回覆: 回覆: ndisc_send_ns: always use link-local

[Moter Du <Moter_Du@xxxxxxxxxxxxxxxxxxx>]

Hi Alexey:

 

Thanks for the fine description.  Although solicitation avoidance doesn't happen to my case I agree it always needs to be taken into consideration.

 

However I do not agree "all global scoped addresses are assigned to all the interfaces in this sense".  For my case, I configured RUT in this way:

 

RUT> ifconfig eth0 add 3ffe:501:ff:100::1/64

RUT> ifconfig eth1 add 3ffe:501:ff:101::2/64

 

It's clear that the former global address was exactly assigned to eth0, and the latter one was assigned exactly to eth1.  Period.

 

The illustration in my first mail was done this way:

 

TN> ping6 3ffe:501:ff:101::2 -I eth0

 

    TN                     RUT

eth0  eth1             eth0   eth1

|     | ECHO_REQUEST     |      |

|----------------------->|      |

|     |                  |  fw  |

|     |                  |.....>|

|     |                  |      |

|     |                  |  fw  |

|     |                  |<.....|

|     | NS               |      |

|<-----------------------|      |

|     | NA               |      |

|----------------------->|      |

|     | ECHO_REPLY       |      |

|<-----------------------|      |

|     |                  |      |

 

It's clear that ECHO_REQUEST and ECHO_REPLY will be the follows:

 

ECHO_REQUEST:

  - Source Address=any of addresses of TN eth0

  - Destination Address=3ffe:501:ff:101::2 (global address of RUT eth1)

 

ECHO_REPLY:

  - Source Address=3ffe:501:ff:101::2 (global address of RUT eth1, the same as ECHO_REQUEST Destination Address)

  - Destination Address=any of addresses of TN eth0 (the same as ECHO_REQUEST Source Address)

 

 

My point is that here NS will contain 3ffe:501:ff:101::2 as its "Source Address", but RFC 2461 specifies totally against to this.

 

The patch uses always fe80::1 (link-local address of RUT eth0) as NS's Source Address, and should not cause more side-effect I think.

 

>       Sincerely
>       Moter Du
>
>       ============================================================
>       Moter Du                                  D410, Siemens STSL
>       phone   +886 2 25186011
>       Fax     +886 2 25053866
>       mailto:moter_du@xxxxxxxxxxxxxxxxxxx
                ============================================================


-----原始郵件-----
寄件者: kuznet@xxxxxxxxxxxxx [mailto:kuznet@xxxxxxxxxxxxx]
寄件日期: 2001年2月16日 AM 04:18
收件者: Moter_Du@xxxxxxxxxxxxxxxxxxx
副本: netdev@xxxxxxxxxxx
主旨: Re: 回覆: ndisc_send_ns: always use link-local


Hello!

> always violates the specification, because it's none of the addresses
> assigned to the outgoing interface (i.e., eth0).

All global scope addresses are "assigned" to all the interfaces in this sense.

You observe this fact, when seeing that packet is sent from
interface eth1 using address, which is address of eth0.


> show me more hints for "solicitation avoidance"?

If you sent solicitation to target, target will want to talk to you
and will have to solicit you if you did not give information about
your address.

This does not happen in your case, because you enforced situation
of pathological asymmetrical routing. However, soliciting host has
no way to know that target is not configured to reply symmetrically.

Alexey