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AirVPN
Hummingbird

AirVPN Suite's Hummingbird for Linux and macOS

AirVPN's free and open source OpenVPN 3 client based on AirVPN's OpenVPN 3 library fork

Version 1.3.0 - Release date 1 June 2023

Main features:

  • Lightweight and stand alone binary
  • No heavy framework required, no GUI
  • Tiny RAM footprint
  • Lightning fast
  • Based on OpenVPN 3 library fork by AirVPN with tons of critical bug fixes from the main branch, new ciphers support and never seen before features
  • ChaCha20-Poly1305 cipher support on both Control and Data Channel providing great performance boost on ARM, Raspberry PI and any Linux-based platform not supporting AES-NI. Note: ChaCha20 support for Android had been already implemented in our free and open source Eddie Android edition
  • robust leaks prevention through Network Lock based either on iptables, nftables or pf through automatic detection
  • proper handling of DNS push by VPN servers, working with resolv.conf as well as any operational mode of systemd-resolved additional features

Contents

How to install AirVPN Hummingbird client for Linux - Raspberry and macOS

Hummingbird is distributed both in binary and source code forms. Both the binary version and the complete source code is available in the official gitlab repository. For more information, feedback and latest news, please refer to AirVPN forum and related threads

Requirements

Linux

  • x86-64 (64 bit), ARM 32 or ARM 64 bit CPU
  • A reasonably recent Linux distribution
  • OpenSSL 3.0
  • tar
  • sha512sum (optional)
  • ldd (optional)

Linux (legacy)

  • x86-64 (64 bit), ARM 32 or ARM 64 bit CPU
  • OpenSSL 1.1.x
  • tar
  • sha512sum (optional)
  • ldd (optional)

macOS

  • Macintosh computer with Intel or M1 architecture
  • macOS High Sierra or higher version
  • tar for plain version, zip for notarized version
  • shasum (optional)
  • otool (optional)

Linux

Hummingbird for Linux x86-64, arm7l (32 bit) and arm64 (aarch64) are distributed with AirVPN Suite. Please refer to AirVPN Suite package for installation instructions.

Please note hummingbird client needs root privileges to run. Your user must therefore be included in your system's "sudoers" (depending on specific Linux distribution)

Note about SELinux

In case your system has SELinux and Hummingbird is included in a systemd unit in order to make it start at boot time, you should note SELinux will prevent nft to be called from Hummingbird because access to stdin is forbidden by the default policy. In this specific case, Hummingbird will be unable to enforce Network Lock rules via nft and you need to create a specific SELinux exception in order to do that.

macOS Installation

Hummingbird for macOS is distributed in four versions according to architecture and code signature. The distribution files are identified as follows:

Intel x86_64 architecture:

  • Signed and notarized version: hummingbird-macos-x86_64-notarized-1.3.0.zip
  • Plain version: hummingbird-macos-x86_64-1.3.0.tar.gz

Apple M1 architecture:

  • Signed and notarized version: hummingbird-macos-arm64-notarized-1.3.0.zip
  • Plain version: hummingbird-macos-arm64-1.3.0.tar.gz

The difference is about how the package is seen by macOS security and it is therefore up to the user to pick the distribution file suiting his or her needs best. The signed/notarized version is compliant to macOS software security scheme and runs "out-of-the-box", whereas the plain version needs to be explicitly granted permission to run by the user in macOS security & privacy settings. Please note both versions are the same and ensure the very same functionality in connecting a VPN server, it is however up to the user to decide whether using the signed and notarized version or not.

Installing the signed and notarized version

Intel x86_64 Architecture

  • Download hummingbird-macos-x86_64-notarized-1.3.0.zip
  • [optional] Download hummingbird-macos-x86_64-notarized-1.3.0.zip.sha512 This file is required to check the integrity of the above zip archive. It is not mandatory but it is strongly advised to download this file and check the zip archive integrity
  • [optional] Open a terminal window
  • [optional] Check the integrity of the zip archive by issuing this command: shasum -a 512 -c hummingbird-macos-x86_64-notarized-1.3.0.zip.sha512
  • [optional] Make sure the command responds with hummingbird-macos-x86_64-notarized-1.3.0.zip: OK
  • Change your current directory to a convenient place, such as your home directory. This can be done by issuing the command cd ~
  • Extract the zip archive by issuing this command on your terminal window: unzip -x hummingbird-macos-x86_64-notarized-1.3.0.zip
  • A new directory will be created: hummingbird-macos-x86_64-1.3.0
  • Move into this new directory by entering command cd hummingbird-macos-x86_64-1.3.0
  • [optional] Check dynamic library availability. Issue the command otool -L hummingbird and make sure all the required dynamic libraries are available. No line of the output must contain "not found". Please note otool is distributed with Xcode
  • the macOS client is now ready to be used and possibly copied to a different directory of your system, such as /usr/bin or /usr/local/bin

