dnet - Man Page

dumb networking library test program

dnet is a simple test program for the dnet(3) library. It can be used to compose and transmit network datagrams as a Unix-style filter (e.g. reading from or writing to files and pipes) or modify the local system network configuration (including the ARP cache, firewall ruleset, network interfaces, and routing table).

Payload generation commands

addr address [...]: Convert the address (specified as a hostname, IP address, or MAC address) into its binary representation on standard output.
hex string [...]: Convert the C-style escaped string (shellcode, for instance) into its binary representation on standard output.
rand len: Write len random bytes to standard output.

Packet encapsulation commands

eth [type type] [src mac] [dst mac]: Prepend the data read from standard input with an Ethernet header on standard output. The Ethernet type may be specified as ‘arp’, ‘ip’, or as a hex, octal, or decimal number.
arp [op op] [sha mac] [spa host] [tha mac] [tpa host]: Prepend the data read from standard input with an ARP header on standard output. The ARP op may be specified as ‘req’, ‘rep’, ‘revreq’, ‘revrep’, or as a hex, octal, or decimal number.
ip [tos num] [id num] [off offset] [ttl num] [proto protocol] [src host] [dst dst]: Prepend the data read from standard input with an IP header on standard output. The fragmentation offset may be specified as a decimal number (optionally concatenated with ‘+’ to indicate more fragments) or as a hex number. The protocol may be specified by name, or as a hex, octal, or decimal number.
icmp [type num] [code num]: Prepend the data read from standard input with an ICMP header on standard output.
tcp [sport port] [dport port] [flags flags] [seq num] [ack num] [win num] [urp num]: Prepend the data read from standard input with a TCP header on standard output. A port may be specified by name or hex, octal, or decimal number. The TCP flags may be specified as some combination of the characters in the set ‘SAFRPU’ or as a hex number.
udp [sport port] [dport port]: Prepend the data read from standard input with a UDP header on standard output. A port may be specified by name or hex, octal, or decimal number.

Packet transmission commands

send [device]: Read a packet from standard input and send it over the network. If no device is specified, the packet is assumed to be an IP datagram and routed to its destination. Otherwise, the packet is assumed to be an Ethernet frame and is transmitted on the specified interface.

Kernel interface commands

arp show: Display the kernel ARP cache.
arp get host: Display the kernel ARP entry for host.
arp add host mac: Add an ARP entry mapping the mac address for host.
arp delete host: Delete the ARP entry for host.
fw show: Display the kernel firewall ruleset.
fw add|delete action direction device protocol src[:port[-max]] dst[:port[-max]] [type[/code]]: Add a rule to or delete a rule from the active firewall ruleset. The action must be either ‘allow’ or ‘block’. The direction must be either ‘in’ or ‘out’. The device may specify an interface name, or ‘any’. The protocol may be specified by name, or as a decimal number. For TCP and UDP protocols, a port (or range, if specified with a max value) may be specified in decimal and appended to the source and/or destination address. For ICMP, a type (and optional code) may be specified in decimal.
intf show: Display the configuration of all network interfaces.
intf get device: Display the configuration for the interface specified by device.
intf set device [alias host] [dst host] [inet host] [link mac] [up|down] [arp|noarp]: Configure the interface specified by device.
route show: Display the kernel routing table.
route get dst: Display the route for the destination dst, specified as a hostname, IP address, or network prefix in CIDR notation.
route add dst gw: Add a route for the destination dst through the gateway gw.
route delete dst: Delete the route for the destination dst.

Examples

Send a UDP datagram containing random shellcode:

dnet hex "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89" \
"\x46\x0c\xb0\x0b\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80" \
"\x31\xdb\x89\xd8\x40\xcd\x80\xe8\xdc\xff\xff\xff/bin/sh" | \
dnet udp sport 555 dport 666 | \
dnet ip proto udp src 1.2.3.4 dst 5.6.7.8 | dnet send

Save an ARP request in a file and send it twice:

dnet arp op req sha 0:d:e:a:d:0 spa 10.0.0.3 tpa 10.0.0.4 | \
dnet eth type arp src 0:d:e:a:d:0 dst ff:ff:ff:ff:ff:ff > arp.pkt
dnet send fxp0 < arp.pkt
dnet send fxp0 < arp.pkt

Send a fragmented ping packet:

# Create ping packet with IP header, to set ICMP checksum
echo "monkey monkey monkey monkey" | dnet icmp type 8 code 0 | \
dnet ip proto icmp src 1.2.3.4 dst 5.6.7.8 > ping.pkt

# Chop off IP header
dd if=ping.pkt of=ping.data bs=20 skip=1

# Fragment IP payload
split -b 24 ping.data p.

# Send fragments
dnet ip id 1 off 0+ proto icmp src 1.2.3.4 dst 5.6.7.8 < p.aa | \
dnet send
dnet ip id 1 off 24 proto icmp src 1.2.3.4 dst 5.6.7.8 < p.ab | \
dnet send

Authors

Dug Song ⟨dugsong@monkey.org⟩

Oliver Falk ⟨oliver@linux-kernel.at⟩

Info

October 17, 2001