From b0062c2d7445a9ae0135715b7d29cf155f093d9a Mon Sep 17 00:00:00 2001 From: Alex Grintsvayg Date: Mon, 12 Apr 2021 15:51:30 -0400 Subject: [PATCH] readme update --- README | 66 ---------------------------- readme.md | 128 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 128 insertions(+), 66 deletions(-) delete mode 100644 README create mode 100644 readme.md diff --git a/README b/README deleted file mode 100644 index 7018134..0000000 --- a/README +++ /dev/null @@ -1,66 +0,0 @@ -seeder -============== - -seeder is a crawler for the LBRY 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 -* accepts nodes down to v0.3.19 to request new IP addresses from, - but only reports good post-v0.3.24 nodes. -* 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-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 - -If you want the DNS server to report SOA records, please provide an -e-mail address (with the @ part replaced by .) using -m. - -COMPILING ---------- -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. - - -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. - -Another solution is allowing a binary to bind to ports < 1024 with setcap (IPv6 access-safe) - -$ setcap 'cap_net_bind_service=+ep' /path/to/dnsseed diff --git a/readme.md b/readme.md new file mode 100644 index 0000000..bc4155a --- /dev/null +++ b/readme.md @@ -0,0 +1,128 @@ +# seeder + +seeder is a crawler for the LBRY 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 +* accepts nodes down to v0.3.19 to request new IP addresses from, + but only reports good post-v0.3.24 nodes. +* 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). + + +## Build + +``` +sudo apt-get install build-essential libboost-dev libssl-dev +make +``` + +## Use + +Assumptions: + +- lbrycrd will use the domain `seed.example.com` to find peer nodes +- you will be running this seeder on a server at domain `vps.example.com` + +### Configure DNS + +You will need two DNS records: + +type | name | value +-----|------------------| --------------- +NS | seed.example.com | vps.example.com +A | vps.example.com | 1.2.3.4 + + +Test your DNS records + +``` +$ dig -t NS seed.example.com + +;; ANSWER SECTION +seed.example.com. 86400 IN NS vps.example.com. +``` + +### Disable systemd resolver (Ubuntu 18.04+) + +You only need this if you want to run the seeder on port 53 and it's taken by +Ubuntu's resolved. Run the following to turn the resolver off and prevent +it from starting on reboot + +``` +sudo systemctl stop systemd-resolved.service +sudo systemctl disable systemd-resolved.service + +``` + +### Open firewall port + +For example, if using UFW, run `ufw allow 53`. Some VPS providers also +have their own firewall that you'll need to configure. + +### Run the seeder + +On the system vps.example.com, you can now run dnsseed: + +``` +./dnsseed -h seed.example.com -n vps.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`. + + +### 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. + +Another solution is allowing a binary to bind to ports < 1024 with setcap (IPv6 access-safe) + +``` +setcap 'cap_net_bind_service=+ep' /path/to/dnsseed +``` + +## Debugging + +### Server-side + +On the server, run `sudo tcpdump port 53`. This will show you all traffic on port 53. As +you send DNS queries, you should see `A` requests come in and response IPs go out. + +- no incoming responses: DNS or firewall issues, or DNS request is cached client-side +- no responses: seeder is not running, or running on the wrong port, or broken +- empty responses: requested domain doesn't match configured domain in seeder + +You can also look at the output of the running seeder. It looks like this + +``` +[21-04-12 19:30:49] 28/104 available (104 tried in 994s, 1 new, 30 active), 0 banned; 38 DNS requests, 1 db queries +``` + +- if # of DNS requests is not going up as you send them, then seeder is not getting your requests +- if DNS requests are increasing but db queries are not, then the -h domain doesn't match +- if seeder didn't find any nodes, then it can't contact the nodes it itself is seeded with + +### Client-side + +Try `dig +short seed.example.com`. If you get node IPs, your setup is working. + +Other things to try + +- `dig @1.2.3.4 seed.example.com` to bypass local DNS cache or incorrect DNS records +- `dig +trace seed.example.com` for detailed routing info +