Add tcp_info.snd_wnd to JSON output.

tcp_info.snd_wnd is available on FreeBSD and NetBSD since TCP_INFO was
added.  It was added to Linux 5.4 in late 2019 and becomes available
in Ubuntu 20.04 and Debian 11.

Tested on:
* Debian 11 running on x86-64 with this field.
* Debian 10 armv7 running on Raspberry Pi 2 without this field.
* NetBSD 9.2 armv7 running on Raspberry Pi 3 with this field.
* FreeBSD 13 aarch64 running on Raspberry Pi 4 with this field.

configure

@@ -1881,6 +1881,63 @@ fi
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
 
 } # ac_fn_c_check_header_mongrel
+
+# ac_fn_c_check_member LINENO AGGR MEMBER VAR INCLUDES
+# ----------------------------------------------------
+# Tries to find if the field MEMBER exists in type AGGR, after including
+# INCLUDES, setting cache variable VAR accordingly.
+ac_fn_c_check_member ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2.$3" >&5
+$as_echo_n "checking for $2.$3... " >&6; }
+if eval \${$4+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$5
+int
+main ()
+{
+static $2 ac_aggr;
+if (ac_aggr.$3)
+return 0;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  eval "$4=yes"
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$5
+int
+main ()
+{
+static $2 ac_aggr;
+if (sizeof ac_aggr.$3)
+return 0;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  eval "$4=yes"
+else
+  eval "$4=no"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+eval ac_res=\$$4
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_c_check_member
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -13383,6 +13440,19 @@ else
 fi
 
 
+for ac_header in linux/tcp.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "linux/tcp.h" "ac_cv_header_linux_tcp_h" "$ac_includes_default"
+if test "x$ac_cv_header_linux_tcp_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LINUX_TCP_H 1
+_ACEOF
+
+fi
+
+done
+
+
 # Check for SCTP support
 if $try_sctp; then
 for ac_header in sys/socket.h
@@ -14020,6 +14090,26 @@ $as_echo "#define HAVE_DONT_FRAGMENT 1" >>confdefs.h
 
 fi
 
+ac_fn_c_check_member "$LINENO" "struct tcp_info" "tcpi_snd_wnd" "ac_cv_member_struct_tcp_info_tcpi_snd_wnd" "#ifdef HAVE_LINUX_TCP_H
+#include <linux/tcp.h>
+#else
+#include <netinet/tcp.h>
+#endif
+
+"
+if test "x$ac_cv_member_struct_tcp_info_tcpi_snd_wnd" = xyes; then :
+  iperf3_cv_header_tcp_info_snd_wnd=yes
+else
+  iperf3_cv_header_tcp_info_snd_wnd=no
+fi
+
+
+if test "x$iperf3_cv_header_tcp_info_snd_wnd" = "xyes"; then
+
+$as_echo "#define HAVE_TCP_INFO_SND_WND 1" >>confdefs.h
+
+fi
+
 # Check if we need -lrt for clock_gettime
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing clock_gettime" >&5
 $as_echo_n "checking for library containing clock_gettime... " >&6; }

configure.ac

@@ -113,6 +113,8 @@ AC_ARG_WITH([sctp],
     ]
 )
 
+AC_CHECK_HEADERS([linux/tcp.h])
+
 # Check for SCTP support
 if $try_sctp; then
 AC_CHECK_HEADERS([sys/socket.h])
@@ -258,6 +260,19 @@ if test "x$iperf3_cv_header_dontfragment" = "xyes"; then
     AC_DEFINE([HAVE_DONT_FRAGMENT], [1], [Have IP_MTU_DISCOVER/IP_DONTFRAG sockopt.])
 fi
 
