net_tstamp: Add SIOCGHWTSTAMP ioctl to match SIOCSHWTSTAMP

SIOCSHWTSTAMP returns the real configuration to the application
using it, but there is currently no way for any other
application to find out the configuration non-destructively.
Add a new ioctl for this, making it unprivileged.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

2 files changed, 9 insertions, 8 deletions

diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
index c9a7de2a6276..f53879c0f590 100644
--- a/include/uapi/linux/net_tstamp.h
+++ b/include/uapi/linux/net_tstamp.h
@@ -26,17 +26,17 @@ enum {
 };
 
 /**
- * struct hwtstamp_config - %SIOCSHWTSTAMP parameter
+ * struct hwtstamp_config - %SIOCGHWTSTAMP and %SIOCSHWTSTAMP parameter
  *
- * @flags:      no flags defined right now, must be zero
+ * @flags:      no flags defined right now, must be zero for %SIOCSHWTSTAMP
  * @tx_type:    one of HWTSTAMP_TX_*
  * @rx_filter:  one of HWTSTAMP_FILTER_*
  *
- * %SIOCSHWTSTAMP expects a &struct ifreq with a ifr_data pointer to
- * this structure.  If the driver or hardware does not support the
- * requested @rx_filter value, the driver may use a more general
- * filter mode.  In this case @rx_filter will indicate the actual mode
- * on return.
+ * %SIOCGHWTSTAMP and %SIOCSHWTSTAMP expect a &struct ifreq with a
+ * ifr_data pointer to this structure.  For %SIOCSHWTSTAMP, if the
+ * driver or hardware does not support the requested @rx_filter value,
+ * the driver may use a more general filter mode.  In this case
+ * @rx_filter will indicate the actual mode on return.
  */
 struct hwtstamp_config {
         int flags;
diff --git a/include/uapi/linux/sockios.h b/include/uapi/linux/sockios.h
index 7997a506ad41..e888b1aed69f 100644
--- a/include/uapi/linux/sockios.h
+++ b/include/uapi/linux/sockios.h
@@ -125,7 +125,8 @@
 #define SIOCBRDELIF     0x89a3          /* remove interface from bridge */
 
 /* hardware time stamping: parameters in linux/net_tstamp.h */
-#define SIOCSHWTSTAMP   0x89b0
+#define SIOCSHWTSTAMP   0x89b0          /* set and get config           */
+#define SIOCGHWTSTAMP   0x89b1          /* get config                   */
 
 /* Device private ioctl calls */