docs: fail-to is not an OpenBSD 8.0 keyword (removed upstream) - correct all references; reply-to gate added

tests/vm/13-replyto.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+# M4 gate: reply-to - force the next hop of the *reply* direction.
+#
+# reply-to is the asymmetric-routing tool: a flow whose request arrives on one
+# link can have its answer pushed out through a different gateway.  Proof is
+# taken on pf0's own interfaces (the lab's host bridge filters forwarded frames
+# that cross networks, so the peer side is not observable):
+#
+#   request  cli -> srv   leaves via $IF_SRV (normal path, untouched)
+#   reply    srv -> cli   leaves via $IF_GW  (forced by reply-to), not $IF_CLI
+set -uo pipefail; cd "$(dirname "$0")"; . ./lib.sh
+
+pf0 'insmod /opt/pf/pf.ko 2>/dev/null || insmod /tmp/pf.ko; true'
+pf0 '/opt/pf/pfctl -e; /opt/pf/pfctl -f /dev/null' >/dev/null
+
+IF_SRV=$(pf0 "ip route get $SRV_IP | grep -o 'dev [a-z0-9]*' | cut -d' ' -f2")
+IF_GW=$(pf0 "ip route get $GW2_IP | grep -o 'dev [a-z0-9]*' | cut -d' ' -f2")
+IF_CLI=$(pf0 "ip route get $CLI_IP | grep -o 'dev [a-z0-9]*' | cut -d' ' -f2")
+[ -n "$IF_SRV" ] && [ -n "$IF_GW" ] && [ -n "$IF_CLI" ] || { bad "interface resolution"; finish; }
+[ "$IF_GW" != "$IF_CLI" ] || { bad "gateway and client share a link"; finish; }
+ok "reply would normally leave via $IF_CLI, forced via $IF_GW"
+
+cat > /tmp/g13.conf <<C
+pass in quick proto icmp from $CLI_IP to $SRV_IP reply-to { $GW2_IP } keep state
+pass out quick keep state
+C
+pfload /tmp/g13.conf || { bad "reply-to rule load"; finish; }
+pf0 '/opt/pf/pfctl -sr' | grep -q 'reply-to' && ok "reply-to rule listed" || bad "reply-to not listed"
+
+pf0 "pkill tcpdump; (tcpdump -ni $IF_GW -c 8 -e icmp > /tmp/rt_gw.td 2>&1 &); (tcpdump -ni $IF_CLI -c 8 -e icmp > /tmp/rt_cli.td 2>&1 &); (tcpdump -ni $IF_SRV -c 8 -e icmp > /tmp/rt_srv.td 2>&1 &); sleep 1" >/dev/null
+cli "ping -c2 -W2 $SRV_IP >/dev/null 2>&1"
+sleep 2
+
+cnt() {
+	local n
+	n=$(pf0 "grep -c -- '$2' /tmp/rt_$1.td 2>/dev/null; true" | tr -dc '0-9')
+	[ -n "$n" ] || n=0
+	printf '%s' "$n"
+}
+
+# the request path must be unchanged
+N=$(cnt srv "$CLI_IP > $SRV_IP"); [ "$N" -gt 0 ] && ok "request left via $IF_SRV ($N)" \
+	|| bad "request did not leave via $IF_SRV"
+
+# the reply must be forced to the gateway link
+N=$(cnt gw "$SRV_IP > $CLI_IP"); [ "$N" -gt 0 ] && ok "reply forced onto $IF_GW ($N)" \
+	|| bad "reply not seen on $IF_GW"
+N=$(cnt cli "$SRV_IP > $CLI_IP"); [ "$N" -eq 0 ] && ok "reply did not use $IF_CLI" \
+	|| bad "reply still left via $IF_CLI ($N)"
+
+pf0 'pkill tcpdump; /opt/pf/pfctl -d' >/dev/null
+finish