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![Jesper Dangaard Brouer](/assets/img/avatar_default.png)
Creating a bpf sample that shows howto use the XDP 'data_meta' infrastructure, created by Daniel Borkmann. Very few drivers support this feature, but I wanted a functional sample to begin with, when working on adding driver support. XDP data_meta is about creating a communication channel between BPF programs. This can be XDP tail-progs, but also other SKB based BPF hooks, like in this case the TC clsact hook. In this sample I show that XDP can store info named "mark", and TC/clsact chooses to use this info and store it into the skb->mark. It is a bit annoying that XDP and TC samples uses different tools/libs when attaching their BPF hooks. As the XDP and TC programs need to cooperate and agree on a struct-layout, it is best/easiest if the two programs can be contained within the same BPF restricted-C file. As the bpf-loader, I choose to not use bpf_load.c (or libbpf), but instead wrote a bash shell scripted named xdp2skb_meta.sh, which demonstrate howto use the iproute cmdline tools 'tc' and 'ip' for loading BPF programs. To make it easy for first time users, the shell script have command line parsing, and support --verbose and --dry-run mode, if you just want to see/learn the tc+ip command syntax: # ./xdp2skb_meta.sh --dev ixgbe2 --dry-run # Dry-run mode: enable VERBOSE and don't call TC+IP tc qdisc del dev ixgbe2 clsact tc qdisc add dev ixgbe2 clsact tc filter add dev ixgbe2 ingress prio 1 handle 1 bpf da obj ./xdp2skb_meta_kern.o sec tc_mark # Flush XDP on device: ixgbe2 ip link set dev ixgbe2 xdp off ip link set dev ixgbe2 xdp obj ./xdp2skb_meta_kern.o sec xdp_mark Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
220 lines
4.5 KiB
Bash
Executable file
220 lines
4.5 KiB
Bash
Executable file
#!/bin/bash
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#
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# SPDX-License-Identifier: GPL-2.0
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# Copyright (c) 2018 Jesper Dangaard Brouer, Red Hat Inc.
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#
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# Bash-shell example on using iproute2 tools 'tc' and 'ip' to load
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# eBPF programs, both for XDP and clsbpf. Shell script function
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# wrappers and even long options parsing is illustrated, for ease of
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# use.
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#
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# Related to sample/bpf/xdp2skb_meta_kern.c, which contains BPF-progs
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# that need to collaborate between XDP and TC hooks. Thus, it is
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# convenient that the same tool load both programs that need to work
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# together.
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#
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BPF_FILE=xdp2skb_meta_kern.o
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DIR=$(dirname $0)
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export TC=/usr/sbin/tc
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export IP=/usr/sbin/ip
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function usage() {
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echo ""
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echo "Usage: $0 [-vfh] --dev ethX"
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echo " -d | --dev : Network device (required)"
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echo " --flush : Cleanup flush TC and XDP progs"
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echo " --list : (\$LIST) List TC and XDP progs"
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echo " -v | --verbose : (\$VERBOSE) Verbose"
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echo " --dry-run : (\$DRYRUN) Dry-run only (echo commands)"
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echo ""
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}
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## -- General shell logging cmds --
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function err() {
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local exitcode=$1
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shift
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echo "ERROR: $@" >&2
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exit $exitcode
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}
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function info() {
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if [[ -n "$VERBOSE" ]]; then
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echo "# $@"
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fi
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}
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## -- Helper function calls --
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# Wrapper call for TC and IP
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# - Will display the offending command on failure
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function _call_cmd() {
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local cmd="$1"
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local allow_fail="$2"
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shift 2
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if [[ -n "$VERBOSE" ]]; then
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echo "$(basename $cmd) $@"
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fi
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if [[ -n "$DRYRUN" ]]; then
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return
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fi
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$cmd "$@"
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local status=$?
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if (( $status != 0 )); then
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if [[ "$allow_fail" == "" ]]; then
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err 2 "Exec error($status) occurred cmd: \"$cmd $@\""
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fi
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fi
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}
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function call_tc() {
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_call_cmd "$TC" "" "$@"
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}
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function call_tc_allow_fail() {
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_call_cmd "$TC" "allow_fail" "$@"
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}
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function call_ip() {
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_call_cmd "$IP" "" "$@"
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}
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## --- Parse command line arguments / parameters ---
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# Using external program "getopt" to get --long-options
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OPTIONS=$(getopt -o vfhd: \
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--long verbose,flush,help,list,dev:,dry-run -- "$@")
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if (( $? != 0 )); then
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err 4 "Error calling getopt"
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fi
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eval set -- "$OPTIONS"
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unset DEV
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unset FLUSH
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while true; do
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case "$1" in
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-d | --dev ) # device
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DEV=$2
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info "Device set to: DEV=$DEV" >&2
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shift 2
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;;
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-v | --verbose)
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VERBOSE=yes
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# info "Verbose mode: VERBOSE=$VERBOSE" >&2
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shift
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;;
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--dry-run )
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DRYRUN=yes
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VERBOSE=yes
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info "Dry-run mode: enable VERBOSE and don't call TC+IP" >&2
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shift
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;;
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-f | --flush )
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FLUSH=yes
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shift
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;;
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--list )
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LIST=yes
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shift
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;;
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-- )
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shift
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break
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;;
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-h | --help )
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usage;
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exit 0
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;;
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* )
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shift
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break
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;;
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esac
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done
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FILE="$DIR/$BPF_FILE"
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if [[ ! -e $FILE ]]; then
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err 3 "Missing BPF object file ($FILE)"
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fi
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if [[ -z $DEV ]]; then
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usage
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err 2 "Please specify network device -- required option --dev"
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fi
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## -- Function calls --
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function list_tc()
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{
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local device="$1"
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shift
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info "Listing current TC ingress rules"
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call_tc filter show dev $device ingress
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}
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function list_xdp()
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{
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local device="$1"
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shift
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info "Listing current XDP device($device) setting"
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call_ip link show dev $device | grep --color=auto xdp
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}
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function flush_tc()
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{
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local device="$1"
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shift
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info "Flush TC on device: $device"
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call_tc_allow_fail filter del dev $device ingress
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call_tc_allow_fail qdisc del dev $device clsact
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}
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function flush_xdp()
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{
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local device="$1"
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shift
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info "Flush XDP on device: $device"
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call_ip link set dev $device xdp off
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}
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function attach_tc_mark()
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{
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local device="$1"
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local file="$2"
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local prog="tc_mark"
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shift 2
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# Re-attach clsact to clear/flush existing role
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call_tc_allow_fail qdisc del dev $device clsact 2> /dev/null
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call_tc qdisc add dev $device clsact
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# Attach BPF prog
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call_tc filter add dev $device ingress \
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prio 1 handle 1 bpf da obj $file sec $prog
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}
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function attach_xdp_mark()
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{
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local device="$1"
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local file="$2"
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local prog="xdp_mark"
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shift 2
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# Remove XDP prog in-case it's already loaded
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# TODO: Need ip-link option to override/replace existing XDP prog
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flush_xdp $device
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# Attach XDP/BPF prog
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call_ip link set dev $device xdp obj $file sec $prog
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}
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if [[ -n $FLUSH ]]; then
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flush_tc $DEV
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flush_xdp $DEV
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exit 0
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fi
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if [[ -n $LIST ]]; then
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list_tc $DEV
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list_xdp $DEV
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exit 0
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fi
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attach_tc_mark $DEV $FILE
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attach_xdp_mark $DEV $FILE
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