FreeBSD 7.0-STABLE: "mount_nfs" vs "mount -t nfs": problems with second one, UDP timeouts and ICMP ports unreach?!

[Lev Serebryakov]

  I have two hosts: host A (FreeBSD 6.3-S) and host B (FreeBSD 7.0-S, 
freshly installed).

   Host A exports "/usr/ports" to host B via NFS.

   Mount with "mount_nfs" works well:

b# mount_nfs a:/usr/ports /usr/ports
b# ls /usr/ports
[---SKIPPED---=
b#

   But mount with "mount -t nfs" FAILS:

b# mount -t nfs a:/usr/ports /usr/ports
[udp] a:/usr/ports: NFSPROC_NULL: RPC: Timed out
[udp] a:/usr/ports: NFSPROC_NULL: RPC: Timed out
^C
b#

   tcpdump on A shows VERY strange picture:

b.960 > a.sunrpc: UDP, length 56
a.sunrpc > b.960: UDP, length 28
b.820 > a.nfs: 40 null
a.nfs > b.820: reply ok 24
b > a: ICMP b udp port 820 unreachable, length 36
b.912 > a.sunrpc: UDP, length 56
a.sunrpc > b.912: UDP, length 28
b.973 > a.nfs: 40 null
a.nfs > b.973: reply ok 24
b > a: ICMP b udp port 973 unreachable, length 36

   You see? b answer with "UDP port unreachable" on each RPC reply!

   There is NO any firewalls on B. And, I repeat, it WORKS when I call 
mount_nfs directly in a moment!

   Main problem is, that "/etc/fstab" is processed by mount, and NFS 
mount hangs up on boot, as shown above :(

-- 
// Lev Serebryakov