Apple M1 Architecture

  • Download hummingbird-macos-arm64-notarized-1.3.0.zip
  • [optional] Download hummingbird-macos-arm64-notarized-1.3.0.zip.sha512 This file is required to check the integrity of the above zip archive. It is not mandatory but it is strongly advised to download this file and check the zip archive integrity
  • [optional] Open a terminal window
  • [optional] Check the integrity of the zip archive by issuing this command: shasum -a 512 -c hummingbird-macos-arm64-notarized-1.3.0.zip.sha512
  • [optional] Make sure the command responds with hummingbird-macos-arm64-notarized-1.3.0.zip: OK
  • Change your current directory to a convenient place, such as your home directory. This can be done by issuing the command cd ~
  • Extract the zip archive by issuing this command on your terminal window: unzip -x hummingbird-macos-arm64-notarized-1.3.0.zip
  • A new directory will be created: hummingbird-macos-arm64-1.3.0
  • Move into this new directory by entering command cd hummingbird-macos-arm64-1.3.0
  • [optional] Check dynamic library availability. Issue the command otool -L hummingbird and make sure all the required dynamic libraries are available. No line of the output must contain "not found". Please note otool is distributed with Xcode
  • the macOS client is now ready to be used and possibly copied to a different directory of your system, such as /usr/bin or /usr/local/bin

Please note hummingbird needs root privileges to run. Also note the notarized version has been signed with AirVPN di Paolo Brini Apple developer certificate (ASC provider ID: A7P5AKGWFC)

Installing the plain version

Intel x86_64 Architecture

  • Download hummingbird-macos-x86_64-1.3.0.tar.gz
  • [optional] Download hummingbird-macos-x86_64-1.3.0.tar.gz.sha512 This file is required to check the integrity of the above tar archive. It is not mandatory but it is strongly advised to download this file and check the tar archive integrity
  • [optional] Open a terminal window
  • [optional] Check the integrity of the tar archive by issuing this command: shasum -a 512 -c hummingbird-macos-x86_64-1.3.0.tar.gz.sha512
  • [optional] Make sure the command responds with hummingbird-macos-x86_64-1.3.0.tar.gz: OK
  • Change your current directory to a convenient place, such as your home directory. This can be done by issuing the command cd ~
  • Extract the tar archive by issuing this command on your terminal window: tar xvf hummingbird-macos-x86_64-1.3.0.tar.gz
  • A new directory will be created: hummingbird-macos-x86_64-1.3.0
  • Move into this new directory by entering command cd hummingbird-macos-x86_64-1.3.0
  • [optional] Check the integrity of the binary file hummingbird. Issue this command from your terminal window: shasum -a 512 -c hummingbird.sha512
  • [optional] Make sure the command responds with hummingbird: OK
  • [optional] Check dynamic library availability. Issue the command otool -L hummingbird and make sure all the required dynamic libraries are available. No line of the output must contain "not found". Please note otool is distributed with Xcode
  • the macOS client is now ready to be used and possibly copied to a different directory of your system, such as /usr/bin or /usr/local/bin

