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net/tstun: simplify code

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Calculate whether the packet is injected directly,
rather than via an else branch.

Unify the exit paths. It is easier here than duplicating them.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This commit is contained in:
Josh Bleecher Snyder 2021-06-30 13:28:52 -07:00 committed by Josh Bleecher Snyder
parent cc23049cd2
commit a4cc7b6d54
1 changed files with 7 additions and 14 deletions
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21
net/tstun/wrap.go
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@ -354,15 +354,13 @@ func (t *Wrapper) Read(buf []byte, offset int) (int, error) {
defer allowSendOnClosedChannel() // for send to t.bufferConsumed defer allowSendOnClosedChannel() // for send to t.bufferConsumed
pkt := res.data pkt := res.data
n := copy(buf[offset:], pkt) n := copy(buf[offset:], pkt)
wasInjectedPacket := false // t.buffer has a fixed location in memory.
// t.buffer has a fixed location in memory, // If the packet is not from t.buffer, then it is an injected packet.
// so this is the easiest way to tell when it has been consumed.
// &pkt[0] can be used because empty packets do not reach t.outbound. // &pkt[0] can be used because empty packets do not reach t.outbound.
if &pkt[0] == &t.buffer[PacketStartOffset] { isInjectedPacket := &pkt[0] != &t.buffer[PacketStartOffset]
if !isInjectedPacket {
// We are done with t.buffer. Let poll re-use it.
t.bufferConsumed <- struct{}{} t.bufferConsumed <- struct{}{}
} else {
// If the packet is not from t.buffer, then it is an injected packet.
wasInjectedPacket = true
} }
p := parsedPacketPool.Get().(*packet.Parsed) p := parsedPacketPool.Get().(*packet.Parsed)
@ -375,13 +373,8 @@ func (t *Wrapper) Read(buf []byte, offset int) (int, error) {
} }
} }
// For injected packets, we return early to bypass filtering. // Do not filter injected packets.
if wasInjectedPacket { if !isInjectedPacket && !t.disableFilter {
t.noteActivity()
return n, nil
}
if !t.disableFilter {
response := t.filterOut(p) response := t.filterOut(p)
if response != filter.Accept { if response != filter.Accept {
// Wireguard considers read errors fatal; pretend nothing was read // Wireguard considers read errors fatal; pretend nothing was read