Index: sys/net/if_epair.c
===================================================================
--- sys/net/if_epair.c
+++ sys/net/if_epair.c
@@ -51,6 +51,7 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/jail.h>
 #include <sys/kernel.h>
 #include <sys/mbuf.h>
 #include <sys/module.h>
@@ -61,6 +62,9 @@
 #include <sys/sockio.h>
 #include <sys/sysctl.h>
 #include <sys/types.h>
+#include <sys/ucred.h>
+#include <sys/systm.h>
+#include <sys/counter.h>
 
 #include <net/bpf.h>
 #include <net/ethernet.h>
@@ -138,6 +142,9 @@
 					/* Original if_qflush routine. */
 };
 
+/* A system-wide conter for the number of epair interfaces. */
+static counter_u64_t epair_cnt;
+
 /*
  * Per-CPU list of ifps with data in the ifq that needs to be flushed
  * to the netisr ``hw'' queue before we allow any further direct queuing
@@ -709,7 +716,7 @@
 	struct epair_softc *sca, *scb;
 	struct ifnet *ifp;
 	char *dp;
-	int error, unit, wildcard;
+	int error, unit, wildcard, jid;
 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
 
 	/*
@@ -718,15 +725,20 @@
 	 * for it to do the official insertion procedure the moment we knew
 	 * it cannot fail anymore. So just do attach it here.
 	 */
+	bzero(eaddr, sizeof(eaddr));
+	jid = curthread->td_ucred->cr_prison->pr_id;
 	if (params) {
 		scb = (struct epair_softc *)params;
 		ifp = scb->ifp;
 		/* Assign a hopefully unique, locally administered etheraddr. */
 		eaddr[0] = 0x02;
-		eaddr[3] = (ifp->if_index >> 8) & 0xff;
-		eaddr[4] = ifp->if_index & 0xff;
+		eaddr[1] = (jid >> 8) & 0xff;
+		eaddr[2] = jid & 0xff;
+		eaddr[3] = (counter_u64_fetch(epair_cnt) >> 8) & 0xff;
+		eaddr[4] = counter_u64_fetch(epair_cnt) & 0xff;
 		eaddr[5] = 0x0b;
 		ether_ifattach(ifp, eaddr);
+		counter_u64_add(epair_cnt, 1);
 		/* Correctly set the name for the cloner list. */
 		strlcpy(name, scb->ifp->if_xname, len);
 		return (0);
@@ -825,10 +837,13 @@
 	ifp->if_snd.ifq_maxlen = ifqmaxlen;
 	/* Assign a hopefully unique, locally administered etheraddr. */
 	eaddr[0] = 0x02;
-	eaddr[3] = (ifp->if_index >> 8) & 0xff;
-	eaddr[4] = ifp->if_index & 0xff;
+	eaddr[1] = (jid >> 8) & 0xff;
+	eaddr[2] = jid & 0xff;
+	eaddr[3] = (counter_u64_fetch(epair_cnt) >> 8) & 0xff;
+	eaddr[4] = counter_u64_fetch(epair_cnt) & 0xff;
 	eaddr[5] = 0x0a;
 	ether_ifattach(ifp, eaddr);
+	counter_u64_add(epair_cnt, 1);
 	sca->if_qflush = ifp->if_qflush;
 	ifp->if_qflush = epair_qflush;
 	ifp->if_transmit = epair_transmit;
@@ -919,6 +934,7 @@
 	 */
 	CURVNET_SET_QUIET(oifp->if_vnet);
 	ether_ifdetach(oifp);
+	counter_u64_add(epair_cnt, -1);
 	/*
 	 * Wait for all packets to be dispatched to if_input.
 	 * The numbers can only go down as the interface is
@@ -938,6 +954,7 @@
 	CURVNET_RESTORE();
 
 	ether_ifdetach(ifp);
+	counter_u64_add(epair_cnt, -1);
 	/*
 	 * Wait for all packets to be dispatched to if_input.
 	 */
@@ -978,6 +995,7 @@
 
 	switch (type) {
 	case MOD_LOAD:
+		epair_cnt = counter_u64_alloc(M_WAITOK);
 		/* For now limit us to one global mutex and one inq. */
 		epair_dpcpu_init();
 		epair_nh.nh_qlimit = 42 * ifqmaxlen; /* 42 shall be the number. */
@@ -990,6 +1008,7 @@
 	case MOD_UNLOAD:
 		netisr_unregister(&epair_nh);
 		epair_dpcpu_detach();
+		counter_u64_free(epair_cnt);
 		if (bootverbose)
 			printf("%s unloaded.\n", epairname);
 		break;