libpcap based Ethernet packet generator

 bittwist (or Bit-Twist) is designed to complement tcpdump, which by itself has
 done a great job in capturing network traffic. Bit-Twist can regenerate the
 captured traffic onto a live network (the packets are generated from tcpdump
 trace file, generating a .pcap file).
 .
 Bit-Twist also comes with a comprehensive trace file editor to allow one to
 change the contents of a trace file (bittwiste).
 .
 Generally, a packet generator is useful in simulating networking traffic or
 scenario, testing firewall, IDS, and IPS, and troubleshooting various network
 problems.
 .
 The Bit-Twist features are:
 .
    * runs on Linux, BSD, macOS, and Windows;
    * send multiple trace files at a time;
    * send packets at a specific speed or up to your NIC line rate in Mbps using
      built-in token bucket algorithm;
    * comprehensive trace file editor with control over most fields in
      Ethernet, ARP, IP, ICMP, TCP, and UDP headers with automatic header
      checksum correction;
    * comprehensive trace file editor to edit most fields in
      Ethernet, ARP, IPv4, IPv6, ICMPv4, ICMPv6, TCP, and UDP headers;
    * automatic header checksum correction;
    * send packets with custom QoS bits to test classification/queuing features
      of switches/routers;
    * append user payload to existing packets after a specific header;
    * append user payload (e.g. copy of hex stream from Wireshark) to existing
      packets after a specific header;
    * select a specific range of packets and save them in another trace file;
    * highly scriptable - with proper manipulation you can turn Bit-Twist
      into an extremely flexible packet generator tool;
    * if you are teaching Computer Networks classes, you may find Bit-Twist
      useful as a practical teaching material. It gives your students a
      hands-on experience to learn various networking protocols etc.