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

@@ -18,11 +18,11 @@
  *
  * CDDL HEADER END
  */
 /*
  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 by Delphix. 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

@@ -38,10 +38,12 @@
 #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>

@@ -65,11 +67,12 @@
  * 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_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().

@@ -151,10 +154,13 @@
 /* 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,

@@ -810,10 +816,46 @@
         }
 
         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)