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Traffic control - Make DNS requests delayed and low priority on Linux
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| #!/bin/sh | |
| # SPDX-License-Identifier: MIT | |
| ## Copyright (C) 2017 Przemyslaw Pawelczyk <[email protected]> | |
| ## | |
| ## This script is licensed under the terms of the MIT license. | |
| ## https://opensource.org/licenses/MIT | |
| # | |
| # Traffic control - Make DNS requests delayed and low priority on Linux. | |
| if [ $# -eq 0 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then | |
| echo "Usage: $0 IFACE [DELAY [JITTER [CORRELATION]]]" | |
| echo | |
| echo "Example: $0 eth1 500ms 100ms" | |
| exit 0 | |
| fi | |
| IFACE=$1 | |
| shift | |
| ip link show dev $IFACE >/dev/null || exit 1 | |
| tc qdisc del dev $IFACE root 2>/dev/null | |
| if [ -z "$*" ] || [ "$1" = "off" ]; then | |
| echo "Traffic control: Set default queueing discipline on $IFACE." | |
| exit 0 | |
| fi | |
| echo "Traffic control: Make DNS requests delayed and low priority on $IFACE." | |
| tc qdisc add dev $IFACE root handle 1: \ | |
| prio bands 2 priomap 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 | |
| tc qdisc add dev $IFACE parent 1:2 handle 53: \ | |
| netem delay "$@" | |
| tc filter add dev $IFACE parent 1: \ | |
| protocol ip prio 1 u32 match ip dport 53 0xffff flowid 1:2 |
@naikrovek Yeah, slow or malfunctioning DNS can literally kill your web experience. It was meant to help test/debug software that may expect DNS replies within short timeframe, which is not always the case.
commit a11585efc32ce26b8b51dcc5ba4eb5e9034d2dd3
Author: Przemyslaw Pawelczyk <[email protected]>
Date: 2018-02-06 14:59:01 +0100
tc-delaydnsreqs.sh: Add copyright notice and MIT license notice.
commit 84b514c728bc3bbf49158393dad3d5ba926557ea
Author: Przemyslaw Pawelczyk <[email protected]>
Date: 2018-02-06 14:59:47 +0100
Add SPDX License Identifier.
The Software Package Data Exchange (SPDX) is a good initiative, it has
matured over time and deserves accelerated adoption in open-source.
https://spdx.org/learn
https://spdx.org/using-spdx
https://spdx.org/license-list
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I haven't used this, but right away this seems like a great way to demonstrate just how influential DNS performance can be to a web browsing overall. I've had difficulty explaining just how many DNS requests are made per page load, and conveying just how important DNS performance can be. This would be a wonderful way to demonstrate it. Starred.