About

udpclone just copies a packet and sends it to as may destinations as needed, and it sends back any traffic that was received from any of these destinations.

flowchart LR
    client[UDP client]
    udpclone[udpclone]
    R0[receiver 1]
    R1[receiver 2]
    R2[receiver 3]

    client <-->|UDP packet| udpclone

    udpclone <-->|UDP packet| R0
    udpclone <-->|UDP packet| R1
    udpclone <-->|UDP packet| R2

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Personally I used it for OpenVPN:

flowchart LR
    OVPN0[OpenVPN client]
    OVPN1[OpenVPN server]
    udpclone[udpclone]
    OVPN1P{port 5743}
    OVPN1P0{port 9000}
    OVPN1P1{port 9001}
    OVPN1P2{port 9002}

    OVPN0 <-->|UDP packet| udpclone

    udpclone <-->|UDP packet| OVPN1P0
    udpclone <-->|UDP packet| OVPN1P1
    udpclone <-->|UDP packet| OVPN1P2

    OVPN1P0 <-->|REDIRECTed by netfilter| OVPN1P
    OVPN1P1 <-->|REDIRECTed by netfilter| OVPN1P
    OVPN1P2 <-->|REDIRECTed by netfilter| OVPN1P
    OVPN1P <-->|UDP packet| OVPN1

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where each connection used different channel via iproute2 rules. OpenVPN drops duplicated packets by itself as part of anti-replay protections.

This helped to mitigate really poor connection of one of my mobile streaming (SRT) setups, that uses 3 SIM cards. I guess I could've duplicated the traffic of SRT itself instead of OpenVPN, but I also wanted to have SSH and other connections work reliably.

Howto

Build

git clone https://github.com/xaionaro-go/udpclone /opt/udpclone
cd /opt/udpclone
go build
ln -s ../../../opt/udpclone /usr/local/bin

Run

Configure buffers:

# increase the buffer, otherwise we get error "No buffer space available"
echo $[ 64 * 1024 * 1024 ] > /proc/sys/net/core/wmem_max

Run udpclone:

udpclone --listen-addr 0.0.0.0:9000 --destinations X.X.X.X:9000,Y.Y.Y.Y:9000,Z.Z.Z.Z:9000

Example

The OpenVPN example from "About":

Client-side configuration:

echo $[ 64 * 1024 * 1024 ] > /proc/sys/net/core/wmem_max # otherwise we get error "No buffer space available"

ip rule add ipproto udp dport 9000 lookup wlan0  pref 4000
ip rule add ipproto udp dport 9001 lookup rmnet1 pref 4010
ip rule add ipproto udp dport 9002 lookup bt-pan pref 4020

udpclone (launched on the client side):

udpclone --listen-addr 0.0.0.0:5743 --destinations my.home.address:9000,my.home.address:9001,my.home.address:9002

In my case my.home.address was a DyDNS-address.

Server-side configuration:

nft add rule nat PREROUTING iif lxc udp dport 9000-9010 ip daddr X.X.X.X dnat X.X.X.X:5743

Similar projects (and the difference)

(feel free to make a PR adding your project here...)

• https://github.com/chenx-dust/paracat. deduplicates traffic automatically, by adding a sequence number to packets and then stripping it back. Supports also Round-Robin mode. But it does not support the case if one of the destinations not available in the beginning or the case of changing the destination IP (a-la DyDNS destinations).
• https://github.com/path-network/UDP-Clone. A minimalistic tool that does essentially the same as udpclone. But it does not support the case if one of the destinations not available in the beginning or the case of changing the destination IP (a-la DyDNS destinations).