device: make allowedips genericjd/generic-aip

The implementation of commonBits uses a horrific unsafe.Slice trick.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 114 insertions, 88 deletions

diff --git a/device/allowedips.go b/device/allowedips.go
index 3cac694..c36ef3a 100644
--- a/device/allowedips.go
+++ b/device/allowedips.go
@@ -16,68 +16,86 @@ import (
 	"unsafe"
 )
 
-type parentIndirection struct {
-	parentBit     **trieEntry
+type ipArray interface {
+	[4]byte | [16]byte
+}
+
+type parentIndirection[B ipArray] struct {
+	parentBit     **trieEntry[B]
 	parentBitType uint8
 }
 
-type trieEntry struct {
+type trieEntry[B ipArray] struct {
 	peer        *Peer
-	child       [2]*trieEntry
-	parent      parentIndirection
+	child       [2]*trieEntry[B]
+	parent      parentIndirection[B]
 	cidr        uint8
 	bitAtByte   uint8
 	bitAtShift  uint8
-	bits        []byte
+	bits        B
 	perPeerElem *list.Element
 }
 
-func commonBits(ip1, ip2 []byte) uint8 {
-	size := len(ip1)
-	if size == net.IPv4len {
-		a := binary.BigEndian.Uint32(ip1)
-		b := binary.BigEndian.Uint32(ip2)
-		x := a ^ b
-		return uint8(bits.LeadingZeros32(x))
-	} else if size == net.IPv6len {
-		a := binary.BigEndian.Uint64(ip1)
-		b := binary.BigEndian.Uint64(ip2)
-		x := a ^ b
-		if x != 0 {
-			return uint8(bits.LeadingZeros64(x))
-		}
-		a = binary.BigEndian.Uint64(ip1[8:])
-		b = binary.BigEndian.Uint64(ip2[8:])
-		x = a ^ b
-		return 64 + uint8(bits.LeadingZeros64(x))
-	} else {
-		panic("Wrong size bit string")
+func commonBits4(ip1, ip2 [4]byte) uint8 {
+	a := binary.BigEndian.Uint32(ip1[:])
+	b := binary.BigEndian.Uint32(ip2[:])
+	x := a ^ b
+	return uint8(bits.LeadingZeros32(x))
+}
+
+func commonBits16(ip1, ip2 [16]byte) uint8 {
+	a := binary.BigEndian.Uint64(ip1[:8])
+	b := binary.BigEndian.Uint64(ip2[:8])
+	x := a ^ b
+	if x != 0 {
+		return uint8(bits.LeadingZeros64(x))
+	}
+	a = binary.BigEndian.Uint64(ip1[8:])
+	b = binary.BigEndian.Uint64(ip2[8:])
+	x = a ^ b
+	return 64 + uint8(bits.LeadingZeros64(x))
+}
+
+func giveMeA4[B ipArray](b B) [4]byte {
+	return *(*[4]byte)(unsafe.Slice(&b[0], 4))
+}
+
+func giveMeA16[B ipArray](b B) [16]byte {
+	return *(*[16]byte)(unsafe.Slice(&b[0], 16))
+}
+
+func commonBits[B ipArray](ip1, ip2 B) uint8 {
+	if len(ip1) == 4 {
+		return commonBits4(giveMeA4(ip1), giveMeA4(ip2))
+	} else if len(ip1) == 16 {
+		return commonBits16(giveMeA16(ip1), giveMeA16(ip2))
 	}
+	panic("Wrong size bit string")
 }
 
-func (node *trieEntry) addToPeerEntries() {
+func (node *trieEntry[B]) addToPeerEntries() {
 	node.perPeerElem = node.peer.trieEntries.PushBack(node)
 }
 
-func (node *trieEntry) removeFromPeerEntries() {
+func (node *trieEntry[B]) removeFromPeerEntries() {
 	if node.perPeerElem != nil {
 		node.peer.trieEntries.Remove(node.perPeerElem)
 		node.perPeerElem = nil
 	}
 }
 
-func (node *trieEntry) choose(ip []byte) byte {
+func (node *trieEntry[B]) choose(ip B) byte {
 	return (ip[node.bitAtByte] >> node.bitAtShift) & 1
 }
 
-func (node *trieEntry) maskSelf() {
+func (node *trieEntry[B]) maskSelf() {
 	mask := net.CIDRMask(int(node.cidr), len(node.bits)*8)
 	for i := 0; i < len(mask); i++ {
 		node.bits[i] &= mask[i]
 	}
 }
 
-func (node *trieEntry) zeroizePointers() {
+func (node *trieEntry[B]) zeroizePointers() {
 	// Make the garbage collector's life slightly easier
 	node.peer = nil
 	node.child[0] = nil
@@ -85,7 +103,7 @@ func (node *trieEntry) zeroizePointers() {
 	node.parent.parentBit = nil
 }
 
