enh: Introduce iperf_set_test_logfile API function (#871)

To be able to set the test->outfile to a different file other than default
if using libiperf API.

Since logfile is now opened in iperf_parse_arguments() and this function
may not be used if running iperf using API, define a dedicated function
iperf_open_logfile() and move the opening of logfile into
iperf_run_client() and iperf_run_server() to make sure logfile will be
opened if iperf_parse_arguments() was not called.

src/iperf_api.c

@@ -390,6 +390,12 @@ iperf_set_test_blksize(struct iperf_test *ipt, int blksize)
     ipt->settings->blksize = blksize;
 }
 
+void
+iperf_set_test_logfile(struct iperf_test *ipt, char *logfile)
+{
+    ipt->logfile = strdup(logfile);
+}
+
 void
 iperf_set_test_rate(struct iperf_test *ipt, uint64_t rate)
 {
@@ -1217,15 +1223,6 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
         }
     }
 
-    /* Set logging to a file if specified, otherwise use the default (stdout) */
-    if (test->logfile) {
-        test->outfile = fopen(test->logfile, "a+");
-        if (test->outfile == NULL) {
-            i_errno = IELOGFILE;
-            return -1;
-        }
-    }
-
     /* Check flag / role compatibility. */
     if (test->role == 'c' && server_flag) {
         i_errno = IESERVERONLY;
@@ -1350,6 +1347,20 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
     return 0;
 }
 
+/*
+ * Open the file specified by test->logfile and set test->outfile to its' FD.
+ */
+int iperf_open_logfile(struct iperf_test *test)
+{
+    test->outfile = fopen(test->logfile, "a+");
+    if (test->outfile == NULL) {
+        i_errno = IELOGFILE;
+        return -1;
+    }
+
+    return 0;
+}
+
 int
 iperf_set_send_state(struct iperf_test *test, signed char state)
 {

src/iperf_api.h

@@ -138,6 +138,7 @@ void	iperf_set_test_reporter_interval( struct iperf_test* ipt, double reporter_i
 void	iperf_set_test_stats_interval( struct iperf_test* ipt, double stats_interval );
 void	iperf_set_test_state( struct iperf_test* ipt, signed char state );
 void	iperf_set_test_blksize( struct iperf_test* ipt, int blksize );
+void	iperf_set_test_logfile( struct iperf_test* ipt, char *logfile );
 void	iperf_set_test_rate( struct iperf_test* ipt, uint64_t rate );
 void    iperf_set_test_pacing_timer( struct iperf_test* ipt, int pacing_timer );
 void    iperf_set_test_bytes( struct iperf_test* ipt, uint64_t bytes );
@@ -267,6 +268,7 @@ int iperf_exchange_results(struct iperf_test *);
 int iperf_init_test(struct iperf_test *);
 int iperf_create_send_timers(struct iperf_test *);
 int iperf_parse_arguments(struct iperf_test *, int, char **);
+int iperf_open_logfile(struct iperf_test *);
 void iperf_reset_test(struct iperf_test *);
 void iperf_reset_stats(struct iperf_test * test);
 

src/iperf_client_api.c

@@ -454,6 +454,10 @@ iperf_run_client(struct iperf_test * test)
     struct timeval* timeout = NULL;
     struct iperf_stream *sp;
 
+    if (test->logfile)
+        if (iperf_open_logfile(test) < 0)
+            return -1;
+
     if (test->affinity != -1)
 	if (iperf_setaffinity(test, test->affinity) != 0)
 	    return -1;

src/iperf_server_api.c

@@ -398,6 +398,10 @@ iperf_run_server(struct iperf_test *test)
     struct timeval* timeout;
     int flag;
 
+    if (test->logfile)
+        if (iperf_open_logfile(test) < 0)
+            return -1;
+
     if (test->affinity != -1) 
 	if (iperf_setaffinity(test, test->affinity) != 0)
 	    return -2;