libpod: Move openUnixSocket to oci_conmon_attach_linux.go

This function depends on linux-specific functionality in /proc/fd to
allow connecting to local domain sockets with pathnames too long for
sockaddr_un.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

libpod/oci_conmon_attach_common.go

@@ -29,15 +29,6 @@ const (
 	AttachPipeStderr = 3
 )
 
-func openUnixSocket(path string) (*net.UnixConn, error) {
-	fd, err := unix.Open(path, unix.O_PATH, 0)
-	if err != nil {
-		return nil, err
-	}
-	defer unix.Close(fd)
-	return net.DialUnix("unixpacket", nil, &net.UnixAddr{Name: fmt.Sprintf("/proc/self/fd/%d", fd), Net: "unixpacket"})
-}
-
 // Attach to the given container.
 // Does not check if state is appropriate.
 // started is only required if startContainer is true.

libpod/oci_conmon_attach_linux.go

@@ -0,0 +1,17 @@
+package libpod
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+func openUnixSocket(path string) (*net.UnixConn, error) {
+	fd, err := unix.Open(path, unix.O_PATH, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer unix.Close(fd)
+	return net.DialUnix("unixpacket", nil, &net.UnixAddr{Name: fmt.Sprintf("/proc/self/fd/%d", fd), Net: "unixpacket"})
+}