Apple M1 Architecture

  • Download hummingbird-macos-arm64-1.3.0.tar.gz
  • [optional] Download hummingbird-macos-arm64-1.3.0.tar.gz.sha512 This file is required to check the integrity of the above tar archive. It is not mandatory but it is strongly advised to download this file and check the tar archive integrity
  • [optional] Open a terminal window
  • [optional] Check the integrity of the tar archive by issuing this command: shasum -a 512 -c hummingbird-macos-arm64-1.3.0.tar.gz.sha512
  • [optional] Make sure the command responds with hummingbird-macos-arm64-1.3.0.tar.gz: OK
  • Change your current directory to a convenient place, such as your home directory. This can be done by issuing the command cd ~
  • Extract the tar archive by issuing this command on your terminal window: tar xvf hummingbird-macos-arm64-1.3.0.tar.gz
  • A new directory will be created: hummingbird-macos-arm64-1.3.0
  • Move into this new directory by entering command cd hummingbird-macos-arm64-1.3.0
  • [optional] Check the integrity of the binary file hummingbird. Issue this command from your terminal window: shasum -a 512 -c hummingbird.sha512
  • [optional] Make sure the command responds with hummingbird: OK
  • [optional] Check dynamic library availability. Issue the command otool -L hummingbird and make sure all the required dynamic libraries are available. No line of the output must contain "not found". Please note otool is distributed with Xcode
  • the macOS client is now ready to be used and possibly copied to a different directory of your system, such as /usr/bin or /usr/local/bin

Please note hummingbird needs root privileges to run.

Note on Checksum Files

We do strongly suggest you to check the integrity both of the distribution package files (tar.gz or zip) and the hummingbird binary in order to make sure you are installing a binary created and fully supported by AirVPN. Please read CHECKSUM.md for more information and to get the checksum codes created and guaranteed by AirVPN.

Note for macOS users: because of the changes and modifications done by Apple tools during the notarization process, please note the corresponding zip packages do not contain the file hummingbird.sha512.

Running the Hummingbird Client

Run hummingbird and display its help in order to become familiar with its options. From your terminal window issue this command:

sudo ./hummingbird --help

After having entered your root account password, hummingbird responds with:

Hummingbird - OpenVPN3 Client 1.3.0 - 1 June 2023
__ OpenVPN core 3.8.4 AirVPN linux x86_64 64-bit
Copyright (C) 2012-2022 OpenVPN Inc. All rights reserved.
OpenSSL 3.0.8 7 Feb 2023
__ usage: hummingbird [options] <config-file>
__ --help, -h : show this help page
--version, -v : show version info
--eval, -e : evaluate profile only (standalone)
--username, -u : username
--password, -p : password
--response, -r : static response
--dc, -D : dynamic challenge/response cookie
--cipher, -C : encrypt packets with specific cipher algorithm (alg)
--list-data-ciphers : list supported data ciphers
--proto, -P : protocol override (udp|tcp)
--server, -s : server override
--port, -R : port override
--tcp-queue-limit, -l : size of TCP packet queue (1-65535, default 8192)
--ncp-disable, -n : disable negotiable crypto parameters
--network-lock, -N : network filter and lock mode (on|iptables|nftables|pf|off, default on)
--gui-version, -E : set custom gui version (text)
--ignore-dns-push, -i : ignore DNS push request and use system DNS settings
--allowuaf, -6 : allow unused address families (yes|no|default)
--timeout, -t : timeout
--compress, -c : compression mode (yes|no|asym)
--pk-password, -z : private key password
--tvm-override, -M : tls-version-min override (disabled, default, tls_1_x)
--tcprof-override, -X : tls-cert-profile override (legacy, preferred, etc.)
--proxy-host, -y : HTTP proxy hostname/IP
--proxy-port, -q : HTTP proxy port
--proxy-username, -U : HTTP proxy username
--proxy-password, -W : HTTP proxy password
--proxy-basic, -b : allow HTTP basic auth
--alt-proxy, -A : enable alternative proxy module
--cache-password, -H : cache password
--no-cert, -x : disable client certificate
--def-keydir, -k : default key direction ('bi', '0', or '1')
--ssl-debug : SSL debug level
--auto-sess, -a : request autologin session
--auth-retry, -Y : retry connection on auth failure
--persist-tun, -j : keep TUN interface open across reconnects
--peer-info, -I : peer info key/value list in the form K1=V1,K2=V2,...
--gremlin, -G : gremlin info (send_delay_ms, recv_delay_ms, send_drop_prob, recv_drop_prob)
--epki-ca : simulate external PKI cert supporting intermediate/root certs
--epki-cert : simulate external PKI cert
--epki-key : simulate external PKI private key
--recover-network : recover network settings after a crash or unexpected exit
__ Open Source Project by AirVPN (https://airvpn.org)
__ Linux and macOS design, development and coding by ProMIND
__ Special thanks to the AirVPN community for the valuable help,
support, suggestions and testing.

