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net: Dial always query DNS for both A and AAAA even if network is tcp4 or tcp6 when pure Go resolver is used #45024

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zhangboyang opened this issue Mar 15, 2021 · 4 comments
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net: Dial always query DNS for both A and AAAA even if network is tcp4 or tcp6 when pure Go resolver is used #45024

zhangboyang opened this issue Mar 15, 2021 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.17

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@zhangboyang
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When pure Go resolver is used, net.Dial always send two DNS query (one for A record and another for AAAA), even if the network parameter set to one of tcp4, tcp6, udp4, udp6. This will add extra latencies when making IPv4-only or IPv6-only connections. In the worst case, for example, a pure IPv4 host with firewall filtered out all AAAA queries, a dial with tcp4 will have to wait 10 second until AAAA query timed out.

The same problem was also found in cgo resolver (#25947), and it was fixed in c659be4.

My pull request will fix this.
@zhangboyang zhangboyang mentioned this issue Mar 15, 2021
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@gopherbot
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Change https://golang.org/cl/301709 mentions this issue: net: make go resolver aware of network parameter

@zhangboyang
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Here is my test code: (build it with CGO_ENABLED=0 go build test46.go)

package main

import "net"

func main() {
	net.Dial("tcp4", "golang.org:80")
}

Dump from wireshark:

No.	Time	Source	Destination	Protocol	Length	Info
11	3.196111458	127.0.0.1	127.0.0.53	DNS	70	Standard query 0x668e AAAA golang.org
12	3.196261224	127.0.0.1	127.0.0.53	DNS	70	Standard query 0x5811 A golang.org

@cherrymui cherrymui changed the title net.Dial always query DNS for both A and AAAA even if network is tcp4 or tcp6 when pure Go resolver is used net: Dial always query DNS for both A and AAAA even if network is tcp4 or tcp6 when pure Go resolver is used Mar 15, 2021
@cherrymui cherrymui added this to the Backlog milestone Mar 15, 2021
@cherrymui cherrymui added the NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. label Mar 15, 2021
@cherrymui
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cc @bradfitz

@networkimprov
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cc @ekalinin

@odeke-em odeke-em modified the milestones: Backlog, Go1.17 Mar 23, 2021
@odeke-em odeke-em added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. labels Mar 23, 2021
@james58899 james58899 mentioned this issue Jun 19, 2021
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@MaxKh MaxKh mentioned this issue Jul 4, 2021
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@antong antong mentioned this issue Aug 25, 2021
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@Undearius Undearius mentioned this issue Sep 30, 2021
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@golang golang locked and limited conversation to collaborators Mar 23, 2022
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.17
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net: make go resolver aware of network parameter
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@networkimprov @odeke-em @zhangboyang @gopherbot @cherrymui