Use thiserror Errors instead of relying on anyhow

This improves matching on particular errors when we need to handle
different conditions downstream.

It's still possible to convert a anyhow::Error to a DecodeError in this
change, but every other error this crate expsoes is now in a variant.

src/errors.rs

@@ -32,29 +32,53 @@ impl From<anyhow::Error> for EncodeError {
 }
 
 #[derive(Debug, Error)]
-#[error("Decode error occurred: {inner}")]
-pub struct DecodeError {
-    inner: anyhow::Error,
+pub enum DecodeError {
+    #[error("Invalid MAC address")]
+    InvalidMACAddress,
+
+    #[error("Invalid IPv6 address")]
+    InvalidIPv6Address,
+
+    #[error("Invalid string")]
+    Utf8Error(#[from] std::string::FromUtf8Error),
+
+    #[error("Invalid u8")]
+    InvalidU8,
+
+    #[error("Invalid u16")]
+    InvalidU16,
+
+    #[error("Invalid u32")]
+    InvalidU32,
+
+    #[error("Invalid u64")]
+    InvalidU64,
+
+    #[error("Invalid u128")]
+    InvalidU128,
+
+    #[error("Invalid i32")]
+    InvalidI32,
+
+    #[error("Invalid {name}: length {len} < {buffer_len}")]
+    InvalidBufferLength {
+        name: &'static str,
+        len: usize,
+        buffer_len: usize,
+    },
+
+    #[error(transparent)]
+    Other(#[from] anyhow::Error),
 }
 
 impl From<&'static str> for DecodeError {
     fn from(msg: &'static str) -> Self {
-        DecodeError {
-            inner: anyhow!(msg),
-        }
+        DecodeError::Other(anyhow!(msg))
     }
 }
 
 impl From<String> for DecodeError {
     fn from(msg: String) -> Self {
-        DecodeError {
-            inner: anyhow!(msg),
-        }
-    }
-}
-
-impl From<anyhow::Error> for DecodeError {
-    fn from(inner: anyhow::Error) -> DecodeError {
-        DecodeError { inner }
+        DecodeError::Other(anyhow!(msg))
     }
 }

src/macros.rs

@@ -192,15 +192,11 @@ macro_rules! buffer_check_length {
             fn check_buffer_length(&self) -> Result<(), DecodeError> {
                 let len = self.buffer.as_ref().len();
                 if len < $buffer_len {
-                    Err(format!(
-                        concat!(
-                            "invalid ",
-                            stringify!($name),
-                            ": length {} < {}"
-                        ),
-                        len, $buffer_len
-                    )
-                    .into())
+                    Err(DecodeError::InvalidBufferLength {
+                        name: stringify!($name),
+                        len,
+                        buffer_len: $buffer_len,
+                    })
                 } else {
                     Ok(())
                 }

src/nla.rs

@@ -1,14 +1,12 @@
 // SPDX-License-Identifier: MIT
 
-use core::ops::Range;
-
-use anyhow::Context;
-use byteorder::{ByteOrder, NativeEndian};
-
 use crate::{
     traits::{Emitable, Parseable},
     DecodeError,
 };
+use byteorder::{ByteOrder, NativeEndian};
+use core::ops::Range;
+use thiserror::Error;
 
 /// Represent a multi-bytes field with a fixed size in a packet
 type Field = Range<usize>;
@@ -25,6 +23,20 @@ pub const NLA_ALIGNTO: usize = 4;
 /// NlA(RTA) header size. (unsigned short rta_len) + (unsigned short rta_type)
 pub const NLA_HEADER_SIZE: usize = 4;
 
+#[derive(Debug, Error)]
+pub enum NLAError {
+    #[error("buffer has length {buffer_len}, but an NLA header is {} bytes", TYPE.end)]
+    BufferTooSmall { buffer_len: usize },
+
+    #[error("buffer has length: {buffer_len}, but the NLA is {nla_len} bytes")]
+    LengthMismatch { buffer_len: usize, nla_len: u16 },
+
+    #[error(
+        "NLA has invalid length: {nla_len} (should be at least {} bytes", TYPE.end
+    )]
+    InvalidLength { nla_len: u16 },
+}
+
 #[macro_export]
 macro_rules! nla_align {
     ($len: expr) => {
@@ -52,33 +64,26 @@ impl<T: AsRef<[u8]>> NlaBuffer<T> {
         NlaBuffer { buffer }
     }
 
