unicast_extensions.sh

#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# By Seth Schoen (c) 2021, for the IPv4 Unicast Extensions Project
# Thanks to David Ahern for help and advice on nettest modifications.
#
# Self-tests for IPv4 address extensions: the kernel's ability to accept
# certain traditionally unused or unallocated IPv4 addresses. For each kind
# of address, we test for interface assignment, ping, TCP, and forwarding.
# Must be run as root (to manipulate network namespaces and virtual
# interfaces).
#
# Things we test for here:
#
# * Currently the kernel accepts addresses in 0/8 and 240/4 as valid.
#
# * Notwithstanding that, 0.0.0.0 and 255.255.255.255 cannot be assigned.
#
# * Currently the kernel DOES NOT accept unicast use of the lowest
#   address in an IPv4 subnet (e.g. 192.168.100.0/32 in 192.168.100.0/24).
#   This is treated as a second broadcast address, for compatibility
#   with 4.2BSD (!).
#
# * Currently the kernel DOES NOT accept unicast use of any of 127/8.
#
# * Currently the kernel DOES NOT accept unicast use of any of 224/4.
#
# These tests provide an easy way to flip the expected result of any
# of these behaviors for testing kernel patches that change them.

# Kselftest framework requirement - SKIP code is 4.
ksft_skip=4

# nettest can be run from PATH or from same directory as this selftest
if ! which nettest >/dev/null; then
	PATH=$PWD:$PATH
	if ! which nettest >/dev/null; then
		echo "'nettest' command not found; skipping tests"
		exit $ksft_skip
	fi
fi

result=0

hide_output(){ exec 3>&1 4>&2 >/dev/null 2>/dev/null; }
show_output(){ exec >&3 2>&4; }

show_result(){
	if [ $1 -eq 0 ]; then
		printf "TEST: %-60s  [ OK ]\n" "${2}"
	else
		printf "TEST: %-60s  [FAIL]\n" "${2}"
		result=1
	fi
}

_do_segmenttest(){
	# Perform a simple set of link tests between a pair of
	# IP addresses on a shared (virtual) segment, using
	# ping and nettest.
	# foo --- bar
	# Arguments: ip_a ip_b prefix_length test_description
	#
	# Caller must set up foo-ns and bar-ns namespaces
	# containing linked veth devices foo and bar,
	# respectively.

	ip -n foo-ns address add $1/$3 dev foo || return 1
	ip -n foo-ns link set foo up || return 1
	ip -n bar-ns address add $2/$3 dev bar || return 1
	ip -n bar-ns link set bar up || return 1

	ip netns exec foo-ns timeout 2 ping -c 1 $2 || return 1
	ip netns exec bar-ns timeout 2 ping -c 1 $1 || return 1

	nettest -B -N bar-ns -O foo-ns -r $1 || return 1
	nettest -B -N foo-ns -O bar-ns -r $2 || return 1

	return 0
}

_do_route_test(){
	# Perform a simple set of gateway tests.
	#
	# [foo] <---> [foo1]-[bar1] <---> [bar]   /prefix
	#  host          gateway          host
	#
	# Arguments: foo_ip foo1_ip bar1_ip bar_ip prefix_len test_description
	# Displays test result and returns success or failure.

	# Caller must set up foo-ns, bar-ns, and router-ns
	# containing linked veth devices foo-foo1, bar1-bar
	# (foo in foo-ns, foo1 and bar1 in router-ns, and
	# bar in bar-ns).

	ip -n foo-ns address add $1/$5 dev foo || return 1
	ip -n foo-ns link set foo up || return 1
	ip -n foo-ns route add default via $2 || return 1
	ip -n bar-ns address add $4/$5 dev bar || return 1
	ip -n bar-ns link set bar up || return 1
	ip -n bar-ns route add default via $3 || return 1
	ip -n router-ns address add $2/$5 dev foo1 || return 1
	ip -n router-ns link set foo1 up || return 1
	ip -n router-ns address add $3/$5 dev bar1 || return 1
	ip -n router-ns link set bar1 up || return 1

	echo 1 | ip netns exec router-ns tee /proc/sys/net/ipv4/ip_forward

	ip netns exec foo-ns timeout 2 ping -c 1 $2 || return 1
	ip netns exec foo-ns timeout 2 ping -c 1 $4 || return 1
	ip netns exec bar-ns timeout 2 ping -c 1 $3 || return 1
	ip netns exec bar-ns timeout 2 ping -c 1 $1 || return 1

	nettest -B -N bar-ns -O foo-ns -r $1 || return 1
	nettest -B -N foo-ns -O bar-ns -r $4 || return 1

	return 0
}

segmenttest(){
	# Sets up veth link and tries to connect over it.
	# Arguments: ip_a ip_b prefix_len test_description
	hide_output
	ip netns add foo-ns
	ip netns add bar-ns
	ip link add foo netns foo-ns type veth peer name bar netns bar-ns

	test_result=0
	_do_segmenttest "$@" || test_result=1

	ip netns pids foo-ns | xargs -r kill -9
	ip netns pids bar-ns | xargs -r kill -9
	ip netns del foo-ns
	ip netns del bar-ns
	show_output

