11554 Want TCP_CONGESTION socket option
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>

*** 19,29 ****
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
!  * Copyright 2016 Joyent, Inc.
   * Copyright (c) 2016 by Delphix. All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/stream.h>
--- 19,29 ----
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
!  * Copyright 2019 Joyent, Inc.
   * Copyright (c) 2016 by Delphix. All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/stream.h>
*** 32,41 ****
--- 32,42 ----
  #include <sys/socket.h>
  #include <sys/xti_xtiopt.h>
  #include <sys/xti_inet.h>
  #include <sys/policy.h>
  
+ #include <inet/cc.h>
  #include <inet/common.h>
  #include <netinet/ip6.h>
  #include <inet/ip.h>
  
  #include <netinet/in.h>
*** 139,148 ****
--- 140,152 ----
  
  { TCP_RTO_MAX, IPPROTO_TCP, OA_RW, OA_RW, OP_NP, 0, sizeof (uint32_t), 0 },
  
  { TCP_LINGER2, IPPROTO_TCP, OA_RW, OA_RW, OP_NP, 0, sizeof (int), 0 },
  
+ { TCP_CONGESTION, IPPROTO_TCP, OA_RW, OA_RW, OP_NP,
+         OP_VARLEN, CC_ALGO_NAME_MAX, 0 },
+ 
  { IP_OPTIONS,   IPPROTO_IP, OA_RW, OA_RW, OP_NP,
          (OP_VARLEN|OP_NODEFAULT),
          IP_MAX_OPT_LENGTH + IP_ADDR_LEN, -1 /* not initialized */ },
  { T_IP_OPTIONS, IPPROTO_IP, OA_RW, OA_RW, OP_NP,
          (OP_VARLEN|OP_NODEFAULT),
*** 431,440 ****
--- 435,451 ----
                          *i1 = tcp->tcp_ka_rinterval / 1000;
                          return (sizeof (int));
                  case TCP_KEEPALIVE_ABORT_THRESHOLD:
                          *i1 = tcp->tcp_ka_abort_thres;
                          return (sizeof (int));
+                 case TCP_CONGESTION: {
+                         size_t len = strlcpy((char *)ptr, CC_ALGO(tcp)->name,
+                             CC_ALGO_NAME_MAX);
+                         if (len >= CC_ALGO_NAME_MAX)
+                                 return (-1);
+                         return (len + 1);
+                 }
                  case TCP_CORK:
                          *i1 = tcp->tcp_cork;
                          return (sizeof (int));
                  case TCP_RTO_INITIAL:
                          *i1 = tcp->tcp_rto_initial;
*** 852,861 ****
--- 863,907 ----
                                  tcp->tcp_ka_abort_thres = *i1;
                                  tcp->tcp_ka_cnt = 0;
                                  tcp->tcp_ka_rinterval = 0;
                          }
                          break;
+                 case TCP_CONGESTION: {
+                         struct cc_algo *algo;
+ 
+                         if (checkonly) {
+                                 break;
+                         }
+ 
+                         /*
+                          * Make sure the string is NUL-terminated. Some
+                          * consumers pass only the number of characters
+                          * in the string, and don't include the NUL
+                          * terminator, so we set it for them.
+                          */
+                         if (inlen < CC_ALGO_NAME_MAX) {
+                                 invalp[inlen] = '\0';
+                         }
+                         invalp[CC_ALGO_NAME_MAX - 1] = '\0';
+ 
+                         if ((algo = cc_load_algo((char *)invalp)) == NULL) {
+                                 return (ENOENT);
+                         }
+ 
+                         if (CC_ALGO(tcp)->cb_destroy != NULL) {
+                                 CC_ALGO(tcp)->cb_destroy(&tcp->tcp_ccv);
+                         }
+ 
+                         CC_DATA(tcp) = NULL;
+                         CC_ALGO(tcp) = algo;
+ 
+                         if (CC_ALGO(tcp)->cb_init != NULL) {
+                                 VERIFY0(CC_ALGO(tcp)->cb_init(&tcp->tcp_ccv));
+                         }
+ 
+                         break;
+                 }
                  case TCP_CORK:
                          if (!checkonly) {
                                  /*
                                   * if tcp->tcp_cork was set and is now
                                   * being unset, we have to make sure that