Hi,
I think it's specified in RFC 2644. It might be useful
to site it in the comments of the code.
Regards,
yushun.
____________________________________________________________________________
Yu-Shun Wang <[EMAIL PROTECTED]> Information Sciences Institute
University of Southern California
On Thu, 9 Aug 2001, Jonathan Chen wrote:
> 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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