-func (node *trieEntry) nodePlacement(ip []byte, cidr uint8) (parent *trieEntry, exact bool) {
+func (node *trieEntry[B]) nodePlacement(ip B, cidr uint8) (parent *trieEntry[B], exact bool) {
 	for node != nil && node.cidr <= cidr && commonBits(node.bits, ip) >= node.cidr {
 		parent = node
 		if parent.cidr == cidr {
@@ -98,9 +116,9 @@ func (node *trieEntry) nodePlacement(ip []byte, cidr uint8) (parent *trieEntry,
 	return
 }
 
-func (trie parentIndirection) insert(ip []byte, cidr uint8, peer *Peer) {
+func (trie parentIndirection[B]) insert(ip B, cidr uint8, peer *Peer) {
 	if *trie.parentBit == nil {
-		node := &trieEntry{
+		node := &trieEntry[B]{
 			peer:       peer,
 			parent:     trie,
 			bits:       ip,
@@ -121,7 +139,7 @@ func (trie parentIndirection) insert(ip []byte, cidr uint8, peer *Peer) {
 		return
 	}
 
-	newNode := &trieEntry{
+	newNode := &trieEntry[B]{
 		peer:       peer,
 		bits:       ip,
 		cidr:       cidr,
@@ -131,14 +149,14 @@ func (trie parentIndirection) insert(ip []byte, cidr uint8, peer *Peer) {
 	newNode.maskSelf()
 	newNode.addToPeerEntries()
 
-	var down *trieEntry
+	var down *trieEntry[B]
 	if node == nil {
 		down = *trie.parentBit
 	} else {
 		bit := node.choose(ip)
 		down = node.child[bit]
 		if down == nil {
-			newNode.parent = parentIndirection{&node.child[bit], bit}
+			newNode.parent = parentIndirection[B]{&node.child[bit], bit}
 			node.child[bit] = newNode
 			return
 		}
@@ -151,21 +169,21 @@ func (trie parentIndirection) insert(ip []byte, cidr uint8, peer *Peer) {
 
 	if newNode.cidr == cidr {
 		bit := newNode.choose(down.bits)
-		down.parent = parentIndirection{&newNode.child[bit], bit}
+		down.parent = parentIndirection[B]{&newNode.child[bit], bit}
 		newNode.child[bit] = down
 		if parent == nil {
 			newNode.parent = trie
 			*trie.parentBit = newNode
 		} else {
 			bit := parent.choose(newNode.bits)
-			newNode.parent = parentIndirection{&parent.child[bit], bit}
+			newNode.parent = parentIndirection[B]{&parent.child[bit], bit}
 			parent.child[bit] = newNode
 		}
 		return
 	}
 
-	node = &trieEntry{
-		bits:       append([]byte{}, newNode.bits...),
+	node = &trieEntry[B]{
+		bits:       newNode.bits,
 		cidr:       cidr,
 		bitAtByte:  cidr / 8,
 		bitAtShift: 7 - (cidr % 8),
@@ -173,22 +191,22 @@ func (trie parentIndirection) insert(ip []byte, cidr uint8, peer *Peer) {
 	node.maskSelf()
 
 	bit := node.choose(down.bits)
-	down.parent = parentIndirection{&node.child[bit], bit}
+	down.parent = parentIndirection[B]{&node.child[bit], bit}
 	node.child[bit] = down
 	bit = node.choose(newNode.bits)
-	newNode.parent = parentIndirection{&node.child[bit], bit}
+	newNode.parent = parentIndirection[B]{&node.child[bit], bit}
 	node.child[bit] = newNode
 	if parent == nil {
 		node.parent = trie
 		*trie.parentBit = node
 	} else {
 		bit := parent.choose(node.bits)
-		node.parent = parentIndirection{&parent.child[bit], bit}
+		node.parent = parentIndirection[B]{&parent.child[bit], bit}
 		parent.child[bit] = node
 	}
 }
 
-func (node *trieEntry) lookup(ip []byte) *Peer {
+func (node *trieEntry[B]) lookup(ip B) *Peer {
 	var found *Peer
 	size := uint8(len(ip))
 	for node != nil && commonBits(node.bits, ip) >= node.cidr {
@@ -205,8 +223,8 @@ func (node *trieEntry) lookup(ip []byte) *Peer {
 }
 
 type AllowedIPs struct {
-	IPv4  *trieEntry
-	IPv6  *trieEntry
+	IPv4  *trieEntry[[4]byte]
+	IPv6  *trieEntry[[16]byte]
 	mutex sync.RWMutex
 }
 
