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fix(pcap): Non-QoS frames are 2 bytes shorter #64

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Merged
jbeyerstedt merged 1 commit into from
Jul 8, 2026
Merged

fix(pcap): Non-QoS frames are 2 bytes shorter #64

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18 changes: 11 additions & 7 deletions src/pcap/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,19 +49,19 @@ fn remove_radiotap_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
#[allow(clippy::missing_errors_doc, reason = "no documentation present")]
fn remove_80211_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
/*
* IEEE 802.11 Header has the following format (26-32 bytes)
* IEEE 802.11 Header has the following format (24-26 bytes)
* - 2 bytes frame control
* byte 0: .... ..00: Version 0
* byte 0: .... 10..: Type data frame
* byte 0: 1000 ....: QoS Data
* byte 0: 1000 ....: QoS Data (or 0 for non-QoS data)
* - 2 bytes duration
* - 6 bytes addr 1 (receiver)
* - 6 bytes addr 2 (transmitter)
* - 6 bytes addr 3 (BSSID)
* - 2 bytes sequence control
* - 0 or 6 bytes addr 4
* - addr 4 not used in 802.11p mode
* - 0 or 2 bytes QOS control
* - 0 or 4 bytes HT control
* - HT control not used in 802.11p mode
*/

let ieee80211_framecontrol: u8 = data[0];
Expand All @@ -82,15 +82,19 @@ fn remove_80211_hdr(data: &[u8]) -> Result<&[u8], alloc::string::String> {
}

let ieee80211_fc_subtype: u8 = (ieee80211_framecontrol & 0xf0) >> 4; // xxxx.0000
if !(ieee80211_fc_subtype == 0b1000 || ieee80211_fc_subtype == 0b0000) {
let qos_hdr_bytes = if ieee80211_fc_subtype == 0b1000 {
2
} else if ieee80211_fc_subtype == 0b0000 {
0
} else {
// only select QoS or "normal" data frames
return Err(
alloc::format!("Unsupported 802.11 frame subtype {ieee80211_fc_subtype:#04x}")
.to_string(),
);
}
};

let hdr_len: usize = 26; // QoS data frame is usually 26 bytes (sequence control, no addr 4, QoS, no HT)
let hdr_len: usize = 24 + qos_hdr_bytes;
let (_, remaining) = data.split_at(hdr_len);

Ok(remaining)
Expand Down