kern/109246: ICMP rejects are not generated with fastforwarding enabled

[Ingo Flaschberger]

>Number:         109246
>Category:       kern
>Synopsis:       ICMP rejects are not generated with fastforwarding enabled
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Feb 16 21:30:03 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Ingo Flaschberger
>Release:        6.1-RELEASE-p12
>Organization:
>Environment:
i386
>Description:
In the routingtable is a blackhole reject route:

Destination        Gateway            Flags    Refs      Use  Netif Expire
192.168.0/16       127.0.0.1          UGR1        0        0    lo0

With fastforwarding disabled, a ICMP reject is generated:
traceroute to 192.168.200.1 (192.168.200.1), 30 hops max, 38 byte packets
 1  10.0.0.175 (10.0.0.175)  2.752 ms  0.231 ms  0.208 ms
 2  10.0.0.175 (10.0.0.175)  0.224 ms !H  0.187 ms !H  0.193 ms !H

With fastforwarding enabled, not:
traceroute to 192.168.200.1 (192.168.200.1), 30 hops max, 38 byte packets
 1  10.0.0.175 (10.0.0.175)  0.620 ms  0.214 ms  0.142 ms
 2  * * *
 3  * * *
 4  * * *


>How-To-Repeat:
No problem:
At the router:
sysctl -w net.inet.ip.forwarding=1
route add -net 192.168.0.0/8 lo0 -reject -nostatic -proto1

At another machine:
route add -net 192.168.100.0/24 gateway <ipoftherouter>
traceroute 192.168.101.1

Problem:
At the router:
sysctl -w net.inet.ip.fastforwarding=1

At another machine:
traceroute 192.168.101.1


>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: