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net/dns,net/dns/resolver: refactor channels/magicDNS out of Resolver

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Moves magicDNS-specific handling out of Resolver & into dns.Manager. This
greatly simplifies the Resolver to solely issuing queries and returning
responses, without channels.

Enforcement of max number of in-flight magicDNS queries, assembly of
synthetic UDP datagrams, and integration with wgengine for
recieving/responding to magicDNS traffic is now entirely in Manager.
This path is being kept around, but ultimately aims to be deleted and
replaced with a netstack-based path.

This commit is part of a series to implement magicDNS using netstack.

Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom DNetto
2022-04-14 13:27:59 -07:00
committed by Tom
parent a54671529b
commit 5b85f848dd
4 changed files with 158 additions and 249 deletions
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27
net/dns/resolver/forwarder.go
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@@ -190,9 +190,6 @@ type forwarder struct {
ctx context.Context // good until Close
ctxCancel context.CancelFunc // closes ctx
// responses is a channel by which responses are returned.
responses chan packet
mu sync.Mutex // guards following
dohClient map[string]*http.Client // urlBase -> client
@@ -229,14 +226,13 @@ func maxDoHInFlight(goos string) int {
return 1000
}
func newForwarder(logf logger.Logf, responses chan packet, linkMon *monitor.Mon, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *forwarder {
func newForwarder(logf logger.Logf, linkMon *monitor.Mon, linkSel ForwardLinkSelector, dialer *tsdial.Dialer) *forwarder {
f := &forwarder{
logf: logger.WithPrefix(logf, "forward: "),
linkMon: linkMon,
linkSel: linkSel,
dialer: dialer,
responses: responses,
dohSem: make(chan struct{}, maxDoHInFlight(runtime.GOOS)),
logf: logger.WithPrefix(logf, "forward: "),
linkMon: linkMon,
linkSel: linkSel,
dialer: dialer,
dohSem: make(chan struct{}, maxDoHInFlight(runtime.GOOS)),
}
f.ctx, f.ctxCancel = context.WithCancel(context.Background())
return f
@@ -601,17 +597,6 @@ type forwardQuery struct {
// ...
}
// forward forwards the query to all upstream nameservers and waits for
// the first response.
//
// It either sends to f.responses and returns nil, or returns a
// non-nil error (without sending to the channel).
func (f *forwarder) forward(query packet) error {
ctx, cancel := context.WithTimeout(f.ctx, responseTimeout)
defer cancel()
return f.forwardWithDestChan(ctx, query, f.responses)
}
// forwardWithDestChan forwards the query to all upstream nameservers
// and waits for the first response.
//