	# inverted tests will expect failure instead of success
	[ -n "$expect_failure" ] && test_result=`expr 1 - $test_result`

	show_result $test_result "$4"
}

route_test(){
	# Sets up a simple gateway and tries to connect through it.
	# [foo] <---> [foo1]-[bar1] <---> [bar]   /prefix
	# Arguments: foo_ip foo1_ip bar1_ip bar_ip prefix_len test_description
	# Returns success or failure.

	hide_output
	ip netns add foo-ns
	ip netns add bar-ns
	ip netns add router-ns
	ip link add foo netns foo-ns type veth peer name foo1 netns router-ns
	ip link add bar netns bar-ns type veth peer name bar1 netns router-ns

	test_result=0
	_do_route_test "$@" || test_result=1

	ip netns pids foo-ns | xargs -r kill -9
	ip netns pids bar-ns | xargs -r kill -9
	ip netns pids router-ns | xargs -r kill -9
	ip netns del foo-ns
	ip netns del bar-ns
	ip netns del router-ns

	show_output

	# inverted tests will expect failure instead of success
	[ -n "$expect_failure" ] && test_result=`expr 1 - $test_result`
	show_result $test_result "$6"
}

echo "###########################################################################"
echo "Unicast address extensions tests (behavior of reserved IPv4 addresses)"
echo "###########################################################################"
#
# Test support for 240/4
segmenttest 240.1.2.1   240.1.2.4    24 "assign and ping within 240/4 (1 of 2) (is allowed)"
segmenttest 250.100.2.1 250.100.30.4 16 "assign and ping within 240/4 (2 of 2) (is allowed)"
#
# Test support for 0/8
segmenttest 0.1.2.17    0.1.2.23  24 "assign and ping within 0/8 (1 of 2) (is allowed)"
segmenttest 0.77.240.17 0.77.2.23 16 "assign and ping within 0/8 (2 of 2) (is allowed)"
#
# Even 255.255/16 is OK!
segmenttest 255.255.3.1 255.255.50.77 16 "assign and ping inside 255.255/16 (is allowed)"
#
# Or 255.255.255/24
segmenttest 255.255.255.1 255.255.255.254 24 "assign and ping inside 255.255.255/24 (is allowed)"
#
# Routing between different networks
route_test 240.5.6.7 240.5.6.1  255.1.2.1    255.1.2.3      24 "route between 240.5.6/24 and 255.1.2/24 (is allowed)"
route_test 0.200.6.7 0.200.38.1 245.99.101.1 245.99.200.111 16 "route between 0.200/16 and 245.99/16 (is allowed)"
#
# Test support for lowest address ending in .0
segmenttest 5.10.15.20 5.10.15.0 24 "assign and ping lowest address (/24)"
#
# Test support for lowest address not ending in .0
segmenttest 192.168.101.192 192.168.101.193 26 "assign and ping lowest address (/26)"
#
# Routing using lowest address as a gateway/endpoint
route_test 192.168.42.1 192.168.42.0 9.8.7.6 9.8.7.0 24 "routing using lowest address"
#
# ==============================================
# ==== TESTS THAT CURRENTLY EXPECT FAILURE =====
# ==============================================
expect_failure=true
# It should still not be possible to use 0.0.0.0 or 255.255.255.255
# as a unicast address.  Thus, these tests expect failure.
segmenttest 0.0.1.5       0.0.0.0         16 "assigning 0.0.0.0 (is forbidden)"
segmenttest 255.255.255.1 255.255.255.255 16 "assigning 255.255.255.255 (is forbidden)"
#
# Test support for not having all of 127 be loopback
# Currently Linux does not allow this, so this should fail too
segmenttest 127.99.4.5 127.99.4.6 16 "assign and ping inside 127/8 (is forbidden)"
#
# Test support for unicast use of class D
# Currently Linux does not allow this, so this should fail too
segmenttest 225.1.2.3 225.1.2.200 24 "assign and ping class D address (is forbidden)"
#
# Routing using class D as a gateway
route_test 225.1.42.1 225.1.42.2 9.8.7.6 9.8.7.1 24 "routing using class D (is forbidden)"
#
# Routing using 127/8
# Currently Linux does not allow this, so this should fail too
route_test 127.99.2.3 127.99.2.4 200.1.2.3 200.1.2.4 24 "routing using 127/8 (is forbidden)"
#
unset expect_failure
# =====================================================
# ==== END OF TESTS THAT CURRENTLY EXPECT FAILURE =====
# =====================================================
exit ${result}