Make ipfw0 logging pseudo-interface clonable. It can be created automatically

by $firewall_logif rc.conf(5) variable at boot time or manually by ifconfig(8)
after a boot.

Discussed on:	freebsd-ipfw@

etc/defaults/rc.conf

@@ -123,6 +123,7 @@ firewall_script="/etc/rc.firewall" # Which script to run to set up the firewall
 firewall_type="UNKNOWN"		# Firewall type (see /etc/rc.firewall)
 firewall_quiet="NO"		# Set to YES to suppress rule display
 firewall_logging="NO"		# Set to YES to enable events logging
+firewall_logif="NO"		# Set to YES to create logging-pseudo interface
 firewall_flags=""		# Flags passed to ipfw when type is a file
 firewall_coscripts=""		# List of executables/scripts to run after
 				# firewall starts/stops

etc/rc.d/ipfw

@@ -57,6 +57,10 @@ ipfw_start()
 		echo 'Firewall logging enabled.'
 		sysctl net.inet.ip.fw.verbose=1 >/dev/null
 	fi
+	if checkyesno firewall_logif; then
+		ifconfig ipfw0 create
+		echo 'Firewall logging pseudo-interface (ipfw0) created.'
+	fi
 }
 
 ipfw_poststart()

sbin/ipfw/ipfw.8

@@ -1,7 +1,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 3, 2012
+.Dd July 9, 2012
 .Dt IPFW 8
 .Os
 .Sh NAME
@@ -560,7 +560,22 @@ is set to 0 (default), one can use
 .Xr bpf 4
 attached to the
 .Li ipfw0
-pseudo interface. There is no overhead if no
+pseudo interface.
+This pseudo interface can be created after a boot
+manually by using the following command:
+.Bd -literal -offset indent
+# ifconfig ipfw0 create
+.Ed
+.Pp
+Or, automatically at boot time by adding the following
+line to the
+.Xr rc.conf 5
+file:
+.Bd -literal -offset indent
+firewall_logif="YES"
+.Ed
+.Pp
+There is no overhead if no
 .Xr bpf 4
 is attached to the pseudo interface.
 .Pp

share/man/man5/rc.conf.5

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 6, 2012
+.Dd July 9, 2012
 .Dt RC.CONF 5
 .Os
 .Sh NAME
@@ -501,6 +501,16 @@ to enable firewall event logging.
 This is equivalent to the
 .Dv IPFIREWALL_VERBOSE
 kernel option.
+.It Va firewall_logif
+.Pq Vt bool
+Set to
+.Dq Li YES
+to create pseudo interface
+.Li ipfw0
+for logging.
+For more details, see
+.Xr ipfw 8
+manual page.
 .It Va firewall_flags
 .Pq Vt str
 Flags passed to

sys/netinet/ipfw/ip_fw_log.c

@@ -44,8 +44,11 @@ __FBSDID("$FreeBSD$");
 #include <sys/socket.h>
 #include <sys/sysctl.h>
 #include <sys/syslog.h>
+#include <sys/lock.h>
+#include <sys/rwlock.h>
 #include <net/ethernet.h> /* for ETHERTYPE_IP */
 #include <net/if.h>
+#include <net/if_clone.h>
 #include <net/vnet.h>
 #include <net/if_types.h>	/* for IFT_ETHER */
 #include <net/bpf.h>		/* for BPF */
@@ -90,6 +93,15 @@ ipfw_log_bpf(int onoff)
 }
 #else /* !WITHOUT_BPF */
 static struct ifnet *log_if;	/* hook to attach to bpf */
+static struct rwlock log_if_lock;
+#define	LOGIF_LOCK_INIT(x)	rw_init(&log_if_lock, "ipfw log_if lock")
+#define	LOGIF_LOCK_DESTROY(x)	rw_destroy(&log_if_lock)
+#define	LOGIF_RLOCK(x)		rw_rlock(&log_if_lock)
+#define	LOGIF_RUNLOCK(x)	rw_runlock(&log_if_lock)
+#define	LOGIF_WLOCK(x)		rw_wlock(&log_if_lock)
+#define	LOGIF_WUNLOCK(x)	rw_wunlock(&log_if_lock)
+
+#define	IPFWNAME	"ipfw"
 
