3942 inject sanity into ipadm tcp buffer size properties
3943 _snd_lowat_fraction tcp tunable has no effect
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Peng Dai <peng.dai@delphix.com>

*** 21,30 ****
--- 21,31 ----
  
  /*
   * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2011, Joyent Inc. All rights reserved.
   * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
+  * Copyright (c) 2013 by Delphix. All rights reserved.
   */
  /* Copyright (c) 1990 Mentat Inc. */
  
  #include <sys/types.h>
  #include <sys/stream.h>
*** 230,244 ****
   * To prevent memory hog, limit the number of entries in tcp_free_list
   * to 1% of available memory / number of cpus
   */
  uint_t tcp_free_list_max_cnt = 0;
  
- #define TCP_XMIT_LOWATER        4096
- #define TCP_XMIT_HIWATER        49152
- #define TCP_RECV_LOWATER        2048
- #define TCP_RECV_HIWATER        128000
- 
  #define TIDUSZ  4096    /* transport interface data unit size */
  
  /*
   * Size of acceptor hash list.  It has to be a power of 2 for hashing.
   */
--- 231,240 ----
*** 2716,2726 ****
--- 2712,2727 ----
                  tcp->tcp_issocket = 1;
          }
  
          connp->conn_rcvbuf = tcps->tcps_recv_hiwat;
          connp->conn_sndbuf = tcps->tcps_xmit_hiwat;
+         if (tcps->tcps_snd_lowat_fraction != 0) {
+                 connp->conn_sndlowat = connp->conn_sndbuf /
+                     tcps->tcps_snd_lowat_fraction;
+         } else {
                  connp->conn_sndlowat = tcps->tcps_xmit_lowat;
+         }
          connp->conn_so_type = SOCK_STREAM;
          connp->conn_wroff = connp->conn_ht_iphc_allocated +
              tcps->tcps_wroff_xtra;
  
          SOCK_CONNID_INIT(tcp->tcp_connid);