tidy code up and make the project more user friendly overall

README.md

@@ -1,34 +1,48 @@
-# Simple DNS Server
+# 🌎 Simple DNS server
+A tiny DNS server that is capable of serving records configured in a MySQL table, or configured statically in a JSON file
 
-## Installation
-1. Create a file with the path `/etc/systemd/system/argondns.service` and with the following content:
+## 🧐 Configuration documentation
+
+- `mode`: Can be either `db` if your records are stored in a MySQL database, or `static_records` if your records are static and stored in the configuration JSON file.
+
+- `db`: The MySQL server & database credentials. This works only if `mode` is set to `db`
+
+- `listener`: The listening/bind settings for the DNS server (usually has to be kept binding on port 53 to be able to accept DNS requests).
+
+- `process_unstored_dns_queries`: Should the DNS server also accept queries of records that are not stored in your database table/static records configuration? Enable this if yes.
+
+- `static_records`: Configure your static records here, one per JSON array. This works only if `mode` is set to `static_records`
+
+## 🛠️ Installation as a service
+
+1. Store your configuration file at `/etc/simpledns/config.json`
+   You can copy the example configuration file and change it to serve your needs.
+2. If running Simple DNS server in the `db` mode, use this database structure for your records table: https://github.com/oddmario/simple-dns-server/blob/main/db_structure.sql
+3. Place the binary file of Simple DNS server at `/usr/local/bin` (e.g. `/usr/local/bin/simpledns`)
+4. Make the binary file executable: `chmod u+x /usr/local/bin/simpledns`
+5. Create a systemd service for the application. This can be done by creating /etc/systemd/system/simpledns.service to have this content:
 ```
 [Unit]
-Description=ArgonDNS
+Description=SimpleDNSserver
 
 [Service]
 User=root
-WorkingDirectory=/root/argondns
+WorkingDirectory=/usr/local/bin
 LimitNOFILE=2097152
 TasksMax=infinity
-ExecStart=/root/argondns/simpledns_linux_amd64
+ExecStart=/usr/local/bin/simpledns /etc/simpledns/config.json
 Restart=on-failure
 StartLimitInterval=180
 StartLimitBurst=30
 RestartSec=5s
 
 [Install]
 WantedBy=multi-user.target
-```
-
-2. Put the `simpledns_linux_amd64` executable file at a directory with path `/root/argondns/` - so the final path of the executable will be `/root/argondns/simpledns_linux_amd64`
-
-3. Run `chmod -R 777 /root/argondns/simpledns_linux_amd64`
-
-4. Place the `config.json` file found in this repository at `/root/argondns` along with the `simpledns_linux_amd64` executable file
-
-5. Run `systemctl enable argondns`
 
+```
 6. Port 53 (the DNS server port) is usually in use by default. To solve this, follow https://unix.stackexchange.com/a/676977/405697 then run `systemctl restart systemd-resolved`
-
-7. Make sure that there are no other DNS servers (such as bind9) are running, then run `systemctl start argondns` to start our DNS server :) 
+7. Make sure that there are no other DNS servers (such as bind9) are running
+8. Enable the Simple DNS server service on startup & start it now:
+```
+systemctl enable --now simpledns.service
+```

config.json

@@ -1,4 +1,5 @@
 {
+    "mode": "db",
     "db": {
         "host": "localhost",
         "username": "root",
@@ -14,5 +15,17 @@
     "process_unstored_dns_queries": {
         "is_enabled": false,
         "dns_server": "8.8.8.8:53"
-    }
+    },
+    "static_records": [
+        {
+            "type": "A",
+            "name": "",
+            "value": "",
+            "ttl": 0,
+            "srv_priority": 0,
+            "srv_weight": 0,
+            "srv_port": 0,
+            "srv_target": ""
+        }
+    ]
 }

constants/constants.go

@@ -0,0 +1,4 @@
+package constants
+
+var ConfigFilePath string = ""
+var Version string = "v1.2"

db/utils.go

@@ -2,6 +2,8 @@ package db
 
 import (
 	"database/sql"
+	"errors"
+	"time"
 )
 
 func EasyQuery(query string, args ...any) (*sql.Rows, error) {
@@ -23,3 +25,31 @@ func EasyExec(query string, args ...any) (sql.Result, error) {
 
 	return res, nil
 }
+
+func RetriedDbQuery(retries int, query string, args ...any) (*sql.Rows, error) {
+	for range retries {
+		res, err := EasyQuery(query, args...)
+		if err != nil {
+			time.Sleep(1 * time.Second)
+			continue
+		} else {
+			return res, err
+		}
+	}
+
+	return nil, errors.New("failed")
+}
+
+func RetriedDbExec(retries int, query string, args ...any) (sql.Result, error) {
+	for range retries {
+		res, err := EasyExec(query, args...)
+		if err != nil {
+			time.Sleep(1 * time.Second)
+			continue
+		} else {
+			return res, err
+		}
+	}
+
+	return nil, errors.New("failed")
+}

dnsparser/A.go

@@ -2,52 +2,32 @@ package dnsparser
 
 import (
 	"mario/simple-dns-server/db"
+	"mario/simple-dns-server/records"
 	"net"
 
 	"github.com/miekg/dns"
 )
 
 func A(m *dns.Msg, name_dot, name_nodot string) bool {
