chore(*) refactor Phantun and fake-tcp to their own crates

fake-tcp/src/packet.rs

@@ -0,0 +1,70 @@
+use bytes::{Bytes, BytesMut};
+use pnet::packet::{ip, ipv4, tcp};
+use std::convert::TryInto;
+use std::net::SocketAddrV4;
+
+const IPV4_HEADER_LEN: usize = 20;
+const TCP_HEADER_LEN: usize = 20;
+pub const MAX_PACKET_LEN: usize = 1500;
+
+pub fn build_tcp_packet(
+    local_addr: SocketAddrV4,
+    remote_addr: SocketAddrV4,
+    seq: u32,
+    ack: u32,
+    flags: u16,
+    payload: Option<&[u8]>,
+) -> Bytes {
+    let wscale = (flags & tcp::TcpFlags::SYN) != 0;
+    let tcp_total_len = TCP_HEADER_LEN + if wscale {4} else {0} // nop + wscale
+                        + payload.map_or(0, |payload| payload.len());
+    let total_len = IPV4_HEADER_LEN + tcp_total_len;
+    let mut buf = BytesMut::with_capacity(total_len);
+    buf.resize(total_len, 0);
+
+    let mut v4_buf = buf.split_to(IPV4_HEADER_LEN);
+    let mut tcp_buf = buf.split_to(tcp_total_len);
+    assert_eq!(0, buf.len());
+
+    let mut v4 = ipv4::MutableIpv4Packet::new(&mut v4_buf).unwrap();
+    v4.set_version(4);
+    v4.set_header_length(IPV4_HEADER_LEN as u8 / 4);
+    v4.set_next_level_protocol(ip::IpNextHeaderProtocols::Tcp);
+    v4.set_ttl(32);
+    v4.set_source(*local_addr.ip());
+    v4.set_destination(*remote_addr.ip());
+    v4.set_total_length(total_len.try_into().unwrap());
+    v4.set_flags(ipv4::Ipv4Flags::DontFragment);
+    v4.set_checksum(ipv4::checksum(&v4.to_immutable()));
+
+    let mut tcp = tcp::MutableTcpPacket::new(&mut tcp_buf).unwrap();
+    tcp.set_window(0xffff);
+    tcp.set_source(local_addr.port());
+    tcp.set_destination(remote_addr.port());
+    tcp.set_sequence(seq);
+    tcp.set_acknowledgement(ack);
+    tcp.set_flags(flags);
+    tcp.set_data_offset(TCP_HEADER_LEN as u8 / 4 + if wscale { 1 } else { 0 });
+    if wscale {
+        let wscale = tcp::TcpOption::wscale(14);
+        tcp.set_options(&[tcp::TcpOption::nop(), wscale]);
+    }
+
+    if let Some(payload) = payload {
+        tcp.set_payload(payload);
+    }
+
+    let checksum = tcp::ipv4_checksum(&tcp.to_immutable(), local_addr.ip(), remote_addr.ip());
+    tcp.set_checksum(checksum);
+
+    v4_buf.unsplit(tcp_buf);
+
+    v4_buf.freeze()
+}
+
+pub fn parse_ipv4_packet(buf: &Bytes) -> (ipv4::Ipv4Packet, tcp::TcpPacket) {
+    let v4 = ipv4::Ipv4Packet::new(buf).unwrap();
+    let tcp = tcp::TcpPacket::new(&buf[IPV4_HEADER_LEN..]).unwrap();
+
+    (v4, tcp)
+}