Definition of canonical is confusing

[zjkmxy]

The concept of canonical in YaNFD is confusing. For ethernetURI, fdURI, internalURI, nullURI, udpURI, canonical means well-formed:

YaNFD/ndn/uri.go

Lines 286 to 302 in 001755f

	case ethernetURI:
	isEthernet, _ := regexp.MatchString(macPattern, u.path)
	return u.scheme == "ether" && isEthernet && u.port == 0
	case fdURI:
	fd, err := strconv.Atoi(u.path)
	return u.scheme == "fd" && err == nil && fd >= 0 && u.port == 0
	case internalURI:
	return u.scheme == "internal" && u.path == "" && u.port == 0
	case nullURI:
	return u.scheme == "null" && u.path == "" && u.port == 0
	case udpURI:
	// Split off zone, if any
	ip := net.ParseIP(u.PathHost())
	// Port number is implicitly limited to <= 65535 by type uint16
	// We have to test whether To16() && not IPv4 because the Go net library considers IPv4 addresses to be valid IPv6 addresses
	isIPv4, _ := regexp.MatchString(ipv4Pattern, u.PathHost())
	return ip != nil && ((u.scheme == "udp4" && ip.To4() != nil) || (u.scheme == "udp6" && ip.To16() != nil && !isIPv4)) && u.port > 0

For devURI and unixURI, canonical means existing interface, which is related to specific machine and operation system:

YaNFD/ndn/uri.go

Lines 303 to 306 in 001755f

	case unixURI:
	// Check whether file exists
	fileInfo, err := os.Stat("/" + u.path)
	return u.scheme == "unix" && ((err == nil && !fileInfo.IsDir()) || os.IsNotExist(err)) && u.port == 0

This restricts that the unit test can be only executed on specific machines:

YaNFD/ndn/uri_test.go

Line 172 in 001755f

uri := ndn.MakeUnixFaceURI("/run/nfd.sock")

Not every machine allows building program access to this path.

Note: ndn-cxx does not check the physical existence of interface in isCanonical.

[eric135]

This concept was inherited from NFD/ndn-cxx. I'd recommend looking at what they did (and trying to stay compatible) :-)

[zjkmxy]

This concept was inherited from NFD/ndn-cxx. I'd recommend looking at what they did (and trying to stay compatible) :-)

ndn-cxx does not check physical existence of faces. For devURI, it always succeed if there is a path; for unixURI, ndn-cxx always fails (not supported).