Index: head/cddl/lib/libdtrace/ip.d
===================================================================
--- head/cddl/lib/libdtrace/ip.d
+++ head/cddl/lib/libdtrace/ip.d
@@ -228,11 +228,11 @@
 	    ((struct ip *)p)->ip_v == 4 ?
 	    ntohs(((struct ip *)p)->ip_len) - (((struct ip *)p)->ip_hl << 2):
 	    ntohs(((struct ip6_hdr *)p)->ip6_ctlun.ip6_un1.ip6_un1_plen);
-	ip_saddr =	p == NULL ? 0 :
+	ip_saddr =	p == NULL ? "<unknown>" :
 	    ((struct ip *)p)->ip_v == 4 ?
 	    inet_ntoa(&((struct ip *)p)->ip_src.s_addr) :
 	    inet_ntoa6(&((struct ip6_hdr *)p)->ip6_src);
-	ip_daddr =	p == NULL ? 0 :
+	ip_daddr =	p == NULL ? "<unknown>" :
 	    ((struct ip *)p)->ip_v == 4 ?
 	    inet_ntoa(&((struct ip *)p)->ip_dst.s_addr) :
 	    inet_ntoa6(&((struct ip6_hdr *)p)->ip6_dst);
@@ -246,11 +246,11 @@
 	    ntohs(((struct ip *)m->m_data)->ip_len) - 
 			(((struct ip *)m->m_data)->ip_hl << 2):
 	    ntohs(((struct ip6_hdr *)m->m_data)->ip6_ctlun.ip6_un1.ip6_un1_plen);
-	ip_saddr =	m == NULL ? 0 :
+	ip_saddr =	m == NULL ? "<unknown>" :
 	    ((struct ip *)m->m_data)->ip_v == 4 ?
 	    inet_ntoa(&((struct ip *)m->m_data)->ip_src.s_addr) :
 	    inet_ntoa6(&((struct ip6_hdr *)m->m_data)->ip6_src);
-	ip_daddr =	m == NULL ? 0 :
+	ip_daddr =	m == NULL ? "<unknown>" :
 	    ((struct ip *)m->m_data)->ip_v == 4 ?
 	    inet_ntoa(&((struct ip *)m->m_data)->ip_dst.s_addr) :
 	    inet_ntoa6(&((struct ip6_hdr *)m->m_data)->ip6_dst);
Index: head/cddl/lib/libdtrace/tcp.d
===================================================================
--- head/cddl/lib/libdtrace/tcp.d
+++ head/cddl/lib/libdtrace/tcp.d
@@ -190,11 +190,11 @@
 	tcps_active =		-1; /* XXX */
 	tcps_lport =		p == NULL ? 0 : ntohs(p->t_inpcb->inp_inc.inc_ie.ie_lport);
 	tcps_rport =		p == NULL ? 0 : ntohs(p->t_inpcb->inp_inc.inc_ie.ie_fport);
-	tcps_laddr =		p == NULL ? 0 :
+	tcps_laddr =		p == NULL ? "<unknown>" :
 	    p->t_inpcb->inp_vflag == INP_IPV4 ?
 	    inet_ntoa(&p->t_inpcb->inp_inc.inc_ie.ie_dependladdr.id46_addr.ia46_addr4.s_addr) :
 	    inet_ntoa6(&p->t_inpcb->inp_inc.inc_ie.ie_dependladdr.id6_addr);
-	tcps_raddr =		p == NULL ? 0 :
+	tcps_raddr =		p == NULL ? "<unknown>" :
 	    p->t_inpcb->inp_vflag == INP_IPV4 ?
 	    inet_ntoa(&p->t_inpcb->inp_inc.inc_ie.ie_dependfaddr.id46_addr.ia46_addr4.s_addr) :
 	    inet_ntoa6(&p->t_inpcb->inp_inc.inc_ie.ie_dependfaddr.id6_addr);
Index: head/cddl/lib/libdtrace/udp.d
===================================================================
--- head/cddl/lib/libdtrace/udp.d
+++ head/cddl/lib/libdtrace/udp.d
@@ -56,11 +56,11 @@
 	udps_addr =	(uintptr_t)p;
 	udps_lport =	p == NULL ? 0 : ntohs(p->inp_inc.inc_ie.ie_lport);
 	udps_rport =	p == NULL ? 0 : ntohs(p->inp_inc.inc_ie.ie_fport);
-	udps_laddr =	p == NULL ? "" :
+	udps_laddr =	p == NULL ? "<unknown>" :
 	    p->inp_vflag == INP_IPV4 ?
 	    inet_ntoa(&p->inp_inc.inc_ie.ie_dependladdr.id46_addr.ia46_addr4.s_addr) :
 	    inet_ntoa6(&p->inp_inc.inc_ie.ie_dependladdr.id6_addr);
-	udps_raddr =	p == NULL ? "" :
+	udps_raddr =	p == NULL ? "<unknown>" :
 	    p->inp_vflag == INP_IPV4 ?
 	    inet_ntoa(&p->inp_inc.inc_ie.ie_dependfaddr.id46_addr.ia46_addr4.s_addr) :
 	    inet_ntoa6(&p->inp_inc.inc_ie.ie_dependfaddr.id6_addr);