pktgen: make /proc/net/pktgen/pgctrl report fail on invalid input

Giving /proc/net/pktgen/pgctrl an invalid command just returns shell
success and prints a warning in dmesg.  This is not very useful for
shell scripting, as it can only detect the error by parsing dmesg.

Instead return -EINVAL when the command is unknown, as this provides
userspace shell scripting a way of detecting this.

Also bump version tag to 2.75, because (1) reading /proc/net/pktgen/pgctrl
output this version number which would allow to detect this small
semantic change, and (2) because the pktgen version tag have not been
updated since 2010.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/pktgen.c

@@ -177,7 +177,7 @@
 #include <asm/dma.h>
 #include <asm/div64.h>		/* do_div */
 
-#define VERSION	"2.74"
+#define VERSION	"2.75"
 #define IP_NAME_SZ 32
 #define MAX_MPLS_LABELS 16 /* This is the max label stack depth */
 #define MPLS_STACK_BOTTOM htonl(0x00000100)
@@ -512,7 +512,7 @@ static ssize_t pgctrl_write(struct file *file, const char __user *buf,
 		pktgen_reset_all_threads(pn);
 
 	else
-		pr_warn("Unknown command: %s\n", data);
+		return -EINVAL;
 
 	return count;
 }