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sansen
@@ -0,0 +1,295 @@
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package discovery
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import (
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"bufio"
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"context"
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"errors"
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"fmt"
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"io"
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"log/slog"
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"net"
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"net/http"
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"net/url"
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"strconv"
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"strings"
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"sync"
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"time"
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)
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var (
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errEmptyAddress = errors.New("empty address")
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errNicknameNotFound = errors.New("nickname not found")
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errEmptyResponseBody = errors.New("empty response")
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errTSDNSNotFound = errors.New("not found")
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)
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const (
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TsDnsDefaultPort = "41144"
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NicknameLookup = "https://named.myteamspeak.com/lookup"
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CacheTTL = 10 * time.Minute
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)
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// ResolvedAddr is one resolved host:port and how it was obtained.
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type ResolvedAddr struct {
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Expiry time.Time
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Addr string
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Source string
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}
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// Resolver resolves TeamSpeak-style addresses (nickname, SRV, TSDNS) with TTL cache.
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type Resolver struct {
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log *slog.Logger
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cache map[string][]ResolvedAddr
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mu sync.RWMutex
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}
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// NewResolver returns a Resolver using log for debug tracing (nil → slog.Default).
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func NewResolver(log *slog.Logger) *Resolver {
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if log == nil {
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log = slog.Default()
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}
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return &Resolver{
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log: log,
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cache: make(map[string][]ResolvedAddr),
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}
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}
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// Resolve tries, in order: MyTeamSpeak nickname, _ts3._udp SRV, TSDNS via SRV and :41144, then plain DNS.
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func (r *Resolver) Resolve(ctx context.Context, inputAddr string) ([]ResolvedAddr, error) {
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if inputAddr == "" {
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return nil, errEmptyAddress
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}
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if cached, ok := r.getValidCache(inputAddr); ok {
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return cached, nil
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}
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host, port := splitHostPortOrDefault(inputAddr)
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if ip := net.ParseIP(host); ip != nil {
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return []ResolvedAddr{{Addr: net.JoinHostPort(host, port), Source: "Direct"}}, nil
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}
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if !strings.Contains(host, ".") && host != "localhost" {
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if nickAddr, ok := r.resolveNicknameAddr(ctx, host); ok {
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return r.Resolve(ctx, nickAddr)
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}
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}
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if results, ok := r.resolveSRV(ctx, host); ok {
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return r.setCache(inputAddr, results), nil
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}
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domainList := getDomainList(host)
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if tsdnsAddr, ok := r.resolveTSDNSSRV(ctx, domainList, host); ok {
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results := []ResolvedAddr{{Addr: tsdnsAddr, Source: "TSDNS-SRV"}}
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return r.setCache(inputAddr, results), nil
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}
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if tsdnsAddr, ok := r.resolveTSDNSDirect(ctx, domainList, host); ok {
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results := []ResolvedAddr{{Addr: tsdnsAddr, Source: "TSDNS-Direct"}}
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return r.setCache(inputAddr, results), nil
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}
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r.log.Debug("falling back to direct dns", slog.String("host", host), slog.String("port", port))
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results := []ResolvedAddr{{
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Addr: net.JoinHostPort(host, port),
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Source: "Direct",
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}}
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return r.setCache(inputAddr, results), nil
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}
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func (r *Resolver) getValidCache(inputAddr string) ([]ResolvedAddr, bool) {
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r.mu.RLock()
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defer r.mu.RUnlock()
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cached, ok := r.cache[inputAddr]
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if !ok || len(cached) == 0 || time.Now().After(cached[0].Expiry) {
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return nil, false
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}
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r.log.Debug("cache hit", slog.String("addr", inputAddr), slog.String("source", cached[0].Source))
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return cached, true
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}
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func splitHostPortOrDefault(inputAddr string) (string, string) {
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host, port, err := net.SplitHostPort(inputAddr)
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if err != nil {
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return inputAddr, "9987"
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}
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return host, port
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}
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func (r *Resolver) resolveNicknameAddr(ctx context.Context, host string) (string, bool) {
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r.log.Debug("trying nickname resolution", slog.String("nickname", host))
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nickAddr, err := resolveNickname(ctx, host)
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if err != nil || nickAddr == "" {
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r.log.Debug("nickname resolution failed", slog.String("nickname", host), slog.Any("error", err))
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return "", false
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}
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r.log.Debug("nickname resolved", slog.String("nickname", host), slog.String("result", nickAddr))
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return nickAddr, true
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}
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func (r *Resolver) resolveSRV(ctx context.Context, host string) ([]ResolvedAddr, bool) {
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r.log.Debug("trying dns srv", slog.String("host", host))
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_, srvs, err := net.DefaultResolver.LookupSRV(ctx, "ts3", "udp", host)
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if err != nil || len(srvs) == 0 {
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r.log.Debug("dns srv failed", slog.String("host", host), slog.Any("error", err))
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return nil, false
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}
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results := make([]ResolvedAddr, 0, len(srvs))
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for _, srv := range srvs {
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target := strings.TrimSuffix(srv.Target, ".")
