[nos-bbs] ugly ax25 linux bug ? no idea SAMB gets 2 UA replies ...

[VE2PKT]

Hello Maiko,

     I do not think this is cause by AX25 Utils, I saw that on VE2PKT-13 
also,

and I have the same system running since 2013 and my last update was 
November 2016.

I could not catch from which station was causing that but will keep and 
eyes on it.


73 de Jean


On 2020-12-10 8:30 p.m., M Langelaar wrote:
> This is a bit technical, but I have stumbled across a problem where if I
> connect to a node that depends on AX25 Linux stack I am receiving 2
> UA to my SABM, the first UA JNOS takes and moves it to LAPB_CONNECTED,
> but the second UA JNOS takes and tries to re-establish the link and 
> instantly
> we get a loop of SABM / UA over and over, just loops and does not 
> stop, basically
> creating a DOS attack. It's unreal to watch.
>
> My instant fix for this (and I confirm it works) is to ignore UA FRMR 
> if we are
> in a LAPB_CONNECTED state, which probably it should. I can fix that on my
> end no problem. I can't find in the AX25 specs what a system should do 
> it it
> receives a UA while in LAPB_CONNECTED, but I never see that situation 
> ever
> happen until recently.
>
> Is anyone aware of an AX25 utils or linux libs bug that might be 
> causing this ?
>
> Maiko / VE4KLM
>
>
>
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-- 

73 de Jean,
VA2OM / VE2PKT

Sysop de: VE2PKT (BBS), VE2PKT-13 (URONode), VE2PKT-4 (XRPI)
         : VE2RCN-1, VE2RGM-1, VE2RGC-1, VE2RVA-1, (The-Net)
         : VE2PKT-9 (DXCluster), VE2PKT-10 (Winlink Gateway)
RF:
147.435 Mhz (1200 Bps),

Internet:
Telnet: ve2pkt.dyndns.org port 23 (URONode)  - VE2PKT-13
Telnet: ve2pkt.dyndns.org port 2323 (Xrpi Node) - VE2PKT-4
Telnet: ve2pkt.dyndns.org port 6300 (FBB BBS) - VE2PKT
Telnet: ve2pkt.dyndns.org port 9000 (DXCluster) - VE2PKT-9

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