tailcfg: introduce HostinfoView

Signed-off-by: Maisem Ali <maisem@tailscale.com>

tailcfg/tailcfg.go

@@ -8,6 +8,7 @@ package tailcfg
 
 import (
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"reflect"
@@ -19,6 +20,7 @@ import (
 	"tailscale.com/types/key"
 	"tailscale.com/types/opt"
 	"tailscale.com/types/structs"
+	"tailscale.com/types/views"
 	"tailscale.com/util/dnsname"
 )
 
@@ -454,6 +456,128 @@ type Hostinfo struct {
 	//       require changes to Hostinfo.Equal.
 }
 
+// View returns a read-only accessor for the Hostinfo object.
+func (hi *Hostinfo) View() HostinfoView { return HostinfoView{hi} }
+
+// HostinfoView is a read-only accessor for Hostinfo.
+// See Hostinfo.
+type HostinfoView struct {
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.
+	ж *Hostinfo
+}
+
+func (v HostinfoView) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.ж)
+}
+
+func (v *HostinfoView) UnmarshalJSON(b []byte) error {
+	if v.ж != nil {
+		return errors.New("HostinfoView is already initialized")
+	}
+	if len(b) == 0 {
+		return nil
+	}
+	hi := &Hostinfo{}
+	if err := json.Unmarshal(b, hi); err != nil {
+		return err
+	}
+	v.ж = hi
+	return nil
+}
+
+// Valid reports whether the underlying value is not nil.
+func (v HostinfoView) Valid() bool { return v.ж != nil }
+
+// AsStruct returns a deep-copy of the underlying value.
+func (v HostinfoView) AsStruct() *Hostinfo { return v.ж.Clone() }
+
+func (v HostinfoView) IPNVersion() string         { return v.ж.IPNVersion }
+func (v HostinfoView) FrontendLogID() string      { return v.ж.FrontendLogID }
+func (v HostinfoView) BackendLogID() string       { return v.ж.BackendLogID }
+func (v HostinfoView) OS() string                 { return v.ж.OS }
+func (v HostinfoView) OSVersion() string          { return v.ж.OSVersion }
+func (v HostinfoView) Package() string            { return v.ж.Package }
+func (v HostinfoView) DeviceModel() string        { return v.ж.DeviceModel }
+func (v HostinfoView) Hostname() string           { return v.ж.Hostname }
+func (v HostinfoView) ShieldsUp() bool            { return v.ж.ShieldsUp }
+func (v HostinfoView) ShareeNode() bool           { return v.ж.ShareeNode }
+func (v HostinfoView) GoArch() string             { return v.ж.GoArch }
+func (v HostinfoView) Equal(h2 HostinfoView) bool { return v.ж.Equal(h2.ж) }
+
+func (v HostinfoView) RoutableIPs() views.IPPrefixSlice {
+	return views.IPPrefixSliceOf(v.ж.RoutableIPs)
+}
+
+func (v HostinfoView) RequestTags() views.StringSlice {
+	return views.StringSliceOf(v.ж.RequestTags)
+}
+
+func (v HostinfoView) Services() ServiceSlice {
+	return ServiceSliceOf(v.ж.Services)
+}
+
+func (v HostinfoView) NetInfo() NetInfoView { return v.ж.NetInfo.View() }
+
+// ServiceSlice is a read-only accessor for a slice of Services
+type ServiceSlice struct {
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.
+	ж []Service
+}
+
+// ServiceSliceOf returns a ServiceSlice for the provided slice.
+func ServiceSliceOf(x []Service) ServiceSlice { return ServiceSlice{x} }
+
+// Len returns the length of the slice.
+func (v ServiceSlice) Len() int { return len(v.ж) }
+
+// At returns the Service at index `i` of the slice.
+func (v ServiceSlice) At(i int) Service { return v.ж[i] }
+
+// Append appends the underlying slice values to dst.
+func (v ServiceSlice) Append(dst []Service) []Service {
+	return append(dst, v.ж...)
+}
+
+// AsSlice returns a copy of underlying slice.
+func (v ServiceSlice) AsSlice() []Service {
+	return v.Append(v.ж[:0:0])
+}
+
+// NetInfoView is a read-only accessor for NetInfo.
+// See NetInfo.
+type NetInfoView struct {
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.
+	ж *NetInfo
+}
+
+// Valid reports whether the underlying value is not nil.
+func (v NetInfoView) Valid() bool { return v.ж != nil }
+
+// AsStruct returns a deep-copy of the underlying value.
+func (v NetInfoView) AsStruct() *NetInfo { return v.ж.Clone() }
+
+func (v NetInfoView) MappingVariesByDestIP() opt.Bool { return v.ж.MappingVariesByDestIP }
+func (v NetInfoView) HairPinning() opt.Bool           { return v.ж.HairPinning }
+func (v NetInfoView) WorkingIPv6() opt.Bool           { return v.ж.WorkingIPv6 }
+func (v NetInfoView) WorkingUDP() opt.Bool            { return v.ж.WorkingUDP }
+func (v NetInfoView) HavePortMap() bool               { return v.ж.HavePortMap }
+func (v NetInfoView) UPnP() opt.Bool                  { return v.ж.UPnP }
+func (v NetInfoView) PMP() opt.Bool                   { return v.ж.PMP }
+func (v NetInfoView) PCP() opt.Bool                   { return v.ж.PCP }
+func (v NetInfoView) PreferredDERP() int              { return v.ж.PreferredDERP }
+func (v NetInfoView) LinkType() string                { return v.ж.LinkType }
+func (v NetInfoView) String() string                  { return v.ж.String() }
+
+// DERPLatencyForEach calls fn for each value in the DERPLatency map.
+func (v NetInfoView) DERPLatencyForEach(fn func(k string, v float64)) {
+	for k, v := range v.ж.DERPLatency {
+		fn(k, v)
+	}
+}
+
 // NetInfo contains information about the host's network state.
 type NetInfo struct {
 	// MappingVariesByDestIP says whether the host's NAT mappings
@@ -532,6 +656,9 @@ func (ni *NetInfo) portMapSummary() string {
 	return prefix + conciseOptBool(ni.UPnP, "U") + conciseOptBool(ni.PMP, "M") + conciseOptBool(ni.PCP, "C")
 }
 