-    pub fn new_checked(buffer: T) -> Result<NlaBuffer<T>, DecodeError> {
+    pub fn new_checked(buffer: T) -> Result<NlaBuffer<T>, NLAError> {
         let buffer = Self::new(buffer);
-        buffer.check_buffer_length().context("invalid NLA buffer")?;
+        buffer.check_buffer_length()?;
         Ok(buffer)
     }
 
-    pub fn check_buffer_length(&self) -> Result<(), DecodeError> {
+    pub fn check_buffer_length(&self) -> Result<(), NLAError> {
         let len = self.buffer.as_ref().len();
         if len < TYPE.end {
-            Err(format!(
-                "buffer has length {}, but an NLA header is {} bytes",
-                len, TYPE.end
-            )
-            .into())
+            Err(NLAError::BufferTooSmall { buffer_len: len }.into())
         } else if len < self.length() as usize {
-            Err(format!(
-                "buffer has length: {}, but the NLA is {} bytes",
-                len,
-                self.length()
-            )
+            Err(NLAError::LengthMismatch {
+                buffer_len: len,
+                nla_len: self.length(),
+            }
             .into())
         } else if (self.length() as usize) < TYPE.end {
-            Err(format!(
-                "NLA has invalid length: {} (should be at least {} bytes",
-                self.length(),
-                TYPE.end,
-            )
+            Err(NLAError::InvalidLength {
+                nla_len: self.length(),
+            }
             .into())
         } else {
             Ok(())
@@ -204,7 +209,9 @@ impl Nla for DefaultNla {
 impl<'buffer, T: AsRef<[u8]> + ?Sized> Parseable<NlaBuffer<&'buffer T>>
     for DefaultNla
 {
-    fn parse(buf: &NlaBuffer<&'buffer T>) -> Result<Self, DecodeError> {
+    type Error = DecodeError;
+
+    fn parse(buf: &NlaBuffer<&'buffer T>) -> Result<Self, Self::Error> {
         let mut kind = buf.kind();
 
         if buf.network_byte_order_flag() {
@@ -314,7 +321,7 @@ impl<T> NlasIterator<T> {
 impl<'buffer, T: AsRef<[u8]> + ?Sized + 'buffer> Iterator
     for NlasIterator<&'buffer T>
 {
-    type Item = Result<NlaBuffer<&'buffer [u8]>, DecodeError>;
+    type Item = Result<NlaBuffer<&'buffer [u8]>, NLAError>;
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.position >= self.buffer.as_ref().len() {

src/parsers.rs

@@ -5,14 +5,13 @@ use std::{
     net::{IpAddr, Ipv4Addr, Ipv6Addr},
 };
 
-use anyhow::Context;
 use byteorder::{BigEndian, ByteOrder, NativeEndian};
 
 use crate::DecodeError;
 
 pub fn parse_mac(payload: &[u8]) -> Result<[u8; 6], DecodeError> {
     if payload.len() != 6 {
-        return Err(format!("invalid MAC address: {payload:?}").into());
+        return Err(DecodeError::InvalidMACAddress);
     }
     let mut address: [u8; 6] = [0; 6];
     for (i, byte) in payload.iter().enumerate() {
@@ -23,7 +22,7 @@ pub fn parse_mac(payload: &[u8]) -> Result<[u8; 6], DecodeError> {
 
 pub fn parse_ipv6(payload: &[u8]) -> Result<[u8; 16], DecodeError> {
     if payload.len() != 16 {
-        return Err(format!("invalid IPv6 address: {payload:?}").into());
+        return Err(DecodeError::InvalidIPv6Address);
     }
     let mut address: [u8; 16] = [0; 16];
     for (i, byte) in payload.iter().enumerate() {
@@ -57,7 +56,7 @@ pub fn parse_ip(payload: &[u8]) -> Result<IpAddr, DecodeError> {
             payload[15],
         ])
         .into()),
-        _ => Err(format!("invalid IPv6 address: {payload:?}").into()),
+        _ => Err(DecodeError::InvalidIPv6Address),
     }
 }
 
