DOKK / manpages / debian 12 / libdumbnet-dev / dumbnet.8.en
DNET(8) System Manager's Manual DNET(8)

dumbnet — dumb networking library test program

dumbnet command args [...]

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).

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.

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.

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.

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.

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

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.

dumbnet(3)

Dug Song ⟨dugsong@monkey.org⟩
Oliver Falk ⟨oliver@linux-kernel.at⟩

October 17, 2001 Debian