net: Add getsockopt support for TCP thin-streams

Initial TCP thin-stream commit did not add getsockopt support for the new
socket options: TCP_THIN_LINEAR_TIMEOUTS and TCP_THIN_DUPACK. This adds support
for them.
Signed-off-by: Josh Hunt <johunt@akamai.com>
Tested-by: Andreas Petlund <apetlund@simula.no>
Acked-by: Andreas Petlund <apetlund@simula.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -2601,6 +2601,12 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 			return -EFAULT;
 		return 0;
 	}
+	case TCP_THIN_LINEAR_TIMEOUTS:
+		val = tp->thin_lto;
+		break;
+	case TCP_THIN_DUPACK:
+		val = tp->thin_dupack;
+		break;
 	default:
 		return -ENOPROTOOPT;
 	}