syscall: don't use AF_LINK on hurd

Patch from Svante Signell.

Fixes PR go/98153

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/275939

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-81687fccc568a088fee8f627ddde599e17c648c2
+3363fc239f642d3c3fb9a138d2833985d85dc083
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/syscall/socket_bsd.go

@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd hurd openbsd netbsd
+// +build darwin dragonfly freebsd openbsd netbsd
 
 package syscall
 

libgo/go/syscall/socket_hurd.go

@@ -0,0 +1,101 @@
+// socket_hurd.go -- Socket handling specific to GNU/Hurd based systems.
+// This file is derived from socket_bsd.go without SockaddrDatalink since
+// AF_LINK is not yet supported on GNU/Hurd.
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build hurd
+
+package syscall
+
+import "unsafe"
+
+const SizeofSockaddrInet4 = 16
+const SizeofSockaddrInet6 = 28
+const SizeofSockaddrUnix = 110
+
+type RawSockaddrInet4 struct {
+	Len    uint8
+	Family uint8
+	Port   uint16
+	Addr   [4]byte /* in_addr */
+	Zero   [8]uint8
+}
+
+func (sa *RawSockaddrInet4) setLen() Socklen_t {
+	sa.Len = SizeofSockaddrInet4
+	return SizeofSockaddrInet4
+}
+
+type RawSockaddrInet6 struct {
+	Len      uint8
+	Family   uint8
+	Port     uint16
+	Flowinfo uint32
+	Addr     [16]byte /* in6_addr */
+	Scope_id uint32
+}
+
+func (sa *RawSockaddrInet6) setLen() Socklen_t {
+	sa.Len = SizeofSockaddrInet6
+	return SizeofSockaddrInet6
+}
+
+type RawSockaddrUnix struct {
+	Len    uint8
+	Family uint8
+	Path   [108]int8
+}
+
+func (sa *RawSockaddrUnix) setLen(n int) {
+	sa.Len = uint8(3 + n) // 2 for Family, Len; 1 for NUL.
+}
+
+func (sa *RawSockaddrUnix) getLen() (int, error) {
+	if sa.Len < 2 || sa.Len > SizeofSockaddrUnix {
+		return 0, EINVAL
+	}
+
+	// Some BSDs include the trailing NUL in the length, whereas
+	// others do not. Work around this by subtracting the leading
+	// family and len. The path is then scanned to see if a NUL
+	// terminator still exists within the length.
+	n := int(sa.Len) - 2 // subtract leading Family, Len
+	for i := 0; i < n; i++ {
+		if sa.Path[i] == 0 {
+			// found early NUL; assume Len included the NUL
+			// or was overestimating.
+			n = i
+			break
+		}
+	}
+	return n, nil
+}
+
+func (sa *RawSockaddrUnix) adjustAbstract(sl Socklen_t) Socklen_t {
+	return sl
+}
+
+type RawSockaddr struct {
+	Len    uint8
+	Family uint8
+	Data   [14]int8
+}
+
+// BindToDevice binds the socket associated with fd to device.
+func BindToDevice(fd int, device string) (err error) {
+	return ENOSYS
+}
+
+func anyToSockaddrOS(rsa *RawSockaddrAny) (Sockaddr, error) {
+	return nil, EAFNOSUPPORT
+}
+
+func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
+	var value IPv6MTUInfo
+	vallen := Socklen_t(SizeofIPv6MTUInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
+	return &value, err
+}