add initial simple and naive solution
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jc
commit
7720b19062
4 changed files with 261 additions and 0 deletions
5
.gitignore
vendored
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.gitignore
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.env
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.env.*
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*.db
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13
go.mod
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go.mod
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module git.juancwu.dev/juancwu/go-ddns
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go 1.25.0
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require (
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github.com/mattn/go-sqlite3 v1.14.32 // indirect
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github.com/miekg/dns v1.1.69 // indirect
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golang.org/x/mod v0.30.0 // indirect
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golang.org/x/net v0.47.0 // indirect
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golang.org/x/sync v0.18.0 // indirect
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golang.org/x/sys v0.38.0 // indirect
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golang.org/x/tools v0.39.0 // indirect
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)
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14
go.sum
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go.sum
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github.com/mattn/go-sqlite3 v1.14.32 h1:JD12Ag3oLy1zQA+BNn74xRgaBbdhbNIDYvQUEuuErjs=
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github.com/mattn/go-sqlite3 v1.14.32/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
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github.com/miekg/dns v1.1.69 h1:Kb7Y/1Jo+SG+a2GtfoFUfDkG//csdRPwRLkCsxDG9Sc=
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github.com/miekg/dns v1.1.69/go.mod h1:7OyjD9nEba5OkqQ/hB4fy3PIoxafSZJtducccIelz3g=
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golang.org/x/mod v0.30.0 h1:fDEXFVZ/fmCKProc/yAXXUijritrDzahmwwefnjoPFk=
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golang.org/x/mod v0.30.0/go.mod h1:lAsf5O2EvJeSFMiBxXDki7sCgAxEUcZHXoXMKT4GJKc=
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golang.org/x/net v0.47.0 h1:Mx+4dIFzqraBXUugkia1OOvlD6LemFo1ALMHjrXDOhY=
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golang.org/x/net v0.47.0/go.mod h1:/jNxtkgq5yWUGYkaZGqo27cfGZ1c5Nen03aYrrKpVRU=
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golang.org/x/sync v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
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golang.org/x/sync v0.18.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
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golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
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golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
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golang.org/x/tools v0.39.0 h1:ik4ho21kwuQln40uelmciQPp9SipgNDdrafrYA4TmQQ=
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golang.org/x/tools v0.39.0/go.mod h1:JnefbkDPyD8UU2kI5fuf8ZX4/yUeh9W877ZeBONxUqQ=
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229
main.go
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main.go
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package main
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import (
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"database/sql"
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"encoding/json"
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"fmt"
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"log"
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"net/http"
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"strings"
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"time"
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_ "github.com/mattn/go-sqlite3"
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"github.com/miekg/dns"
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)
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const (
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DBPath = "./dns_records.db"
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DNSPort = "53"
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APIPort = ":8080"
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DefaultTTL = 300
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)
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type RecordRequest struct {
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Domain string `json:"domain"`
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IP string `json:"ip"`
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Type string `json:"type"`
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}
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type UpstreamRequest struct {
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Address string `json:"address"`
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}
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func initDB() *sql.DB {
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db, err := sql.Open("sqlite3", DBPath)
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if err != nil {
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log.Fatal(err)
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}
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queryRecords := `
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CREATE TABLE IF NOT EXISTS records (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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domain TEXT NOT NULL UNIQUE,
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ip TEXT NOT NULL,
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record_type TEXT DEFAULT 'A'
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);`
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queryUpstreams := `
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CREATE TABLE IF NOT EXISTS upstreams (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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address TEXT NOT NULL UNIQUE
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);`
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if _, err := db.Exec(queryRecords); err != nil {
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log.Fatalf("Error creating records table: %v", err)
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}
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if _, err := db.Exec(queryUpstreams); err != nil {
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log.Fatalf("Error creating upstreams table: %v", err)
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}
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return db
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}
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type DNSResolver struct {
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db *sql.DB
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}
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func (resolver *DNSResolver) handleDNSRequest(w dns.ResponseWriter, r *dns.Msg) {
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m := new(dns.Msg)
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m.SetReply(r)
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m.Compress = false
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switch r.Opcode {
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case dns.OpcodeQuery:
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for _, q := range m.Question {
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ip, err := resolver.getRecordFromDB(q.Name)
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if err == nil && ip != "" {
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log.Printf("[LOCAL] Resolved %s -> %s", q.Name, ip)
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rr, err := dns.NewRR(fmt.Sprintf("%s %d A %s", q.Name, DefaultTTL, ip))
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if err == nil {
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m.Answer = append(m.Answer, rr)
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}
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} else {
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resp, err := resolver.resolveUpstream(r)
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if err == nil && resp != nil {
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log.Printf("[UPSTREAM] Forwarded %s", q.Name)
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m.Answer = resp.Answer
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m.Ns = resp.Ns
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m.Extra = resp.Extra
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m.Rcode = resp.Rcode
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} else {
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log.Printf("[ERROR] Could not resolve %s", q.Name)
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m.Rcode = dns.RcodeServerFailure
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}
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}
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}
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}
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w.WriteMsg(m)
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}
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func (resolver *DNSResolver) getRecordFromDB(domain string) (string, error) {
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// DNS queries usually come with a trailing dot (e.g., "google.com.")
