Improve error message for TCP congestion algorithm setting failure.

Also remove a couple of places where we were saving and restoring errno
where we didn't need to.

Submitted by:	Susant Sahani <ssahani@redhat.com>
Issue:		121 (TCP congestion control algorithm support for client)

src/iperf_error.c

@@ -291,8 +291,8 @@ iperf_strerror(int i_errno)
             perr = 1;
             break;
         case IESETCONGESTION:
-            snprintf(errstr, len, "unable to set TCP_CONGESTION");
-            perr = 1;
+            snprintf(errstr, len, "unable to set TCP_CONGESTION: " 
+                                  "Supplied congestion control algorithm not supported on this host");
             break;
     }
 

src/iperf_tcp.c

@@ -187,10 +187,8 @@ iperf_tcp_listen(struct iperf_test *test)
 #if defined(linux)
 	if (test->congestion) {
 	    if (setsockopt(s, IPPROTO_TCP, TCP_CONGESTION, test->congestion, strlen(test->congestion)) < 0) {
-		saved_errno = errno;
 		close(s);
 		freeaddrinfo(res);
-		errno = saved_errno;
 		i_errno = IESETCONGESTION;
 		return -1;
 	    } 
@@ -378,10 +376,8 @@ iperf_tcp_connect(struct iperf_test *test)
 #if defined(linux)
     if (test->congestion) {
 	if (setsockopt(s, IPPROTO_TCP, TCP_CONGESTION, test->congestion, strlen(test->congestion)) < 0) {
-	    saved_errno = errno;
 	    close(s);
 	    freeaddrinfo(server_res);
-	    errno = saved_errno;
 	    i_errno = IESETCONGESTION;
 	    return -1;
 	}