TCPv4 broken without INET6 in kernel

[Boris Kochergin]

Hi, list. I have some Ultra 5s onto which I've installed 7.0-RELEASE. I 
then built custom kernels on them--without INET6 support. After booting 
with the new kernels, I noticed that networking seemed broken (the 
machines would not talk TCP to anything) and proceeded to investigate. 
With INET6 in the kernel, a telnet to port 22 of one of the Ultra 5s 
running sshd looks like this:

# telnet 128.238.9.55 22
Trying 128.238.9.55...
Connected to 128.238.9.55.
Escape character is '^]'.
SSH-2.0-OpenSSH_4.5p1 FreeBSD-20061110

Without INET6 in the kernel, it looks like this:

# telnet 128.238.9.55 22
Trying 128.238.9.55...
Connected to 128.238.9.55.
Escape character is '^]'.

Nothing happens after that.

A packet capture of the latter attempt taken on the Ultra 5 is available 
at http://acm.poly.edu/~spawk/tcp-sparc64.pcap, and one taken on the 
other end is at http://acm.poly.edu/~spawk/tcp-i386.pcap. The kernel 
configuration and dmesg of the Ultra 5 I've dedicated to debugging this 
are up at http://acm.poly.edu/~spawk/TEST and 
http://acm.poly.edu/~spawk/dmesg, respectively, and I'm willing to 
provide access to the machine to any developers who may want to poke at it.

Any help is appreciated. Thanks.

-Boris