Information on forwarding queue occupation in a Linux router Post: 303039947

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Special Forums UNIX and Linux Applications Information on forwarding queue occupation in a Linux router Post 303039947 by i_mll on Friday 18th of October 2019 12:29:31 PM

10-18-2019

Registered User

Information on forwarding queue occupation in a Linux router

Hello.
I have an OpenWrt router forwarding traffic from a network to another and I'm building a monitoring tool that requires information about the packet queue/ ring buffer (in the receiving side/interface - rx) occupation, alerting me when it is close to its maximum capacity.

However, after analysing the following files (linux filesystem):

tcp_mem/tcp_rmem/tcp_wmem in /proc/sys/net/ipv4
tx_queue_len in /sys/class/net/(interface)
sockstat in /proc/net

I concluded these files would only be relevant for my program if the router was the destination or source of the TCP packets, which is not the case. So, as I discussed with a professor of mine, the metrics these files provide are not relevant in a forwarding situation, as the packets do not go to the TCP queues.

If that's true, then where (in what folder/file) can I find information about the router's forwarding queue's current occupation and its maximum occupation, if there's any information on the matter? Note that this question is not limited to the OpenWrt OS, but any linux system.

i_mll

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LEARN ABOUT MINIX

irdpd

IRDPD(8)						      System Manager's Manual							  IRDPD(8)

NAME

       irdpd - internet router discovery protocol daemon

SYNOPSIS

       irdpd [-bsd] [-U udp-device] [-I ip-device] [-o priority-offset]

DESCRIPTION

       Irdpd  looks for routers.  This should be a simple task, but many routers are hard to find because they do not implement the router discov-
       ery protocol.  This daemon collects information that routers do send out and makes it available.

       At startup irdpd sends out several router solicitation broadcasts.  A good router should respond to this with a router advertisement.

       If a router advertisement arrives then no more solicitations are sent.  The TCP/IP server has filled its routing table with the	info  from
       the  advertisement,  so it now has at least one router.	If the advertisement is sent by a genuine router (the sender is in the table) then
       the irdpd daemon goes dormant for the time the advert is valid.	Routers send new adverts periodically, keeping the daemon silent.

       Otherwise irdpd will listen for RIP (Router Information Protocol) packets.  These packets are sent  between  routers  to  exchange  routing
       information.  Irdpd uses this information to build a routing table.

       Every now and then a router advertisement is sent to the local host to give it router information build from the RIP packets.

       Lastly,	if a router solicitation arrives and there is no router around that sends advertisements, then irdpd sends an advertisement to the
       requestor.  Note that this is a direct violation of RFC1256, as no host is supposed to sent those adverts.   But  alas  the  world  is  not
       always  perfect,  and those adverts make booting hosts find routers quickly with this help from their brothers.	(Of course, they will lose
       the router soon if they don't have an irdpd daemon themselves.)

OPTIONS

       -b     Broadcast advertisements instead of sending them to the local host only.	This may be used to keep (non-Minix) hosts alive on a  net
	      without adverts.

       -s     Be silent, do not send advertisements to hosts that ask for them.

       -d     Debug  mode,  tell  where  info  is  coming from and where it is sent.  Debugging can also be turned on at runtime by sending signal
	      SIGUSR1 or turned off with SIGUSR2.

       -o priority-offset
	      Offset used to make the gateway's preferences collected from RIP packets look worse than those found in genuine router adverts.	By
	      default -1024.

SEE ALSO

       set_net_default(8), boot(8), inetd(8), nonamed(8), rarpd(8).

BUGS

       Under  standard	Minix this daemon can't listen to two both IRDP and RIP at the same time, so it starts out with IRDP.  It switches over to
       RIP if it can't find a router, or if it threatens to lose its router.  It does not switch back.

       Irdpd may help a host that should not be helped, i.e. if it doesn't have an irdpd daemon with RIP collecting trickery.  It will make System
       Administrators pull out their remaining hair trying to find out why a host can access outside networks for a some time after boot, but goes
       blind afterwards.

AUTHOR

       Kees J. Bot (kjb@cs.vu.nl)

																	  IRDPD(8)