@@ -215,14 +233,51 @@ func (table *AllowedIPs) EntriesForPeer(peer *Peer, cb func(prefix netip.Prefix)
 	defer table.mutex.RUnlock()
 
 	for elem := peer.trieEntries.Front(); elem != nil; elem = elem.Next() {
-		node := elem.Value.(*trieEntry)
-		a, _ := netip.AddrFromSlice(node.bits)
-		if !cb(netip.PrefixFrom(a, int(node.cidr))) {
-			return
+		if node, ok := elem.Value.(*trieEntry[[4]byte]); ok {
+			if !cb(netip.PrefixFrom(netip.AddrFrom4(node.bits), int(node.cidr))) {
+				return
+			}
+		} else if node, ok := elem.Value.(*trieEntry[[16]byte]); ok {
+			if !cb(netip.PrefixFrom(netip.AddrFrom16(node.bits), int(node.cidr))) {
+				return
+			}
 		}
 	}
 }
 
+func (node *trieEntry[B]) remove() {
+	node.removeFromPeerEntries()
+	node.peer = nil
+	if node.child[0] != nil && node.child[1] != nil {
+		return
+	}
+	bit := 0
+	if node.child[0] == nil {
+		bit = 1
+	}
+	child := node.child[bit]
+	if child != nil {
+		child.parent = node.parent
+	}
+	*node.parent.parentBit = child
+	if node.child[0] != nil || node.child[1] != nil || node.parent.parentBitType > 1 {
+		node.zeroizePointers()
+		return
+	}
+	parent := (*trieEntry[B])(unsafe.Pointer(uintptr(unsafe.Pointer(node.parent.parentBit)) - unsafe.Offsetof(node.child) - unsafe.Sizeof(node.child[0])*uintptr(node.parent.parentBitType)))
+	if parent.peer != nil {
+		node.zeroizePointers()
+		return
+	}
+	child = parent.child[node.parent.parentBitType^1]
+	if child != nil {
+		child.parent = parent.parent
+	}
+	*parent.parent.parentBit = child
+	node.zeroizePointers()
+	parent.zeroizePointers()
+}
+
 func (table *AllowedIPs) RemoveByPeer(peer *Peer) {
 	table.mutex.Lock()
 	defer table.mutex.Unlock()
@@ -230,38 +285,11 @@ func (table *AllowedIPs) RemoveByPeer(peer *Peer) {
 	var next *list.Element
 	for elem := peer.trieEntries.Front(); elem != nil; elem = next {
 		next = elem.Next()
-		node := elem.Value.(*trieEntry)
-
-		node.removeFromPeerEntries()
-		node.peer = nil
-		if node.child[0] != nil && node.child[1] != nil {
-			continue
-		}
-		bit := 0
-		if node.child[0] == nil {
-			bit = 1
-		}
-		child := node.child[bit]
-		if child != nil {
-			child.parent = node.parent
+		if node, ok := elem.Value.(*trieEntry[[4]byte]); ok {
+			node.remove()
+		} else if node, ok := elem.Value.(*trieEntry[[16]byte]); ok {
+			node.remove()
 		}
-		*node.parent.parentBit = child
-		if node.child[0] != nil || node.child[1] != nil || node.parent.parentBitType > 1 {
-			node.zeroizePointers()
-			continue
-		}
-		parent := (*trieEntry)(unsafe.Pointer(uintptr(unsafe.Pointer(node.parent.parentBit)) - unsafe.Offsetof(node.child) - unsafe.Sizeof(node.child[0])*uintptr(node.parent.parentBitType)))
-		if parent.peer != nil {
-			node.zeroizePointers()
-			continue
-		}
-		child = parent.child[node.parent.parentBitType^1]
-		if child != nil {
-			child.parent = parent.parent
-		}
-		*parent.parent.parentBit = child
-		node.zeroizePointers()
-		parent.zeroizePointers()
 	}
 }
 
@@ -270,11 +298,9 @@ func (table *AllowedIPs) Insert(prefix netip.Prefix, peer *Peer) {
 	defer table.mutex.Unlock()
 
 	if prefix.Addr().Is6() {
-		ip := prefix.Addr().As16()
-		parentIndirection{&table.IPv6, 2}.insert(ip[:], uint8(prefix.Bits()), peer)
+		parentIndirection[[16]byte]{&table.IPv6, 2}.insert(prefix.Addr().As16(), uint8(prefix.Bits()), peer)
 	} else if prefix.Addr().Is4() {
-		ip := prefix.Addr().As4()
-		parentIndirection{&table.IPv4, 2}.insert(ip[:], uint8(prefix.Bits()), peer)
+		parentIndirection[[4]byte]{&table.IPv4, 2}.insert(prefix.Addr().As4(), uint8(prefix.Bits()), peer)
 	} else {
 		panic(errors.New("inserting unknown address type"))
 	}
@@ -285,9 +311,9 @@ func (table *AllowedIPs) Lookup(ip []byte) *Peer {
 	defer table.mutex.RUnlock()
 	switch len(ip) {
 	case net.IPv6len:
-		return table.IPv6.lookup(ip)
+		return table.IPv6.lookup(*(*[16]byte)(ip))
 	case net.IPv4len:
-		return table.IPv4.lookup(ip)
+		return table.IPv4.lookup(*(*[4]byte)(ip))
 	default:
 		panic(errors.New("looking up unknown address type"))
 	}