The maximum send length for UDP is the maximum size of a UDP datagram.

For UDP over IPv4, this is the maximum IPv4 packet size (65535) minus
the size of the IPv4 and UDP headers, arriving at 65507.

In theory for a system implementing IPv6 jumbogram support, there is
no maximum packet size for UDP.  In practice we've observed with
CentOS 5 a limitation of 65535 - 8, which is dictated by the size
field in the UDP header (it has a maximum value of 65535, but needs
to count both payload and header bytes, thus subtracting off the 8
bytes for the UDP header).

We take the most conservative approach and use the 65507 value
for UDP / IPv4.

This is (I believe) the last part of issue #212.

(cherry picked from commit 96d0c77ca2)
Signed-off-by: Bruce A. Mah <bmah@es.net>

Conflicts:
	src/iperf_api.h
	src/iperf_error.c

src/iperf.h

@@ -270,6 +270,8 @@ struct iperf_test
 #define MB (1024 * 1024)
 #define MAX_TCP_BUFFER (512 * MB)
 #define MAX_BLOCKSIZE MB
+/* Maximum size UDP send is (64K - 1) - IP and UDP header sizes */
+#define MAX_UDP_BLOCKSIZE (65535 - 8 - 20)
 #define MIN_INTERVAL 0.1
 #define MAX_INTERVAL 60.0
 #define MAX_TIME 86400

src/iperf_api.c

@@ -820,6 +820,11 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
 	i_errno = IEBLOCKSIZE;
 	return -1;
     }
+    if (test->protocol->id == Pudp &&
+	blksize > MAX_UDP_BLOCKSIZE) {
+	i_errno = IEUDPBLOCKSIZE;
+	return -1;
+    }
     test->settings->blksize = blksize;
 
     if (!rate_flag)

src/iperf_api.h

@@ -268,6 +268,7 @@ enum {
     IEFILE = 14,            // -F file couldn't be opened
     IEBURST = 15,           // Invalid burst count. Maximum value = %dMAX_BURST
     IEENDCONDITIONS = 16,   // Only one test end condition (-t, -n, -k) may be specified
+    IEUDPBLOCKSIZE = 20,    // Block size too large. Maximum value = %dMAX_UDP_BLOCKSIZE
     /* Test errors */
     IENEWTEST = 100,        // Unable to create a new test (check perror)
     IEINITTEST = 101,       // Test initialization failed (check perror)

src/iperf_error.c

@@ -110,6 +110,9 @@ iperf_strerror(int i_errno)
         case IEINTERVAL:
             snprintf(errstr, len, "invalid report interval (min = %g, max = %g seconds)", MIN_INTERVAL, MAX_INTERVAL);
             break;
+        case IEUDPBLOCKSIZE:
+            snprintf(errstr, len, "block size too large (maximum = %d bytes)", MAX_UDP_BLOCKSIZE);
+            break;
         case IEMSS:
             snprintf(errstr, len, "TCP MSS too large (maximum = %d bytes)", MAX_MSS);
             break;