Re: [Nsis-imp] Assigned numbers for version GIMPS -06

To be a little bit more specific:

For IPv6, you theoretically do not even need to use a RAW socket, to 
read RAO options, of course, you need them to intercept the packets 
which are not addressed to us but to the flow sink/source... "man ipv6" 
tells us:

>      IPV6_RTHDR, IPV6_AUTHHDR, IPV6_DSTOPS, IPV6_HOPOPTS, IPV6_FLOWINFO, IPV6_HOPLIMIT
>               Set delivery of control messages for incoming datagrams containing extension headers from the received packet.   IPV6_RTHDR  delivers  the
>               routing  header, IPV6_AUTHHDR delivers the authentication header, IPV6_DSTOPTS delivers the destination options, IPV6_HOPOPTS delivers the
>               hop options, IPV6_FLOWINFO delivers an integer containing the flow id, IPV6_HOPLIMIT delivers an integer containing the hop count  of  the
>               packet.   The  control  messages have the same type as the socket option. All these header options can also be set for outgoing packets by
>               putting the appropriate control message into the control buffer of sendmsg(2).  Only allowed for SOCK_DGRAM or SOCK_RAW sockets.  Argument
>               is a pointer to a boolean value.
> 

A recvmsg on the socket should deliver the packet in a msghdr structure 
along with all the Hop-by-Hop options in the ancillary data.

On a different approach, via iptables/libipq, also all RAO values can be 
read easily in both IPv4 and IPv6.

Cheers,
Thomas

Lang, Christopher wrote:
> To be more specific: 
> 
> We have been using standard raw IP sockets with the IP_ROUTER_ALERT option to intercept packets. This method only works on Linux when the RAO value is 0 (see http://lxr.linux.no/source/net/ipv4/ip_options.c#L428). Also we only looked at IPv4 before we stuck to an RAO of 0. I don't know if raw IPv6 sockets work better or not.
> 
> It appears, from comments from Thomas, that it is possible to use any RAO value if the packets are intercepted using iptables and libipq (using a standard unpatched kernel) :-)
> 
> Chris Lang
> 
>>-----Original Message-----
>>From: Lang, Christopher 
>>Sent: 11 July 2005 10:46
>>To: 'Xiaoming Fu'; Hancock, Robert
>>Cc: nsis-imp@ietf.org
>>Subject: RE: [Nsis-imp] Assigned numbers for version GIMPS -06
>>
>>
>>Hi,
>>
>>We have been using Linux as a platform (with a 2.6.7 kernel). 
>>Using non-zero RAO values we intially found that GIMPS 
>>messages were not being picked up by intermediate nodes. 
>>Inspection of the Kernel source revealed that the Linux 
>>kernel ignores all RAO values except 0. 
>>
>>There also does not appear to be support for picking out any 
>>RAO packets in Windows.
>>
>>Which platform have you been using?
>>
>>Chris Lang
>>

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