5 files changed, 19 insertions, 10 deletions

diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 98097d8cb910..661d3c316a17 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
@@ -85,7 +85,7 @@ Filled in if SOF_TIMESTAMPING_SYS_HARDWARE is set. Requires support
 by the network device and will be empty without that support.
 
 
-SIOCSHWTSTAMP:
+SIOCSHWTSTAMP, SIOCGHWTSTAMP:
 
 Hardware time stamping must also be initialized for each device driver
 that is expected to do hardware time stamping. The parameter is defined in
@@ -115,6 +115,10 @@ Only a processes with admin rights may change the configuration. User
 space is responsible to ensure that multiple processes don't interfere
 with each other and that the settings are reset.
 
+Any process can read the actual configuration by passing this
+structure to ioctl(SIOCGHWTSTAMP) in the same way.  However, this has
+not been implemented in all drivers.
+
 /* possible values for hwtstamp_config->tx_type */
 enum {
         /*
@@ -157,7 +161,8 @@ DEVICE IMPLEMENTATION
 
 A driver which supports hardware time stamping must support the
 SIOCSHWTSTAMP ioctl and update the supplied struct hwtstamp_config with
-the actual values as described in the section on SIOCSHWTSTAMP.
+the actual values as described in the section on SIOCSHWTSTAMP.  It
+should also support SIOCGHWTSTAMP.
 
 Time stamps for received packets must be stored in the skb. To get a pointer
 to the shared time stamp structure of the skb call skb_hwtstamps(). Then
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 */
 
diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 5b7d0e1d0664..cf999e09bcd2 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -327,6 +327,7 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, unsigned int cmd)
                     cmd == SIOCBRADDIF ||
                     cmd == SIOCBRDELIF ||
                     cmd == SIOCSHWTSTAMP ||
+                    cmd == SIOCGHWTSTAMP ||
                     cmd == SIOCWANDEV) {
                         err = -EOPNOTSUPP;
                         if (ops->ndo_do_ioctl) {
@@ -546,6 +547,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
          */
         default:
                 if (cmd == SIOCWANDEV ||
+                    cmd == SIOCGHWTSTAMP ||
                     (cmd >= SIOCDEVPRIVATE &&
                      cmd <= SIOCDEVPRIVATE + 15)) {
                         dev_load(net, ifr.ifr_name);
diff --git a/net/socket.c b/net/socket.c
index 7a766ab83ca5..1a548b70ef3a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3231,6 +3231,7 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
         case SIOCBONDSLAVEINFOQUERY:
         case SIOCBONDINFOQUERY:
         case SIOCSHWTSTAMP:
+        case SIOCGHWTSTAMP:
                 return compat_ifr_data_ioctl(net, cmd, argp);
 
         case FIOSETOWN: