chore: stop using go:linkname for net.lookupStaticHost

component/resolver/host.go

@@ -9,6 +9,7 @@ import (
 	_ "unsafe"
 
 	"github.com/metacubex/mihomo/common/utils"
+	"github.com/metacubex/mihomo/component/resolver/hosts"
 	"github.com/metacubex/mihomo/component/trie"
 	"github.com/zhangyunhao116/fastrand"
 )
@@ -28,11 +29,6 @@ func NewHosts(hosts *trie.DomainTrie[HostValue]) Hosts {
 	}
 }
 
-// lookupStaticHost looks up the addresses and the canonical name for the given host from /etc/hosts.
-//
-//go:linkname lookupStaticHost net.lookupStaticHost
-func lookupStaticHost(host string) ([]string, string)
-
 // Return the search result and whether to match the parameter `isDomain`
 func (h *Hosts) Search(domain string, isDomain bool) (*HostValue, bool) {
 	if value := h.DomainTrie.Search(domain); value != nil {
@@ -56,7 +52,7 @@ func (h *Hosts) Search(domain string, isDomain bool) (*HostValue, bool) {
 	}
 
 	if !isDomain && !DisableSystemHosts && UseSystemHosts {
-		addr, _ := lookupStaticHost(domain)
+		addr, _ := hosts.LookupStaticHost(domain)
 		if hostValue, err := NewHostValue(addr); err == nil {
 			return &hostValue, true
 		}

