Dumpcap is a network traffic dump tool. It captures packet data from a live network and writes the packets to a file. Dumpcap's native capture file format is libpcap format, which is also the format used by Wireshark, tcpdump and various other tools.
Without any options set it will use the pcap library to capture traffic from the first available network interface and write the received raw packet data, along with the packets' time stamps into a libpcap file.
Packet capturing is performed with the pcap library. The capture filter syntax follows the rules of the pcap library.
Example D.2. Help information available from dumpcap
Dumpcap 1.11.0 (SVN Rev 52564 from /trunk) Capture network packets and dump them into a pcapng file. See http://www.wireshark.org for more information. Usage: dumpcap [options] ... Capture interface: -i <interface> name or idx of interface (def: first non-loopback) or for remote capturing, use one of these formats: rpcap://<host>/<interface> TCP@<host>:<port> -f <capture filter> packet filter in libpcap filter syntax -s <snaplen> packet snapshot length (def: 65535) -p don't capture in promiscuous mode -I capture in monitor mode, if available -B <buffer size> size of kernel buffer in MB (def: 2MB) -y <link type> link layer type (def: first appropriate) -D print list of interfaces and exit -L print list of link-layer types of iface and exit -d print generated BPF code for capture filter -k set channel on wifi interface <freq>,[<type>] -S print statistics for each interface once per second -M for -D, -L, and -S, produce machine-readable output RPCAP options: -r don't ignore own RPCAP traffic in capture -u use UDP for RPCAP data transfer -A <user>:<password> use RPCAP password authentication -m <sampling type> use packet sampling count:NUM - capture one packet of every NUM timer:NUM - capture no more than 1 packet in NUM ms Stop conditions: -c <packet count> stop after n packets (def: infinite) -a <autostop cond.> ... duration:NUM - stop after NUM seconds filesize:NUM - stop this file after NUM KB files:NUM - stop after NUM files Output (files): -w <filename> name of file to save (def: tempfile) -g enable group read access on the output file(s) -b <ringbuffer opt.> ... duration:NUM - switch to next file after NUM secs filesize:NUM - switch to next file after NUM KB files:NUM - ringbuffer: replace after NUM files -n use pcapng format instead of pcap (default) -P use libpcap format instead of pcapng --capture-comment <comment> add a capture comment to the output file (only for pcapng) Miscellaneous: -N <packet_limit> maximum number of packets buffered within dumpcap -C <byte_limit> maximum number of bytes used for buffering packets within dumpcap -t use a separate thread per interface -q don't report packet capture counts -v print version information and exit -h display this help and exit Example: dumpcap -i eth0 -a duration:60 -w output.pcapng "Capture packets from interface eth0 until 60s passed into output.pcapng" Use Ctrl-C to stop capturing at any time.