Commit 2e642810 authored by Ido Schimmel's avatar Ido Schimmel Committed by Paolo Abeni
Browse files

selftests: traceroute: Test traceroute with different source IPs 



When generating ICMP error messages, the kernel will prefer a source IP
that is on the same subnet as the destination IP (see
inet_select_addr()). Test this behavior by invoking traceroute with
different source IPs and checking that the ICMP error message is
generated with a source IP in the same subnet.

Reviewed-by: default avatarPetr Machata <petrm@nvidia.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarIdo Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250908073238.119240-8-idosch@nvidia.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 5c9c7822

tools/testing/selftests/net/traceroute.sh

+9 −4
Original line number Diff line number Diff line
@@ -196,9 +196,10 @@ run_traceroute6() 
################################################################################

# traceroute test

#

# Verify that traceroute from H1 to H2 shows 1.0.1.1 in this scenario

# Verify that traceroute from H1 to H2 shows 1.0.3.1 and 1.0.1.1 when

# traceroute uses 1.0.3.3 and 1.0.1.3 as the source IP, respectively.

#

#                    1.0.3.1/24

#      1.0.3.3/24    1.0.3.1/24

# ---- 1.0.1.3/24    1.0.1.1/24 ---- 1.0.2.1/24    1.0.2.4/24 ----

# |H1|--------------------------|R1|--------------------------|H2|

# ----            N1            ----            N2            ----
@@ -226,6 +227,7 @@ setup_traceroute() 


	connect_ns $h1 eth0 1.0.1.3/24 - \

	           $router eth1 1.0.3.1/24 -

	ip -n "$h1" addr add 1.0.3.3/24 dev eth0

	ip netns exec $h1 ip route add default via 1.0.1.1



	ip netns exec $router ip addr add 1.0.1.1/24 dev eth1
@@ -248,9 +250,12 @@ run_traceroute() 


	RET=0



	# traceroute host-2 from host-1 (expects 1.0.1.1). Takes a while.

	run_cmd $h1 "traceroute 1.0.2.4 | grep -q 1.0.1.1"

	# traceroute host-2 from host-1. Expect a source IP that is on the same

	# subnet as destination IP of the ICMP error message.

	run_cmd "$h1" "traceroute -s 1.0.1.3 1.0.2.4 | grep -q 1.0.1.1"

	check_err $? "traceroute did not return 1.0.1.1"

	run_cmd "$h1" "traceroute -s 1.0.3.3 1.0.2.4 | grep -q 1.0.3.1"

	check_err $? "traceroute did not return 1.0.3.1"

	log_test "IPv4 traceroute"



	cleanup_traceroute