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

*** 18,28 ****
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
!  * Copyright (c) 2013 by Delphix. All rights reserved.
   */
  
  /*
   * This file contains routines that are used to modify/retrieve protocol or
   * interface property values. It also holds all the supported properties for
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
!  * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
   */
  
  /*
   * This file contains routines that are used to modify/retrieve protocol or
   * interface property values. It also holds all the supported properties for
*** 38,47 ****
--- 38,49 ----
  #include <errno.h>
  #include <ctype.h>
  #include <fcntl.h>
  #include <strings.h>
  #include <stdlib.h>
+ #include <sys/types.h>
+ #include <dirent.h>
  #include <netinet/in.h>
  #include <arpa/inet.h>
  #include <sys/sockio.h>
  #include <assert.h>
  #include <libdllink.h>
*** 65,75 ****
   * a given property.
   */
  static ipadm_pd_getf_t  i_ipadm_get_prop, i_ipadm_get_ifprop_flags,
                          i_ipadm_get_mtu, i_ipadm_get_metric,
                          i_ipadm_get_usesrc, i_ipadm_get_forwarding,
!                         i_ipadm_get_ecnsack, i_ipadm_get_hostmodel;
  
  /*
   * Callback function to set property values. These functions translate the
   * values to a format suitable for kernel consumption, allocates the necessary
   * ioctl buffers and then invokes ioctl().
--- 67,78 ----
   * a given property.
   */
  static ipadm_pd_getf_t  i_ipadm_get_prop, i_ipadm_get_ifprop_flags,
                          i_ipadm_get_mtu, i_ipadm_get_metric,
                          i_ipadm_get_usesrc, i_ipadm_get_forwarding,
!                         i_ipadm_get_ecnsack, i_ipadm_get_hostmodel,
!                         i_ipadm_get_cc;
  
  /*
   * Callback function to set property values. These functions translate the
   * values to a format suitable for kernel consumption, allocates the necessary
   * ioctl buffers and then invokes ioctl().
*** 151,160 ****
--- 154,166 ----
  /* possible values for TCP properties `ecn' and `sack' */
  static const char *ecn_sack_vals[] = {"never", "passive", "active", NULL};
  
  /* Supported TCP protocol properties */
  static ipadm_prop_desc_t ipadm_tcp_prop_table[] = {
+         { "congestion_control", NULL, IPADMPROP_CLASS_MODULE, MOD_PROTO_TCP, 0,
+             i_ipadm_set_prop, i_ipadm_get_cc, i_ipadm_get_prop },
+ 
          { "ecn", NULL, IPADMPROP_CLASS_MODULE, MOD_PROTO_TCP, 0,
              i_ipadm_set_ecnsack, i_ipadm_get_ecnsack, i_ipadm_get_ecnsack },
  
          { "extra_priv_ports", NULL, IPADMPROP_CLASS_MODULE, MOD_PROTO_TCP,
              IPADMPROP_MULVAL, i_ipadm_set_eprivport, i_ipadm_get_prop,
*** 810,819 ****
--- 816,861 ----
          }
  
          return (status);
  }
  
+ /*
+  * Retrieves the list of possible congestion control algorithms by enumerating
+  * the modules in /kernel/cc.
+  */
+ /* ARGSUSED */
+ ipadm_status_t
+ i_ipadm_get_cc(ipadm_handle_t iph, const void *arg, ipadm_prop_desc_t *pdp,
+     char *buf, uint_t *bufsize, uint_t proto, uint_t valtype)
+ {
+         DIR *dir;
+         struct dirent *ent;
+         boolean_t first = B_TRUE;
+         uint_t bytes = 0;
+ 
+         assert(valtype == MOD_PROP_POSSIBLE);
+ 
+         /* We assume that all platforms have the same algorithms installed. */
+         if ((dir = opendir("/kernel/cc")) != NULL) {
+                 while ((ent = readdir(dir)) != NULL) {
+                         /* By convention, modules are named cc_<algo>. */
+                         if (strstr(ent->d_name, "cc_") != NULL) {
+                                 bytes += snprintf(buf + bytes,
+                                     bytes < *bufsize ? *bufsize - bytes : 0,
+                                     "%s%s", first ? "" : ",", ent->d_name + 3);
+                                 first = B_FALSE;
+                         }
+                 }
+                 (void) closedir(dir);
+         }
+         if (bytes >= *bufsize) {
+                 *bufsize = bytes + 1;
+                 return (IPADM_NO_BUFS);
+         }
+         return (IPADM_SUCCESS);
+ }
+ 
  /* ARGSUSED */
  static ipadm_status_t
  i_ipadm_get_forwarding(ipadm_handle_t iph, const void *arg,
      ipadm_prop_desc_t *pdp, char *buf, uint_t *bufsize, uint_t proto,
      uint_t valtype)