Rename directories (again)

lib/src/pcap.rs

@@ -0,0 +1,120 @@
+use crate::gsmtap::GsmtapMessage;
+use crate::diag::Timestamp;
+
+use std::io::Write;
+use std::borrow::Cow;
+use chrono::prelude::*;
+use deku::prelude::*;
+use pcap_file::pcapng::blocks::enhanced_packet::EnhancedPacketBlock;
+use pcap_file::pcapng::blocks::interface_description::InterfaceDescriptionBlock;
+use pcap_file::pcapng::PcapNgWriter;
+use pcap_file::PcapError;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum GsmtapPcapError {
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("Pcap error: {0}")]
+    Pcap(#[from] PcapError),
+    #[error("Timestamp out of range: {0}")]
+    TimestampOutOfRange(#[from] chrono::OutOfRangeError),
+    #[error("Deku error: {0}")]
+    Deku(#[from] DekuError),
+}
+
+pub struct GsmtapPcapWriter<T> where T: Write {
+    writer: PcapNgWriter<T>,
+    ip_id: u16,
+}
+
+const IP_HEADER_LEN: u16 = 20;
+#[derive(DekuWrite)]
+#[deku(endian = "big")]
+struct IpHeader {
+    version_and_ihl: u8,
+    dscp: u8,
+    total_len: u16,
+    identification: u16,
+    flags_and_frag_offset: u8,
+    idk: u8,
+    ttl: u8,
+    protocol: u8,
+    checksum: u16,
+    src_addr: u32,
+    dst_addr: u32,
+}
+
+const UDP_HEADER_LEN: u16 = 8;
+const GSMTAP_PORT: u16 = 4729;
+#[derive(DekuWrite)]
+#[deku(endian = "big")]
+struct UdpHeader {
+    src_port: u16,
+    dst_port: u16,
+    length: u16,
+    checksum: u16,
+}
+
+impl<T> GsmtapPcapWriter<T> where T: Write {
+    pub fn new(writer: T) -> Result<Self, GsmtapPcapError> {
+        let writer = PcapNgWriter::new(writer)?;
+        Ok(GsmtapPcapWriter { writer, ip_id: 0 })
+    }
+
+    pub fn write_iface_header(&mut self) -> Result<(), GsmtapPcapError> {
+        let interface = InterfaceDescriptionBlock {
+            linktype: pcap_file::DataLink::IPV4,
+            snaplen: 0xffff,
+            options: vec![],
+        };
+        self.writer.write_pcapng_block(interface)?;
+        Ok(())
+    }
+
+    pub fn write_gsmtap_message(&mut self, msg: GsmtapMessage, timestamp: Timestamp) -> Result<(), GsmtapPcapError> {
+        let duration = timestamp.to_datetime()
+            .signed_duration_since(DateTime::UNIX_EPOCH)
+            .to_std()?;
+
+        // despite the timestamp above being correct, we have reduce it by
+        // orders of magnitude due to a bug in pcap_file:
+        // https://github.com/courvoif/pcap-file/pull/32
+        let duration = std::time::Duration::from_nanos(duration.as_micros() as u64);
+
+        let msg_bytes = msg.to_bytes()?;
+        let ip_header = IpHeader {
+            version_and_ihl: 0x45,
+            dscp: 0,
+            total_len: msg_bytes.len() as u16 + IP_HEADER_LEN + UDP_HEADER_LEN,
+            identification: self.ip_id,
+            flags_and_frag_offset: 0x40,
+            idk: 0,
+            ttl: 64,
+            protocol: 0x11, // UDP
+            checksum: 0xffff,
+            src_addr: 0x7f000001,
+            dst_addr: 0x7f000001, // TODO increment by radio_id
+        };
+        let udp_header = UdpHeader {
+            src_port: 13337,
+            dst_port: GSMTAP_PORT,
+            length: msg_bytes.len() as u16 + UDP_HEADER_LEN,
+            checksum: 0xffff,
+        };
+        let mut data: Vec<u8> = Vec::new();
+        data.extend(&ip_header.to_bytes()?);
+        data.extend(&udp_header.to_bytes()?);
+        data.extend(&msg_bytes);
+        let packet = EnhancedPacketBlock {
+            interface_id: 0,
+            timestamp: duration,
+            original_len: data.len() as u32,
+            data: Cow::Owned(data),
+            options: vec![],
+        };
+        self.writer.write_pcapng_block(packet)?;
+        self.ip_id = self.ip_id.wrapping_add(1);
+        Ok(())
+    }
+}