component/resolver/hosts/hosts.go

@@ -0,0 +1,309 @@
+package hosts
+
+// this file copy and modify from golang's std net/hosts.go
+
+import (
+	"errors"
+	"io"
+	"io/fs"
+	"net/netip"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+var hostsFilePath = "/etc/hosts"
+
+const cacheMaxAge = 5 * time.Second
+
+func parseLiteralIP(addr string) string {
+	ip, err := netip.ParseAddr(addr)
+	if err != nil {
+		return ""
+	}
+	return ip.String()
+}
+
+type byName struct {
+	addrs         []string
+	canonicalName string
+}
+
+// hosts contains known host entries.
+var hosts struct {
+	sync.Mutex
+
+	// Key for the list of literal IP addresses must be a host
+	// name. It would be part of DNS labels, a FQDN or an absolute
+	// FQDN.
+	// For now the key is converted to lower case for convenience.
+	byName map[string]byName
+
+	// Key for the list of host names must be a literal IP address
+	// including IPv6 address with zone identifier.
+	// We don't support old-classful IP address notation.
+	byAddr map[string][]string
+
+	expire time.Time
+	path   string
+	mtime  time.Time
+	size   int64
+}
+
+func readHosts() {
+	now := time.Now()
+	hp := hostsFilePath
+
+	if now.Before(hosts.expire) && hosts.path == hp && len(hosts.byName) > 0 {
+		return
+	}
+	mtime, size, err := stat(hp)
+	if err == nil && hosts.path == hp && hosts.mtime.Equal(mtime) && hosts.size == size {
+		hosts.expire = now.Add(cacheMaxAge)
+		return
+	}
+
+	hs := make(map[string]byName)
+	is := make(map[string][]string)
+
+	file, err := open(hp)
+	if err != nil {
+		if !errors.Is(err, fs.ErrNotExist) && !errors.Is(err, fs.ErrPermission) {
+			return
+		}
+	}
+
+	if file != nil {
+		defer file.close()
+		for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+			if i := strings.IndexByte(line, '#'); i >= 0 {
+				// Discard comments.
+				line = line[0:i]
+			}
+			f := getFields(line)
+			if len(f) < 2 {
+				continue
+			}
+			addr := parseLiteralIP(f[0])
+			if addr == "" {
+				continue
+			}
+
+			var canonical string
+			for i := 1; i < len(f); i++ {
+				name := absDomainName(f[i])
+				h := []byte(f[i])
+				lowerASCIIBytes(h)
+				key := absDomainName(string(h))
+
+				if i == 1 {
+					canonical = key
+				}
+
+				is[addr] = append(is[addr], name)
+
+				if v, ok := hs[key]; ok {
+					hs[key] = byName{
+						addrs:         append(v.addrs, addr),
+						canonicalName: v.canonicalName,
+					}
+					continue
+				}
+
+				hs[key] = byName{
+					addrs:         []string{addr},
+					canonicalName: canonical,
+				}
+			}
+		}
+	}
+	// Update the data cache.
+	hosts.expire = now.Add(cacheMaxAge)
+	hosts.path = hp
+	hosts.byName = hs
+	hosts.byAddr = is
+	hosts.mtime = mtime
+	hosts.size = size
+}
+
+// LookupStaticHost looks up the addresses and the canonical name for the given host from /etc/hosts.
+func LookupStaticHost(host string) ([]string, string) {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	if len(hosts.byName) != 0 {
+		if hasUpperCase(host) {
+			lowerHost := []byte(host)
+			lowerASCIIBytes(lowerHost)
+			host = string(lowerHost)
+		}
+		if byName, ok := hosts.byName[absDomainName(host)]; ok {
+			ipsCp := make([]string, len(byName.addrs))
+			copy(ipsCp, byName.addrs)
+			return ipsCp, byName.canonicalName
+		}
+	}
+	return nil, ""
+}
+
+// LookupStaticAddr looks up the hosts for the given address from /etc/hosts.
+func LookupStaticAddr(addr string) []string {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	addr = parseLiteralIP(addr)
+	if addr == "" {
+		return nil
+	}
+	if len(hosts.byAddr) != 0 {
+		if hosts, ok := hosts.byAddr[addr]; ok {
+			hostsCp := make([]string, len(hosts))
+			copy(hostsCp, hosts)
+			return hostsCp
+		}
+	}
+	return nil
+}
+
+func stat(name string) (mtime time.Time, size int64, err error) {
+	st, err := os.Stat(name)
+	if err != nil {
+		return time.Time{}, 0, err
+	}
+	return st.ModTime(), st.Size(), nil
+}
+
+type file struct {
+	file  *os.File
+	data  []byte
+	atEOF bool
+}
+
+func (f *file) close() { f.file.Close() }
+
+func (f *file) getLineFromData() (s string, ok bool) {
+	data := f.data
+	i := 0
+	for i = 0; i < len(data); i++ {
+		if data[i] == '\n' {
+			s = string(data[0:i])
+			ok = true
+			// move data
+			i++
+			n := len(data) - i
+			copy(data[0:], data[i:])
+			f.data = data[0:n]
+			return
+		}
+	}
+	if f.atEOF && len(f.data) > 0 {
+		// EOF, return all we have
+		s = string(data)
+		f.data = f.data[0:0]
+		ok = true
+	}
+	return
+}
+
+func (f *file) readLine() (s string, ok bool) {
+	if s, ok = f.getLineFromData(); ok {
+		return
+	}
+	if len(f.data) < cap(f.data) {
+		ln := len(f.data)
+		n, err := io.ReadFull(f.file, f.data[ln:cap(f.data)])
+		if n >= 0 {
+			f.data = f.data[0 : ln+n]
+		}
+		if err == io.EOF || err == io.ErrUnexpectedEOF {
+			f.atEOF = true
+		}
+	}
+	s, ok = f.getLineFromData()
+	return
+}
+
+func (f *file) stat() (mtime time.Time, size int64, err error) {
+	st, err := f.file.Stat()
+	if err != nil {
+		return time.Time{}, 0, err
+	}
+	return st.ModTime(), st.Size(), nil
+}
+
+func open(name string) (*file, error) {
+	fd, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return &file{fd, make([]byte, 0, 64*1024), false}, nil
+}
+
+func getFields(s string) []string { return splitAtBytes(s, " \r\t\n") }
+
+// Count occurrences in s of any bytes in t.
+func countAnyByte(s string, t string) int {
+	n := 0
+	for i := 0; i < len(s); i++ {
+		if strings.IndexByte(t, s[i]) >= 0 {
+			n++
+		}
+	}
+	return n
+}
+
+// Split s at any bytes in t.
+func splitAtBytes(s string, t string) []string {
+	a := make([]string, 1+countAnyByte(s, t))
+	n := 0
+	last := 0
+	for i := 0; i < len(s); i++ {
+		if strings.IndexByte(t, s[i]) >= 0 {
+			if last < i {
+				a[n] = s[last:i]
+				n++
+			}
+			last = i + 1
+		}
+	}
+	if last < len(s) {
+		a[n] = s[last:]
+		n++
+	}
+	return a[0:n]
+}
+
+// lowerASCIIBytes makes x ASCII lowercase in-place.
+func lowerASCIIBytes(x []byte) {
+	for i, b := range x {
+		if 'A' <= b && b <= 'Z' {
+			x[i] += 'a' - 'A'
+		}
+	}
+}
+
+// hasUpperCase tells whether the given string contains at least one upper-case.
+func hasUpperCase(s string) bool {
+	for i := range s {
+		if 'A' <= s[i] && s[i] <= 'Z' {
+			return true
+		}
+	}
+	return false
+}
+
+// absDomainName returns an absolute domain name which ends with a
+// trailing dot to match pure Go reverse resolver and all other lookup
+// routines.
+// See golang.org/issue/12189.
+// But we don't want to add dots for local names from /etc/hosts.
+// It's hard to tell so we settle on the heuristic that names without dots
+// (like "localhost" or "myhost") do not get trailing dots, but any other
+// names do.
+func absDomainName(s string) string {
+	if strings.IndexByte(s, '.') != -1 && s[len(s)-1] != '.' {
+		s += "."
+	}
+	return s
+}

component/resolver/hosts/hosts_windows.go

@@ -0,0 +1,13 @@
+package hosts
+
+// this file copy and modify from golang's std net/hook_windows.go
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+func init() {
+	if dir, err := windows.GetSystemDirectory(); err == nil {
+		hostsFilePath = dir + "/Drivers/etc/hosts"
+	}
+}