Bitcoin-seeder
Bitcoin-seeder is a crawler for the Bitcoin network, which exposes a list of reliable nodes via a built-in DNS server.
Features:
- Regularly revisits known nodes to check their availability.
- Bans nodes after enough failures, or bad behaviour.
- Keeps statistics over (exponential) windows of 2 hours, 8 hours, 1 day and 1 week, to base decisions on.
- Very low memory (a few tens of megabytes) and CPU requirements.
- Crawlers run in parallel (by default 24 threads simultaneously).
Requirements
sudo apt-get install build-essential libboost-all-dev libssl-dev
Usage
Assuming you want to run a DNS seed on dnsseed.example.com, you will need an authorative NS record in example.com's domain record, pointing to for example vps.example.com:
$ dig -t NS dnsseed.example.com
;; ANSWER SECTION
dnsseed.example.com. 86400 IN NS vps.example.com.
On the system vps.example.com, you can now run dnsseed:
./dnsseed -h dnsseed.example.com -n vps.example.com -m root.example.com
If you want the DNS server to report SOA records, please provide an e-mail address (with the @ part replaced by .) using -m.
Building
Compiling will require boost and ssl. On debian systems, these are provided
by libboost-dev and libssl-dev respectively.
make
This will produce the dnsseed binary executable.
Running as non-root
Typically, you'll need root privileges to listen to port 53 (name service).
One solution is using an iptables rule (Linux only) to redirect it to a non-privileged port:
iptables -t nat -A PREROUTING -p udp --dport 53 -j REDIRECT --to-port 5353
If properly configured, this will allow you to run dnsseed in userspace, using
the -p 5353 option.
Alternatively, non-root binding to privileged ports is possible on Linux supporting
"POSIX capabilities". If the setcap and getcap commands are available just issue
this command as root or via sudo
sudo setcap cap_net_bind_service=+ep /path/to/dnsseed