+AC_CHECK_MEMBER([struct tcp_info.tcpi_snd_wnd],
+[iperf3_cv_header_tcp_info_snd_wnd=yes], [iperf3_cv_header_tcp_info_snd_wnd=no],
+[#ifdef HAVE_LINUX_TCP_H
+#include <linux/tcp.h>
+#else
+#include <netinet/tcp.h>
+#endif
+])
+
+if test "x$iperf3_cv_header_tcp_info_snd_wnd" = "xyes"; then
+  AC_DEFINE([HAVE_TCP_INFO_SND_WND], [1], [Have tcpi_snd_wnd field in tcp_info.])
+fi
+
 # Check if we need -lrt for clock_gettime
 AC_SEARCH_LIBS(clock_gettime, [rt posix4])
 # Check for clock_gettime support

src/iperf.h

@@ -39,7 +39,11 @@
 #ifndef _GNU_SOURCE
 # define _GNU_SOURCE
 #endif
+#ifdef HAVE_LINUX_TCP_H
+#include <linux/tcp.h>
+#else
 #include <netinet/tcp.h>
+#endif
 #include <net/if.h> // for IFNAMSIZ
 
 #if defined(HAVE_CPUSET_SETAFFINITY)
@@ -100,6 +104,7 @@ struct iperf_interval_results
     int interval_retrans;
     int interval_sacks;
     int snd_cwnd;
+    int snd_wnd;
     TAILQ_ENTRY(iperf_interval_results) irlistentries;
     void     *custom_data;
     int rtt;
@@ -123,6 +128,7 @@ struct iperf_stream_result
     int stream_sum_rtt;
     int stream_count_rtt;
     int stream_max_snd_cwnd;
+    int stream_max_snd_wnd;
     struct iperf_time start_time;
     struct iperf_time end_time;
     struct iperf_time start_time_fixed;

src/iperf_api.c

@@ -49,7 +49,6 @@
 #ifdef HAVE_STDINT_H
 #include <stdint.h>
 #endif
-#include <netinet/tcp.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/mman.h>
@@ -3070,6 +3069,11 @@ iperf_stats_callback(struct iperf_test *test)
 			rp->stream_max_snd_cwnd = temp.snd_cwnd;
 		    }
 
+		    temp.snd_wnd = get_snd_wnd(&temp);
+		    if (temp.snd_wnd > rp->stream_max_snd_wnd) {
+			rp->stream_max_snd_wnd = temp.snd_wnd;
+		    }
+
 		    temp.rtt = get_rtt(&temp);
 		    if (temp.rtt > rp->stream_max_rtt) {
 			rp->stream_max_rtt = temp.rtt;
@@ -3501,7 +3505,7 @@ iperf_print_results(struct iperf_test *test)
                     if (test->sender_has_retransmits) {
                         /* Sender summary, TCP and SCTP with retransmits. */
                         if (test->json_output)
-                            cJSON_AddItemToObject(json_summary_stream, "sender", iperf_json_printf("socket: %d  start: %f  end: %f  seconds: %f  bytes: %d  bits_per_second: %f  retransmits: %d  max_snd_cwnd:  %d  max_rtt:  %d  min_rtt:  %d  mean_rtt:  %d sender: %b", (int64_t) sp->socket, (double) start_time, (double) sender_time, (double) sender_time, (int64_t) bytes_sent, bandwidth * 8, (int64_t) sp->result->stream_retrans, (int64_t) sp->result->stream_max_snd_cwnd, (int64_t) sp->result->stream_max_rtt, (int64_t) sp->result->stream_min_rtt, (int64_t) ((sp->result->stream_count_rtt == 0) ? 0 : sp->result->stream_sum_rtt / sp->result->stream_count_rtt), stream_must_be_sender));
+                            cJSON_AddItemToObject(json_summary_stream, "sender", iperf_json_printf("socket: %d  start: %f  end: %f  seconds: %f  bytes: %d  bits_per_second: %f  retransmits: %d  max_snd_cwnd:  %d  max_snd_wnd:  %d  max_rtt:  %d  min_rtt:  %d  mean_rtt:  %d sender: %b", (int64_t) sp->socket, (double) start_time, (double) sender_time, (double) sender_time, (int64_t) bytes_sent, bandwidth * 8, (int64_t) sp->result->stream_retrans, (int64_t) sp->result->stream_max_snd_cwnd, (int64_t) sp->result->stream_max_snd_wnd, (int64_t) sp->result->stream_max_rtt, (int64_t) sp->result->stream_min_rtt, (int64_t) ((sp->result->stream_count_rtt == 0) ? 0 : sp->result->stream_sum_rtt / sp->result->stream_count_rtt), stream_must_be_sender));
                         else
                             if (test->role == 's' && !sp->sender) {
                                 if (test->verbose)
@@ -3915,7 +3919,7 @@ print_interval_results(struct iperf_test *test, struct iperf_stream *sp, cJSON *
 	if (test->sender_has_retransmits == 1 && sp->sender) {
 	    /* Interval, TCP with retransmits. */
 	    if (test->json_output)
-		cJSON_AddItemToArray(json_interval_streams, iperf_json_printf("socket: %d  start: %f  end: %f  seconds: %f  bytes: %d  bits_per_second: %f  retransmits: %d  snd_cwnd:  %d  rtt:  %d  rttvar: %d  pmtu: %d  omitted: %b sender: %b", (int64_t) sp->socket, (double) st, (double) et, (double) irp->interval_duration, (int64_t) irp->bytes_transferred, bandwidth * 8, (int64_t) irp->interval_retrans, (int64_t) irp->snd_cwnd, (int64_t) irp->rtt, (int64_t) irp->rttvar, (int64_t) irp->pmtu, irp->omitted, sp->sender));
+		cJSON_AddItemToArray(json_interval_streams, iperf_json_printf("socket: %d  start: %f  end: %f  seconds: %f  bytes: %d  bits_per_second: %f  retransmits: %d  snd_cwnd:  %d  snd_wnd:  %d  rtt:  %d  rttvar: %d  pmtu: %d  omitted: %b sender: %b", (int64_t) sp->socket, (double) st, (double) et, (double) irp->interval_duration, (int64_t) irp->bytes_transferred, bandwidth * 8, (int64_t) irp->interval_retrans, (int64_t) irp->snd_cwnd, (int64_t) irp->snd_wnd, (int64_t) irp->rtt, (int64_t) irp->rttvar, (int64_t) irp->pmtu, irp->omitted, sp->sender));
 	    else {
 		unit_snprintf(cbuf, UNIT_LEN, irp->snd_cwnd, 'A');
 		iperf_printf(test, report_bw_retrans_cwnd_format, sp->socket, mbuf, st, et, ubuf, nbuf, irp->interval_retrans, cbuf, irp->omitted?report_omitted:"");

