internal/netlink: export generic connection

This enables abstractions around some families to be implemented in a separate package.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/netlink/rtnl_test.go

@@ -9,7 +9,7 @@ func TestPayloadRTNETLINK(t *testing.T) {
 	t.Parallel()
 
 	checkPayload(t, []payloadTestCase{
-		{"RTM_NEWADDR lo", func(c *conn) {
+		{"RTM_NEWADDR lo", func(c *Conn) {
 			(&RouteConn{c}).writeNewaddrLo(1)
 		}, []byte{
 			/* Len   */ 0x28, 0, 0, 0,
@@ -33,7 +33,7 @@ func TestPayloadRTNETLINK(t *testing.T) {
 			/* in_addr */ 127, 0, 0, 1,
 		}},
 
-		{"RTM_NEWLINK", func(c *conn) {
+		{"RTM_NEWLINK", func(c *Conn) {
 			c.seq++
 			(&RouteConn{c}).writeIfInfomsg(
 				syscall.RTM_NEWLINK, 0,