divert rewrite

[Ronald Klop]

You could make it a google summer of code project?

Ronald.

On Sat, 05 Feb 2011 23:20:14 +0100, Julian Elischer <julian at freebsd.org>  
wrote:

> for some time now it has been apparent that the divert socket protocol  
> was a little too heavily tied to IPv4.
>
> With IPv6 coming along now, it seems that we should look at how to  
> extend it.
>
> I see a couple of possible ways to do this:
>
> --- the first way: ----
>
> One would be to add an IPV6 version of divert sockets, possibly from the  
> same base code. The ipfw code to call it would pass on whether it was an  
> ipv4 or ipv6 packet that is passed out (or it can just look)
> and the divert packet would pass it to the correct socket if it was  
> openned.
>
>  From an application point of view, this means you would have to open an  
> ipv4 divert socket and an ipv6 divert socket.
>
> if you didn't have the right one open.. you would just never see the  
> packet.
>
> Since applications that use divert would probably have to be rewritten  
> to cope with ipv6 anyhwo this seems to be an
> ok solution/cost.
>
> Any app that was not updated would continue to run with ipv4 but would  
> never see IPV6 packets even if diverted.
>
> ------ another way ----
>
> Another way to do this would be to recode divert to be its own protocol  
> family with its own sockaddr type.
>
> that socket addr would include the family as now, but would have enough  
> room to support ipv4 and ipv6 addresses, as well as special fields that  
> are curently not available in divert or are just 'hacked'
> (such as the fact that the name of the interface is hidden in the  
> 'sa_zero' bytes of the ipv4 socket address, and if you keep it and pass  
> it back you are effectively passing that information back too).
>
> In this scheme we would allow the socket address structure to have
> enough fields to be able to encode some of the more intersting
> packet layer information that is in the mbuf.
> For example, the FIB, or somefo the other packet flags
> or maybe even one or two of the common tags.
>
> I could see that some of these flags might be useful to a divert agent  
> that understood the protocol stack it was working with:
>
> #define M_PROTO1        0x00000010 /* protocol-specific */
> #define M_PROTO2        0x00000020 /* protocol-specific */
> #define M_PROTO3        0x00000040 /* protocol-specific */
> #define M_PROTO4        0x00000080 /* protocol-specific */
> #define M_PROTO5        0x00000100 /* protocol-specific */
> #define M_BCAST         0x00000200 /* send/received as link-level  
> broadcast */
> #define M_MCAST         0x00000400 /* send/received as link-level  
> multicast */
> #define M_SKIP_FIREWALL 0x00004000 /* skip firewall processing */
>
> #define M_VLANTAG       0x00010000 /* ether_vtag is valid */
> #define M_PROMISC       0x00020000 /* packet was not for us */
> #define M_PROTO6        0x00080000 /* protocol-specific */
> #define M_PROTO7        0x00100000 /* protocol-specific */
> #define M_PROTO8        0x00200000 /* protocol-specific */
> #define M_FLOWID        0x00400000 /* flowid is valid */
>
>
> If we really wanted to do more, we could also define an OOB format
> that could be used with recvmsg() and sendmsg() that would be
> extensible enough to really give a lot of information.
>
> This would be the least compatible, and to tell the truth, I'd be  
> tempted to leave the old ipv4 interface in place as an upgrade aid.
> it could however handle all sorts of protocols, not just ipv4 and ipv6
> but possibly L2 packets etc. as well.
> It may also be more work than I hope to do :-)
>
> ------
>
> If anyone else has suggetions or man-power or would like to help..
> pipe up!
>
>
> Julian
>
>
>
>
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