+// View returns a read-only accessor for the NetInfo object.
+func (ni *NetInfo) View() NetInfoView { return NetInfoView{ni} }
+
 func conciseOptBool(b opt.Bool, trueVal string) string {
 	if b == "" {
 		return "_"

types/views/views.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package views provides read-only accessors for commonly used
+// value types.
+package views
+
+import (
+	"inet.af/netaddr"
+	"tailscale.com/net/tsaddr"
+)
+
+// StringSlice is a read-only accessor for a slice of strings.
+type StringSlice struct {
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.
+	ж []string
+}
+
+// StringSliceOf returns a StringSlice for the provided slice.
+func StringSliceOf(x []string) StringSlice { return StringSlice{x} }
+
+// Len returns the length of the slice.
+func (v StringSlice) Len() int { return len(v.ж) }
+
+// At returns the string at index `i` of the slice.
+func (v StringSlice) At(i int) string { return v.ж[i] }
+
+// AppendTo appends the underlying slice values to dst.
+func (v StringSlice) AppendTo(dst []string) []string {
+	return append(dst, v.ж...)
+}
+
+// AsSlice returns a copy of underlying slice.
+func (v StringSlice) AsSlice() []string {
+	return v.AppendTo(v.ж[:0:0])
+}
+
+// IPPrefixSlice is a read-only accessor for a slice of netaddr.IPPrefix.
+type IPPrefixSlice struct {
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.jd
+	ж []netaddr.IPPrefix
+}
+
+// IPPrefixSliceOf returns a IPPrefixSlice for the provided slice.
+func IPPrefixSliceOf(x []netaddr.IPPrefix) IPPrefixSlice { return IPPrefixSlice{x} }
+
+// Len returns the length of the slice.
+func (v IPPrefixSlice) Len() int { return len(v.ж) }
+
+// At returns the IPPrefix at index `i` of the slice.
+func (v IPPrefixSlice) At(i int) netaddr.IPPrefix { return v.ж[i] }
+
+// Append appends the underlying slice values to dst.
+func (v IPPrefixSlice) AppendTo(dst []netaddr.IPPrefix) []netaddr.IPPrefix {
+	return append(dst, v.ж...)
+}
+
+// AsSlice returns a copy of underlying slice.
+func (v IPPrefixSlice) AsSlice() []netaddr.IPPrefix {
+	return v.AppendTo(v.ж[:0:0])
+}
+
+// PrefixesContainsIP reports whether any IPPrefix contains IP.
+func (v IPPrefixSlice) ContainsIP(ip netaddr.IP) bool {
+	return tsaddr.PrefixesContainsIP(v.ж, ip)
+}
+
+// PrefixesContainsFunc reports whether f is true for any IPPrefix in the slice.
+func (v IPPrefixSlice) ContainsFunc(f func(netaddr.IPPrefix) bool) bool {
+	return tsaddr.PrefixesContainsFunc(v.ж, f)
+}