proxy: rm unsafe

proxy/cache.go

@@ -8,7 +8,6 @@ import (
 	"strings"
 	"sync"
 	"time"
-	"unsafe"
 
 	glcache "github.com/AdguardTeam/golibs/cache"
 	"github.com/AdguardTeam/golibs/log"
@@ -48,13 +47,15 @@ type cacheItem struct {
 }
 
 const (
-	// uint16sz is the size of uint16 type in bytes.
-	uint16sz = int(unsafe.Sizeof(uint16(0)))
-	// uint32sz is the size of uint32 type in bytes.
-	uint32sz = int(unsafe.Sizeof(uint32(0)))
+	// packedMsgLenSz is the exact length of byte slice capable to store the
+	// length of packed DNS message.  It's essentially the size of an int.
+	packedMsgLenSz = 2
+	// expTimeSz is the exact length of byte slice capable to store the
+	// expiration time the response.  It's essentially the size of a uint32.
+	expTimeSz = 4
 
 	// minPackedLen is the minimum length of the packed cacheItem.
-	minPackedLen = uint32sz + uint16sz
+	minPackedLen = expTimeSz + packedMsgLenSz
 )
 
 // pack converts the ci into bytes slice.
@@ -67,7 +68,7 @@ func (ci *cacheItem) pack() (packed []byte) {
 	binary.BigEndian.PutUint32(packed, uint32(time.Now().Unix())+lowestTTL(ci.m))
 
 	// Put the length of the packed message.
-	binary.BigEndian.PutUint16(packed[4:], uint16(pmLen))
+	binary.BigEndian.PutUint16(packed[expTimeSz:], uint16(pmLen))
 
 	// Put the packed message itself.
 	packed = append(packed, pm...)
@@ -90,7 +91,7 @@ func (c *cache) unpackItem(data []byte, req *dns.Msg) (ci *cacheItem, expired bo
 	}
 
 	b := bytes.NewBuffer(data)
-	expire := int64(binary.BigEndian.Uint32(b.Next(uint32sz)))
+	expire := int64(binary.BigEndian.Uint32(b.Next(expTimeSz)))
 	now := time.Now().Unix()
 	var ttl uint32
 	if expired = expire <= now; expired {
@@ -103,7 +104,7 @@ func (c *cache) unpackItem(data []byte, req *dns.Msg) (ci *cacheItem, expired bo
 		ttl = uint32(expire - now)
 	}
 
-	l := int(binary.BigEndian.Uint16(b.Next(uint16sz)))
+	l := int(binary.BigEndian.Uint16(b.Next(packedMsgLenSz)))
 	if l == 0 {
 		return nil, expired
 	}
@@ -414,12 +415,12 @@ func respectTTLOverrides(ttl uint32, cacheMinTTL uint32, cacheMaxTTL uint32) uin
 func msgToKey(m *dns.Msg) (b []byte) {
 	q := m.Question[0]
 	name := q.Name
-	b = make([]byte, uint16sz+uint16sz+len(name))
+	b = make([]byte, packedMsgLenSz+packedMsgLenSz+len(name))
 
 	// Put QTYPE, QCLASS, and QNAME.
 	binary.BigEndian.PutUint16(b, q.Qtype)
-	binary.BigEndian.PutUint16(b[uint16sz:], q.Qclass)
-	copy(b[2*uint16sz:], strings.ToLower(name))
+	binary.BigEndian.PutUint16(b[packedMsgLenSz:], q.Qclass)
+	copy(b[2*packedMsgLenSz:], strings.ToLower(name))
 
 	return b
 }
@@ -428,7 +429,7 @@ func msgToKey(m *dns.Msg) (b []byte) {
 // mask, client's IP address and question's name of m.
 func msgToKeyWithSubnet(m *dns.Msg, clientIP net.IP, mask uint8) (key []byte) {
 	q := m.Question[0]
-	cap := 1 + 2*uint16sz + 1 + len(q.Name)
+	cap := 1 + 2*packedMsgLenSz + 1 + len(q.Name)
 	ipLen := len(clientIP)
 	masked := mask != 0
 	if masked {
@@ -449,11 +450,11 @@ func msgToKeyWithSubnet(m *dns.Msg, clientIP net.IP, mask uint8) (key []byte) {
 
 	// Put Qtype.
 	binary.BigEndian.PutUint16(key[:], q.Qtype)
-	k += uint16sz
+	k += packedMsgLenSz
 
 	// Put Qclass.
 	binary.BigEndian.PutUint16(key[k:], q.Qclass)
-	k += uint16sz
+	k += packedMsgLenSz
 
 	// Add mask.
 	key[k] = mask