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net: restore per-query timeout logic

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The handling of "options timeout:n" is supposed to be per individual
DNS server exchange, not per Lookup call.

Fixes #16865.

Change-Id: I2304579b9169c1515292f142cb372af9d37ff7c1
Reviewed-on: https://go-review.googlesource.com/28057
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Matthew Dempsky 2016-08-29 13:53:32 -07:00
parent aaa6b53524
commit 11e3955e10
2 changed files with 92 additions and 21 deletions
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17
src/net/dnsclient_unix.go
View file

@ -141,7 +141,7 @@ func (d *Dialer) dialDNS(ctx context.Context, network, server string) (dnsConn,
}
// exchange sends a query on the connection and hopes for a response.
func exchange(ctx context.Context, server, name string, qtype uint16) (*dnsMsg, error) {
func exchange(ctx context.Context, server, name string, qtype uint16, timeout time.Duration) (*dnsMsg, error) {
d := testHookDNSDialer()
out := dnsMsg{
dnsMsgHdr: dnsMsgHdr{
@ -152,6 +152,12 @@ func exchange(ctx context.Context, server, name string, qtype uint16) (*dnsMsg,
},
}
for _, network := range []string{"udp", "tcp"} {
// TODO(mdempsky): Refactor so defers from UDP-based
// exchanges happen before TCP-based exchange.
ctx, cancel := context.WithDeadline(ctx, time.Now().Add(timeout))
defer cancel()
c, err := d.dialDNS(ctx, network, server)
if err != nil {
return nil, err
@ -180,17 +186,10 @@ func tryOneName(ctx context.Context, cfg *dnsConfig, name string, qtype uint16)
return "", nil, &DNSError{Err: "no DNS servers", Name: name}
}
deadline := time.Now().Add(cfg.timeout)
if old, ok := ctx.Deadline(); !ok || deadline.Before(old) {
var cancel context.CancelFunc
ctx, cancel = context.WithDeadline(ctx, deadline)
defer cancel()
}
var lastErr error
for i := 0; i < cfg.attempts; i++ {
for _, server := range cfg.servers {
msg, err := exchange(ctx, server, name, qtype)
msg, err := exchange(ctx, server, name, qtype, cfg.timeout)
if err != nil {
lastErr = &DNSError{
Err: err.Error(),