RTNETLINK answers: No such file or directory

Question

When I run this cmd:

tc qdisc add dev eth0 root red limit 51200000 min 128000 max 512000 avpkt 1024 burst 200 ecn probability 0.5

i get

RTNETLINK answers: No such file or directory

I have configured the kernel for netfilters , and all the networking options in menuconfig .

I don't understand why this error occurs. I'm using iproute2-2.6.23 and Fedora 8.

This was working fine on my laptop, but not on my Desktop PC?

Answer 1

On my system your command autoloads the sch_red module. The question is rather old so on a modern system the autoloading should work fine if you have the required module. Check if you miss the kernel module by running:

modprobe sch_red

If it prints nothing, then retry running tc command and see if it helps.

If not, ensure you have CONFIG_NET_SCH_RED (Random Early Detection) compiled in your kernel. More info at kernel documentation .

Answer 2

The error could be due to a lack of support for traffic control in Linux kernel.

Here is an excerpt from documentation that lists kernel compilation options needed for proper operation of traffic control functionality in Linux:

Source: Traffic Control HOWTO - Kernel requirements

# # QoS and/or fair queueing # CONFIG_NET_SCHED=y CONFIG_NET_SCH_CBQ=m CONFIG_NET_SCH_HTB=m CONFIG_NET_SCH_CSZ=m CONFIG_NET_SCH_PRIO=m CONFIG_NET_SCH_RED=m CONFIG_NET_SCH_SFQ=m CONFIG_NET_SCH_TEQL=m CONFIG_NET_SCH_TBF=m CONFIG_NET_SCH_GRED=m CONFIG_NET_SCH_DSMARK=m CONFIG_NET_SCH_INGRESS=m CONFIG_NET_QOS=y CONFIG_NET_ESTIMATOR=y CONFIG_NET_CLS=y CONFIG_NET_CLS_TCINDEX=m CONFIG_NET_CLS_ROUTE4=m CONFIG_NET_CLS_ROUTE=y CONFIG_NET_CLS_FW=m CONFIG_NET_CLS_U32=m CONFIG_NET_CLS_RSVP=m CONFIG_NET_CLS_RSVP6=m CONFIG_NET_CLS_POLICE=y

A kernel compiled with the above set of options will provide modular support for almost everything discussed in this documentation. The user may need to modprobe module before using a given feature.

Answer 3

I got this one after compiling the (in-tree) ralink wifi drivers on a system that did not include the usual array of pre-built modules. The modules loaded and the interface was there, but could not be set up:

ip link set wlanB up
RTNETLINK answers: No such file or directory

(Yes, wlanB is correct.) Eventually figured out the system was also missing the usual array of firmware in /lib/firmware . This was fixed with apt install firmware-ralink .