On FreeBSD -CURRENT and -STABLE, packets to broadcast addresses are not
forwarded. For instance, if I have a FreeBSD router with interfaces
192.168.1.1 and 192.168.2.1, and I send packets from 192.168.1.2 to
192.168.2.255, the packets are dropped to the floor. IMO, this is wrong...
but I haven't consulted all the RFC's so I'm not sure if some standard out
there calls for it. In any case, the following patch creates a sysctl knob
to turn on or off this feature (since it can be considered a security risk
by some). I just want to ask around in case I turned out to be doing
something incredibly evil. Comments?
-Jon
Index: in.h
===================================================================
RCS file: /export/ncvs/src/sys/netinet/in.h,v
retrieving revision 1.55
diff -u -r1.55 in.h
--- in.h 2001/06/15 00:37:27 1.55
+++ in.h 2001/08/09 15:12:19
@@ -452,7 +452,8 @@
#define IPCTL_FASTFORWARDING 14 /* use fast IP forwarding code */
#define IPCTL_KEEPFAITH 15 /* FAITH IPv4->IPv6 translater ctl */
#define IPCTL_GIF_TTL 16 /* default TTL for gif encap packet */
-#define IPCTL_MAXID 17
+#define IPCTL_FORWARD_BROADCAST 18 /* forward broadcast packets */
+#define IPCTL_MAXID 18
#define IPCTL_NAMES { \
{ 0, 0 }, \
Index: ip_input.c
===================================================================
RCS file: /export/ncvs/src/sys/netinet/ip_input.c,v
retrieving revision 1.174
diff -u -r1.174 ip_input.c
--- ip_input.c 2001/06/23 17:17:58 1.174
+++ ip_input.c 2001/08/09 15:33:59
@@ -103,6 +103,10 @@
SYSCTL_INT(_net_inet_ip, IPCTL_FORWARDING, forwarding, CTLFLAG_RW,
&ipforwarding, 0, "Enable IP forwarding between interfaces");
+int ipforward_broadcast = 0;
+SYSCTL_INT(_net_inet_ip, IPCTL_FORWARD_BROADCAST, forward_broadcast, CTLFLAG_RW,
+ &ipforward_broadcast, 0, "Enable broadcast packets when forwarding IP packets");
+
static int ipsendredirects = 1; /* XXX */
SYSCTL_INT(_net_inet_ip, IPCTL_SENDREDIRECTS, redirect, CTLFLAG_RW,
&ipsendredirects, 0, "Enable sending IP redirects");
@@ -1684,7 +1688,8 @@
}
error = ip_output(m, (struct mbuf *)0, &ipforward_rt,
- IP_FORWARDING, 0);
+ IP_FORWARDING|
+ (ipforward_broadcast?IP_ALLOWBROADCAST:0), 0);
if (error)
ipstat.ips_cantforward++;
else {
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