if pf_route{,6} route isn't valid, generate an icmp error

[David Gwynne]

at the moment if the route is invalid, we drop the packet. this
generates an icmp error.

ok?

Index: pf.c
===================================================================
RCS file: /cvs/src/sys/net/pf.c,v
retrieving revision 1.1103
diff -u -p -r1.1103 pf.c
--- pf.c        27 Jan 2021 04:46:21 -0000      1.1103
+++ pf.c        27 Jan 2021 06:38:12 -0000
@@ -6055,6 +6055,10 @@ pf_route(struct pf_pdesc *pd, struct pf_
 
        rt = rtalloc(sintosa(dst), RT_RESOLVE, rtableid);
        if (!rtisvalid(rt)) {
+               if (r->rt != PF_DUPTO) {
+                       pf_send_icmp(m0, ICMP_UNREACH, ICMP_UNREACH_HOST,
+                           0, pd->af, s->rule.ptr, pd->rdomain);
+               }
                ipstat_inc(ips_noroute);
                goto bad;
        }
@@ -6210,6 +6214,11 @@ pf_route6(struct pf_pdesc *pd, struct pf
                dst->sin6_addr.s6_addr16[1] = htons(ifp->if_index);
        rt = rtalloc(sin6tosa(dst), RT_RESOLVE, rtableid);
        if (!rtisvalid(rt)) {
+               if (r->rt != PF_DUPTO) {
+                       pf_send_icmp(m0, ICMP6_DST_UNREACH,
+                           ICMP6_DST_UNREACH_NOROUTE, 0,
+                           pd->af, s->rule.ptr, pd->rdomain);
+               }
                ip6stat_inc(ip6s_noroute);
                goto bad;
        }