NAME
dumbnet - dumb networking library test program
SYNOPSIS
dumbnet command args [...]
DESCRIPTION
dumbnet is a simple test program for the dumbnet(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:
dumbnet 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" | \
dumbnet udp sport 555 dport 666 | \
dumbnet ip proto udp src 1.2.3.4 dst 5.6.7.8 | dumbnet send
Save an ARP request in a file and send it twice:
dumbnet arp op req sha 0:d:e:a:d:0 spa 10.0.0.3 tpa 10.0.0.4 | \
dumbnet eth type arp src 0:d:e:a:d:0 dst ff:ff:ff:ff:ff:ff > arp.pkt
dumbnet send fxp0 < arp.pkt
dumbnet send fxp0 < arp.pkt
Send a fragmented ping packet:
# Create ping packet with IP header, to set ICMP checksum
echo "monkey monkey monkey monkey" | dumbnet icmp type 8 code 0 | \
dumbnet 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
dumbnet ip id 1 off 0+ proto icmp src 1.2.3.4 dst 5.6.7.8 < p.aa | \
dumbnet send
dumbnet ip id 1 off 24 proto icmp src 1.2.3.4 dst 5.6.7.8 < p.ab | \
dumbnet send
COMPATIBILITY
The library was originally named dnet but was renamed to dumbnet due to a
conflict with the DECnet library. This decision affects not only the
filename of the shared library, but also the header file names and the
library’s SONAME tag, which means that software built on a non-Debian-
derived distribution will not run with this library and recompiling the
software will only work if some adjustments to header include directives
and compiler/linker flags are made.
SEE ALSO
dumbnet(3)
AUTHORS
Dug Song 〈dugsong@monkey.org〉