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conn,device: provide 8 free bytes at packet head to conn.Bind.Send()

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This enables a conn.Bind to bring its own encapsulating transport, e.g.
VXLAN/Geneve.

Updates tailscale/corp#27502

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited 2025-05-30 13:14:43 -07:00 • committed by Jordan Whited
parent 022546570f
commit 65cd6eed7d
10 changed files with 58 additions and 39 deletions
Download patch file Download diff file Expand all files Collapse all files

9
conn/bind_std.go
View file

@ -341,7 +341,7 @@ func (e ErrUDPGSODisabled) Unwrap() error {
return e.RetryErr
}
func (s *StdNetBind) Send(bufs [][]byte, endpoint Endpoint) error {
func (s *StdNetBind) Send(bufs [][]byte, endpoint Endpoint, offset int) error {
s.mu.Lock()
blackhole := s.blackhole4
conn := s.ipv4
@ -384,7 +384,7 @@ func (s *StdNetBind) Send(bufs [][]byte, endpoint Endpoint) error {
)
retry:
if offload {
n := coalesceMessages(ua, endpoint.(*StdNetEndpoint), bufs, *msgs, setGSOSize)
n := coalesceMessages(ua, endpoint.(*StdNetEndpoint), bufs, offset, *msgs, setGSOSize)
err = s.send(conn, br, (*msgs)[:n])
if err != nil && offload && errShouldDisableUDPGSO(err) {
offload = false
@ -401,7 +401,7 @@ retry:
} else {
for i := range bufs {
(*msgs)[i].Addr = ua
(*msgs)[i].Buffers[0] = bufs[i]
(*msgs)[i].Buffers[0] = bufs[i][offset:]
setSrcControl(&(*msgs)[i].OOB, endpoint.(*StdNetEndpoint))
}
err = s.send(conn, br, (*msgs)[:len(bufs)])
@ -450,7 +450,7 @@ const (
type setGSOFunc func(control *[]byte, gsoSize uint16)
func coalesceMessages(addr *net.UDPAddr, ep *StdNetEndpoint, bufs [][]byte, msgs []ipv6.Message, setGSO setGSOFunc) int {
func coalesceMessages(addr *net.UDPAddr, ep *StdNetEndpoint, bufs [][]byte, offset int, msgs []ipv6.Message, setGSO setGSOFunc) int {
var (
base = -1 // index of msg we are currently coalescing into
gsoSize int // segmentation size of msgs[base]
@ -462,6 +462,7 @@ func coalesceMessages(addr *net.UDPAddr, ep *StdNetEndpoint, bufs [][]byte, msgs
maxPayloadLen = maxIPv6PayloadLen
}
for i, buf := range bufs {
buf = buf[offset:]
if i > 0 {
msgLen := len(buf)
baseLenBefore := len(msgs[base].Buffers[0])

2
conn/bind_std_test.go
View file

@ -98,7 +98,7 @@ func Test_coalesceMessages(t *testing.T) {
msgs[i].Buffers = make([][]byte, 1)
msgs[i].OOB = make([]byte, 0, 2)
}
got := coalesceMessages(addr, &StdNetEndpoint{AddrPort: addr.AddrPort()}, tt.buffs, msgs, mockSetGSOSize)
got := coalesceMessages(addr, &StdNetEndpoint{AddrPort: addr.AddrPort()}, tt.buffs, 0, msgs, mockSetGSOSize)
if got != len(tt.wantLens) {
t.Fatalf("got len %d want: %d", got, len(tt.wantLens))
}

3
conn/bind_windows.go
View file

@ -486,7 +486,7 @@ func (bind *afWinRingBind) Send(buf []byte, nend *WinRingEndpoint, isOpen *atomi
return winrio.SendEx(bind.rq, dataBuffer, 1, nil, addressBuffer, nil, nil, 0, 0)
}
func (bind *WinRingBind) Send(bufs [][]byte, endpoint Endpoint) error {
func (bind *WinRingBind) Send(bufs [][]byte, endpoint Endpoint, offset int) error {
nend, ok := endpoint.(*WinRingEndpoint)
if !ok {
return ErrWrongEndpointType
@ -494,6 +494,7 @@ func (bind *WinRingBind) Send(bufs [][]byte, endpoint Endpoint) error {
bind.mu.RLock()
defer bind.mu.RUnlock()
for _, buf := range bufs {
buf = buf[offset:]
switch nend.family {
case windows.AF_INET:
if bind.v4.blackhole {

