syncookied

syncookied emulates linux kernel syncookie functionality by intercepting SYN packets and sending replies to them using the same cookie generation alghorithm. It can achieve better performance under SYN flood attacks thanks to kernel bypass (netmap).

Installation

1. Install rust (instructions here: https://www.rust-lang.org/en-US/downloads.html)
2. Install build-essential and libpcap-dev or equivalent package for your distribution
3. Install netmap. Make sure netmap.h / netmap_user.h can be found in /usr/include. Alternative you can point CFLAGS variable to their location: example.
4. run cargo build --release, resulting binary will be found in target/release/syncookied.

Note: we use AVX-accelerated SHA1 function by default. SSE3 implementation is also available under sse3 feature flag, i.e.: cargo build --features=sse3 --no-default-features --release.

How to run

On server you want to protect

1. Install tcpsecrets linux kernel mode to expose tcp syncookie key and timestamp
2. Start syncookied in server mode: syncookied server <proto://ip:port>. Running this commands automatically starts a TCP or UDP server on specified ip/port and sets net.ipv4.tcp_syncookies to 2 on first request.

On server you want to use for packet processing

1. Install netmap and make sure it works (pkt-gen)

2. Disable NIC offloading features on the interface you want to use (eth2 here):

   ethtool -K eth2 gro off gso off tso off lro off rx off tx off 
   ethtool -A eth2 rx off tx off
   ethtool -G eth2 rx 2048 tx 2048
   

3. Set up queues and affinities. Here we bind 12 queues to first 12 cpu cores:

   QUEUES=12
   ethtool -L eth2 combined $QUEUES
   ./set_irq_affinity -x 0-11 eth2
   

   set_irq_affinity is available at https://github.com/majek/ixgbe/blob/master/scripts/set_irq_affinity

4. Create hosts.yml file in the working directory, which looks like this

   - ip: 185.50.25.4
     secrets_addr: udp://192.168.3.231:1488
     mac: 0c:c4:7a:6a:fa:bf
   

Here ip is external ip you want to protect, secrets_addr is the address of syncookied server running on protected host, and mac is its MAC address.

5. Run syncookied -i eth2. It will print something like this:

   Configuration: 185.50.25.4 -> c:c4:7a:6a:fa:bf
   interfaces: [Rx: eth2/3c:fd:fe:9f:a8:82, Tx: eth2/3c:fd:fe:9f:a8:82] Cores: 24
   12 Rx rings @ eth2, 12 Tx rings @ eth2 Queue: 1048576
   Starting RX thread for ring 0 at eth2
   Starting TX thread for ring 0 at eth2
   Uptime reader for 185.50.25.4 starting
   ...
   

6. Configure your network equipment to direct traffic for protected ip to syncookied.

7. You can reload configuration at any time by changing hosts.yml and sending HUP signal to syncookied. It will print something like this:

   Uptime reader for 185.50.25.4 exiting
   All uptime readers dead
   Old readers are dead, all hail to new readers
   Uptime reader for 185.50.25.4 starting
   ...
   

8. Enjoy your ddos protection

Notes

syncookied has some options you may want to tune, see syncookied --help. If you have more than 1 interface on your server, you may want to look into -O to use second one for TX. This greatly improves performance and latency as forwarding and syn-reply traffic is separated.

Traffic filtering

It's possible to filter traffic by adding "filters" section to host configuration like this:

- ip: 185.50.25.4
  secrets_addr: 127.0.0.1:1488
  mac: 0c:c4:7a:6b:0a:78
  filters:
   tcp and dst port 53: drop
   tcp and dst port 22: pass
   default: pass

Filters are written in pcap syntax. Consult pcap-filter(7) for more information. Default policy is "pass". It can be changed by using default key. Note that filtering happens on layer 4.

Troubleshooting

Please check the FAQ before filing an issue.

Need help?

Join us on Telegram: https://telegram.me/syncookied

Performance

syncookied under 12.65 Mpps syn flood attack utilizing 12 cores of Xeon E5-2680v3:

License

syncookied is distributed under the term of GPLv2.