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results = append(results, ResolvedAddr{
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Addr: net.JoinHostPort(target, strconv.FormatUint(uint64(srv.Port), 10)),
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Source: "SRV",
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})
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}
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r.log.Debug("dns srv succeeded", slog.String("host", host), slog.String("result", results[0].Addr))
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return results, true
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}
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func (r *Resolver) resolveTSDNSSRV(ctx context.Context, domains []string, queryHost string) (string, bool) {
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for _, domain := range domains {
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r.log.Debug("trying tsdns srv", slog.String("domain", domain))
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_, srvs, err := net.DefaultResolver.LookupSRV(ctx, "tsdns", "tcp", domain)
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if err != nil || len(srvs) == 0 {
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r.log.Debug("tsdns srv failed", slog.String("domain", domain))
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continue
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}
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for _, srv := range srvs {
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target := strings.TrimSuffix(srv.Target, ".")
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tsdnsAddr, queryErr := queryTSDNS(
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ctx, net.JoinHostPort(target, strconv.FormatUint(uint64(srv.Port), 10)), queryHost,
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)
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if queryErr == nil && tsdnsAddr != "" {
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r.log.Debug("tsdns srv succeeded", slog.String("domain", domain), slog.String("result", tsdnsAddr))
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return tsdnsAddr, true
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}
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}
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}
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return "", false
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}
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func (r *Resolver) resolveTSDNSDirect(ctx context.Context, domains []string, queryHost string) (string, bool) {
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for _, domain := range domains {
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r.log.Debug("trying tsdns direct", slog.String("domain", domain))
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tsdnsAddr, err := queryTSDNS(ctx, net.JoinHostPort(domain, TsDnsDefaultPort), queryHost)
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if err == nil && tsdnsAddr != "" {
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r.log.Debug("tsdns direct succeeded", slog.String("domain", domain), slog.String("result", tsdnsAddr))
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return tsdnsAddr, true
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}
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r.log.Debug("tsdns direct failed", slog.String("domain", domain))
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}
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return "", false
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}
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func (r *Resolver) setCache(key string, results []ResolvedAddr) []ResolvedAddr {
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expiry := time.Now().Add(CacheTTL)
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for i := range results {
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results[i].Expiry = expiry
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}
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r.mu.Lock()
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r.cache[key] = results
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r.mu.Unlock()
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return results
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}
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// getDomainList returns host suffixes ordered longest-first (for TSDNS), capped at three.
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func getDomainList(host string) []string {
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parts := strings.Split(host, ".")
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list := make([]string, 0, len(parts)-1)
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for i := range len(parts) - 1 {
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list = append(list, strings.Join(parts[i:], "."))
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}
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if len(list) > 3 {
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return list[:3]
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}
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return list
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}
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func resolveNickname(ctx context.Context, nickname string) (string, error) {
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lookupURL, err := url.Parse(NicknameLookup)
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if err != nil {
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return "", err
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}
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query := lookupURL.Query()
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query.Set("name", nickname)
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lookupURL.RawQuery = query.Encode()
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req, err := http.NewRequestWithContext(ctx, http.MethodGet, lookupURL.String(), nil)
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if err != nil {
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return "", err
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}
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client := &http.Client{Timeout: 5 * time.Second}
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resp, err := client.Do(req)
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if err != nil {
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return "", err
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}
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defer func() { _ = resp.Body.Close() }()
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if resp.StatusCode != http.StatusOK {
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return "", errNicknameNotFound
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}
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body, err := io.ReadAll(resp.Body)
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if err != nil {
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return "", err
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}
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lines := strings.Split(string(body), "\n")
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if len(lines) > 0 && lines[0] != "" {
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return strings.TrimSpace(lines[0]), nil
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}
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return "", errEmptyResponseBody
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}
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func queryTSDNS(ctx context.Context, tsdnsFullAddr, queryHost string) (string, error) {
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d := net.Dialer{Timeout: 2 * time.Second}
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conn, err := d.DialContext(ctx, "tcp", tsdnsFullAddr)
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if err != nil {
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return "", err
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}
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defer func() { _ = conn.Close() }()
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_ = conn.SetDeadline(time.Now().Add(3 * time.Second))
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_, err = fmt.Fprintf(conn, "%s\n", queryHost)
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if err != nil {
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return "", err
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}
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reader := bufio.NewReader(conn)
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line, err := reader.ReadString('\n')
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if err != nil {
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return "", err
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}
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line = strings.TrimSpace(line)
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if line == "" || line == "404" || line == "errors" {
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return "", errTSDNSNotFound
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}
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return line, nil
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}
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