Date: Thu, 27 Jun 2002 12:44:08 -0400 From: Anthony Volodkin <anthonyv@brainlink.com> To: freebsd-net@freebsd.org Subject: Re: Forwarding UDP packets Message-ID: <3D1B40D8.4080809@brainlink.com> References: <Pine.BSF.4.21.0206261321130.64758-100000@InterJet.elischer.org>
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PopTop also uses proxy arp supposedly (i got that option enabled). I
even read that that feature is supposed to allow broadcasts to function
properly. It doesn't however.
A friend suggested i try to bridge two interfaces (tun0 and fxp0). I
first tried using briding implemented by 'options BRIDGE'. That failed
to set the tun0 into promiscious mode and hence did not produce the
desired effect. Then I tried using the
/usr/share/examples/netgraph/ether.bridge script to bridge the two
interfaces. That failed as well. Netgraph complained that 'tun0' does
not exist, even though it was up and running. Any more clues on
forwarding packets with destination 255.255.255.255 across interfaces
are welcome.
-Anthony Volodkin
>Try use mpd
>it does proxy arp and handles some broadcast features I believe.
>
>
>
>On Wed, 26 Jun 2002, Anthony Volodkin wrote:
>
>
>
>>I use poptop+the pppd that is included with 4.6-RELEASE. On the XP
>>side, my friend just sets up a "Virtual Private Networking Connection"
>>using the native XP client.
>>
>>Here are my /etc/ppp/options, if you wanted protocol info:
>>lock
>>debug
>>auth
>>proxyarp
>>+chap
>>+chapms
>>+chapms-v2
>>
>>and the relevant portion of ppp.conf:
>>pptp:
>> enable chap
>> enable proxy
>> set ifaddr 192.168.1.100 192.168.2.200-192.168.2.205 255.255.255.0
>>
>>
>>
>>>what method of doing pptp are you using?
>>>
>>>
>>>On Wed, 26 Jun 2002, Anthony Volodkin wrote:
>>>
>>>
>>>
>>>
>>>
>>>>Hi,
>>>>
>>>>Recently I've been faced with an odd problem. I setup a pptp link to my
>>>>network from my friend's XP machine. While the link functions fine
>>>>(both ends can ping each other, etc), there is one problem with it. I
>>>>cannot get any broadcast packets through the link. I receive them on
>>>>the tun0 interface, but no matter what I try i can't get them out of the
>>>>fxp0 interface. I cannot get them to go the other way either. I know
>>>>this is against standards, as they suggest routers should not forward
>>>>broadcast packets, but I would still like to have this ability.
>>>>
>>>>Did anyone ever write a patch of some sort or maybe found a tool that
>>>>does this type of thing?
>>>>(many people suggested natd, and after playing with that i was able to
>>>>redirect some bcast packets from tun0 to 1 host on my lan. I was not
>>>>able to do that in the other direction, however.)
>>>>
>>>>I've found an old post on the hackers list by Jonathan Chen that
>>>>included a patch to enable this kind of functionality. I applied it to
>>>>my 4.6-RELEASE kernel and it didn't do anything but add a sysctl
>>>>variable. Any help would be greatly appreciated.
>>>>
>>>>Here is that post:
>>>>
>>>>---------------------------------------------------
>>>>
>>>>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 {
>>>>
>>>>
>>>>--
>>>>Anthony Volodkin
>>>>
>>>>
>>>>To Unsubscribe: send mail to majordomo@FreeBSD.org
>>>>with "unsubscribe freebsd-net" in the body of the message
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
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