[Top] [All Lists]

Re: How to route a skb to a particular oif, when the fib_lookup suggests

To: netdev@xxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx
Subject: Re: How to route a skb to a particular oif, when the fib_lookup suggests another one.
From: Devesh Agrawal <devesh.agrawal@xxxxxxxxx>
Date: Sun, 27 Mar 2005 08:04:18 +0530
Cc: Vinay Reddy <vinayvinay@xxxxxxxxx>
Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=beta;; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:references; b=UH4aK1NbWI0tSTXTMUIza8vhV1wS+iCFbV25OaruF7qTADAK9zhEOomUTYeO5KWb7LcxmCe1HvNmzjI+r9W4EN9ue2Dn3ZJ+O1PLWSekhSyg+plKSsw2b3U/1EMlxluIsEYbZV74UHflfTk7ims/1odAZMycSeoJWButiFZCW6g=
In-reply-to: <>
References: <> <> <> <>
Reply-to: Devesh Agrawal <devesh.agrawal@xxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
I don't think that will solve the problem cos: 
rt_intern_hash called in the finall stages of make_route in
ip_route_output_slow tries to arp bind a the next hop. If you give a
different ip address, then it may not either ever know of the mac
address of this ghost ip or worse may get a wrong mac address and go
to a wrong next hop.
What happens if we set the tos flag to have RTO_ONLINK set, so that
the scope is RT_SCOPE_LINK, with oif set to the desired output
interface, can I then force the skb thru that ouput interface?
I would be really grateful if some one helps me out with this.
Eagerly awaiting your replies.
Devesh Agrawal

On Sat, 26 Mar 2005 22:44:53 +0530, Vinay Reddy <vinayvinay@xxxxxxxxx> wrote:
> Hi,
> Say packets for is always routed through wlan0, and you want
> packets for to be routed through one of eth0 or wlan0
> depending on their IPs(required for mobile IP). Also assume that the
> default routing for a network IP is done through eth0. Now
> you want to route a packet destined for through wlan0. You
> can just call ip_route_output_key for This way the packet
> will surely go through wlan0.
> Am I missing anything??
> Cheers,
> Vinay
> On Sat, 26 Mar 2005 11:20:22 +0530, Devesh Agrawal
> <devesh.agrawal@xxxxxxxxx> wrote:
> > Hi,
> > I have to route a packet thru a particular output interface, however
> > my routing tables have two routes, that match it : one to eth0 and one
> > to wlan0, with the eth0 being chosen as it is more specific.  I am
> > using ip_route_output_key, with fl->oif = index of device I want this
> > packet to go (=wlan0).
> > However, in the ip_route_output_slow I found that even when oif is not
> > 0, you get a valid dev_out, however when the fib_lookup succeeds, you
> > merely free this old dev_out, and assign dev_out to the (ie
> > the one found out by the fib_lookup),
> > So this means that even if I specify the oif, the packet will still
> > get routed to eth0.
> > Am I correct, or is there something I am missing. Also I am setting
> > tos bit RTO_ONLINK .
> > Please help me. I am quite perplexed by this.
> > Sincerely,
> > --
> > Devesh Agrawal
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-net" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at
> >
> --
> Vinay Kumar Reddy B
> 238, Mandakini Hostel,
> IIT Madras,
> Chennai  - 600036

Devesh Agrawal
4th year Dual Degree.
Dept of CSE 
Indian Institute of Technology , Madras
Room No . 309 , Alakananda Hostel 
Chennai 600036 ,India
Ph : +91 9382102431

<Prev in Thread] Current Thread [Next in Thread>