Hummingbird needs a valid OpenVPN profile in order to connect to a server. You can create an OpenVPN profile by using the config generator available at AirVPN website in your account's Client Area

Start a connection

sudo ./hummingbird your_openvpn_file.ovpn

Stop a connection

Type CTRL+C in the terminal window where hummingbird is running. The client will initiate the disconnection process and will restore your original network settings according to your options.

Start a connection with a specific cipher

sudo ./hummingbird --ncp-disable --cipher CHACHA20-POLY1305 your_openvpn_file.ovpn

Please note: in order to properly work, the server you are connecting to must support the cipher specified with the --cipher option.

Disable the network filter and lock

sudo ./hummingbird --network-lock off your_openvpn_file.ovpn

Ignore the DNS servers pushed by the VPN server

sudo ./hummingbird --ignore-dns-push your_openvpn_file.ovpn

Please note: the above options can be combined together according to their use and function.

Controlling Hummingbird

Hummingbird uses the following system signals to control specific actions. You can send a signal to Hummingbird by using the kill command from a terminal.

  • SIGTERM, SIGINT, SIGPIPE, SIGHUP : Disconnect the active VPN connection

  • SIGUSR1: This is actually a toggle signal to be used to both pause and resume VPN connection. In case Goldcrest is connected to a VPN server, the connection is paused, whereas in case it is paused, VPN connection will be resumed. When the VPN connection is paused, tunnel device status is controlled according to --persist-tun option. Also consider that pausing and resuming a connection is allowed only in case TUN persistence is enabled.

  • SIGUSR2: Reconnect (restart) the current VPN connection. Reconnecting a connection is allowed only in case TUN persistence is enabled.

Note on macOS and UDP

Because of some architectural specifications and implementation in macOS, in particular in case of high speed traffic - a condition becoming more and more common in modern internet technology and infrastructure - Hummingbird may warn the user about shortage of buffer space, specifically when connected with the UDP protocol.

This condition is signaled by Hummingbird with the below messages in the log:

UDP send exception: send: No buffer space available
ERROR: NETWORK_SEND_ERROR

This error is caused by the maximum size set in macOS for network sockets, a value usually small and unsuited for modern high speed networks, specifically in case the VPN is connected with the UDP protocol. The solution to this problem consists in increasing the maximum allowed size for socket buffers and, in case the problem persists, to increase the number of mbuf clusters.

In this regard, it should be considered each mbuf cluster in macOS has a fixed size of 2Kb and the maximum socket buffer size cannot be greater than 1/16 of the total memory allocated by the system for mbuf clusters.

For example, in case the number of mbuf clusters is set to 32768 (this is likely to be the default value in most macOS systems), the total memory allocated for this purpose is 32768 * 2Kb, therefore 64Mb. The maximum socket buffer size is hence set to 1/16 of 64Mb, therefore 4Mb.

To find out the current values set in your system, you can use the following commands. Please note, you need to be root in order to manipulate these settings according to the commands provided below.

sysctl -a kern.ipc.nmbclusters

and

sysctl -a kern.ipc.maxsockbuf

in order to respectively get the current values set for the number of mbuf clusters and the maximum socket buffer size.

In case the current number of mbuf clusters set in your systems allows to do so, you can change the maximum socket buffer size by issuing the following command:

sysctl -w kern.ipc.maxsockbuf=<size_in_bytes>

For example, to set the maximum socket buffer size to 16Mb, this can be done with the below command:

sysctl -w kern.ipc.maxsockbuf=16777216

The above value is accepted by the system only in case the number of mbuf clusters is equal to or greater than 131072 (131072 * 2Kb = 268435456 = 256Mb)

Important note: by using sysctl command as described above, the value is set for the current session only and it is not permanent. This means when the machine is restarted or powered on, the above values will be reset to their respectively default values and according to the macOS version in use. To make these changes permanent and properly set up at system start-up, please refer to the procedures provided for the specific macOS version in use.

In case the current kern.ipc.nmbclusters value is not enough to properly increase kern.ipc.maxsockbuf, you can permanently change the value of ncl boot argument by issuing this command:

nvram boot-args="ncl=<number_of_mbuf_clusters>"

Please remember each mbuf cluster equates to 2Kb of RAM, therefore in case you want to set the size of memory used for mbuf clusters to 256Mb, therefore allowing a maximum value for kern.ipc.maxsockbuf of 16Mb, you can multiply this value (in bytes) by 16 then divided by 2048 (2Kb in bytes), therefore yielding the number of mbuf clusters.

