---
name: "dumbnet"
section: "8"
platform: "linux"
package: "libdumbnet-dev"
version: "1.18.0-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/dumbnet"
---

# dumbnet(8)

dumb networking library test program

## NAME

**dumbnet** – dumb networking library test program

## SYNOPSIS

**dumbnet** *command* *args* \[...\]

## DESCRIPTION

**dumbnet** is a simple test program for the [dumbnet(3)](/dumbnet/3.md) 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)](/dumbnet/3.md)

## AUTHORS

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