SO_LINGER brokenness...

[Sean Chittenden]

Howdy.  Looks like SO_LINGER is broken on loopback.  Here's the test  
case:

    0. Install memcached (databases/memcached)
    1. Download test_linger.c: fetch http://sean.chittenden.org/pubfiles/freebsd/test_linger.c
    2. Compile: gcc test_linger.c -o test_linger
    3. Fire up memcached in a new window: memcached -vvv -p 11211
    4. Test: ./test_linger localhost 11211
    5. Watch for either:

<16 new client connection
<16 set valid_key 0 0 8
 >16 STORED
<16 set valid_key 0 0 8
 >16 STORED
<16 connection closed.

Fail.

       or

<16 new client connection
<16 set valid_key 0 0 8
 >16 STORED
<16 set valid_key 0 0 8
 >16 STORED
<16 get ENOENT_key
 >16 END
<16 connection closed.

Win.


Can someone verify that my test case is correct?  If it is, I'll port  
it to src/tools/regression/sockets/.

Broken or not, I don't think the behavior suggested in src/netinet/ 
tcp_usrreq.c:1498 is correct.  A The test above write(2)'s and  
read(2)'s some data successfully before testing the validity of the  
half-close(2)'ed state, so I'm not worried about whether or not a SYN  
has been received.  I haven't looked too closely yet, but it looks  
like tcp_close() needs to call to sbflush() if SO_LINGER is set (in  
fact, it doesn't look like there's any special handling of linger in  
tcp_subr.c, so I'm not sure if I'm glancing in the right area).

/*
  * User issued close, and wish to trail through shutdown states:
  * if never received SYN, just forget it.  If got a SYN from peer,
  * but haven't sent FIN, then go to FIN_WAIT_1 state to send peer a  
FIN.
  * If already got a FIN from peer, then almost done; go to LAST_ACK
  * state.  In all other cases, have already sent FIN to peer (e.g.
  * after PRU_SHUTDOWN), and just have to play tedious game waiting
  * for peer to send FIN or not respond to keep-alives, etc.
  * We can let the user exit from the close as soon as the FIN is acked.
  */

Thoughts/guidance?  -sc

--
Sean Chittenden
sean at chittenden.org
http://sean.chittenden.org/