16777216 * 16 = 268435456 (256Mb)

268435456 / 2048 = 131072

to make this value permanent you the need to issue the command:

nvram boot-args="ncl=131072"

then restart your system:

shutdown -r now

Upon reboot you are now allowed to set kern.ipc.maxsockbuf to 16Mb.

Network Filter and Lock

Hummingbird's network filter and lock natively uses iptables, iptables-legacy, nftables and pf in order to provide a "best effort leak prevention". Hummingbird will automatically detect and use the infrastructure available on your system.

You can also override this default behavior by manually selecting your preferred firewall by using --network-lock option, which defaults to on and, in this specific case, hummingbird will automatically detect and use the firewall installed on your system by using this specific priority: iptables-legacy, iptables, nftables and finally pf.

In case you want to force the use of a specific firewall, you can do that by specifying its name in the --network-lock option. For example, in case you want to force hummingbird to use nftables, you can specify --network-lock nftables. Please note the firewall must be properly installed on your system.

Also note in case both iptables and iptables-legacy are installed on your system, hummingbird will use iptables-legacy.

Note on nftables: Nftables rules created and issued by Hummingbird follow the specification and behavior of nftables version 0.9. In case you detect nftables errors or it seems to not be working properly, please check nftables installed on your system and make sure it is compatible with 0.9 specifications.

Please note: Linux services firewalld and ufw may interfere with the hummingbird's network filter and lock and you are strongly advised to not issue any firewall related command while the VPN connection is active.

DNS Management in Linux

Hummingbird currently supports both resolv.conf and systemd-resolved service. It is also aware of Network Manager, in case it is running. While the client is running, you are strongly advised to not issue any resolved related command (such as resolvectl) or change the resolv.conf file in order to make sure the system properly uses DNS pushed by the VPN server. Please note: DNS system settings are not changed in case the client has been started with --ignore-dns-push. In this specific case, the connection will use your system's DNS.

Furthermore, please note that if your network interfaces are managed by Network Manager, DNS settings might be changed under peculiar circumstances during a VPN connection, even when DNS push had been previously accepted.

DNS Management in macOS

DNS setting and management is done through OpenVPN 3 native support

Recover Your Network Settings

In case hummingbird crashes or it is killed by the user (i.e. kill -9 `pidof hummingbird` ) as well as in case of system reboot while the connection is active, the system may keep and use some or all of the netwrok settings determined by the client, therefore your network connection might not work as expected, every connection might be refused and the system might seem to be "network locked". . To restore and recover your system network, you can use the client with the --recover-network option.

sudo ./hummingbird --recover-network

Please note in case of crash or unexpected exit, when you subsequently run hummingbird it will warn you about the unexpected exit and will require you to run it again with the --recover-network option. It will also refuse to start any connection until the network has been properly restored and recovered.

Building Hummingbird from Sources

In order to build hummingbird from sources, you need the following dependencies:

Clone AirVPN-Suite repository into your computer:

git clone https://gitlab.com/AirVPN/AirVPN-Suite

Move into the project's directory:

cd AirVPN-Suite

Build Linux Dynamic Binary

Edit build-hummingbird.sh script and set INC_DIR, OPENVPN3 and ASIO variables according to your system configuration

Run the build shell script:

sh build-hummingbird.sh

The script will compile the project and create hummingbird binary in the current directory.

Build Linux - ARM and macOS Static Binary

Edit build-hummingbird-static.sh script and set INC_DIR, OPENVPN3 and ASIO variables according to your system configuration. Also set STATIC_LIB_DIR and SSL_LIB_DIR according to your system architecture.

Run the build shell script:

sh build-hummingbird-static.sh

The script will create a hummingbird static binary file according to your system and will also create the associated distribution compressed tarball file in the current directory. To install the binary in your system, please refer to the installation instructions provided above.

Hummingbird is an open source project by AirVPN

Linux and macOS design, development and coding by ProMIND

Special thanks to the AirVPN community for the valuable help, support, suggestions and testing.

OpenVPN is Copyright (C) 2012-2022 OpenVPN Inc. All rights reserved.

Hummingbird is released and licensed under the GNU General Public License Version 3 (GPLv3)

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