Set Custom Max Size For DNS Packets?

Post new topic   Reply to topic    DD-WRT Forum Index -> Atheros WiSOC based Hardware
Author Message
CR_Apollo
DD-WRT User


Joined: 25 Dec 2020
Posts: 90
Location: Toronto - Canada

PostPosted: Tue Jan 31, 2023 0:26    Post subject: Set Custom Max Size For DNS Packets? Reply with quote
Hi there, I have never played around with the DNS settings other than to use dnscrypt and ignore my ISP DNS to use another static DNS setting. I am receiving the following message in my logs. Does not happen very often, maybe a couple times an hour max, on average, but mostly around once per hour.

dnsmasq[11956]: reducing DNS packet size for nameserver 127.0.0.1 to 1232

I do not have anything setup for internal DNS and that is still set to zeros, and I am using dnscrypt.

Will the following command in the DNS additional options stop this, or is there something else I can do to ensure all DNS request stay at or below 1232?

edns-packet-max=1232
Sponsor
Alozaros
DD-WRT Guru


Joined: 16 Nov 2015
Posts: 6407
Location: UK, London, just across the river..

PostPosted: Tue Jan 31, 2023 8:40    Post subject: Reply with quote
In general its not a big concern...i do have it all the time..as i also have multiple servers selected...in my DoT..
In this is case, some servers especially those with DNScypt or encrypted DNS are using smaller size, so, DNSmasq will concur those request and those with smaller size will come first..and the others will be ignored..in this case DNSmasq will reduce the packet size for short period of time like 60 sec or so..

It wont hurt to try fixing the packet size to smaller, but than.. those with large size will be ignored so, no point of heaving them...as a servers

The other option is to use roundrobin=0 or use strict order so, it will query only one server at the time.. and if this one needs smaller size DNSmasq will do its thing, so you dont have to bother.. Cool

_________________
Atheros
TP-Link WR740Nv1 ---DD-WRT 55179 WAP
TP-Link WR1043NDv2 -DD-WRT 55303 Gateway/DoT,Forced DNS,Ad-Block,Firewall,x4VLAN,VPN
TP-Link WR1043NDv2 -Gargoyle OS 1.15.x AP,DNS,QoS,Quotas
Qualcomm-Atheros
Netgear XR500 --DD-WRT 55460 Gateway/DoH,Forced DNS,AP Isolation,4VLAN,Ad-Block,Firewall,Vanilla
Netgear R7800 --DD-WRT 55460 Gateway/DoT,AD-Block,Forced DNS,AP&Net Isolation,x3VLAN,Firewall,Vanilla
Netgear R9000 --DD-WRT 55363 Gateway/DoT,AD-Block,AP Isolation,Firewall,Forced DNS,x2VLAN,Vanilla
Broadcom
Netgear R7000 --DD-WRT 55460 Gateway/SmartDNS/DoH,AD-Block,Firewall,Forced DNS,x3VLAN,VPN
NOT USING 5Ghz ANYWHERE
------------------------------------------------------
Stubby DNS over TLS I DNSCrypt v2 by mac913


Last edited by Alozaros on Wed Feb 01, 2023 11:13; edited 1 time in total
CR_Apollo
DD-WRT User


Joined: 25 Dec 2020
Posts: 90
Location: Toronto - Canada

PostPosted: Wed Feb 01, 2023 3:26    Post subject: Reply with quote
Alozaros wrote:
In general its not a big concern...i do have it all the time..as i also have multiple servers selected...in my DoT..
In this is case some servers especially those with DNScypt or encrypted DNS are using smaller size, so DNSmasq will concur those request and those with smaller size will come first..and other will be ignored..and in this case DNSmasq will reduce packet size for short period of time like 60 sec or so..

It wont hurt to try fixing the packet size to smaller, but than those will large size will be ignored so, no point of heaving them...

The other option is to use roundrobin=0 or use strict order so, it will query only one server at the time.. and if this one needs smaller size DNSmasq will do its thing, so you dont have to bother.. Cool


Understood. Thanks for the quick reply and suggestions. As you say, does not matter so much and it's not happening too often like the rebind warnings I am getting, so I think I will take your advice and leave as is. Thanks again! Cool
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12834
Location: Netherlands

PostPosted: Wed Feb 01, 2023 8:41    Post subject: Reply with quote
I think it has been discussed in the DNSMasq mailing list to lower the default from 1280 to 1232 but it was down voted.

Too busy to look it up, but as @Alozaros already commented no big deal

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
Display posts from previous:    Page 1 of 1
Post new topic   Reply to topic    DD-WRT Forum Index -> Atheros WiSOC based Hardware All times are GMT

Navigation

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum