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net/dns, net/dns/resolver, wgengine: refactor DNS request path (#4364)

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* net/dns, net/dns/resolver, wgengine: refactor DNS request path

Previously, method calls into the DNS manager/resolver types handled DNS
requests rather than DNS packets. This is fine for UDP as one packet
corresponds to one request or response, however will not suit an
implementation that supports DNS over TCP.

To support PRs implementing this in the future, wgengine delegates
all handling/construction of packets to the magic DNS endpoint, to
the DNS types themselves. Handling IP packets at this level enables
future support for both UDP and TCP.

Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom
2022-04-08 12:17:31 -07:00
committed by GitHub
parent 3b3d1b9350
commit 24bdcbe5c7
4 changed files with 97 additions and 57 deletions
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net/dns/resolver/tsdns_test.go
+8 -5
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@@ -27,6 +27,7 @@ import (
"tailscale.com/net/tsdial"
"tailscale.com/tstest"
"tailscale.com/types/dnstype"
"tailscale.com/types/ipproto"
"tailscale.com/util/dnsname"
"tailscale.com/wgengine/monitor"
)
@@ -37,6 +38,8 @@ var (
testipv4Arpa = dnsname.FQDN("4.3.2.1.in-addr.arpa.")
testipv6Arpa = dnsname.FQDN("f.0.e.0.d.0.c.0.b.0.a.0.9.0.8.0.7.0.6.0.5.0.4.0.3.0.2.0.1.0.0.0.ip6.arpa.")
magicDNSv4Port = netaddr.MustParseIPPort("100.100.100.100:53")
)
var dnsCfg = Config{
@@ -231,10 +234,10 @@ func unpackResponse(payload []byte) (dnsResponse, error) {
}
func syncRespond(r *Resolver, query []byte) ([]byte, error) {
if err := r.EnqueueRequest(query, netaddr.IPPort{}); err != nil {
return nil, fmt.Errorf("EnqueueRequest: %w", err)
if err := r.enqueueRequest(query, ipproto.UDP, netaddr.IPPort{}, magicDNSv4Port); err != nil {
return nil, fmt.Errorf("enqueueRequest: %w", err)
}
payload, _, err := r.NextResponse()
payload, _, err := r.nextResponse()
return payload, err
}
@@ -727,14 +730,14 @@ func TestDelegateCollision(t *testing.T) {
// packets will have the same dns txid.
for _, p := range packets {
payload := dnspacket(p.qname, p.qtype, noEdns)
err := r.EnqueueRequest(payload, p.addr)
err := r.enqueueRequest(payload, ipproto.UDP, p.addr, magicDNSv4Port)
if err != nil {
t.Error(err)
}
}
// Despite the txid collision, the answer(s) should still match the query.
resp, addr, err := r.NextResponse()
resp, addr, err := r.nextResponse()
if err != nil {
t.Error(err)
}