Index: sys/kern/uipc_domain.c
===================================================================
--- sys/kern/uipc_domain.c
+++ sys/kern/uipc_domain.c
@@ -479,6 +479,18 @@
 				(*pr->pr_ctlinput)(cmd, sa, (void *)0);
 }
 
+int
+pr_milli_to_slowtimo(int ms)
+{
+	return (ms * PR_SLOWHZ / 1000);
+}
+
+int
+pr_milli_to_fasttimo(int ms)
+{
+	return (ms * PR_FASTHZ / 1000);
+}
+
 static void
 pfslowtimo(void *arg)
 {
Index: sys/net/route.h
===================================================================
--- sys/net/route.h
+++ sys/net/route.h
@@ -85,21 +85,15 @@
 	u_long	rmx_recvpipe;	/* inbound delay-bandwidth product */
 	u_long	rmx_sendpipe;	/* outbound delay-bandwidth product */
 	u_long	rmx_ssthresh;	/* outbound gateway buffer limit */
-	u_long	rmx_rtt;	/* estimated round trip time */
-	u_long	rmx_rttvar;	/* estimated rtt variance */
+	u_long	rmx_rtt;	/* estimated round trip time (microseconds) */
+	u_long	rmx_rttvar;	/* estimated rtt variance (microseconds) */
 	u_long	rmx_pksent;	/* packets sent using this route */
 	u_long	rmx_weight;	/* route weight */
 	u_long	rmx_nhidx;	/* route nexhop index */
 	u_long	rmx_filler[2];	/* will be used for T/TCP later */
 };
 
-/*
- * rmx_rtt and rmx_rttvar are stored as microseconds;
- * RTTTOPRHZ(rtt) converts to a value suitable for use
- * by a protocol slowtimo counter.
- */
 #define	RTM_RTTUNIT	1000000	/* units for rtt, rttvar, as units per sec */
-#define	RTTTOPRHZ(r)	((r) / (RTM_RTTUNIT / PR_SLOWHZ))
 
 /* lle state is exported in rmx_state rt_metrics field */
 #define	rmx_state	rmx_weight
Index: sys/netinet/igmp.c
===================================================================
--- sys/netinet/igmp.c
+++ sys/netinet/igmp.c
@@ -816,7 +816,7 @@
 		case IGMP_AWAKENING_MEMBER:
 			inm->inm_state = IGMP_REPORTING_MEMBER;
 			inm->inm_timer = IGMP_RANDOM_DELAY(
-			    IGMP_V1V2_MAX_RI * PR_FASTHZ);
+			    pr_milli_to_fasttimo(IGMP_V1V2_MAX_RI * 1000));
 			V_current_state_timers_running = 1;
 			break;
 		case IGMP_LEAVING_MEMBER:
@@ -886,7 +886,7 @@
 
 	igmp_set_version(igi, IGMP_VERSION_2);
 
-	timer = igmp->igmp_code * PR_FASTHZ / IGMP_TIMER_SCALE;
+	timer = pr_milli_to_fasttimo(igmp->igmp_code * 1000) / IGMP_TIMER_SCALE;
 	if (timer == 0)
 		timer = 1;
 
@@ -1026,7 +1026,7 @@
 		     (IGMP_EXP(igmpv3->igmp_qqi) + 3);
 	}
 
-	timer = maxresp * PR_FASTHZ / IGMP_TIMER_SCALE;
+	timer = pr_milli_to_fasttimo(maxresp * 1000) / IGMP_TIMER_SCALE;
 	if (timer == 0)
 		timer = 1;
 
@@ -1740,8 +1740,8 @@
 
 		if (igi->igi_version == IGMP_VERSION_3) {
 			loop = (igi->igi_flags & IGIF_LOOPBACK) ? 1 : 0;
-			uri_fasthz = IGMP_RANDOM_DELAY(igi->igi_uri *
-			    PR_FASTHZ);
+			uri_fasthz = IGMP_RANDOM_DELAY(
+			    pr_milli_to_fasttimo(igi->igi_uri * 1000));
 			mbufq_init(&qrq, IGMP_MAX_G_GS_PACKETS);
 			mbufq_init(&scq, IGMP_MAX_STATE_CHANGE_PACKETS);
 		}
@@ -2000,7 +2000,7 @@
 		 * Section 8.12.
 		 */
 		old_version_timer = igi->igi_rv * igi->igi_qi + igi->igi_qri;
-		old_version_timer *= PR_SLOWHZ;
+		old_version_timer *= pr_milli_to_slowtimo(1000);
 
