Add ARP statistics to the kernel and netstat.

New counters now exist for:
requests sent
replies sent
requests received
replies received
packets received
total packets dropped due to no ARP entry
entrys timed out
Duplicate IPs seen

The new statistics are seen in the netstat command
when it is given the -s command line switch.

MFC after:	2 weeks
In collaboration with: bz

sys/net/if_arp.h

@@ -108,6 +108,31 @@ struct	arpcom {
 #define IFP2AC(ifp) ((struct arpcom *)(ifp->if_l2com))
 #define AC2IFP(ac) ((ac)->ac_ifp)
 
-#endif
+#endif /* _KERNEL */
+
+struct arpstat {
+	/* Normal things that happen: */
+	u_long txrequests;	/* # of ARP requests sent by this host. */
+	u_long txreplies;	/* # of ARP replies sent by this host. */
+	u_long rxrequests;	/* # of ARP requests received by this host. */
+	u_long rxreplies;	/* # of ARP replies received by this host. */
+	u_long received;	/* # of ARP packets received by this host. */
+
+	u_long arp_spares[4];	/* For either the upper or lower half. */
+	/* Abnormal event and error  counting: */
+	u_long dropped;		/* # of packets dropped waiting for a reply. */
+	u_long timeouts;	/* # of times with entries removed */
+				/* due to timeout. */
+	u_long dupips;		/* # of duplicate IPs detected. */
+};
+
+/*
+ * In-kernel consumers can use these accessor macros directly to update
+ * stats.
+ */
+#define	ARPSTAT_ADD(name, val)	V_arpstat.name += (val)
+#define	ARPSTAT_SUB(name, val)	V_arpstat.name -= (val)
+#define	ARPSTAT_INC(name)	ARPSTAT_ADD(name, 1)
+#define	ARPSTAT_DEC(name)	ARPSTAT_SUB(name, 1)
 
 #endif /* !_NET_IF_ARP_H_ */

sys/netinet/if_ether.c

@@ -80,6 +80,7 @@ __FBSDID("$FreeBSD$");
 
 SYSCTL_DECL(_net_link_ether);
 SYSCTL_NODE(_net_link_ether, PF_INET, inet, CTLFLAG_RW, 0, "");
+SYSCTL_NODE(_net_link_ether, PF_ARP, arp, CTLFLAG_RW, 0, "");
 
 VNET_DEFINE(int, useloopback) = 1;	/* use loopback interface for
 					 * local traffic */
@@ -89,10 +90,12 @@ static VNET_DEFINE(int, arpt_keep) = (20*60);	/* once resolved, good for 20
 						 * minutes */
 static VNET_DEFINE(int, arp_maxtries) = 5;
 static VNET_DEFINE(int, arp_proxyall);
+static VNET_DEFINE(struct arpstat, arpstat);  /* ARP statistics, see if_arp.h */
 
 #define	V_arpt_keep		VNET(arpt_keep)
 #define	V_arp_maxtries		VNET(arp_maxtries)
 #define	V_arp_proxyall		VNET(arp_proxyall)
+#define	V_arpstat		VNET(arpstat)
 
 SYSCTL_VNET_INT(_net_link_ether_inet, OID_AUTO, max_age, CTLFLAG_RW,
 	&VNET_NAME(arpt_keep), 0,
@@ -107,6 +110,9 @@ SYSCTL_VNET_INT(_net_link_ether_inet, OID_AUTO, useloopback, CTLFLAG_RW,
 SYSCTL_VNET_INT(_net_link_ether_inet, OID_AUTO, proxyall, CTLFLAG_RW,
 	&VNET_NAME(arp_proxyall), 0,
 	"Enable proxy ARP for all suitable requests");
+SYSCTL_VNET_STRUCT(_net_link_ether_arp, OID_AUTO, stats, CTLFLAG_RW,
+	&VNET_NAME(arpstat), arpstat,
+	"ARP statistics (struct arpstat, net/if_arp.h)");
 
 static void	arp_init(void);
 void		arprequest(struct ifnet *,
@@ -163,20 +169,23 @@ arptimer(void *arg)
 		return;
 	}
 	ifp = lle->lle_tbl->llt_ifp;
+	CURVNET_SET(ifp->if_vnet);
 	IF_AFDATA_LOCK(ifp);
 	LLE_WLOCK(lle);
-	if (((lle->la_flags & LLE_DELETED)
-		|| (time_second >= lle->la_expire))
-	    && (!callout_pending(&lle->la_timer) &&
-		callout_active(&lle->la_timer)))
+	if (((lle->la_flags & LLE_DELETED) ||
+	    (time_second >= lle->la_expire)) &&
+	    (!callout_pending(&lle->la_timer) &&
+	    callout_active(&lle->la_timer))) {
 		(void) llentry_free(lle);
-	else {
+		ARPSTAT_INC(timeouts);
+	} else {
 		/*
 		 * Still valid, just drop our reference
 		 */
 		LLE_FREE_LOCKED(lle);
 	}
 	IF_AFDATA_UNLOCK(ifp);
+	CURVNET_RESTORE();
 }
 
 /*
@@ -238,6 +247,7 @@ arprequest(struct ifnet *ifp, struct in_addr *sip, struct in_addr  *tip,
 	sa.sa_len = 2;
 	m->m_flags |= M_BCAST;
 	(*ifp->if_output)(ifp, m, &sa, NULL);
+	ARPSTAT_INC(txrequests);
 }
 
