kern/99484: enabling net.inet.ip.fastforwarding breaks rfc2644

[Colin Petrie]

>Number:         99484
>Category:       kern
>Synopsis:       enabling net.inet.ip.fastforwarding breaks rfc2644
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jun 26 10:40:28 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Colin Petrie
>Release:        6.1-RELEASE
>Organization:
>Environment:
FreeBSD xxxxxxxx 6.1-RELEASE FreeBSD 6.1-RELEASE #1: Mon May 15 12:15:49 BST 2006     root at xxxxxxxx:/usr/src/sys/i386/compile/ROUTER  i386

>Description:
When net.inet.ip.fastforwarding=1, FreeBSD 6.1-RELEASE will forward packets to network prefix broadcast addresses. This is in violation of RFC2644 (Changing the Default for Directed Broadcasts in Routers)

(while ping'ing 217.8.240.255)

# sysctl net.inet.ip.fastforwarding=1
# tcpdump -qnei vlan200 ether broadcast and icmp
11:28:37.473427 00:30:48:84:ff:b1 > ff:ff:ff:ff:ff:ff, IPv4, length 154: 217.133.19.77 > 217.8.240.255: ICMP echo request, id 3408, seq 0, length 120
11:28:38.569223 00:30:48:84:ff:b1 > ff:ff:ff:ff:ff:ff, IPv4, length 154: 217.133.19.77 > 217.8.240.255: ICMP echo request, id 3408, seq 0, length 120

# sysctl net.inet.ip.fastforwarding=0
# tcpdump -qnei vlan200 ether broadcast and icmp

(no packets returned)


>How-To-Repeat:
sysctl net.inet.ip.fastforwarding=1

Then ping the broadcast address on a LAN from a host on a different subnet
>Fix:
sysctl net.inet.ip.fastforwarding=0
>Release-Note:
>Audit-Trail:
>Unformatted: