1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
use std::{
    collections::HashMap,
    convert::{TryFrom, TryInto},
};

use super::{name::Label, Name, WireFormat, QCLASS, QTYPE};

/// Question represents a query in the DNS Packet
#[derive(Debug, Clone)]
pub struct Question<'a> {
    /// a [Name](`Name`)  to query for
    pub qname: Name<'a>,
    /// a [QTYPE](`QTYPE`) which specifies the type of the query.
    pub qtype: QTYPE,
    /// a [QCLASS](`QCLASS`) whire specifics the class of the query, For Example: IN
    pub qclass: QCLASS,
    /// indicates if the queries prefers a unicast response.  
    /// MDNS related, See [RFC 6762](https://tools.ietf.org/html/rfc6762#section-5.4)
    pub unicast_response: bool,
}

impl<'a> Question<'a> {
    /// Creates a new question
    pub fn new(qname: Name<'a>, qtype: QTYPE, qclass: QCLASS, unicast_response: bool) -> Self {
        Self {
            qname,
            qtype,
            qclass,
            unicast_response,
        }
    }

    /// Transforms the inner data into its owned type
    pub fn into_owned<'b>(self) -> Question<'b> {
        Question {
            qname: self.qname.into_owned(),
            qtype: self.qtype,
            qclass: self.qclass,
            unicast_response: self.unicast_response,
        }
    }

    fn write_common<T: std::io::Write>(&self, out: &mut T) -> crate::Result<()> {
        let qclass: u16 = match self.unicast_response {
            true => Into::<u16>::into(self.qclass) | 0x8000,
            false => self.qclass.into(),
        };

        out.write_all(&Into::<u16>::into(self.qtype).to_be_bytes())?;
        out.write_all(&qclass.to_be_bytes())
            .map_err(crate::SimpleDnsError::from)
    }
}

impl<'a> WireFormat<'a> for Question<'a> {
    fn parse(data: &'a [u8], position: &mut usize) -> crate::Result<Self> {
        let qname = Name::parse(data, position)?;
        if *position + 4 > data.len() {
            return Err(crate::SimpleDnsError::InsufficientData);
        }

        let qtype = u16::from_be_bytes(data[*position..*position + 2].try_into()?);
        let qclass = u16::from_be_bytes(data[*position + 2..*position + 4].try_into()?);

        *position += 4;

        Ok(Self {
            qname,
            qtype: QTYPE::try_from(qtype)?,
            qclass: QCLASS::try_from(qclass & 0x7FFF)?,
            unicast_response: qclass & 0x8000 == 0x8000,
        })
    }

    fn len(&self) -> usize {
        self.qname.len() + 4
    }

    fn write_to<T: std::io::Write>(&self, out: &mut T) -> crate::Result<()> {
        self.qname.write_to(out)?;
        self.write_common(out)
    }

    fn write_compressed_to<T: std::io::Write + std::io::Seek>(
        &'a self,
        out: &mut T,
        name_refs: &mut HashMap<&'a [Label<'a>], usize>,
    ) -> crate::Result<()> {
        self.qname.write_compressed_to(out, name_refs)?;
        self.write_common(out)
    }
}

#[cfg(test)]
mod tests {
    use crate::{CLASS, TYPE};

    use super::*;
    use std::convert::TryInto;

    #[test]
    fn parse_question() {
        let bytes = b"\x00\x00\x04_srv\x04_udp\x05local\x00\x00\x10\x00\x01";
        let question = Question::parse(bytes, &mut 2);

        assert!(question.is_ok());
        let question = question.unwrap();

        assert_eq!(QCLASS::CLASS(CLASS::IN), question.qclass);
        assert_eq!(QTYPE::TYPE(TYPE::TXT), question.qtype);
        assert!(!question.unicast_response);
    }

    #[test]
    fn append_to_vec() {
        let question = Question::new(
            "_srv._udp.local".try_into().unwrap(),
            TYPE::TXT.into(),
            CLASS::IN.into(),
            false,
        );
        let mut bytes = Vec::new();
        question.write_to(&mut bytes).unwrap();

        assert_eq!(b"\x04_srv\x04_udp\x05local\x00\x00\x10\x00\x01", &bytes[..]);
        assert_eq!(bytes.len(), question.len());
    }

    #[test]
    fn unicast_response() {
        let mut bytes = Vec::new();
        Question::new(
            "x.local".try_into().unwrap(),
            TYPE::TXT.into(),
            CLASS::IN.into(),
            true,
        )
        .write_to(&mut bytes)
        .unwrap();
        let parsed = Question::parse(&bytes, &mut 0).unwrap();

        assert!(parsed.unicast_response);
    }
}