/go-cty-yaml v1.0.3
 	go.etcd.io/bbolt v1.3.9
@@ -277,6 +277,7 @@ require (
 	github.com/softlayer/softlayer-go v0.0.0-20180806151055-260589d94c7d // indirect
 	github.com/spf13/cast v1.5.0 // indirect
 	github.com/stretchr/objx v0.5.2 // indirect
+	github.com/syndtr/gocapability v0.0.0-20200815063812-42c35b437635 // indirect
 	github.com/tencentcloud/tencentcloud-sdk-go v1.0.162 // indirect
 	github.com/tj/go-spin v1.1.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect

go.sum

@@ -901,6 +901,8 @@ github.com/mitchellh/reflectwalk v1.0.2 h1:G2LzWKi524PWgd3mLHV8Y5k7s6XUvT0Gef6zx
 github.com/mitchellh/reflectwalk v1.0.2/go.mod h1:mSTlrgnPZtwu0c4WaC2kGObEpuNDbx0jmZXqmk4esnw=
 github.com/moby/docker-image-spec v1.3.1 h1:jMKff3w6PgbfSa69GfNg+zN/XLhfXJGnEx3Nl2EsFP0=
 github.com/moby/docker-image-spec v1.3.1/go.mod h1:eKmb5VW8vQEh/BAr2yvVNvuiJuY6UIocYsFu/DxxRpo=
+github.com/moby/sys/capability v0.3.0 h1:kEP+y6te0gEXIaeQhIi0s7vKs/w0RPoH1qPa6jROcVg=
+github.com/moby/sys/capability v0.3.0/go.mod h1:4g9IK291rVkms3LKCDOoYlnV8xKwoDTpIrNEE35Wq0I=
 github.com/moby/sys/mount v0.3.3 h1:fX1SVkXFJ47XWDoeFW4Sq7PdQJnV2QIDZAqjNqgEjUs=
 github.com/moby/sys/mount v0.3.3/go.mod h1:PBaEorSNTLG5t/+4EgukEQVlAvVEc6ZjTySwKdqp5K0=
 github.com/moby/sys/mountinfo v0.6.2/go.mod h1:IJb6JQeOklcdMU9F5xQ8ZALD+CUr5VlGpwtX+VE0rpI=