@@ -71,62 +70,62 @@ pub fn parse_string(payload: &[u8]) -> Result<String, DecodeError> {
     } else {
         &payload[..payload.len()]
     };
-    let s = String::from_utf8(slice.to_vec()).context("invalid string")?;
+    let s = String::from_utf8(slice.to_vec())?;
     Ok(s)
 }
 
 pub fn parse_u8(payload: &[u8]) -> Result<u8, DecodeError> {
     if payload.len() != 1 {
-        return Err(format!("invalid u8: {payload:?}").into());
+        return Err(DecodeError::InvalidU8);
     }
     Ok(payload[0])
 }
 
 pub fn parse_u32(payload: &[u8]) -> Result<u32, DecodeError> {
     if payload.len() != size_of::<u32>() {
-        return Err(format!("invalid u32: {payload:?}").into());
+        return Err(DecodeError::InvalidU32);
     }
     Ok(NativeEndian::read_u32(payload))
 }
 
 pub fn parse_u64(payload: &[u8]) -> Result<u64, DecodeError> {
     if payload.len() != size_of::<u64>() {
-        return Err(format!("invalid u64: {payload:?}").into());
+        return Err(DecodeError::InvalidU64);
     }
     Ok(NativeEndian::read_u64(payload))
 }
 
 pub fn parse_u128(payload: &[u8]) -> Result<u128, DecodeError> {
     if payload.len() != size_of::<u128>() {
-        return Err(format!("invalid u128: {payload:?}").into());
+        return Err(DecodeError::InvalidU128);
     }
     Ok(NativeEndian::read_u128(payload))
 }
 
 pub fn parse_u16(payload: &[u8]) -> Result<u16, DecodeError> {
     if payload.len() != size_of::<u16>() {
-        return Err(format!("invalid u16: {payload:?}").into());
+        return Err(DecodeError::InvalidU16);
     }
     Ok(NativeEndian::read_u16(payload))
 }
 
 pub fn parse_i32(payload: &[u8]) -> Result<i32, DecodeError> {
     if payload.len() != 4 {
-        return Err(format!("invalid u32: {payload:?}").into());
+        return Err(DecodeError::InvalidI32);
     }
     Ok(NativeEndian::read_i32(payload))
 }
 
 pub fn parse_u16_be(payload: &[u8]) -> Result<u16, DecodeError> {
     if payload.len() != size_of::<u16>() {
-        return Err(format!("invalid u16: {payload:?}").into());
+        return Err(DecodeError::InvalidU16);
     }
     Ok(BigEndian::read_u16(payload))
 }
 
 pub fn parse_u32_be(payload: &[u8]) -> Result<u32, DecodeError> {
     if payload.len() != size_of::<u32>() {
-        return Err(format!("invalid u32: {payload:?}").into());
+        return Err(DecodeError::InvalidU32);
     }
     Ok(BigEndian::read_u32(payload))
 }

src/traits.rs

@@ -1,7 +1,5 @@
 // SPDX-License-Identifier: MIT
 
-use crate::DecodeError;
-
 /// A type that implements `Emitable` can be serialized.
 pub trait Emitable {
     /// Return the length of the serialized data.
@@ -26,8 +24,10 @@ where
     Self: Sized,
     T: ?Sized,
 {
+    type Error;
+
     /// Deserialize the current type.
-    fn parse(buf: &T) -> Result<Self, DecodeError>;
+    fn parse(buf: &T) -> Result<Self, Self::Error>;
 }
 
 /// A `Parseable` type can be used to deserialize data from the type `T` for
@@ -37,6 +37,8 @@ where
     Self: Sized,
     T: ?Sized,
 {
+    type Error;
+
     /// Deserialize the current type.
-    fn parse_with_param(buf: &T, params: P) -> Result<Self, DecodeError>;
+    fn parse_with_param(buf: &T, params: P) -> Result<Self, Self::Error>;
 }