-	res, err := db.EasyQuery("SELECT id, record_type, record_name, record_value, record_ttl, is_disposable FROM dns_records WHERE record_name = ? AND record_type = 'A'", name_nodot)
-	if err != nil {
-		// an error has occured while preparing the SQL statement
-		return false
-	}
-	defer res.Close()
-
-	var recordsFound bool = false
+	recordsFound, records := records.GetDNSRecord(name_nodot, "A")
 
-	for res.Next() {
-		recordsFound = true
-
-		var record_id int64
-		var record_type string
-		var record_name string
-		var record_value string
-		var record_ttl int64
-		var record_isdisposable int64
+	if !recordsFound {
+		// DNS record(s) was/were not found
 
-		err = res.Scan(&record_id, &record_type, &record_name, &record_value, &record_ttl, &record_isdisposable)
-		if err != nil {
-			// an error has occured
-			return false
-		}
+		return false
+	}
 
+	for _, record := range records {
 		r := new(dns.A)
-		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(record_ttl)}
-		r.A = net.ParseIP(record_value)
+		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(record.TTL)}
+		r.A = net.ParseIP(record.Value)
 
 		m.Answer = append(m.Answer, r)
 
-		if record_isdisposable > 0 {
-			db.EasyExec("DELETE FROM dns_records WHERE id = ?", record_id)
+		if record.IsDisposable {
+			db.RetriedDbExec(10, "DELETE FROM dns_records WHERE id = ?", record.ID)
 		}
 	}
 
-	if !recordsFound {
-		// DNS record not found in the database
-		return false
-	}
-
 	return true
 }

dnsparser/CNAME.go

@@ -2,51 +2,31 @@ package dnsparser
 
 import (
 	"mario/simple-dns-server/db"
+	"mario/simple-dns-server/records"
 
 	"github.com/miekg/dns"
 )
 
 func CNAME(m *dns.Msg, name_dot, name_nodot string) bool {
-	res, err := db.EasyQuery("SELECT id, record_type, record_name, record_value, record_ttl, is_disposable FROM dns_records WHERE record_name = ? AND record_type = 'CNAME'", name_nodot)
-	if err != nil {
-		// an error has occured while preparing the SQL statement
-		return false
-	}
-	defer res.Close()
-
-	var recordsFound bool = false
+	recordsFound, records := records.GetDNSRecord(name_nodot, "CNAME")
 
-	for res.Next() {
-		recordsFound = true
-
-		var record_id int64
-		var record_type string
-		var record_name string
-		var record_value string
-		var record_ttl int64
-		var record_isdisposable int64
+	if !recordsFound {
+		// DNS record(s) was/were not found
 
-		err = res.Scan(&record_id, &record_type, &record_name, &record_value, &record_ttl, &record_isdisposable)
-		if err != nil {
-			// an error has occured
-			return false
-		}
+		return false
+	}
 
+	for _, record := range records {
 		r := new(dns.CNAME)
-		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: uint32(record_ttl)}
-		r.Target = dns.Fqdn(record_value)
+		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: uint32(record.TTL)}
+		r.Target = dns.Fqdn(record.Value)
 
 		m.Answer = append(m.Answer, r)
 
-		if record_isdisposable > 0 {
-			db.EasyExec("DELETE FROM dns_records WHERE id = ?", record_id)
+		if record.IsDisposable {
+			db.RetriedDbExec(10, "DELETE FROM dns_records WHERE id = ?", record.ID)
 		}
 	}
 
-	if !recordsFound {
-		// DNS record not found in the database
-		return false
-	}
-
 	return true
 }

dnsparser/NS.go

@@ -2,51 +2,31 @@ package dnsparser
 
 import (
 	"mario/simple-dns-server/db"
+	"mario/simple-dns-server/records"
 
 	"github.com/miekg/dns"
 )
 
 func NS(m *dns.Msg, name_dot, name_nodot string) bool {
-	res, err := db.EasyQuery("SELECT id, record_type, record_name, record_value, record_ttl, is_disposable FROM dns_records WHERE record_name = ? AND record_type = 'NS'", name_nodot)
-	if err != nil {
-		// an error has occured while preparing the SQL statement
-		return false
-	}
-	defer res.Close()
-
-	var recordsFound bool = false
+	recordsFound, records := records.GetDNSRecord(name_nodot, "NS")
 
-	for res.Next() {
-		recordsFound = true
-
-		var record_id int64
-		var record_type string
-		var record_name string
-		var record_value string
-		var record_ttl int64
-		var record_isdisposable int64
+	if !recordsFound {
+		// DNS record(s) was/were not found
 
-		err = res.Scan(&record_id, &record_type, &record_name, &record_value, &record_ttl, &record_isdisposable)
-		if err != nil {
-			// an error has occured
-			return false
-		}
+		return false
+	}
 
+	for _, record := range records {
 		r := new(dns.NS)
-		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeNS, Class: dns.ClassINET, Ttl: uint32(record_ttl)}
-		r.Ns = dns.Fqdn(record_value)
+		r.Hdr = dns.RR_Header{Name: name_dot, Rrtype: dns.TypeNS, Class: dns.ClassINET, Ttl: uint32(record.TTL)}
+		r.Ns = dns.Fqdn(record.Value)
 
 		m.Answer = append(m.Answer, r)
 
-		if record_isdisposable > 0 {
-			db.EasyExec("DELETE FROM dns_records WHERE id = ?", record_id)
+		if record.IsDisposable {
+			db.RetriedDbExec(10, "DELETE FROM dns_records WHERE id = ?", record.ID)
 		}
 	}
 
-	if !recordsFound {
-		// DNS record not found in the database
-		return false
-	}
-
 	return true
 }