 		if (version == IGMP_VERSION_1) {
 			igi->igi_v1_timer = old_version_timer;
@@ -2433,7 +2433,7 @@
 			     IGMP_v1_HOST_MEMBERSHIP_REPORT);
 			if (error == 0) {
 				inm->inm_timer = IGMP_RANDOM_DELAY(
-				    IGMP_V1V2_MAX_RI * PR_FASTHZ);
+				    pr_milli_to_fasttimo(IGMP_V1V2_MAX_RI * 1000));
 				V_current_state_timers_running = 1;
 			}
 			break;
@@ -3422,7 +3422,7 @@
 	 */
 	if (mbufq_first(&igi->igi_gq) != NULL) {
 		igi->igi_v3_timer = 1 + IGMP_RANDOM_DELAY(
-		    IGMP_RESPONSE_BURST_INTERVAL);
+		    pr_milli_to_fasttimo(IGMP_RESPONSE_BURST_INTERVAL_MS));
 		V_interface_timers_running = 1;
 	}
 }
Index: sys/netinet/igmp_var.h
===================================================================
--- sys/netinet/igmp_var.h
+++ sys/netinet/igmp_var.h
@@ -148,7 +148,7 @@
 #define IGMP_MAX_STATE_CHANGE_PACKETS	8 /* # of packets per state change */
 #define IGMP_MAX_RESPONSE_PACKETS	16 /* # of packets for general query */
 #define IGMP_MAX_RESPONSE_BURST		4 /* # of responses to send at once */
-#define IGMP_RESPONSE_BURST_INTERVAL	(PR_FASTHZ / 2)	/* 500ms */
+#define IGMP_RESPONSE_BURST_INTERVAL_MS	500
 
 /*
  * IGMP-specific mbuf flags.
Index: sys/netinet/ip6.h
===================================================================
--- sys/netinet/ip6.h
+++ sys/netinet/ip6.h
@@ -254,7 +254,7 @@
  */
 #define IPV6_MAXHLIM	255	/* maximum hoplimit */
 #define IPV6_DEFHLIM	64	/* default hlim */
-#define IPV6_FRAGTTL	120	/* ttl for fragment packets, in slowtimo tick */
+#define IPV6_DEFFRAGTTL	60	/* ttl for fragment packets, in seconds */
 #define IPV6_HLIMDEC	1	/* subtracted when forwarding */
 
 #define IPV6_MMTU	1280	/* minimal MTU and reassembly. 1024 + 256 */
Index: sys/netinet6/frag6.c
===================================================================
--- sys/netinet6/frag6.c
+++ sys/netinet6/frag6.c
@@ -124,6 +124,10 @@
 #define	V_ip6_maxfragpackets		VNET(ip6_maxfragpackets)
 #define	V_frag6_nfragpackets		VNET(frag6_nfragpackets)
 
+/* Maximum per-VNET reassembly timeout (seconds) */
+VNET_DEFINE_STATIC(u_int,		ip6_maxfragttl) = IPV6_DEFFRAGTTL;
+#define	V_ip6_maxfragttl		VNET(ip6_maxfragttl)
+
 /* Maximum per-VNET reassembly queues per bucket and fragments per packet. */
 VNET_DEFINE_STATIC(int,			ip6_maxfragbucketsize);
 VNET_DEFINE_STATIC(int,			ip6_maxfragsperpacket);
@@ -212,6 +216,26 @@
 	CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip6_maxfragbucketsize), 0,
 	"Maximum number of reassembly queues per hash bucket");
 
+static int
+sysctl_ip6_maxfragttl(SYSCTL_HANDLER_ARGS)
+{
+	int error, val;
+
+	val = V_ip6_maxfragttl;
+	error = sysctl_handle_int(oidp, &val, 0, req);
+	if (error != 0 || !req->newptr)
+		return (error);
+	if (val <= 0)
+		val = IPV6_DEFFRAGTTL;
+	V_ip6_maxfragpackets = val;
+	frag6_set_bucketsize();
+	return (0);
+}
+SYSCTL_PROC(_net_inet6_ip6, OID_AUTO, maxfragttl,
+	CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
+	NULL, 0, sysctl_ip6_maxfragttl, "I",
+	"Maximum TTL of fragments, in seconds");
+
 /*
  * Remove the IPv6 fragmentation header from the mbuf.
  */
@@ -551,7 +575,7 @@
 		/* ip6q_nxt will be filled afterwards, from 1st fragment. */
 		TAILQ_INIT(&q6->ip6q_frags);
 		q6->ip6q_ident	= ip6f->ip6f_ident;
-		q6->ip6q_ttl	= IPV6_FRAGTTL;
+		q6->ip6q_ttl	= pr_milli_to_slowtimo(V_ip6_maxfragttl * 1000);
 		q6->ip6q_src	= ip6->ip6_src;
 		q6->ip6q_dst	= ip6->ip6_dst;
 		q6->ip6q_ecn	= IPV6_ECN(ip6);
Index: sys/netinet6/in6.c
===================================================================
--- sys/netinet6/in6.c
+++ sys/netinet6/in6.c
@@ -733,7 +733,7 @@
 		return (NULL);
 	}
 
