http://vincentbernat.github.com/lldpd/

LLDP (Link Layer Discovery Protocol) is an industry standard protocol designed to supplant proprietary Link-Layer protocols such as Extreme's EDP (Extreme Discovery Protocol) and CDP (Cisco Discovery Protocol). The goal of LLDP is to provide an inter-vendor compatible mechanism to deliver Link-Layer notifications to adjacent network devices.

lldpd implements both reception and sending. It also implements an SNMP subagent for net-snmp to get local and remote LLDP information. The LLDP MIB is partially implemented but the most useful tables are here. lldpd also partially implements LLDP-MED.

lldpd supports bridge, vlan and bonding. bonding need to be done on real physical devices, not on bridges, vlans, etc. However, vlans can be mapped on the bonding device. You can bridge vlan but not add vlans on bridges. More complex setups may give false results.

The following OS are supported:

• FreeBSD
• GNU/Linux
• NetBSD
• OpenBSD
• Mac OS X

To compile lldpd, use the following:

./configure
make
sudo make install

You need libevent that you can grab from http://libevent.org or install from your package system (libevent-dev for Debian/Ubuntu and libevent-devel for Redhat/Fedora/CentOS/SuSE).

If your system does not have libevent, ./configure will use the shipped copy and compile it statically.

If it complains about a missing agent/struct.h, your installation of Net-SNMP is incomplete. The easiest way to fix this is to provide an empty struct.h:

touch src/struct.h

lldpd uses privilege separation to increase its security. Two processes, one running as root and doing minimal stuff and the other running as an unprivileged user into a chroot doing most of the stuff, are cooperating. You need to create a user called _lldpd in a group _lldpd (this can be change with ./configure). You also need to create an empty directory /var/run/lldpd (it needs to be owned by root, not _lldpd!). If you get fuzzy timestamps from syslog, copy /etc/locatime into the chroot.

lldpcli lets one query information collected through the command line. If you don't want to run it as root, just install it setuid or setgid _lldpd.

The same procedure as above applies for Mac OS X. However, you may want to install libevent from Homebrew, as well as Readline:

brew install libevent
brew install readline
./configure CPPFLAGS="-I$(brew --prefix readline)/include" \
            LDFLAGS="-L$(brew --prefix readline)/lib" \
            --with-privsep-chroot=/var/empty
make
sudo make install

You need to create the _lldpd user and group:

dscl . list /Users uid
dscl . list /Groups gid
# Find a free UID/GID, let's say 274
dscl . -create /Groups/_lldpd
dscl . -create /Groups/_lldpd PrimaryGroupID 274
dscl . -create /Groups/_lldpd Password "*"
dscl . -create /Groups/_lldpd RealName "lldpd privilege separation group"
dscl . -create /Users/_lldpd
dscl . -create /Users/_lldpd UserShell /usr/bin/false
dscl . -create /Users/_lldpd NFSHomeDirectory /var/empty
dscl . -create /Users/_lldpd PrimaryGroupID 274
dscl . -create /Users/_lldpd UniqueID 274
dscl . -create /Users/_lldpd Password "*"
dscl . -create /Users/_lldpd RealName "lldpd privilege separation user"

Alternatively, you can use a convenient brew formula:

brew install https://raw.github.com/vincentbernat/lldpd/master/osx/lldpd.rb

This formula includes the ability to interface properly with launchd to start lldpd at boot.

lldpd also implements CDP (Cisco Discovery Protocol), FDP (Foundry Discovery Protocol), SONMP (Nortel Discovery Protocol) and EDP (Extreme Discovery Protocol). However, recent versions of IOS should support LLDP and most Extreme stuff support LLDP. When a EDP, CDP or SONMP frame is received on a given interface, lldpd starts sending EDP, CDP, FDP or SONMP frame on this interface. Informations collected through EDP/CDP/FDP/SONMP are integrated with other informations and can be queried with lldpcli or through SNMP.

For bonding, you need 2.6.24 (in previous version, PACKET_ORIGDEV affected only non multicast packets). See:

• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=80feaacb8a6400a9540a961b6743c69a5896b937
• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8032b46489e50ef8f3992159abd0349b5b8e476c

Otherwise, a packet received on a bond will be affected to all interfaces of the bond.

On 2.6.27, we are able to receive packets on real interface for bonded devices. This allows one to get neighbor information on active/backup bonds. Without the 2.6.27, lldpd won't receive any information on inactive slaves. Here are the patchs (thanks to Joe Eykholt):

• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=0d7a3681232f545c6a59f77e60f7667673ef0e93
• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=cc9bd5cebc0825e0fabc0186ab85806a0891104f
• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f982307f22db96201e41540295f24e8dcc10c78f

On FreeBSD, only a recent 9 kernel (9.1 or more recent) will allow to send LLDP frames on enslaved devices. See this bug report for more information:

• http://www.freebsd.org/cgi/query-pr.cgi?pr=138620

Some devices (notably Cisco IOS) send frames on the native VLAN while they should send them untagged. If your network card does not support accelerated VLAN, you will receive those frames as well. However, if your network card handles VLAN encapsulation/decapsulation, you need a recent kernel to be able to receive those frames without listening on all available VLAN. Starting from Linux 2.6.27, lldpd is able to capture VLAN frames when VLAN acceleration is supported by the network card. Here is the patch: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=bc1d0411b804ad190cdadabac48a10067f17b9e6

More information:

• http://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol
• http://standards.ieee.org/getieee802/download/802.1AB-2005.pdf
• http://wiki.wireshark.org/LinkLayerDiscoveryProtocol

To embed lldpd into an existing system, there are two point of entries:

1. If your system does not use standard Linux interface, you can support additional interfaces by implementing the appropriate struct lldpd_ops. You can look at src/daemon/interfaces-linux.c for examples. Also, have a look at interfaces_update() which is responsible for discovering and registering interfaces.

2. lldpcli provides a convenient way to query lldpd. It also comes with various outputs, including XML which allows one to parse its output for integration and automation purpose. Another way is to use SNMP support. A third way is to write your own controller using liblldpctl.so. Its API is described in src/lib/lldpctl.h. The custom binary protocol between liblldpctl.so and lldpd is not stable. Therefore, the library should always be shipped with lldpd. On the other hand, programs using liblldpctl.so can rely on the classic ABI rules.

lldpd is distributed under the ISC license:

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Also, lldpcli will be linked to GNU Readline (which is GPL licensed) if available. To avoid this, use --without-readline as a configure option.