Extended partitions under FreeBSD: more info, and how to mount?

[Kai Grossjohann]

I'm running -current as of a couple of days ago (using the GENERIC
kernel).  I have this disk layout:

~> fdisk
******* Working on device /dev/ad0 *******
parameters extracted from in-core disklabel are:
cylinders=232632 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=232632 heads=16 sectors/track=63 (1008 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 12 (0x0c),(DOS or Windows 95 with 32 bit FAT (LBA))
    start 63, size 10474317 (5114 Meg), flag 0
        beg: cyl 0/ head 1/ sector 1;
        end: cyl 651/ head 254/ sector 63
The data for partition 2 is:
sysid 12 (0x0c),(DOS or Windows 95 with 32 bit FAT (LBA))
    start 10474380, size 20964825 (10236 Meg), flag 0
        beg: cyl 652/ head 0/ sector 1;
        end: cyl 1023/ head 254/ sector 63
The data for partition 3 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 31439205, size 62910540 (30718 Meg), flag 80 (active)
        beg: cyl 1023/ head 255/ sector 63;
        end: cyl 1023/ head 254/ sector 63
The data for partition 4 is:
sysid 15 (0x0f),(Extended DOS (LBA))
    start 94349745, size 140140287 (68427 Meg), flag 0
        beg: cyl 1023/ head 255/ sector 63;
        end: cyl 1023/ head 83/ sector 63

First question: how to find out what is inside that extended DOS
partition?

And devd has created these devices for me:

~> ls /dev/ad*
/dev/ad0        /dev/ad0s2      /dev/ad0s3a     /dev/ad0s3c     /dev/ad0s5
/dev/ad0s1      /dev/ad0s3      /dev/ad0s3b     /dev/ad0s4

So it seems to me that /dev/ad0s5 ought to be the right place to
look for my FAT32 partition inside the extended DOS partition:

~> mount_msdosfs /dev/ad0s5 /mnt
mount_msdosfs: /dev/ad0s5: Invalid argument

Second question: how to mount that partition?
-- 
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