diff options
| author | Josh Bleecher Snyder <josh@tailscale.com> | 2020-12-14 18:30:13 -0800 |
|---|---|---|
| committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2021-01-07 14:49:44 +0100 |
| commit | 41cd68416c8f35e80523fb3102b6a9c9982446c4 (patch) | |
| tree | 643119e80c844893c01453d3f52bf36d50e55b0f | |
| parent | 94b33ba705c75a6c02fc0567f0d6a776d4f03d07 (diff) | |
device: simplify copying counter to nonce
Since we already have it packed into a uint64
in a known byte order, write it back out again
the same byte order instead of copying byte by byte.
This should also generate more efficient code,
because the compiler can do a single uint64 write,
instead of eight bounds checks and eight byte writes.
Due to a missed optimization, it actually generates a mishmash
of smaller writes: 1 byte, 4 bytes, 2 bytes, 1 byte.
This is https://golang.org/issue/41663.
The code is still better than before, and will get better yet
once that compiler bug gets fixed.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
| -rw-r--r-- | device/receive.go | 14 |
1 files changed, 2 insertions, 12 deletions
diff --git a/device/receive.go b/device/receive.go index 839b735..852bd89 100644 --- a/device/receive.go +++ b/device/receive.go @@ -268,22 +268,12 @@ func (device *Device) RoutineDecryption() { counter := elem.packet[MessageTransportOffsetCounter:MessageTransportOffsetContent] content := elem.packet[MessageTransportOffsetContent:] - // expand nonce - - nonce[0x4] = counter[0x0] - nonce[0x5] = counter[0x1] - nonce[0x6] = counter[0x2] - nonce[0x7] = counter[0x3] - - nonce[0x8] = counter[0x4] - nonce[0x9] = counter[0x5] - nonce[0xa] = counter[0x6] - nonce[0xb] = counter[0x7] - // decrypt and release to consumer var err error elem.counter = binary.LittleEndian.Uint64(counter) + // copy counter to nonce + binary.LittleEndian.PutUint64(nonce[0x4:0xc], elem.counter) elem.packet, err = elem.keypair.receive.Open( content[:0], nonce[:], |