Implement bt_packet_logger

tools/src/pcap.rs

@@ -0,0 +1,60 @@
+use idevice::bt_packet_logger::BtPacketKind;
+use tokio::io::{AsyncWrite, AsyncWriteExt};
+
+// Classic PCAP (big-endian) global header for DLT_BLUETOOTH_HCI_H4_WITH_PHDR (201)
+const PCAP_GLOBAL_HEADER_BE: [u8; 24] = [
+    0xA1, 0xB2, 0xC3, 0xD4, // magic (big-endian stream)
+    0x00, 0x02, // version maj
+    0x00, 0x04, // version min
+    0x00, 0x00, 0x00, 0x00, // thiszone
+    0x00, 0x00, 0x00, 0x00, // sigfigs
+    0x00, 0x00, 0x08, 0x00, // snaplen = 2048
+    0x00, 0x00, 0x00, 201, // network = 201 (HCI_H4_WITH_PHDR)
+];
+
+#[inline]
+fn be32(x: u32) -> [u8; 4] {
+    [(x >> 24) as u8, (x >> 16) as u8, (x >> 8) as u8, x as u8]
+}
+
+#[inline]
+fn dir_flag(kind: BtPacketKind) -> Option<u32> {
+    use BtPacketKind::*;
+    Some(match kind {
+        HciCmd | AclSent | ScoSent => 0,
+        HciEvt | AclRecv | ScoRecv => 1,
+        _ => return None,
+    })
+}
+
+pub async fn write_pcap_header<W: AsyncWrite + Unpin>(w: &mut W) -> std::io::Result<()> {
+    w.write_all(&PCAP_GLOBAL_HEADER_BE).await
+}
+
+pub async fn write_pcap_record<W: AsyncWrite + Unpin>(
+    w: &mut W,
+    ts_sec: u32,
+    ts_usec: u32,
+    kind: BtPacketKind,
+    h4_payload: &[u8], // starts with H4 type followed by HCI bytes
+) -> std::io::Result<()> {
+    // Prepend 4-byte direction flag to the packet body
+    let Some(dir) = dir_flag(kind) else {
+        return Ok(());
+    };
+    let cap_len = 4u32 + h4_payload.len() as u32;
+
+    // PCAP record header (big-endian fields to match magic above)
+    // ts_sec, ts_usec, incl_len, orig_len
+    let mut rec = [0u8; 16];
+    rec[0..4].copy_from_slice(&be32(ts_sec));
+    rec[4..8].copy_from_slice(&be32(ts_usec));
+    rec[8..12].copy_from_slice(&be32(cap_len));
+    rec[12..16].copy_from_slice(&be32(cap_len));
+
+    // Write: rec hdr, dir flag (as 4 BE bytes), then H4 bytes
+    w.write_all(&rec).await?;
+    w.write_all(&be32(dir)).await?;
+    w.write_all(h4_payload).await?;
+    Ok(())
+}