src/iperf_api.h

@@ -277,6 +277,7 @@ int has_tcpinfo_retransmits(void);
 void save_tcpinfo(struct iperf_stream *sp, struct iperf_interval_results *irp);
 long get_total_retransmits(struct iperf_interval_results *irp);
 long get_snd_cwnd(struct iperf_interval_results *irp);
+long get_snd_wnd(struct iperf_interval_results *irp);
 long get_rtt(struct iperf_interval_results *irp);
 long get_rttvar(struct iperf_interval_results *irp);
 long get_pmtu(struct iperf_interval_results *irp);

src/iperf_config.h.in

@@ -30,6 +30,9 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
+/* Define to 1 if you have the <linux/tcp.h> header file. */
+#undef HAVE_LINUX_TCP_H
+
 /* Define to 1 if you have the <memory.h> header file. */
 #undef HAVE_MEMORY_H
 
@@ -90,6 +93,9 @@
 /* Have TCP_CONGESTION sockopt. */
 #undef HAVE_TCP_CONGESTION
 
+/* Have tcpi_snd_wnd field in tcp_info. */
+#undef HAVE_TCP_INFO_SND_WND
+
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 

src/tcp_info.c

@@ -143,6 +143,26 @@ get_snd_cwnd(struct iperf_interval_results *irp)
 #endif
 }
 
+/*************************************************************/
+/*
+ * Return snd_wnd in octets.
+ */
+long
+get_snd_wnd(struct iperf_interval_results *irp)
+{
+#if !defined(HAVE_TCP_INFO_SND_WND)
+    return -1;
+#elif defined(linux) && defined(TCP_MD5SIG)
+    return irp->tcpInfo.tcpi_snd_wnd;
+#elif defined(__FreeBSD__) && __FreeBSD_version >= 600000
+    return irp->tcpInfo.tcpi_snd_wnd;
+#elif defined(__NetBSD__) && defined(TCP_INFO)
+    return irp->tcpInfo.tcpi_snd_wnd * irp->tcpInfo.tcpi_snd_mss;
+#else
+    return -1;
+#endif
+}
+
 /*************************************************************/
 /*
  * Return rtt in usec.