 /*
@@ -339,8 +349,10 @@ arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
 	 * latest one.
 	 */
 	if (m != NULL) {
-		if (la->la_hold != NULL)
+		if (la->la_hold != NULL) {
 			m_freem(la->la_hold);
+			ARPSTAT_INC(dropped);
+		}
 		la->la_hold = m;
 		if (renew == 0 && (flags & LLE_EXCLUSIVE)) {
 			flags &= ~LLE_EXCLUSIVE;
@@ -413,6 +425,7 @@ arpintr(struct mbuf *m)
 		ar = mtod(m, struct arphdr *);
 	}
 
+	ARPSTAT_INC(received);
 	switch (ntohs(ar->ar_pro)) {
 #ifdef INET
 	case ETHERTYPE_IP:
@@ -493,6 +506,9 @@ in_arpinput(struct mbuf *m)
 	(void)memcpy(&isaddr, ar_spa(ah), sizeof (isaddr));
 	(void)memcpy(&itaddr, ar_tpa(ah), sizeof (itaddr));
 
+	if (op == ARPOP_REPLY)
+		ARPSTAT_INC(rxreplies);
+
 	/*
 	 * For a bridge, we want to check the address irrespective
 	 * of the receive interface. (This will change slightly
@@ -603,6 +619,7 @@ in_arpinput(struct mbuf *m)
 		   ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
 		   inet_ntoa(isaddr), ifp->if_xname);
 		itaddr = myaddr;
+		ARPSTAT_INC(dupips);
 		goto reply;
 	}
 	if (ifp->if_flags & IFF_STATICARP)
@@ -686,6 +703,7 @@ in_arpinput(struct mbuf *m)
 reply:
 	if (op != ARPOP_REQUEST)
 		goto drop;
+	ARPSTAT_INC(rxrequests);
 
 	if (itaddr.s_addr == myaddr.s_addr) {
 		/* Shortcut.. the receiving interface is the target. */
@@ -774,6 +792,7 @@ in_arpinput(struct mbuf *m)
 	sa.sa_family = AF_ARP;
 	sa.sa_len = 2;
 	(*ifp->if_output)(ifp, m, &sa, NULL);
+	ARPSTAT_INC(txreplies);
 	return;
 
 drop:

usr.bin/netstat/inet.c

@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 
 #include <net/route.h>
+#include <net/if_arp.h>
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
 #include <netinet/ip.h>
@@ -871,6 +872,47 @@ ip_stats(u_long off, const char *name, int af1 __unused, int proto __unused)
 #undef p1a
 }
 
+/*
+ * Dump ARP statistics structure.
+ */
+void
+arp_stats(u_long off, const char *name, int af1 __unused, int proto __unused)
+{
+	struct arpstat arpstat, zerostat;
+	size_t len = sizeof(arpstat);
+
+	if (live) {
+		if (zflag)
+			memset(&zerostat, 0, len);
+		if (sysctlbyname("net.link.ether.arp.stats", &arpstat, &len,
+		    zflag ? &zerostat : NULL, zflag ? len : 0) < 0) {
+			warn("sysctl: net.link.ether.arp.stats");
+			return;
+		}
+	} else
+		kread(off, &arpstat, len);
+
+	printf("%s:\n", name);
+
+#define	p(f, m) if (arpstat.f || sflag <= 1) \
+    printf(m, arpstat.f, plural(arpstat.f))
+#define	p2(f, m) if (arpstat.f || sflag <= 1) \
+    printf(m, arpstat.f, pluralies(arpstat.f))
+
+	p(txrequests, "\t%lu ARP request%s sent\n");
+	p2(txreplies, "\t%lu ARP repl%s sent\n");
+	p(rxrequests, "\t%lu ARP request%s received\n");
+	p2(rxreplies, "\t%lu ARP repl%s received\n");
+	p(received, "\t%lu ARP packet%s received\n");
+	p(dropped, "\t%lu total packet%s dropped due to no ARP entry\n");
+	p(timeouts, "\t%lu ARP entry%s timed out\n");
+	p(dupips, "\t%lu Duplicate IP%s seen\n");
+#undef p
+#undef p2
+}
+
+
+
 static	const char *icmpnames[ICMP_MAXTYPE + 1] = {
 	"echo reply",			/* RFC 792 */
 	"#1",

usr.bin/netstat/main.c

@@ -184,6 +184,8 @@ static struct nlist nl[] = {
 	{ .n_name = "_sctpstat" },
 #define	N_MFCTABLESIZE	54
 	{ .n_name = "_mfctablesize" },
+#define N_ARPSTAT       55
+	{ .n_name = "_arpstat" },
 	{ .n_name = NULL },
 };
 
@@ -232,6 +234,8 @@ struct protox {
 	  carp_stats,	NULL,		"carp",	1,	0 },
 	{ -1,		N_PFSYNCSTAT,	1,	NULL,
 	  pfsync_stats,	NULL,		"pfsync", 1,	0 },
+	{ -1,		N_ARPSTAT,	1,	NULL,
+	  arp_stats,	NULL,		"arp", 1,	0 },
 	{ -1,		-1,		0,	NULL,
 	  NULL,		NULL,		NULL,	0,	0 }
 };

usr.bin/netstat/netstat.h

@@ -75,6 +75,7 @@ void	udp_stats(u_long, const char *, int, int);
 void	sctp_protopr(u_long, const char *, int, int);
 void	sctp_stats(u_long, const char *, int, int);
 #endif
+void	arp_stats(u_long, const char *, int, int);
 void	ip_stats(u_long, const char *, int, int);
 void	icmp_stats(u_long, const char *, int, int);
 void	igmp_stats(u_long, const char *, int, int);