TCP listenall

[Bruce M. Simpson]

Matus Harvan wrote:
> Hi,
>   
> I was wondering if I could get some feedback about the patch and
> whether others think it could be committed. A slightly update version
> of the patch is at the end of this email.
>   

I have mixed feelings about this patch.

The idea of a TCP socket which magically loses its TCP semantics is 
unattractive -- SOCK_RAW is traditionally where we've put things which 
don't fit the rest of the BSD socket API -- however in this case I don't 
see we have much choice, if what we desire is the ability for a client 
to establish a connection to any ephemeral port with the mtund returning 
from an accept() as usual.

We are bending the rules of the usual TCP semantics here, but that is OK 
because if we directed tlistenall to be a raw IP socket, we'd need a way 
to say to TCP, 'I'd like to create a socket which is already in SYN_RCVD 
state with a SYN whose mbuf has now gone to lunch', assuming we wish to 
create TCP streams business as usual.

The relay port idea I pointed out in my message about udp catchall would 
be especially applicable here -- we may not always want catchalls for 
the entire 16-bit tcp port space.

listenallr is static and is going to get trashed by concurrent threads, 
unless there is a serialization with a lock, which I don't see.

How will inp_tlistenall appear in netstat output? Perhaps assigning a 
LISTEN_ALL state would be helpful for an administrator to clearly see 
that a listenall socket is active? Perhaps checking for TCP_LISTENALL 
set on an unbound socket in tcp_usr_listen() when listen() is called is 
the way to go instead of, or in addition to, using inp_tlistenall?

Again, good work, but needs more polish before it can go into mainline 
(IMHO).

best,
BMS