bacnet_encoding/npdu/
decode_error.rs

1//! Why [`decode_npdu`](super::decode_npdu) refused an NPDU.
2
3use core::fmt;
4
5use bacnet_npdu::{AddressField, MAX_MAC_LEN, Malformed};
6use bacnet_types::error::{DecodeError, DecodingKind, Error, RangeError};
7
8use super::NpduAddress;
9
10/// Why [`decode_npdu`](super::decode_npdu) refused an NPDU: `bacnet-npdu`'s
11/// [`DecodeError`](bacnet_npdu::DecodeError), with the source behind an
12/// over-long DADR owned.
13#[derive(Debug, Clone, PartialEq, Eq)]
14pub enum NpduDecodeError {
15    /// The DLEN or SLEN octet is larger than [`MAX_MAC_LEN`] (#1141), so the
16    /// address names no node on a standard data link or on one this stack
17    /// serves.
18    ///
19    /// Clause 6.4.4 gives routers Reject-Message-To-Network reason 6
20    /// (`ADDRESSING_ERROR`) for an NPDU whose DADR or SADR length is invalid.
21    /// [`dnet`](Self::AddressTooLong::dnet) is the network the reject names,
22    /// and [`source`](Self::AddressTooLong::source) is where it goes when a
23    /// router relayed the refused NPDU (#1158).
24    AddressTooLong {
25        /// Which address the length octet introduces.
26        field: AddressField,
27        /// The DLEN or SLEN octet as received.
28        length: u8,
29        /// The NPDU's DNET, when its control octet announces one. It precedes
30        /// both length octets on the wire, so it is always known here.
31        dnet: Option<u16>,
32        /// The NPDU's SNET/SADR, when the over-long field is the DADR and a
33        /// complete, valid source follows the DLEN octets the frame announces.
34        /// It is `None` when the SADR itself is the over-long field, since
35        /// that source names no node.
36        source: Option<NpduAddress>,
37    },
38    /// Any other malformation: a short buffer, an unknown protocol version, a
39    /// reserved network number, SLEN 0, or a truncated address or field.
40    Malformed(Malformed),
41}
42
43impl fmt::Display for NpduDecodeError {
44    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
45        match self {
46            Self::AddressTooLong { field, length, .. } => write!(
47                f,
48                "NPDU {}={length} exceeds the {MAX_MAC_LEN}-octet address limit",
49                field.length_octet(),
50            ),
51            Self::Malformed(fault) => fault.fmt(f),
52        }
53    }
54}
55
56impl core::error::Error for NpduDecodeError {}
57
58impl From<NpduDecodeError> for Error {
59    /// An over-long address becomes [`Error::Range`]: the length octet is
60    /// well formed, but its value is past the limit. Its text is the
61    /// refusal's own. Any other fault becomes [`Error::Decoding`], with the
62    /// fault's text: [`DecodingKind::Missing`] for a frame that ends inside
63    /// a field, [`DecodingKind::InvalidEncoding`] for the rest. Neither
64    /// knows the offset, so it reads 0.
65    fn from(error: NpduDecodeError) -> Self {
66        match error {
67            NpduDecodeError::AddressTooLong { field, length, .. } => {
68                let label = match field {
69                    AddressField::Destination => "NPDU DLEN={} exceeds the {}-octet address limit",
70                    AddressField::Source => "NPDU SLEN={} exceeds the {}-octet address limit",
71                };
72                RangeError::new(label)
73                    .with_values(length.into(), MAX_MAC_LEN as u64)
74                    .into()
75            }
76            NpduDecodeError::Malformed(fault) => {
77                let (kind, label) = match fault {
78                    Malformed::Truncated => (DecodingKind::Missing, "NPDU truncated"),
79                    Malformed::Version => (
80                        DecodingKind::InvalidEncoding,
81                        "unsupported BACnet protocol version",
82                    ),
83                    Malformed::ReservedNetwork => (
84                        DecodingKind::InvalidEncoding,
85                        "NPDU names a reserved network number",
86                    ),
87                    Malformed::EmptySource => (
88                        DecodingKind::InvalidEncoding,
89                        "NPDU source SLEN=0 is invalid",
90                    ),
91                    // A fault a later bacnet-npdu adds.
92                    _ => (DecodingKind::InvalidEncoding, "NPDU malformed"),
93                };
94                Error::Decoding(DecodeError::new(kind, 0, label))
95            }
96        }
97    }
98}
bacnet_encoding/npdu/decode_error.rs

bacnet_encoding/npdu/
decode_error.rs
