Update dependencies

vendor/tailscale.com/net/dns/resolvconffile/resolvconffile.go

@@ -0,0 +1,124 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package resolvconffile parses & serializes /etc/resolv.conf-style files.
+//
+// It's a leaf package so both net/dns and net/dns/resolver can depend
+// on it and we can unify a handful of implementations.
+//
+// The package is verbosely named to disambiguate it from resolvconf
+// the daemon, which Tailscale also supports.
+package resolvconffile
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"net/netip"
+	"os"
+	"strings"
+
+	"tailscale.com/util/dnsname"
+)
+
+// Path is the canonical location of resolv.conf.
+const Path = "/etc/resolv.conf"
+
+// Config represents a resolv.conf(5) file.
+type Config struct {
+	// Nameservers are the IP addresses of the nameservers to use.
+	Nameservers []netip.Addr
+
+	// SearchDomains are the domain suffixes to use when expanding
+	// single-label name queries. SearchDomains is additive to
+	// whatever non-Tailscale search domains the OS has.
+	SearchDomains []dnsname.FQDN
+}
+
+// Write writes c to w. It does so in one Write call.
+func (c *Config) Write(w io.Writer) error {
+	buf := new(bytes.Buffer)
+	io.WriteString(buf, "# resolv.conf(5) file generated by tailscale\n")
+	io.WriteString(buf, "# For more info, see https://tailscale.com/s/resolvconf-overwrite\n")
+	io.WriteString(buf, "# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN\n\n")
+	for _, ns := range c.Nameservers {
+		io.WriteString(buf, "nameserver ")
+		io.WriteString(buf, ns.String())
+		io.WriteString(buf, "\n")
+	}
+	if len(c.SearchDomains) > 0 {
+		io.WriteString(buf, "search")
+		for _, domain := range c.SearchDomains {
+			io.WriteString(buf, " ")
+			io.WriteString(buf, domain.WithoutTrailingDot())
+		}
+		io.WriteString(buf, "\n")
+	}
+	_, err := w.Write(buf.Bytes())
+	return err
+}
+
+// Parse parses a resolv.conf file from r.
+func Parse(r io.Reader) (*Config, error) {
+	config := new(Config)
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		line, _, _ = strings.Cut(line, "#") // remove any comments
+		line = strings.TrimSpace(line)
+
+		if s, ok := strings.CutPrefix(line, "nameserver"); ok {
+			nameserver := strings.TrimSpace(s)
+			if len(nameserver) == len(s) {
+				return nil, fmt.Errorf("missing space after \"nameserver\" in %q", line)
+			}
+			ip, err := netip.ParseAddr(nameserver)
+			if err != nil {
+				return nil, err
+			}
+			config.Nameservers = append(config.Nameservers, ip)
+			continue
+		}
+
+		if s, ok := strings.CutPrefix(line, "search"); ok {
+			domains := strings.TrimSpace(s)
+			if len(domains) == len(s) {
+				// No leading space?!
+				return nil, fmt.Errorf("missing space after \"search\" in %q", line)
+			}
+			for len(domains) > 0 {
+				domain := domains
+				i := strings.IndexAny(domain, " \t")
+				if i != -1 {
+					domain = domain[:i]
+					domains = strings.TrimSpace(domains[i+1:])
+				} else {
+					domains = ""
+				}
+				fqdn, err := dnsname.ToFQDN(domain)
+				if err != nil {
+					return nil, fmt.Errorf("parsing search domain %q in %q: %w", domain, line, err)
+				}
+				config.SearchDomains = append(config.SearchDomains, fqdn)
+			}
+		}
+	}
+	return config, nil
+}
+
+// ParseFile parses the named resolv.conf file.
+func ParseFile(name string) (*Config, error) {
+	fi, err := os.Stat(name)
+	if err != nil {
+		return nil, err
+	}
+	if n := fi.Size(); n > 10<<10 {
+		return nil, fmt.Errorf("unexpectedly large %q file: %d bytes", name, n)
+	}
+	all, err := os.ReadFile(name)
+	if err != nil {
+		return nil, err
+	}
+	return Parse(bytes.NewReader(all))
+}