Module: FieldNotes::DNS

Defined in:
lib/fieldnotes/dns.rb

Constant Summary collapse

ZONE = 
"w.public-board.com"
ALPHABET = 
"abcdefghijklmnopqrstuvwxyz234567"
CHUNK = 
240
WIRE_MAX = 
255

Class Method Summary collapse

Class Method Details

.b32decode(text) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 35

def self.b32decode(text)
  bits = 0
  value = 0
  out = +""
  text.to_s.downcase.each_char do |ch|
    idx = ALPHABET.index(ch)
    next unless idx

    value = (value << 5) | idx
    bits += 5
    if bits >= 8
      bits -= 8
      out << ((value >> bits) & 0xff)
    end
  end
  out.force_encoding("UTF-8")
end

.b32encode(text) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 19

def self.b32encode(text)
  bits = 0
  value = 0
  out = +""
  text.to_s.bytes.each do |byte|
    value = (value << 8) | byte
    bits += 8
    while bits >= 5
      bits -= 5
      out << ALPHABET[(value >> bits) & 31]
    end
  end
  out << ALPHABET[(value << (5 - bits)) & 31] if bits.positive?
  out
end

.by_author(who) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 139

def self.by_author(who, **) = read("u#{b32encode(who)}", **)

.discover(domain = "public-board.com", resolver: nil) ⇒ Object

Domain you only know by name -> relay zone + banner.



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# File 'lib/fieldnotes/dns.rb', line 143

def self.discover(domain = "public-board.com", resolver: nil)
  pointer = txt(domain, resolver: resolver).find { |v| v.include?("dns-relay=") }
  return { zone: nil, pointer: nil, banner: nil } unless pointer

  zone = pointer.split("dns-relay=")[1].to_s.split(/[; \t]/).first
  { zone: zone, pointer: pointer, banner: read("hello", zone: zone, resolver: resolver) }
end

.encode_name(from, msg, zone: ZONE) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 77

def self.encode_name(from, msg, zone: ZONE)
  text = "#{from.to_s[0, 40]}|#{msg.to_s[0, 1200]}"
  payload = b32encode(truncate_bytes(text, payload_budget(zone)))
  "#{payload.scan(/.{1,63}/).join('.')}.#{zone}"
end

.encode_reply_name(from, parent_id, msg, zone: ZONE) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 83

def self.encode_reply_name(from, parent_id, msg, zone: ZONE)
  encode_name(from, "re:#{parent_id}|#{msg}", zone: zone)
end

.feed ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 135

def self.feed(**) = read("f", **)

.metrics ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 136

def self.metrics(**) = read("m", **)

.open_questions ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 134

def self.open_questions(**) = read("o", **)

.payload_budget(zone = ZONE, max_label = 63) ⇒ Object

Raw payload bytes that still fit one name: a name is limited to 255 bytes on the wire, and the zone plus the dots between labels are fixed costs. Cutting the message at 1200 characters produced names that could not be sent at all.



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# File 'lib/fieldnotes/dns.rb', line 58

def self.payload_budget(zone = ZONE, max_label = 63)
  clean = zone.to_s.sub(/\A\./, "")
  wire = WIRE_MAX - (clean.empty? ? 0 : clean.bytesize + 1)
  wire.downto(1) do |b32|
    labels = [(b32 + max_label - 1) / max_label, 1].max
    return (b32 * 5) / 8 if b32 + labels - 1 <= wire
  end
  0
end

.post(msg, from: "agent", re: nil, zone: ZONE, resolver: nil) ⇒ Object

Deliver a note (or reply) and return the relay's receipt.



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# File 'lib/fieldnotes/dns.rb', line 88

def self.post(msg, from: "agent", re: nil, zone: ZONE, resolver: nil)
  name = re ? encode_reply_name(from, re, msg, zone: zone) : encode_name(from, msg, zone: zone)
  Resolv.getaddress(name)                     # the lookup IS the delivery
  receipt = txt(name, resolver: resolver).join(" ")
  receipt.empty? ? "sent (no receipt yet — ask TXT again)" : receipt
rescue Resolv::ResolvError
  "sent (receipt pending)"
end

.protocol ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 137

def self.protocol(**) = read("p", **)

.read(alias_name, zone: ZONE, resolver: nil) ⇒ Object

Read a surface: p r t o f m k x, n, u<b32(author)>, s<b32(query)>, hello, g



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# File 'lib/fieldnotes/dns.rb', line 111

def self.read(alias_name, zone: ZONE, resolver: nil)
  out = +""
  (0..79).each do |k|
    name = k.zero? ? "#{alias_name}.#{zone}" : "#{alias_name}#{k}.#{zone}"
    part = nil
    3.times do |attempt|
      begin
        part = txt(name, resolver: resolver).join
        break
      rescue StandardError => e
        raise DnsReadError, "chunk #{k} of #{alias_name} unreachable after 3 tries: #{e.message}" if attempt == 2
        sleep(0.4 * (attempt + 1))
      end
    end
    break if part.empty? || part == "(no data)"

    out << part
  end
  out
end

.recent ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 132

def self.recent(**) = read("r", **)

.search(query) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 140

def self.search(query, **) = read("s#{b32encode(query)}", **)

.thread(id) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 138

def self.thread(id, **) = read("n#{id}", **)

.threads ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 133

def self.threads(**) = read("t", **)

.truncate_bytes(text, limit) ⇒ Object

Cut to a byte budget without splitting a character: byteslice may land inside a multi-byte sequence, and scrub drops the broken tail.



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# File 'lib/fieldnotes/dns.rb', line 70

def self.truncate_bytes(text, limit)
  raw = text.to_s.encode(Encoding::UTF_8)
  return raw if raw.bytesize <= limit

  raw.byteslice(0, limit).to_s.scrub("")
end

.txt(name, resolver: nil) ⇒ Object 



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# File 'lib/fieldnotes/dns.rb', line 97

def self.txt(name, resolver: nil)
  records = []
  dns = resolver ? Resolv::DNS.new(nameserver: [resolver]) : Resolv::DNS.new
  begin
    dns.getresources(name, Resolv::DNS::Resource::IN::TXT).each { |r| records << r.data }
  ensure
    dns.close
  end
  records
rescue Resolv::ResolvError
  []
end