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control/controlbase: use less memory when idle (remove txState.buf)

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Uses 4KB less per Conn.

Updates #4113

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2022-03-20 16:12:11 -07:00 committed by Brad Fitzpatrick
parent bfb4a4d9e9
commit 21445b56a5
1 changed files with 18 additions and 7 deletions
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25
control/controlbase/conn.go
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@ -63,7 +63,6 @@ type txState struct {
sync.Mutex sync.Mutex
cipher cipher.AEAD cipher cipher.AEAD
nonce nonce nonce nonce
buf [maxMessageSize]byte
err error // records the first partial write error for all future calls err error // records the first partial write error for all future calls
} }
@ -134,19 +133,19 @@ func (c *Conn) decryptLocked(msg []byte) (err error) {
return err return err
} }
// encryptLocked encrypts plaintext into c.tx.buf (including the // encryptLocked encrypts plaintext into buf (including the
// packet header) and returns a slice of the ciphertext, or an error // packet header) and returns a slice of the ciphertext, or an error
// if the cipher is exhausted (i.e. can no longer be used safely). // if the cipher is exhausted (i.e. can no longer be used safely).
func (c *Conn) encryptLocked(plaintext []byte) ([]byte, error) { func (c *Conn) encryptLocked(plaintext []byte, buf *maxMsgBuffer) ([]byte, error) {
if !c.tx.nonce.Valid() { if !c.tx.nonce.Valid() {
// Received 2^64-1 messages on this cipher state. Connection // Received 2^64-1 messages on this cipher state. Connection
// is no longer usable. // is no longer usable.
return nil, errCipherExhausted{} return nil, errCipherExhausted{}
} }
c.tx.buf[0] = msgTypeRecord buf[0] = msgTypeRecord
binary.BigEndian.PutUint16(c.tx.buf[1:headerLen], uint16(len(plaintext)+chp.Overhead)) binary.BigEndian.PutUint16(buf[1:headerLen], uint16(len(plaintext)+chp.Overhead))
ret := c.tx.cipher.Seal(c.tx.buf[:headerLen], c.tx.nonce[:], plaintext, nil) ret := c.tx.cipher.Seal(buf[:headerLen], c.tx.nonce[:], plaintext, nil)
c.tx.nonce.Increment() c.tx.nonce.Increment()
return ret, nil return ret, nil
@ -257,6 +256,9 @@ func (c *Conn) Write(bs []byte) (n int, err error) {
return 0, net.ErrClosed return 0, net.ErrClosed
} }
buf := bufPool.Get().(*maxMsgBuffer)
defer bufPool.Put(buf)
var sent int var sent int
for len(bs) > 0 { for len(bs) > 0 {
toSend := bs toSend := bs
@ -265,7 +267,7 @@ func (c *Conn) Write(bs []byte) (n int, err error) {
} }
bs = bs[len(toSend):] bs = bs[len(toSend):]
ciphertext, err := c.encryptLocked(toSend) ciphertext, err := c.encryptLocked(toSend, buf)
if err != nil { if err != nil {
return sent, err return sent, err
} }
@ -355,3 +357,12 @@ func (n *nonce) Increment() {
} }
binary.BigEndian.PutUint64(n[4:], 1+binary.BigEndian.Uint64(n[4:])) binary.BigEndian.PutUint64(n[4:], 1+binary.BigEndian.Uint64(n[4:]))
} }
type maxMsgBuffer [maxMessageSize]byte
// bufPool holds the temporary buffers for Conn.Read & Write.
var bufPool = &sync.Pool{
New: func() interface{} {
return new(maxMsgBuffer)
},
}