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Clean up the flow a bit (partly because I am allergic to huge compounded if statements)

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This commit is contained in:
Neil Alexander 2018-07-30 11:46:44 +01:00
parent 68a482ed92
commit ebb4ec7c33
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1 changed files with 23 additions and 26 deletions
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49
src/yggdrasil/session.go
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@ -423,40 +423,37 @@ func (sinfo *sessionInfo) doWorker() {
func (sinfo *sessionInfo) doSend(bs []byte) {
defer util_putBytes(bs)
if !sinfo.init {
// To prevent using empty session keys
return
} // To prevent using empty session keys
}
coords := sinfo.coords
// Read IPv6 flowlabel field (20 bits).
// Assumes packet at least contains IPv6 header.
flowkey := uint64(bs[1]&0x0f)<<16 | uint64(bs[2])<<8 | uint64(bs[3])
if flowkey == 0 /* not specified */ &&
len(bs) >= 48 /* min UDP len, others are bigger */ &&
(bs[6] == 0x06 || bs[6] == 0x11 || bs[6] == 0x84) /* TCP UDP SCTP */ {
// if flowlabel was unspecified (0), try to use known protocols' ports
// protokey: proto | sport | dport
flowkey = uint64(bs[6])<<32 /* proto */ |
uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
uint64(bs[42])<<8 | uint64(bs[43]) /* dport */
// Check if the flowlabel was specified
if flowkey == 0 {
// Does the packet meet the minimum UDP packet size? (others are bigger)
if len(bs) >= 48 {
// Is the protocol TCP, UDP, SCTP?
if bs[6] == 0x06 || bs[6] == 0x11 || bs[6] == 0x84 {
// if flowlabel was unspecified (0), try to use known protocols' ports
// protokey: proto | sport | dport
flowkey = uint64(bs[6])<<32 /* proto */ |
uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
uint64(bs[42])<<8 | uint64(bs[43]) /* dport */
}
}
}
var coords []byte
// If we have a flowkey, either through the IPv6 flowlabel field or through
// known TCP/UDP/SCTP proto-sport-dport triplet, then append it to the coords.
// Appending extra coords after a 0 ensures that we still target the local router
// but lets us send extra data (which is otherwise ignored) to help separate
// traffic streams into independent queues
if flowkey != 0 {
// Now we append something to the coords
// Specifically, we append a 0, and then arbitrary data
// The 0 ensures that the destination node switch forwards to the self peer (router)
// The rest is ignored, but it's still part as the coords, so it affects switch queues
// This helps separate traffic streams (coords, flowlabel) to be queued independently
// TODO could we avoid allocations there and put this work into wire_trafficPacket.encode()?
coords = append(coords, sinfo.coords...) // Start with the real coords
coords = append(coords, 0) // Then target the local switchport
coords = append(coords, 0) // First target the local switchport
coords = wire_put_uint64(flowkey, coords) // Then variable-length encoded flowkey
} else {
// flowlabel was unspecified (0) and protocol unrecognised.
// To save bytes, we're not including it, therefore we won't need self-port override either.
// So just use sinfo.coords directly to avoid golang GC allocations.
// Recent enough Linux and BSDs support flowlabels (auto_flowlabel) out of the box so this will be rare.
coords = sinfo.coords
}
// Prepare the payload
payload, nonce := boxSeal(&sinfo.sharedSesKey, bs, &sinfo.myNonce)
defer util_putBytes(payload)
p := wire_trafficPacket{