From mboxrd@z Thu Jan 1 00:00:00 1970 From: syedk Subject: Re: Splitter Date: 23 Mar 2004 19:01:17 +0530 Sender: linux-c-programming-owner@vger.kernel.org Message-ID: <1080048682.7452.69.camel@one.test.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Id: Content-Type: text/plain; charset="us-ascii" To: "K.Anantha Kiran" Cc: linux-c-programming@vger.kernel.org hi ananth, yes u can directly send it to other interface... but be very careful in this : u need to take care of lot of things otherwise u may face lot of kernel panics: 1) u shud return NF_STOLEN; in the PRE_ROUTING hook... otherwise the dev_queue_xmit will try to free the sk_buff (which might be already freed if u use NF_DROP)... 2)u need to fill( or rather change existing ones) the relevant information in the sk_buff... that might include the i) source and destination address in the IP .. ii) changing the pkt_type to PACKET_OUTGOING, iii) u also need to take care of changing datalink layer stuff in sk_buff.. for example if packet came on ppp or loopback and u want to redirect it to ethernet interface..... all u need to care of is this : it shud be a correct sk_buff while xmiting it.... probably u wont succeed first time itself .... u may find some problems or worst some crashes... but u will succeed finally... Better read this document: http://uqconnect.net/~zzoklan/documents/netfilter.html i hope this would help... best regards Syed SK On Tue, 2004-03-23 at 17:24, K.Anantha Kiran wrote: > Hi, > Whenever we receive a packet( let it is stored in skb), can we directly > change the skbuff->dev and call dev_queue_xmit(skbuff) without undergoing > any processing in this system. That means this will simply take one packet and > keep it in another interface( for suppose there are no packets destined > for this system) . Doing this will cause any problems? > > > > On 23 Mar 2004, syedk wrote: > > > Date: 23 Mar 2004 17:08:20 +0530 > > From: syedk > > To: K.Anantha Kiran > > Cc: Jad Saklawi , linux-c-programming@vger.kernel.org > > Subject: Re: Splitter > > > > you can look into dev_queue_xmit(sk_buff) function in net/core/dev.c > > > > sk_buff->dev has the information abt the device (can be any interface > > registered using register_netdevice() for that matter)... > > > > dev_queue_xmit just transfers the sk_buff for the device for > > delivery.... > > > > I feel the best way to solve your problem would be use NF_IP_PRE_ROUTING > > hook of netfilter by which u get all packets ( even before any routing > > decisions has been made : that is what u wanted RIGHT??) and then call > > dev_queue_xmit function by setting the sk_buff->dev as whatever > > interface u wish to redirect.... > > > > I hope this would help.... > > > > Best regards > > syed sk > > > > > > On Tue, 2004-03-23 at 15:09, K.Anantha Kiran wrote: > > > Hi, > > > Thanks a lot for ur guidance. > > > I am following the same files(i mean NET directory).But i am facing > > > following problem. > > > " where the output interface variable (rtable->key->oif) is changed to > > > the index of interface through which packet has to go out. In the function > > > /net/route.c ip_route_input_slow() they are setting it to 0 what is it > > > mean. > > > > > > When a packet has to be put on to an interface what are the fields > > > will it use to decide that( in skbuff structure). > > > > > > Thanks > > > regards, > > > K. Anantha kiran > > > > > > > > > On Mon, 22 Mar 2004, Jad Saklawi wrote: > > > > > > > Date: Mon, 22 Mar 2004 09:41:22 +0200 > > > > From: Jad Saklawi > > > > To: K.Anantha Kiran > > > > Cc: linux-c-programming@vger.kernel.org > > > > Subject: Re: Splitter > > > > > > > > K.Anantha Kiran wrote: > > > > > > > > >Hi, > > > > > Thanks for ur suggetsion. > > > > > But we are not clear about the sentece "re invent the loop". > > > > > Can u give clear explanantion about the "iptables" solution. > > > > > IMP: Our machine should not work like a router.I should be able to decide > > > > >to which interface i want to redirect to , on the fly for each packet > > > > >using a HASH like functions. > > > > > > > > > > > > > > It`s your choice then, check out net/core/dev.c net/core/dv.c > > > > net/ipv4/tcp_input.c net/ipv4/tcp_output.c net/ethernet/eth.c You have > > > > to take a look at the whole net directory and modify accordingly. I > > > > doubt you will be able to do any thing. Any way good luck!!! > > > > > > > > Greets, > > > > Jad > > > > > > > > > > - > > > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > > > the body of a message to majordomo@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > - > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html