pf: Log the intended action when a NAT rule matches a packet

When a packet matches a binat/nat/rdr rule, pf logs the match.  The log
metadata includes the rule's action on the packet, e.g., PF_PASS.  NAT
rules have their own actions: PF_BINAT, PF_NAT, PF_RDR.

Before commit 948e8413ab ("pflog: pass the action to pflog directly"),
pflog_packet() would obtain the action from the rule definition, whereas
after that commit the action is passed as a parameter.  When a NAT rule
matches, we want to log the rule action, but after that commit, PF_PASS
is hard-coded.  Restore the previous behaviour.

Add a regression test which installs a redirect, logs packets matching
the redirect rule, and verifies that the corresponding pflog entry
includes the correct action.

Reviewed by:	kp
Fixes:		948e8413ab ("pflog: pass the action to pflog directly")
MFC after:	2 weeks
Sponsored by:	Klara, Inc.
Sponsored by:	OPNsense
Differential Revision:	https://reviews.freebsd.org/D48911

sys/netpfil/pf/pf.c

@@ -5535,7 +5535,7 @@ pf_test_rule(struct pf_krule **rm, struct pf_kstate **sm,
 		KASSERT(nk != NULL, ("%s: null nk", __func__));
 
 		if (nr->log) {
-			PFLOG_PACKET(PF_PASS, PFRES_MATCH, nr, a,
+			PFLOG_PACKET(nr->action, PFRES_MATCH, nr, a,
 			    ruleset, pd, 1);
 		}
 

tests/sys/netpfil/pf/pflog.sh

@@ -264,10 +264,69 @@ unspecified_v6_cleanup()
 	pft_cleanup
 }
 
+atf_test_case "rdr_action" "cleanup"
+rdr_head()
+{
+	atf_set descr 'Ensure that NAT rule actions are logged correctly'
+	atf_set require.user root
+}
+
+rdr_action_body()
+{
+	j="pflog:rdr_action"
+	epair_c=$(vnet_mkepair)
+	epair_srv=$(vnet_mkepair)
+
+	vnet_mkjail ${j}srv ${epair_srv}a
+	vnet_mkjail ${j}gw ${epair_srv}b ${epair_c}a
+	vnet_mkjail ${j}c ${epair_c}b
+
+	jexec ${j}srv ifconfig ${epair_srv}a 198.51.100.1/24 up
+	# No default route in srv jail, to ensure we're NAT-ing
+	jexec ${j}gw ifconfig ${epair_srv}b 198.51.100.2/24 up
+	jexec ${j}gw ifconfig ${epair_c}a 192.0.2.1/24 up
+	jexec ${j}gw sysctl net.inet.ip.forwarding=1
+	jexec ${j}c ifconfig ${epair_c}b 192.0.2.2/24 up
+	jexec ${j}c route add default 192.0.2.1
+
+	jexec ${j}gw pfctl -e
+	jexec ${j}gw ifconfig pflog0 up
+	pft_set_rules ${j}gw \
+		"rdr log on ${epair_srv}b proto tcp from 198.51.100.0/24 to any port 1234 -> 192.0.2.2 port 1234" \
+		"block quick inet6" \
+		"pass in log"
+
+	jexec ${j}gw tcpdump -n -e -ttt --immediate-mode -l -U -i pflog0 >> ${PWD}/pflog.txt &
+	sleep 1 # Wait for tcpdump to start
+
+	# send a SYN to catch in the log
+	jexec ${j}srv nc -N -w 0 198.51.100.2 1234
+
+	echo "Log"
+	cat ${PWD}/pflog.txt
+
+	# log line generated for rdr hit (pre-NAT)
+	atf_check -o match:".*.*rule 0/0\(match\): rdr in on ${epair_srv}b: 198.51.100.1.[0-9]* > 198.51.100.2.1234: Flags \[S\].*" \
+	    cat pflog.txt
+
+	# log line generated for pass hit (post-NAT)
+	atf_check -o match:".*.*rule 1/0\(match\): pass in on ${epair_srv}b: 198.51.100.1.[0-9]* > 192.0.2.2.1234: Flags \[S\].*" \
+	    cat pflog.txt
+
+	# only two log lines shall be written
+	atf_check -o match:2 grep -c . pflog.txt
+}
+
+rdr_action_cleanup()
+{
+	pft_cleanup
+}
+
 atf_init_test_cases()
 {
 	atf_add_test_case "malformed"
 	atf_add_test_case "matches"
+	atf_add_test_case "rdr_action"
 	atf_add_test_case "state_max"
 	atf_add_test_case "unspecified_v4"
 	atf_add_test_case "unspecified_v6"