3
conn/bindtest/bindtest.go
View file

@ -107,8 +107,9 @@ func (c *ChannelBind) makeReceiveFunc(ch chan []byte) conn.ReceiveFunc {
}
}
func (c *ChannelBind) Send(bufs [][]byte, ep conn.Endpoint) error {
func (c *ChannelBind) Send(bufs [][]byte, ep conn.Endpoint, offset int) error {
for _, b := range bufs {
b = b[offset:]
select {
case <-c.closeSignal:
return net.ErrClosed

8
conn/conn.go
View file

@ -45,9 +45,11 @@ type Bind interface {
// This mark is passed to the kernel as the socket option SO_MARK.
SetMark(mark uint32) error
// Send writes one or more packets in bufs to address ep. The length of
// bufs must not exceed BatchSize().
Send(bufs [][]byte, ep Endpoint) error
// Send writes one or more packets in bufs to address ep. A nonzero offset
// can be used to instruct the Bind on where packet data begins in each
// element of the bufs slice. Space preceding offset is free to use for
// additional encapsulation. The length of bufs must not exceed BatchSize().
Send(bufs [][]byte, ep Endpoint, offset int) error
// ParseEndpoint creates a new endpoint from a string.
ParseEndpoint(s string) (Endpoint, error)

6
device/constants.go
View file

@ -27,9 +27,9 @@ const (
)
const (
MinMessageSize = MessageKeepaliveSize // minimum size of transport message (keepalive)
MaxMessageSize = MaxSegmentSize // maximum size of transport message
MaxContentSize = MaxSegmentSize - MessageTransportSize // maximum size of transport message content
MinMessageSize = MessageKeepaliveSize // minimum size of transport message (keepalive)
MaxMessageSize = MaxSegmentSize // maximum size of transport message
MaxContentSize = MaxSegmentSize - MessageTransportSize - MessageEncapsulatingTransportSize // maximum size of transport message content
)
/* Implementation constants */

10
device/device_test.go
View file

@ -426,11 +426,11 @@ type fakeBindSized struct {
func (b *fakeBindSized) Open(port uint16) (fns []conn.ReceiveFunc, actualPort uint16, err error) {
return nil, 0, nil
}
func (b *fakeBindSized) Close() error { return nil }
func (b *fakeBindSized) SetMark(mark uint32) error { return nil }
func (b *fakeBindSized) Send(bufs [][]byte, ep conn.Endpoint) error { return nil }
func (b *fakeBindSized) ParseEndpoint(s string) (conn.Endpoint, error) { return nil, nil }
func (b *fakeBindSized) BatchSize() int { return b.size }
func (b *fakeBindSized) Close() error { return nil }
func (b *fakeBindSized) SetMark(mark uint32) error { return nil }
func (b *fakeBindSized) Send(bufs [][]byte, ep conn.Endpoint, offset int) error { return nil }
func (b *fakeBindSized) ParseEndpoint(s string) (conn.Endpoint, error) { return nil, nil }
func (b *fakeBindSized) BatchSize() int { return b.size }
type fakeTUNDeviceSized struct {
size int

15
device/noise-protocol.go
View file

@ -61,13 +61,14 @@ const (
)
const (
MessageInitiationSize = 148 // size of handshake initiation message
MessageResponseSize = 92 // size of response message
MessageCookieReplySize = 64 // size of cookie reply message
MessageTransportHeaderSize = 16 // size of data preceding content in transport message
MessageTransportSize = MessageTransportHeaderSize + poly1305.TagSize // size of empty transport
MessageKeepaliveSize = MessageTransportSize // size of keepalive
MessageHandshakeSize = MessageInitiationSize // size of largest handshake related message
MessageInitiationSize = 148 // size of handshake initiation message
MessageResponseSize = 92 // size of response message
MessageCookieReplySize = 64 // size of cookie reply message
MessageTransportHeaderSize = 16 // size of data preceding content in transport message
MessageEncapsulatingTransportSize = 8 // size of optional, free (for use by conn.Bind.Send()) space preceding the transport header
MessageTransportSize = MessageTransportHeaderSize + poly1305.TagSize // size of empty transport
MessageKeepaliveSize = MessageTransportSize // size of keepalive
MessageHandshakeSize = MessageInitiationSize // size of largest handshake related message
)
const (