-	delay = (delay * PR_FASTHZ) / hz;
+	delay = pr_milli_to_fasttimo(delay * 1000) / hz;
 
 	error = in6_joingroup(ifp, mcaddr, NULL, &imm->i6mm_maddr, delay);
 	if (error) {
Index: sys/netinet6/mld6.c
===================================================================
--- sys/netinet6/mld6.c
+++ sys/netinet6/mld6.c
@@ -670,7 +670,7 @@
 	KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));
 	mld_set_version(mli, MLD_VERSION_1);
 
-	timer = (ntohs(mld->mld_maxdelay) * PR_FASTHZ) / MLD_TIMER_SCALE;
+	timer = (pr_milli_to_fasttimo(ntohs(mld->mld_maxdelay) * 1000)) / MLD_TIMER_SCALE;
 	if (timer == 0)
 		timer = 1;
 
@@ -821,7 +821,7 @@
 		maxdelay = (MLD_MRC_MANT(maxdelay) | 0x1000) <<
 			   (MLD_MRC_EXP(maxdelay) + 3);
 	}
-	timer = (maxdelay * PR_FASTHZ) / MLD_TIMER_SCALE;
+	timer = (pr_milli_to_fasttimo(maxdelay * 1000)) / MLD_TIMER_SCALE;
 	if (timer == 0)
 		timer = 1;
 
@@ -1380,7 +1380,7 @@
 
 		if (mli->mli_version == MLD_VERSION_2) {
 			uri_fasthz = MLD_RANDOM_DELAY(mli->mli_uri *
-			    PR_FASTHZ);
+			    pr_milli_to_fasttimo(1000));
 			mbufq_init(&qrq, MLD_MAX_G_GS_PACKETS);
 			mbufq_init(&scq, MLD_MAX_STATE_CHANGE_PACKETS);
 		}
@@ -1616,7 +1616,7 @@
 		 * Section 9.12.
 		 */
 		old_version_timer = (mli->mli_rv * mli->mli_qi) + mli->mli_qri;
-		old_version_timer *= PR_SLOWHZ;
+		old_version_timer *= pr_milli_to_slowtimo(1000);
 		mli->mli_v1_timer = old_version_timer;
 	}
 
@@ -2003,7 +2003,7 @@
 			 * and delay sending the initial MLDv1 report
 			 * by not transitioning to the IDLE state.
 			 */
-			odelay = MLD_RANDOM_DELAY(MLD_V1_MAX_RI * PR_FASTHZ);
+			odelay = MLD_RANDOM_DELAY(pr_milli_to_fasttimo(MLD_V1_MAX_RI * 1000));
 			if (delay) {
 				inm->in6m_timer = max(delay, odelay);
 				V_current_state_timers_running6 = 1;
@@ -3039,7 +3039,7 @@
 	 */
 	if (mbufq_first(&mli->mli_gq) != NULL) {
 		mli->mli_v2_timer = 1 + MLD_RANDOM_DELAY(
-		    MLD_RESPONSE_BURST_INTERVAL);
+		    pr_milli_to_fasttimo(MLD_RESPONSE_BURST_INTERVAL_MS));
 		V_interface_timers_running6 = 1;
 	}
 }
Index: sys/netinet6/mld6_var.h
===================================================================
--- sys/netinet6/mld6_var.h
+++ sys/netinet6/mld6_var.h
@@ -83,7 +83,7 @@
 #define MLD_MAX_STATE_CHANGE_PACKETS	8 /* # of packets per state change */
 #define MLD_MAX_RESPONSE_PACKETS	16 /* # of packets for general query */
 #define MLD_MAX_RESPONSE_BURST		4 /* # of responses to send at once */
-#define MLD_RESPONSE_BURST_INTERVAL	(PR_FASTHZ / 2)	/* 500ms */
+#define MLD_RESPONSE_BURST_INTERVAL_MS	500
 
 /*
  * MLD-specific mbuf flags.
Index: sys/sys/protosw.h
===================================================================
--- sys/sys/protosw.h
+++ sys/sys/protosw.h
@@ -100,6 +100,9 @@
 #define	PR_SLOWHZ	2		/* 2 slow timeouts per second */
 #define	PR_FASTHZ	5		/* 5 fast timeouts per second */
 
+int pr_milli_to_slowtimo(int ms);
+int pr_milli_to_fasttimo(int ms);
+
 /*
  * This number should be defined again within each protocol family to avoid
  * confusion.