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Egress DNS: Get lowest TTL from the dns resolution chain #19982

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merged 2 commits into from
Jun 14, 2018
Merged

Egress DNS: Get lowest TTL from the dns resolution chain #19982

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fc18c00
Egress DNS: Get lowest TTL from the dns resolution chain
Jun 12, 2018
abcc7f6
Increased DNS request timeout from 2 secs to 5 secs
Jun 13, 2018
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14 changes: 7 additions & 7 deletions pkg/network/common/dns.go
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Original file line number Diff line number Diff line change
Expand Up @@ -142,7 +142,7 @@ func (d *DNS) getIPsAndMinTTL(domain string) ([]net.IP, time.Duration, error) {
dialServer = net.JoinHostPort(server, d.port)
}
c := new(dns.Client)
c.Timeout = 2 * time.Second
c.Timeout = 5 * time.Second
in, _, err := c.Exchange(msg, dialServer)
if err != nil {
return nil, defaultTTL, err
Expand All @@ -153,20 +153,20 @@ func (d *DNS) getIPsAndMinTTL(domain string) ([]net.IP, time.Duration, error) {

if in != nil && len(in.Answer) > 0 {
for _, a := range in.Answer {
if !ttlSet || a.Header().Ttl < minTTL {
minTTL = a.Header().Ttl
ttlSet = true
}

switch t := a.(type) {
case *dns.A:
ips = append(ips, t.A)

if !ttlSet || t.Hdr.Ttl < minTTL {
minTTL = t.Hdr.Ttl
ttlSet = true
}
}
}
}
}

if !ttlSet {
if !ttlSet || (len(ips) == 0) {
return nil, defaultTTL, fmt.Errorf("IPv4 addr not found for domain: %q, nameservers: %v", domain, d.nameservers)
}

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2 changes: 1 addition & 1 deletion pkg/network/common/dns_test.go
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Expand Up @@ -50,7 +50,7 @@ func TestAddDNS(t *testing.T) {
domainName: "example.com",
dnsResolverOutput: "example.com. 200 IN CNAME foo.example.com.\nfoo.example.com. 600 IN A 10.11.12.13",
ips: []net.IP{ip},
ttl: 600,
ttl: 200,
expectFailure: false,
},
{
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