c_its_parser/pcap/
mod.rs

1use alloc::string::ToString;
2
3/// Strips Radiotap, IEEE 802.11p and LLC headers from a binary message buffer
4///
5/// Convenience function combining [`remove_radiotap_hdr`], [`remove_80211_hdr`] and [`remove_llc_hdr`].
6///
7/// # Errors
8/// Returns a human-readable error when parsing failed
9pub fn remove_pcap_headers(data: &[u8]) -> Result<&[u8], alloc::string::String> {
10    remove_radiotap_hdr(data).and_then(remove_wlan_headers)
11}
12
13/// Strips IEEE 802.11p and LLC headers from a binary message buffer
14///
15/// Convenience function combining [`remove_80211_hdr`] and [`remove_llc_hdr`].
16///
17/// IEEE 802.11 data frames always have an LLC header.
18/// Since `remove_80211_hdr` only allows data frames, we usually need to remove them, too.
19///
20/// # Errors
21/// Returns a human-readable error when parsing failed
22pub fn remove_wlan_headers(data: &[u8]) -> Result<&[u8], alloc::string::String> {
23    remove_80211_hdr(data).and_then(remove_llc_hdr)
24}
25
26#[allow(clippy::missing_errors_doc, reason = "no documentation present")]
27fn remove_radiotap_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
28    /*
29     * Radiotap Header has the following format
30     * - u_int8_t   header version (currently always zero)
31     * - u_int8_t   (padding for byte alignment);
32     * - u_int16_t  entire header length;
33     * - u_int32_t  bitmask which subsequent data is present
34     */
35
36    let radiotap_version: u8 = data[0];
37    if radiotap_version != 0 {
38        return Err(alloc::format!(
39            "Unknown header version {radiotap_version:#x}"
40        ));
41    }
42
43    let hdr_len: usize = u16::from_le_bytes([data[2], data[3]]).into();
44    let (_, remaining) = data.split_at(hdr_len);
45
46    Ok(remaining)
47}
48
49#[allow(clippy::missing_errors_doc, reason = "no documentation present")]
50fn remove_80211_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
51    /*
52     * IEEE 802.11 Header has the following format (24-26 bytes)
53     * - 2 bytes frame control
54     *      byte 0: .... ..00: Version 0
55     *      byte 0: .... 10..: Type data frame
56     *      byte 0: 1000 ....: QoS Data (or 0 for non-QoS data)
57     * - 2 bytes duration
58     * - 6 bytes addr 1 (receiver)
59     * - 6 bytes addr 2 (transmitter)
60     * - 6 bytes addr 3 (BSSID)
61     * - 2 bytes sequence control
62     * - addr 4 not used in 802.11p mode
63     * - 0 or 2 bytes QOS control
64     * - HT control not used in 802.11p mode
65     */
66
67    let ieee80211_framecontrol: u8 = data[0];
68
69    let ieee80211_fc_version: u8 = ieee80211_framecontrol & 0x03; // 0000.00xx
70    if ieee80211_fc_version != 0 {
71        return Err(
72            alloc::format!("Unknown 802.11 header version {ieee80211_fc_version}").to_string(),
73        );
74    }
75
76    let ieee80211_fc_type: u8 = (ieee80211_framecontrol & 0x0c) >> 2; // 0000.xx00
77    if ieee80211_fc_type != 0b10 {
78        // only select data frames
79        return Err(
80            alloc::format!("Unsupported 802.11 frame type {ieee80211_fc_type}").to_string(),
81        );
82    }
83
84    let ieee80211_fc_subtype: u8 = (ieee80211_framecontrol & 0xf0) >> 4; // xxxx.0000
85    let qos_hdr_bytes = if ieee80211_fc_subtype == 0b1000 {
86        2
87    } else if ieee80211_fc_subtype == 0b0000 {
88        0
89    } else {
90        // only select QoS or "normal" data frames
91        return Err(
92            alloc::format!("Unsupported 802.11 frame subtype {ieee80211_fc_subtype:#04x}")
93                .to_string(),
94        );
95    };
96
97    let hdr_len: usize = 24 + qos_hdr_bytes;
98    let (_, remaining) = data.split_at(hdr_len);
99
100    Ok(remaining)
101}
102
103#[allow(clippy::missing_errors_doc, reason = "no documentation present")]
104fn remove_llc_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
105    /*
106     * LLC Header has the following format (8 bytes)
107     * - 1 bytes DSAP
108     * - 1 bytes SSAP
109     * - 1 bytes control field
110     * - 3 bytes organization code
111     * - 2 bytes Type (0x8947 BE is GeoNetworking)
112     */
113
114    let llc_type: u16 = (u16::from(data[6]) << 8) | u16::from(data[7]);
115
116    if llc_type != 0x8947 {
117        return Err(alloc::format!("Unknown LLC payload type {llc_type:#x}").to_string());
118    }
119
120    let hdr_len: usize = 8; // TODO: Is this the right size?
121    let (_, remaining) = data.split_at(hdr_len);
122
123    Ok(remaining)
124}
c_its_parser/pcap/mod.rs

c_its_parser/pcap/
mod.rs
