DLPX-25998 TCP congestion control is inadequate
Reviewed at: http://reviews.delphix.com/r/34808/

*** 20,35 ****
   */
  /*
   * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright 2016 Joyent, Inc.
   * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
!  * Copyright (c) 2013 by Delphix. All rights reserved.
   */
  /* Copyright (c) 1990 Mentat Inc. */
  
  #include <inet/ip.h>
  #include <inet/tcp_impl.h>
  #include <sys/multidata.h>
  #include <sys/sunddi.h>
  
  /* Max size IP datagram is 64k - 1 */
  #define TCP_MSS_MAX_IPV4 (IP_MAXPACKET - (sizeof (ipha_t) + sizeof (tcpha_t)))
--- 20,36 ----
   */
  /*
   * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright 2016 Joyent, Inc.
   * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
!  * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
   */
  /* Copyright (c) 1990 Mentat Inc. */
  
  #include <inet/ip.h>
  #include <inet/tcp_impl.h>
+ #include <inet/cc.h>
  #include <sys/multidata.h>
  #include <sys/sunddi.h>
  
  /* Max size IP datagram is 64k - 1 */
  #define TCP_MSS_MAX_IPV4 (IP_MAXPACKET - (sizeof (ipha_t) + sizeof (tcpha_t)))
*** 237,246 ****
--- 238,289 ----
                  return (ERANGE);
          pinfo->prop_cur_uval = (uint32_t)new_value;
          return (0);
  }
  
+ /* ARGSUSED */
+ static int
+ tcp_set_cc_algorithm(netstack_t *stack, cred_t *cr, mod_prop_info_t *pinfo,
+     const char *ifname, const void *pval, uint_t flags)
+ {
+         tcp_stack_t *tcps = stack->netstack_tcp;
+         char *name = (flags & MOD_PROP_DEFAULT) ?
+             CC_DEFAULT_ALGO_NAME : (char *)pval;
+         struct cc_algo *algo = cc_load_algo(name);
+ 
+         if (algo == NULL)
+                 return (EINVAL);
+ 
+         tcps->tcps_default_cc_algo = algo;
+         return (0);
+ }
+ 
+ /* ARGSUSED */
+ static int
+ tcp_get_cc_algorithm(netstack_t *stack, mod_prop_info_t *pinfo,
+     const char *ifname, void *pval, uint_t psize, uint_t flags)
+ {
+         size_t nbytes;
+ 
+         if (flags & MOD_PROP_POSSIBLE) {
+                 /* libipadm doesn't call down for possible values. */
+                 return (ENOTSUP);
+         }
+ 
+         if (flags & MOD_PROP_PERM) {
+                 nbytes = snprintf(pval, psize, "%u", MOD_PROP_PERM_RW);
+         } else if (flags & MOD_PROP_DEFAULT) {
+                 nbytes = snprintf(pval, psize, "%s", CC_DEFAULT_ALGO_NAME);
+         } else {
+                 nbytes = snprintf(pval, psize, "%s",
+                     stack->netstack_tcp->tcps_default_cc_algo->name);
+         }
+         if (nbytes >= psize)
+                 return (ENOBUFS);
+         return (0);
+ }
+ 
  /*
   * All of these are alterable, within the min/max values given, at run time.
   *
   * Note: All those tunables which do not start with "_" are Committed and
   * therefore are public. See PSARC 2010/080.
*** 525,534 ****
--- 568,588 ----
          { "_iss_incr", MOD_PROTO_TCP,
              mod_set_uint32, mod_get_uint32,
              {1, ISS_INCR, ISS_INCR},
              {ISS_INCR} },
  
+         { "congestion_control", MOD_PROTO_TCP,
+             tcp_set_cc_algorithm, tcp_get_cc_algorithm, {0}, {0} },
+ 
+         /* RFC 3465 - TCP Congestion Control with Appropriate Byte Counting */
+         { "_abc", MOD_PROTO_TCP,
+             mod_set_boolean, mod_get_boolean, {B_TRUE}, {B_TRUE} },
+ 
+         /* "L" value from RFC 3465 */
+         { "_abc_l_var", MOD_PROTO_TCP,
+             mod_set_uint32, mod_get_uint32, {1, UINT32_MAX, 2}, {2} },
+ 
          { "?", MOD_PROTO_TCP, NULL, mod_get_allprop, {0}, {0} },
  
          { NULL, 0, NULL, NULL, {0}, {0} }
  };