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Date: Wed, 09 Feb 2011 17:56:18 +0300
From: Sergey Matveychuk <sem@FreeBSD.org>
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Subject: route messages from NDP
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Hello.

In my routing table I see entries after Neighbor Discovery Protocol 
processed:

...
2a02:6b8:0:401:51:4809:8158:1dcd  00:22:fb:3d:82:fe   UHLW    vlan438
...

I'd like to catch them via a routing socket when they appear.

First, try to add a static entry:
ndp -s 2a02:6b8:0:403::1:1 00:0e:0c:09:2e:7b

and look at route -n monitor output:
got message of size 240 on Wed Feb  9 17:26:50 2011
RTM_ADD: Add Route: len 240, pid: 82741, seq 2, errno 0, 
flags:<HOST,DONE,STATIC>
locks:  inits:
sockaddrs: <DST,GATEWAY>
  2a02:6b8:0:403::1:1 0.e.c.9.2e.7b

We have two sections here - DST and GATEWAY. DST is a IPv6 address 
(sa_family == AF_INET6) and GATEWAY is a MAC (sa_family == AF_LINK).

Just for info sockaddr_dl looks like this:
$1 = {sdl_len = 54 '6', sdl_family = 18 '\022', sdl_index = 24, sdl_type 
= 135 '\207', sdl_nlen = 0 '\0',
   sdl_alen = 6 '\006', sdl_slen = 0 '\0', sdl_data = "\000\016\f\t.{", 
'\0' <repeats 39 times>}

Looks good. Lets wait for NDP entry...

Here is it:
got message of size 328 on Wed Feb  9 17:27:11 2011
RTM_ADD: Add Route: len 328, pid: 0, seq 0, errno 0, 
flags:<UP,HOST,DONE,LLINFO,WASCLONED>
locks:  inits:
sockaddrs: <DST,GATEWAY,IFP,IFA>
  2a02:6b8:0:40c:daa2:5eff:fe8c:139  vlan438:0.30.48.33.4.92 
fe80::230:48ff:fe33:492%vlan438

We have four section here DST, GATEWAY, IFP, IFA.
DST is IPv6 address, IFP and IFA I don't care and GATEWAY section is empty.
Let's see why:
$1 = {sdl_len = 54 '6', sdl_family = 18 '\022', sdl_index = 8, sdl_type 
= 135 '\207', sdl_nlen = 0 '\0',
   sdl_alen = 0 '\0', sdl_slen = 0 '\0', sdl_data = '\0' <repeats 45 times>}

family is AF_LINK (18), it's a correct one. But sdl_alen, sdl_data are 
zeros.

I see this for all routing messages from NDP. All created routing table 
entries are good (no problems here).
Why sockaddr_dl in GATEWAY section has a zero address? Is it a bug?

-- 
Sem.