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// Ensure consistency by checking both with and without it if needed,
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// or enforcing it in the DB. Here we assume DB stores with trailing dot.
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var ip string
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err := resolver.db.QueryRow("SELECT ip FROM records WHERE domain = ?", domain).Scan(&ip)
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if err != nil {
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return "", err
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}
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return ip, nil
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}
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func (resolver *DNSResolver) resolveUpstream(r *dns.Msg) (*dns.Msg, error) {
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rows, err := resolver.db.Query("SELECT address FROM upstreams")
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if err != nil {
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return nil, err
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}
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defer rows.Close()
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c := new(dns.Client)
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c.Net = "udp"
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c.Timeout = 5 * time.Second
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for rows.Next() {
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var upstreamAddr string
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if err := rows.Scan(&upstreamAddr); err != nil {
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continue
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}
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resp, _, err := c.Exchange(r, upstreamAddr)
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if err == nil && resp != nil && resp.Rcode != dns.RcodeServerFailure {
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return resp, nil
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}
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}
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return nil, fmt.Errorf("all upstreams failed")
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}
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func startAPIServer(db *sql.DB) {
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http.HandleFunc("/records", func(w http.ResponseWriter, r *http.Request) {
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if r.Method == http.MethodPost {
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var req RecordRequest
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if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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// Normalize domain to ensure trailing dot
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if !strings.HasSuffix(req.Domain, ".") {
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req.Domain += "."
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}
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_, err := db.Exec("INSERT OR REPLACE INTO records (domain, ip, record_type) VALUES (?, ?, ?)", req.Domain, req.IP, "A")
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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w.WriteHeader(http.StatusCreated)
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fmt.Fprintf(w, "Added %s -> %s", req.Domain, req.IP)
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} else if r.Method == http.MethodDelete {
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var req RecordRequest
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if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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if !strings.HasSuffix(req.Domain, ".") {
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req.Domain += "."
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}
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_, err := db.Exec("DELETE FROM records WHERE domain = ?", req.Domain)
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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fmt.Fprintf(w, "Deleted %s", req.Domain)
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}
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})
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http.HandleFunc("/upstreams", func(w http.ResponseWriter, r *http.Request) {
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if r.Method == http.MethodPost {
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var req UpstreamRequest
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if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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_, err := db.Exec("INSERT INTO upstreams (address) VALUES (?)", req.Address)
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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w.WriteHeader(http.StatusCreated)
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fmt.Fprintf(w, "Added upstream %s", req.Address)
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} else if r.Method == http.MethodDelete {
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var req UpstreamRequest
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if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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_, err := db.Exec("DELETE FROM upstreams WHERE address = ?", req.Address)
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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fmt.Fprintf(w, "Deleted upstream %s", req.Address)
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}
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})
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log.Printf("API Listening on %s...", APIPort)
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log.Fatal(http.ListenAndServe(APIPort, nil))
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}
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func main() {
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db := initDB()
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defer db.Close()
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go startAPIServer(db)
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resolver := &DNSResolver{db: db}
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dns.HandleFunc(".", resolver.handleDNSRequest)
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server := &dns.Server{Addr: ":" + DNSPort, Net: "udp"}
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log.Printf("DNS Server listening on port %s...", DNSPort)
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if err := server.ListenAndServe(); err != nil {
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log.Fatalf("Failed to set up DNS server: %v", err)
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}
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}
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