ssh-stress: disable resource penalties

Our tests create a number of ssh sessions in the
background which are immediately killed. Some of
them haven't finished the authentication stage yet
and they close the connection incurring penalties from
the ssh daemon.

debug1: srclimit_penalise: active penalty for ipv4 10.0.0.1/32
already exists, 16 seconds remaining

Then when we try to reconnect to the daemon we are bounced
because of the active penalty which leads to a failed test.

ssh-stress 1 TINFO: Killing all ssh sessions
kex_exchange_identification: read: Connection reset by peer
Connection reset by fd00:1:1:1::2 port 58373
ssh-stress 1 TFAIL: SSH not reachable

>From the sshd logs we can see

debug1: srclimit_penalise: active penalty for ipv4 10.0.0.1/32
already exists, 16 seconds remaining

This feature was added to OpenSSH 9.8 in the 2024 release in the
81c1099d2 commit. Lets disable penalties for the versions that
support them.

Link: https://lore.kernel.org/ltp/20251222141331.121827-1-vasileios.almpanis@virtuozzo.com/
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Vasileios Almpanis <vasileios.almpanis@virtuozzo.com>
[ pvorel: fix version check, simplify version evaluation ]
Signed-off-by: Petr Vorel <pvorel@suse.cz>

Author: Vasileios Almpanis

testcases/network/stress/ssh/ssh-stress.sh

@@ -39,8 +39,13 @@ cleanup()
 
 setup()
 {
-	local port rc
+	local port rc version
+	local major=0 minor=0
 
+	version=$(sshd -V 2>&1 | sed -nE 's/^.*OpenSSH_([0-9]+)\.([0-9]+).*$/\1 \2/p' | head -n1)
+	set -- $version
+	major=$1
+	minor=$2
 
 	port=$(tst_rhost_run -c "tst_get_unused_port ipv${TST_IPVER} stream")
 
@@ -60,6 +65,11 @@ HostKey $TST_TMPDIR/ssh_host_ecdsa_key
 HostKey $TST_TMPDIR/ssh_host_ed25519_key
 EOF
 
+	if [ "$major" -gt 9 ] || [ "$major" -eq 9 -a "$minor" -ge 8 ]; then
+		cat << EOF >> sshd_config
+PerSourcePenalties no
+EOF
+	fi
 	ssh-keygen -q -N "" -t rsa -b 4096 -f $TST_TMPDIR/ssh_host_rsa_key
 	ssh-keygen -q -N "" -t ecdsa -f $TST_TMPDIR/ssh_host_ecdsa_key
 	ssh-keygen -q -N "" -t ed25519 -f $TST_TMPDIR/ssh_host_ed25519_key