Fix data length field

example.config

@@ -1,5 +1,7 @@
 # base domain for all records
 baseDomain = "acme.example.com"
+# the domain this dns server can be reached at
+serverDomain = "dns.example.com"
 dnsPort = 15353
 apiPort = 18000
 

lib/dns.nim

@@ -61,7 +61,7 @@ type
     header*: DnsHeader
     questions*: seq[DnsQuestion]
     answer*: seq[DnsRecord]
-    authroity*: seq[DnsRecord]
+    authority*: seq[DnsRecord]
     additional*: seq[DnsRecord]
 
 func parseNameField*(data: string, startOffset: uint16): (seq[string], uint16) =
@@ -158,13 +158,14 @@ func parseResourceRecord*(data: string, startOffset: uint16): (DnsRecord, uint16
 
 func packResourceRecord*(data: DnsRecord): string =
   var record = ""
+  let body = (if data.rtype == DnsType.NS: packNameField(data.rdata) else: data.rdata)
 
   record.add(packNameField(data.name))
   record.add(uint16ToString(data.rtype.uint16))
   record.add(uint16ToString(data.class.uint16))
   record.add(uint32ToString(data.ttl.uint32))
-  record.add(uint16ToString(data.rdlength.uint16))
+  record.add(uint16ToString(body.len.uint16))
-  record.add(data.rdata)
+  record.add(body)
 
   return record
 
@@ -186,6 +187,9 @@ func packMessage*(message: DnsMessage): string =
   for answer in message.answer:
     encoded.add(packResourceRecord(answer))
 
+  for authroity in message.authority:
+    encoded.add(packResourceRecord(authroity))
+
   return encoded
 
 func mkRecord*(rtype: DnsType, question: string, answer: string): DnsRecord =
@@ -198,14 +202,16 @@ func mkRecord*(rtype: DnsType, question: string, answer: string): DnsRecord =
     rdata: (if rtype == DnsType.TXT: chr(len(answer)) & answer else: answer)
   )
 
-func mkResponse*(id: uint16, question: DnsQuestion, answer: seq[string]): DnsMessage =
+func mkResponse*(id: uint16, question: DnsQuestion, answer: seq[string], authority: string, base: string): DnsMessage =
   return DnsMessage(
     header: DnsHeader(
       id: id,
       qr: DnsQr.RESPONSE,
       aa: true,
       rcode: Rcode.NO_ERROR,
-      ancount: len(answer).uint16
+      ancount: len(answer).uint16,
+      nscount: 1
     ),
+    authority: @[mkRecord(DnsType.NS, base, authority)],
     answer: answer.map(proc (a: string): DnsRecord = mkRecord(question.qtype, question.qname, a))
   )

norbert.nim

@@ -22,8 +22,15 @@ proc initConfig(): AppConfig =
       echo "Error parsing port config"
       quit 1
 
+    let serverName = configFile.getSectionValue("", "serverDomain")
+
+    if serverName == "":
+      echo "Missing serverDomain"
+      quit 1
+
     let config = AppConfig(
       base: configFile.getSectionValue("", "baseDomain"),
+      serverName: serverName,
       users: newStringTable(),
       apiPort: Port(apiPort),
       dnsPort: Port(dnsPort)

src/dnsserver.nim

@@ -2,7 +2,7 @@ import asyncnet, asyncdispatch, nativesockets
 import strutils, options, tables, strformat
 import ../lib/dns, state
 
-proc handleDnsRequest(records: RecordsTable, data: string): Option[string] =
+proc handleDnsRequest(records: RecordsTable, data: string, config: AppConfig): Option[string] =
   let msg = parseMessage(data)
 
   echo msg
@@ -14,7 +14,9 @@ proc handleDnsRequest(records: RecordsTable, data: string): Option[string] =
   let response = mkResponse(
     msg.header.id,
     question,
-    records.getOrDefault((name: question.qname.toLowerAscii(), dtype: question.qtype), @[])
+    records.getOrDefault((name: question.qname.toLowerAscii(), dtype: question.qtype), @[]),
+    config.serverName,
+    config.base
   )
 
   echo response
@@ -31,7 +33,7 @@ proc serveDns*(config: AppConfig) {.async.} =
   while true:
     try:
       let request = await dns.recvFrom(size=512)
-      let response = handleDnsRequest(records, request.data)
+      let response = handleDnsRequest(records, request.data, config)
 
       if (response.isSome):
         await dns.sendTo(request.address, request.port, response.unsafeGet)

src/state.nim

@@ -1,4 +1,4 @@
-import tables, strtabs, sequtils, nativesockets, strutils
+import tables, strtabs, sequtils, nativesockets
 import ../lib/dns
 
 type
@@ -13,6 +13,7 @@ type
   AppConfig* = object
     users*: StringTableRef
     base*: string
+    serverName*: string
     apiPort*: Port
     dnsPort*: Port