diff options
author | jfbus <jf@bustarret.com> | 2019-03-26 18:21:53 +0000 |
---|---|---|
committer | Brad Fitzpatrick <bradfitz@golang.org> | 2019-04-17 14:42:35 +0000 |
commit | dbc17037815bdce5df3f355f2171c57804f7870e (patch) | |
tree | d1b7e6669f254f3642b3e9aa3c11d151cc6d9bb5 /src/net/dnsclient_unix_test.go | |
parent | 33e5da48d5d22a722f2363b15e2d53061fb71cf4 (diff) | |
download | go-dbc17037815bdce5df3f355f2171c57804f7870e.tar.gz go-dbc17037815bdce5df3f355f2171c57804f7870e.zip |
net: support single-request resolv.conf option in pure Go resolver
There is a DNS resolution issue in Kubernetes (UDP response packets get dropped due to a race in conntrack between the parallel A and AAAA queries, causing timeouts in DNS queries).
A workaround is to enable single-request / single-request-reopen in resolv.conf in order to use sequential A and AAAA queries instead of parallel queries.
With this PR, the pure Go resolver searches for "single-request" and "single-request-reopen" in resolv.conf and send A and AAAA queries sequentially when found.
Fixes #29644
Change-Id: I906b3484008c1b9adf2e3e9241ea23767e29df59
GitHub-Last-Rev: d481acfb4c49d82fd474078b31a1a4697b57dadf
GitHub-Pull-Request: golang/go#29661
Reviewed-on: https://go-review.googlesource.com/c/go/+/157377
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Diffstat (limited to 'src/net/dnsclient_unix_test.go')
-rw-r--r-- | src/net/dnsclient_unix_test.go | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/net/dnsclient_unix_test.go b/src/net/dnsclient_unix_test.go index 810f400f0bd..51d54a4ccad 100644 --- a/src/net/dnsclient_unix_test.go +++ b/src/net/dnsclient_unix_test.go @@ -17,6 +17,7 @@ import ( "reflect" "strings" "sync" + "sync/atomic" "testing" "time" @@ -1621,3 +1622,76 @@ func TestTXTRecordTwoStrings(t *testing.T) { t.Errorf("txt[1], got %q, want %q", txt[1], want) } } + +// Issue 29644: support single-request resolv.conf option in pure Go resolver. +// The A and AAAA queries will be sent sequentially, not in parallel. +func TestSingleRequestLookup(t *testing.T) { + defer dnsWaitGroup.Wait() + var ( + firstcalled int32 + ipv4 int32 = 1 + ipv6 int32 = 2 + ) + fake := fakeDNSServer{rh: func(n, s string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) { + r := dnsmessage.Message{ + Header: dnsmessage.Header{ + ID: q.ID, + Response: true, + }, + Questions: q.Questions, + } + for _, question := range q.Questions { + switch question.Type { + case dnsmessage.TypeA: + if question.Name.String() == "slowipv4.example.net." { + time.Sleep(10 * time.Millisecond) + } + if !atomic.CompareAndSwapInt32(&firstcalled, 0, ipv4) { + t.Errorf("the A query was received after the AAAA query !") + } + r.Answers = append(r.Answers, dnsmessage.Resource{ + Header: dnsmessage.ResourceHeader{ + Name: q.Questions[0].Name, + Type: dnsmessage.TypeA, + Class: dnsmessage.ClassINET, + Length: 4, + }, + Body: &dnsmessage.AResource{ + A: TestAddr, + }, + }) + case dnsmessage.TypeAAAA: + atomic.CompareAndSwapInt32(&firstcalled, 0, ipv6) + r.Answers = append(r.Answers, dnsmessage.Resource{ + Header: dnsmessage.ResourceHeader{ + Name: q.Questions[0].Name, + Type: dnsmessage.TypeAAAA, + Class: dnsmessage.ClassINET, + Length: 16, + }, + Body: &dnsmessage.AAAAResource{ + AAAA: TestAddr6, + }, + }) + } + } + return r, nil + }} + r := Resolver{PreferGo: true, Dial: fake.DialContext} + + conf, err := newResolvConfTest() + if err != nil { + t.Fatal(err) + } + defer conf.teardown() + if err := conf.writeAndUpdate([]string{"options single-request"}); err != nil { + t.Fatal(err) + } + for _, name := range []string{"hostname.example.net", "slowipv4.example.net"} { + firstcalled = 0 + _, err := r.LookupIPAddr(context.Background(), name) + if err != nil { + t.Error(err) + } + } +} |