Add support for SCMP_FLTATR_CTL_WAITKILL

Introduce (*ScmpFilter).GetWaitKill and (*ScmpFilter).SetWaitKill
methods, together with the documentation and trivial tests.

The functionality appears in libseccomp v2.6.0 and requires API Level 7.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

seccomp.go

@@ -961,6 +961,25 @@ func (f *ScmpFilter) GetRawRC() (bool, error) {
 	return true, nil
 }
 
+// GetWaitKill returns the current state of WaitKill flag,
+// or an error if an issue was encountered retrieving the value.
+// See SetWaitKill for more details.
+func (f *ScmpFilter) GetWaitKill() (bool, error) {
+	val, err := f.getFilterAttr(filterAttrWaitKill)
+	if err != nil {
+		if e := checkAPI("GetWaitKill", 7, 2, 6, 0); e != nil {
+			err = e
+		}
+
+		return false, err
+	}
+	if val == 0 {
+		return false, nil
+	}
+
+	return true, nil
+}
+
 // SetBadArchAction sets the default action taken on a syscall for an
 // architecture not in the filter, or an error if an issue was encountered
 // setting the value.
@@ -1073,6 +1092,25 @@ func (f *ScmpFilter) SetRawRC(state bool) error {
 	return err
 }
 
+// SetWaitKill sets whether libseccomp should request wait killable semantics
+// when possible. Defaults to false.
+func (f *ScmpFilter) SetWaitKill(state bool) error {
+	var toSet C.uint32_t = 0x0
+
+	if state {
+		toSet = 0x1
+	}
+
+	err := f.setFilterAttr(filterAttrWaitKill, toSet)
+	if err != nil {
+		if e := checkAPI("SetWaitKill", 7, 2, 6, 0); e != nil {
+			err = e
+		}
+	}
+
+	return err
+}
+
 // SetSyscallPriority sets a syscall's priority.
 // This provides a hint to the filter generator in libseccomp about the
 // importance of this syscall. High-priority syscalls are placed

seccomp_internal.go

@@ -148,6 +148,11 @@ const uint32_t C_ACT_NOTIFY        = SCMP_ACT_NOTIFY;
 #define SCMP_FLTATR_API_SYSRAWRC _SCMP_FLTATR_MIN
 #endif
 
+// Added in libseccomp v2.6.0.
+#if SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR < 6
+#define SCMP_FLTATR_CTL_WAITKILL _SCMP_FLTATR_MIN
+#endif
+
 const uint32_t C_ATTRIBUTE_DEFAULT  = (uint32_t)SCMP_FLTATR_ACT_DEFAULT;
 const uint32_t C_ATTRIBUTE_BADARCH  = (uint32_t)SCMP_FLTATR_ACT_BADARCH;
 const uint32_t C_ATTRIBUTE_NNP      = (uint32_t)SCMP_FLTATR_CTL_NNP;
@@ -156,6 +161,7 @@ const uint32_t C_ATTRIBUTE_LOG      = (uint32_t)SCMP_FLTATR_CTL_LOG;
 const uint32_t C_ATTRIBUTE_SSB      = (uint32_t)SCMP_FLTATR_CTL_SSB;
 const uint32_t C_ATTRIBUTE_OPTIMIZE = (uint32_t)SCMP_FLTATR_CTL_OPTIMIZE;
 const uint32_t C_ATTRIBUTE_SYSRAWRC = (uint32_t)SCMP_FLTATR_API_SYSRAWRC;
+const uint32_t C_ATTRIBUTE_WAITKILL = (uint32_t)SCMP_FLTATR_CTL_WAITKILL;
 
 const int      C_CMP_NE            = (int)SCMP_CMP_NE;
 const int      C_CMP_LT            = (int)SCMP_CMP_LT;
@@ -283,6 +289,7 @@ const (
 	filterAttrSSB
 	filterAttrOptimize
 	filterAttrRawRC
+	filterAttrWaitKill
 )
 
 const (
@@ -709,6 +716,8 @@ func (a scmpFilterAttr) toNative() uint32 {
 		return uint32(C.C_ATTRIBUTE_OPTIMIZE)
 	case filterAttrRawRC:
 		return uint32(C.C_ATTRIBUTE_SYSRAWRC)
+	case filterAttrWaitKill:
+		return uint32(C.C_ATTRIBUTE_WAITKILL)
 	default:
 		return 0x0
 	}

seccomp_test.go

@@ -503,6 +503,24 @@ func TestFilterAttributeGettersAndSetters(t *testing.T) {
 	} else if rawrc != true {
 		t.Error("RawRC flag was not set correctly")
 	}
+
+	// Checks that require API level >= 7 and libseccomp >= 2.6.0.
+	if err := checkAPI(t.Name(), 7, 2, 6, 0); err != nil {
+		t.Logf("Skipping the rest of the test: %v", err)
+		return
+	}
+
+	err = filter.SetWaitKill(true)
+	if err != nil {
+		t.Errorf("Error setting WaitKill flag: %v", err)
+	}
+
+	wk, err := filter.GetWaitKill()
+	if err != nil {
+		t.Errorf("Error getting WaitKill flag: %v", err)
+	} else if wk != true {
+		t.Error("WaitKill flag was not set correctly")
+	}
 }
 
 func TestMergeFilters(t *testing.T) {