tools/testing/selftests/netfilter/xt_string.sh

#!/bin/bash
# SPDX-License-Identifier: GPL-2.0

# return code to signal skipped test
ksft_skip=4
rc=0

if ! iptables --version >/dev/null 2>&1; then
	echo "SKIP: Test needs iptables"
	exit $ksft_skip
fi
if ! ip -V >/dev/null 2>&1; then
	echo "SKIP: Test needs iproute2"
	exit $ksft_skip
fi
if ! nc -h >/dev/null 2>&1; then
	echo "SKIP: Test needs netcat"
	exit $ksft_skip
fi

pattern="foo bar baz"
patlen=11
hdrlen=$((20 + 8)) # IPv4 + UDP
ns="ns-$(mktemp -u XXXXXXXX)"
trap 'ip netns del $ns' EXIT
ip netns add "$ns"
ip -net "$ns" link add d0 type dummy
ip -net "$ns" link set d0 up
ip -net "$ns" addr add 10.1.2.1/24 dev d0

#ip netns exec "$ns" tcpdump -npXi d0 &
#tcpdump_pid=$!
#trap 'kill $tcpdump_pid; ip netns del $ns' EXIT

add_rule() { # (alg, from, to)
	ip netns exec "$ns" \
		iptables -A OUTPUT -o d0 -m string \
			--string "$pattern" --algo $1 --from $2 --to $3
}
showrules() { # ()
	ip netns exec "$ns" iptables -v -S OUTPUT | grep '^-A'
}
zerorules() {
	ip netns exec "$ns" iptables -Z OUTPUT
}
countrule() { # (pattern)
	showrules | grep -c -- "$*"
}
send() { # (offset)
	( for ((i = 0; i < $1 - $hdrlen; i++)); do
		printf " "
	  done
	  printf "$pattern"
	) | ip netns exec "$ns" nc -w 1 -u 10.1.2.2 27374
}

add_rule bm 1000 1500
add_rule bm 1400 1600
add_rule kmp 1000 1500
add_rule kmp 1400 1600

zerorules
send 0
send $((1000 - $patlen))
if [ $(countrule -c 0 0) -ne 4 ]; then
	echo "FAIL: rules match data before --from"
	showrules
	((rc--))
fi

zerorules
send 1000
send $((1400 - $patlen))
if [ $(countrule -c 2) -ne 2 ]; then
	echo "FAIL: only two rules should match at low offset"
	showrules
	((rc--))
fi

zerorules
send $((1500 - $patlen))
if [ $(countrule -c 1) -ne 4 ]; then
	echo "FAIL: all rules should match at end of packet"
	showrules
	((rc--))
fi

zerorules
send 1495
if [ $(countrule -c 1) -ne 1 ]; then
	echo "FAIL: only kmp with proper --to should match pattern spanning fragments"
	showrules
	((rc--))
fi

zerorules
send 1500
if [ $(countrule -c 1) -ne 2 ]; then
	echo "FAIL: two rules should match pattern at start of second fragment"
	showrules
	((rc--))
fi

zerorules
send $((1600 - $patlen))
if [ $(countrule -c 1) -ne 2 ]; then
	echo "FAIL: two rules should match pattern at end of largest --to"
	showrules
	((rc--))
fi

zerorules
send $((1600 - $patlen + 1))
if [ $(countrule -c 1) -ne 0 ]; then
	echo "FAIL: no rules should match pattern extending largest --to"
	showrules
	((rc--))
fi

zerorules
send 1600
if [ $(countrule -c 1) -ne 0 ]; then
	echo "FAIL: no rule should match pattern past largest --to"
	showrules
	((rc--))
fi

exit $rc