5
device/peer.go
View file

@ -113,6 +113,9 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
return peer, nil
}
// SendBuffers sends buffers to peer. WireGuard packet data in each element of
// buffers must be preceded by MessageEncapsulatingTransportSize number of
// bytes.
func (peer *Peer) SendBuffers(buffers [][]byte) error {
peer.device.net.RLock()
defer peer.device.net.RUnlock()
@ -133,7 +136,7 @@ func (peer *Peer) SendBuffers(buffers [][]byte) error {
}
peer.endpoint.Unlock()
err := peer.device.net.bind.Send(buffers, endpoint)
err := peer.device.net.bind.Send(buffers, endpoint, MessageEncapsulatingTransportSize)
if err == nil {
var totalLen uint64
for _, b := range buffers {

36
device/send.go
View file

@ -45,11 +45,15 @@ import (
*/
type QueueOutboundElement struct {
buffer *[MaxMessageSize]byte // slice holding the packet data
packet []byte // slice of "buffer" (always!)
nonce uint64 // nonce for encryption
keypair *Keypair // keypair for encryption
peer *Peer // related peer
buffer *[MaxMessageSize]byte // slice holding the packet data
// packet is always a slice of "buffer". The starting offset in buffer
// is either:
// a) MessageEncapsulatingTransportSize+MessageTransportHeaderSize (plaintext)
// b) 0 (post-encryption)
packet []byte
nonce uint64 // nonce for encryption
keypair *Keypair // keypair for encryption
peer *Peer // related peer
}
type QueueOutboundElementsContainer struct {
@ -123,14 +127,15 @@ func (peer *Peer) SendHandshakeInitiation(isRetry bool) error {
return err
}
packet := make([]byte, MessageInitiationSize)
buf := make([]byte, MessageEncapsulatingTransportSize+MessageInitiationSize)
packet := buf[MessageEncapsulatingTransportSize:]
_ = msg.marshal(packet)
peer.cookieGenerator.AddMacs(packet)
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketSent()
err = peer.SendBuffers([][]byte{packet})
err = peer.SendBuffers([][]byte{buf})
if err != nil {
peer.device.log.Errorf("%v - Failed to send handshake initiation: %v", peer, err)
}
@ -152,7 +157,8 @@ func (peer *Peer) SendHandshakeResponse() error {
return err
}
packet := make([]byte, MessageResponseSize)
buf := make([]byte, MessageEncapsulatingTransportSize+MessageResponseSize)
packet := buf[MessageEncapsulatingTransportSize:]
_ = response.marshal(packet)
peer.cookieGenerator.AddMacs(packet)
@ -167,7 +173,7 @@ func (peer *Peer) SendHandshakeResponse() error {
peer.timersAnyAuthenticatedPacketSent()
// TODO: allocation could be avoided
err = peer.SendBuffers([][]byte{packet})
err = peer.SendBuffers([][]byte{buf})
if err != nil {
peer.device.log.Errorf("%v - Failed to send handshake response: %v", peer, err)
}
@ -184,10 +190,11 @@ func (device *Device) SendHandshakeCookie(initiatingElem *QueueHandshakeElement)
return err
}
packet := make([]byte, MessageCookieReplySize)
buf := make([]byte, MessageEncapsulatingTransportSize+MessageCookieReplySize)
packet := buf[MessageEncapsulatingTransportSize:]
_ = reply.marshal(packet)
// TODO: allocation could be avoided
device.net.bind.Send([][]byte{packet}, initiatingElem.endpoint)
device.net.bind.Send([][]byte{buf}, initiatingElem.endpoint, MessageEncapsulatingTransportSize)
return nil
}
@ -220,7 +227,7 @@ func (device *Device) RoutineReadFromTUN() {
elemsByPeer = make(map[*Peer]*QueueOutboundElementsContainer, batchSize)
count = 0
sizes = make([]int, batchSize)
offset = MessageTransportHeaderSize
offset = MessageEncapsulatingTransportSize + MessageTransportHeaderSize
)
for i := range elems {
@ -446,7 +453,7 @@ func (device *Device) RoutineEncryption(id int) {
for elemsContainer := range device.queue.encryption.c {
for _, elem := range elemsContainer.elems {
// populate header fields
header := elem.buffer[:MessageTransportHeaderSize]
header := elem.buffer[MessageEncapsulatingTransportSize : MessageEncapsulatingTransportSize+MessageTransportHeaderSize]
fieldType := header[0:4]
fieldReceiver := header[4:8]
@ -469,6 +476,9 @@ func (device *Device) RoutineEncryption(id int) {
elem.packet,
nil,
)
// re-slice packet to include encapsulating transport space
elem.packet = elem.buffer[:MessageEncapsulatingTransportSize+len(elem.packet)]
}
elemsContainer.Unlock()
}