Separate UDP GSO and GRO controls for Linux (--gso and --gro options) #2037

src/iperf3.1

@@ -525,6 +525,27 @@ settings to the server automatically.
 This feature is disabled by default and must be explicitly enabled
 with this flag.
 .TP
+.BR --gsro/s
+Enable UDP Generic Segmentation Offload (GSO) on the sender, where 
+supported by the operating system and network hardware (currently Linux only).
+GSO allows the network stack to aggregate multiple UDP datagrams
+into larger packets, improving throughput and reducing CPU overhead.
+This is a client-only option; the client communicates the GSO
+settings to the server automatically.
+This feature is disabled by default and must be explicitly enabled
+with this flag.
+.TP
+.BR --gsro/r
+Enable UDP Generic Receive Offload (GRO) on the receiver, where supported by
+the operating system and network hardware (currently Linux only).
+GRO is an aggregation technique to coalesce several receive packets from a 
+stream into a single large packet, thus saving CPU cycles as fewer packets 
+need to be processed by the kernel. By default, GRO is accomplished in the Linux kernel. 
+This is a client-only option; the client communicates the GRO
+settings to the server automatically.
+This feature is disabled by default and must be explicitly enabled
+with this flag.
+.TP
 .BR --repeating-payload
 Use repeating pattern in payload, instead of random bytes.
 The same payload is used in iperf2 (ASCII '0..9' repeating).

src/iperf_api.c

@@ -1194,6 +1194,8 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
         {"mptcp", no_argument, NULL, 'm'},
 #endif
         {"gsro", no_argument, NULL, OPT_GSRO},
+        {"gsro/s", no_argument, NULL, OPT_GSRO_S},
+        {"gsro/r", no_argument, NULL, OPT_GSRO_R},
         {"debug", optional_argument, NULL, 'd'},
         {"help", no_argument, NULL, 'h'},
         {NULL, 0, NULL, 0}
@@ -1813,6 +1815,20 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
 		test->settings->gso = 1;
 		test->settings->gro = 1;
                 break;
+        case OPT_GSRO_S:
+        /* Enable GSO which is disabled by default */
+        /* Flag is available regardless of local support to allow client to request server to use it */
+        gsro_flag = 1;
+        test->settings->gso = 1;
+        test->settings->gro = 0;
+        break;
+        case OPT_GSRO_R:
+        /* Enable GRO which is disabled by default */
+        /* Flag is available regardless of local support to allow client to request server to use it */
+        gsro_flag = 1;
+        test->settings->gso = 0;
+        test->settings->gro = 1;
+        break;
 	    case 'h':
 		usage_long(stdout);
 		exit(0);
@@ -1840,11 +1856,11 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
     /* Show platform support warnings only after confirming we're in client mode */
     if (gsro_flag) {
 #if !defined(HAVE_UDP_SEGMENT) && !defined(HAVE_UDP_GRO)
-        warning("--gsro requested but UDP GSO/GRO not supported on this client; will only be enabled on server if supported");
+        warning("GSO/GRO requested but UDP GSO/GRO not supported on this client; will only be enabled on server if supported");
 #elif !defined(HAVE_UDP_SEGMENT)
-        warning("--gsro requested but UDP GSO not supported on this client; will be enabled on server if supported");
+        warning("GSO requested but UDP GSO not supported on this client; will be enabled on server if supported");
 #elif !defined(HAVE_UDP_GRO)
-        warning("--gsro requested but UDP GRO not supported on this client; will be enabled on server if supported");
+        warning("GRO requested but UDP GRO not supported on this client; will be enabled on server if supported");
 #endif
     }
 
@@ -3455,10 +3471,10 @@ iperf_defaults(struct iperf_test *testp)
     testp->settings->pacing_timer = DEFAULT_PACING_TIMER;
     testp->settings->burst = 0;
     /* Always initialize GSO/GRO fields to allow client-server negotiation */
-    testp->settings->gso = 0;  /* Disable GSO by default, enabled via --gsro */
+    testp->settings->gso = 0;  /* Disable GSO by default, enabled via --gsro or --gsro/s*/
     testp->settings->gso_dg_size = 0;
     testp->settings->gso_bf_size = GSO_BF_MAX_SIZE;
-    testp->settings->gro = 0;  /* Disable GRO by default, enabled via --gsro */
+    testp->settings->gro = 0;  /* Disable GRO by default, enabled via --gsro or --gsro/r*/
     testp->settings->gro_bf_size = GRO_BF_MAX_SIZE;
     testp->settings->mss = 0;
     testp->settings->bytes = 0;

src/iperf_api.h

@@ -107,6 +107,8 @@ typedef atomic_uint_fast64_t atomic_iperf_size_t;
 #define OPT_JSON_STREAM_FULL_OUTPUT 33
 #define OPT_SERVER_MAX_DURATION 34
 #define OPT_GSRO 35
+#define OPT_GSRO_S 36
+#define OPT_GSRO_R 37
 
 /* states */
 #define TEST_START 1

src/iperf_client_api.c

@@ -521,7 +521,7 @@ iperf_connect(struct iperf_test *test)
 		printf("Setting UDP block size to %d\n", test->settings->blksize);
 	    }
 	}
-	/* Initialize GSO parameters when --gsro is used */
+	/* Initialize GSO parameters when --gsro or --gsro/s is used */
 	if (test->settings->gso) {
 	    test->settings->gso_dg_size = test->settings->blksize;
 	    /* use the multiple of datagram size for the best efficiency. */

src/iperf_locale.c

@@ -219,7 +219,12 @@ const char usage_longstr[] = "Usage: iperf3 [-s|-c host] [options]\n"
                            "  --extra-data str          data string to include in client and server JSON\n"
                            "  --get-server-output       get results from server\n"
                            "  --udp-counters-64bit      use 64-bit counters in UDP test packets\n"
-                           "  --gsro                    enable UDP GSO/GRO on both client and server (client-only option)\n"
+                           "  --gsro | --gsro/s | --gsro/r enable UDP GSO and/or GRO on both client and server.\n"
+                           "                            Exclusive options (choose only one):\n"
+                           "                            --gsro   : Enable both GSO and GRO\n"
+                           "                            --gsro/s : Enable GSO only\n"
+                           "                            --gsro/r : Enable GRO only\n"
+                           "                            (client-only options)\n"
                            "  --repeating-payload       use repeating pattern in payload, instead of\n"
                            "                            randomized payload (like in iperf2)\n"
 #if defined(HAVE_DONT_FRAGMENT)