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wgengine/magicsock: make ReceiveIPv4 a little easier to follow.

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The previous code used a lot of whole-function variables and shared
behavior that only triggered based on prior action from a single codepath.
Instead of that, move the small amounts of "shared" code into each switch
case.

Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-12-18 00:49:50 -08:00 committed by Dave Anderson
parent 0ad109f63d
commit c8c493f3d9
1 changed files with 25 additions and 20 deletions
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45
wgengine/magicsock/magicsock.go
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@ -1489,10 +1489,7 @@ func (c *Conn) ReceiveIPv4(b []byte) (n int, ep conn.Endpoint, addr *net.UDPAddr
// to udpRecvCh. The code below must not access b until it's
// completed a successful receive on udpRecvCh.
var addrSet *addrSet
var discoEp *discoEndpoint
var ipp netaddr.IPPort
var didNoteRecvActivity bool
select {
case dm := <-c.derpRecvCh:
@ -1531,6 +1528,11 @@ func (c *Conn) ReceiveIPv4(b []byte) (n int, ep conn.Endpoint, addr *net.UDPAddr
goto Top
}
var (
didNoteRecvActivity bool
discoEp *discoEndpoint
asEp *addrSet
)
c.mu.Lock()
if dk, ok := c.discoOfNode[tailcfg.NodeKey(dm.src)]; ok {
discoEp = c.endpointOfDisco[dk]
@ -1550,24 +1552,39 @@ func (c *Conn) ReceiveIPv4(b []byte) (n int, ep conn.Endpoint, addr *net.UDPAddr
c.mu.Lock()
discoEp = c.endpointOfDisco[dk]
c.logf("magicsock: DERP packet received from idle peer %v; created=%v", dm.src.ShortString(), discoEp != nil)
c.logf("magicsock: DERP packet received from idle peer %v; created=%v", dm.src.ShortString(), ep != nil)
}
}
if discoEp == nil {
addrSet = c.addrsByKey[dm.src]
}
asEp = c.addrsByKey[dm.src]
c.mu.Unlock()
if addrSet == nil && discoEp == nil {
if discoEp != nil {
ep = discoEp
} else if asEp != nil {
ep = asEp
} else {
key := wgcfg.Key(dm.src)
c.logf("magicsock: DERP packet from unknown key: %s", key.ShortString())
// TODO(danderson): after we fail to find a DERP endpoint, we
// seem to be falling through to passing the packet to
// wireguard with a garbage singleEndpoint. This feels wrong,
// should we goto Top above?
ep = c.findEndpoint(ipp, addr)
}
if !didNoteRecvActivity {
c.noteRecvActivityFromEndpoint(ep)
}
return n, ep, wgRecvAddr(ep, ipp, addr), nil
case um := <-c.udpRecvCh:
if um.err != nil {
return 0, nil, nil, err
}
n, addr, ipp = um.n, um.addr, um.ipp
ep = c.findEndpoint(ipp, addr)
c.noteRecvActivityFromEndpoint(ep)
return n, ep, wgRecvAddr(ep, ipp, addr), nil
case <-c.donec():
// Socket has been shut down. All the producers of packets
@ -1582,18 +1599,6 @@ func (c *Conn) ReceiveIPv4(b []byte) (n int, ep conn.Endpoint, addr *net.UDPAddr
// with an error so it can clean up.
return 0, nil, nil, errors.New("socket closed")
}
if addrSet != nil {
ep = addrSet
} else if discoEp != nil {
ep = discoEp
} else {
ep = c.findEndpoint(ipp, addr)
}
if !didNoteRecvActivity {
c.noteRecvActivityFromEndpoint(ep)
}
return n, ep, wgRecvAddr(ep, ipp, addr), nil
}
func (c *Conn) ReceiveIPv6(b []byte) (int, conn.Endpoint, *net.UDPAddr, error) {