Set SOCK_CLOEXEC on netlink socket (#165)

Set `SOCK_CLOEXEC` when creating the socket to avoid leaking file
descriptors.

Signed-off-by: Noel Georgi <git@frezbo.dev>

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - Fix panic in `parseSockaddr` for malformed socket address. [#152](https://github.com/elastic/go-libaudit/pull/152)
+- Set `SOCK_CLOEXEC` when creating the netlink socket to avoid leaking file descriptors. [#165](https://github.com/elastic/go-libaudit/pull/165)
 
 ### Removed
 

netlink.go

@@ -77,7 +77,7 @@ type NetlinkClient struct {
 //
 // The returned NetlinkClient must be closed with Close() when finished.
 func NewNetlinkClient(proto int, groups uint32, readBuf []byte, resp io.Writer) (*NetlinkClient, error) {
-	s, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW, proto)
+	s, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW|syscall.SOCK_CLOEXEC, proto)
 	if err != nil {
 		return nil, err
 	}