 /* we use this dummy function for all ifnet callbacks */
 static int
@@ -116,37 +128,105 @@ ipfw_log_start(struct ifnet* ifp)
 static const u_char ipfwbroadcastaddr[6] =
 	{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 
+static int
+ipfw_log_clone_match(struct if_clone *ifc, const char *name)
+{
+
+	return (strncmp(name, IPFWNAME, sizeof(IPFWNAME) - 1) == 0);
+}
+
+static int
+ipfw_log_clone_create(struct if_clone *ifc, char *name, size_t len,
+    caddr_t params)
+{
+	int error;
+	int unit;
+	struct ifnet *ifp;
+
+	error = ifc_name2unit(name, &unit);
+	if (error)
+		return (error);
+
+	error = ifc_alloc_unit(ifc, &unit);
+	if (error)
+		return (error);
+
+	ifp = if_alloc(IFT_ETHER);
+	if (ifp == NULL) {
+		ifc_free_unit(ifc, unit);
+		return (ENOSPC);
+	}
+	ifp->if_dname = IPFWNAME;
+	ifp->if_dunit = unit;
+	snprintf(ifp->if_xname, IFNAMSIZ, "%s%d", IPFWNAME, unit);
+	strlcpy(name, ifp->if_xname, len);
+	ifp->if_mtu = 65536;
+	ifp->if_flags = IFF_UP | IFF_SIMPLEX | IFF_MULTICAST;
+	ifp->if_init = (void *)log_dummy;
+	ifp->if_ioctl = log_dummy;
+	ifp->if_start = ipfw_log_start;
+	ifp->if_output = ipfw_log_output;
+	ifp->if_addrlen = 6;
+	ifp->if_hdrlen = 14;
+	ifp->if_broadcastaddr = ipfwbroadcastaddr;
+	ifp->if_baudrate = IF_Mbps(10);
+
+	LOGIF_WLOCK();
+	if (log_if == NULL)
+		log_if = ifp;
+	else {
+		LOGIF_WUNLOCK();
+		if_free(ifp);
+		ifc_free_unit(ifc, unit);
+		return (EEXIST);
+	}
+	LOGIF_WUNLOCK();
+	if_attach(ifp);
+	bpfattach(ifp, DLT_EN10MB, 14);
+
+	return (0);
+}
+
+static int
+ipfw_log_clone_destroy(struct if_clone *ifc, struct ifnet *ifp)
+{
+	int unit;
+
+	if (ifp == NULL)
+		return (0);
+
+	LOGIF_WLOCK();
+	if (log_if != NULL && ifp == log_if)
+		log_if = NULL;
+	else {
+		LOGIF_WUNLOCK();
+		return (EINVAL);
+	}
+	LOGIF_WUNLOCK();
+
+	unit = ifp->if_dunit;
+	bpfdetach(ifp);
+	if_detach(ifp);
+	if_free(ifp);
+	ifc_free_unit(ifc, unit);
+
+	return (0);
+}
+
+static struct if_clone ipfw_log_cloner = IFC_CLONE_INITIALIZER(
+    IPFWNAME, NULL, IF_MAXUNIT,
+    NULL, ipfw_log_clone_match, ipfw_log_clone_create, ipfw_log_clone_destroy);
+
 void
 ipfw_log_bpf(int onoff)
 {
-	struct ifnet *ifp;
 
 	if (onoff) {
-		if (log_if)
-			return;
-		ifp = if_alloc(IFT_ETHER);
-		if (ifp == NULL)
-			return;
-		if_initname(ifp, "ipfw", 0);
-		ifp->if_mtu = 65536;
-		ifp->if_flags = IFF_UP | IFF_SIMPLEX | IFF_MULTICAST;
-		ifp->if_init = (void *)log_dummy;
-		ifp->if_ioctl = log_dummy;
-		ifp->if_start = ipfw_log_start;
-		ifp->if_output = ipfw_log_output;
-		ifp->if_addrlen = 6;
-		ifp->if_hdrlen = 14;
-		if_attach(ifp);
-		ifp->if_broadcastaddr = ipfwbroadcastaddr;
-		ifp->if_baudrate = IF_Mbps(10);
-		bpfattach(ifp, DLT_EN10MB, 14);
-		log_if = ifp;
+		LOGIF_LOCK_INIT();
+		if_clone_attach(&ipfw_log_cloner);
 	} else {
-		if (log_if) {
-			ether_ifdetach(log_if);
-			if_free(log_if);
-		}
-		log_if = NULL;
+		if_clone_detach(&ipfw_log_cloner);
+		LOGIF_LOCK_DESTROY();
 	}
 }
 #endif /* !WITHOUT_BPF */
@@ -166,9 +246,11 @@ ipfw_log(struct ip_fw *f, u_int hlen, struct ip_fw_args *args,
 
 	if (V_fw_verbose == 0) {
 #ifndef WITHOUT_BPF
-
-		if (log_if == NULL || log_if->if_bpf == NULL)
+		LOGIF_RLOCK();
+		if (log_if == NULL || log_if->if_bpf == NULL) {
+			LOGIF_RUNLOCK();
 			return;
+		}
 
 		if (args->eh) /* layer2, use orig hdr */
 			BPF_MTAP2(log_if, args->eh, ETHER_HDR_LEN, m);
@@ -177,6 +259,7 @@ ipfw_log(struct ip_fw *f, u_int hlen, struct ip_fw_args *args,
 			 * more info in the header.
 			 */
 			BPF_MTAP2(log_if, "DDDDDDSSSSSS\x08\x00", ETHER_HDR_LEN, m);
+		LOGIF_RUNLOCK();
 #endif /* !WITHOUT_BPF */
 		return;
 	}