net-timestamp: no-payload option
Add timestamping option SOF_TIMESTAMPING_OPT_TSONLY. For transmit
timestamps, this loops timestamps on top of empty packets.
Doing so reduces the pressure on SO_RCVBUF. Payload inspection and
cmsg reception (aside from timestamps) are no longer possible. This
works together with a follow on patch that allows administrators to
only allow tx timestamping if it does not loop payload or metadata.
Signed-off-by: Willem de Bruijn <willemb@google.com>
----
Changes (rfc -> v1)
- add documentation
- remove unnecessary skb->len test (thanks to Richard Cochran)
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 56db472..65a3798 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3710,19 +3710,28 @@
struct sock *sk, int tstype)
{
struct sk_buff *skb;
+ bool tsonly = sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TSONLY;
if (!sk)
return;
- if (hwtstamps)
- *skb_hwtstamps(orig_skb) = *hwtstamps;
+ if (tsonly)
+ skb = alloc_skb(0, GFP_ATOMIC);
else
- orig_skb->tstamp = ktime_get_real();
-
- skb = skb_clone(orig_skb, GFP_ATOMIC);
+ skb = skb_clone(orig_skb, GFP_ATOMIC);
if (!skb)
return;
+ if (tsonly) {
+ skb_shinfo(skb)->tx_flags = skb_shinfo(orig_skb)->tx_flags;
+ skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
+ }
+
+ if (hwtstamps)
+ *skb_hwtstamps(skb) = *hwtstamps;
+ else
+ skb->tstamp = ktime_get_real();
+
__skb_complete_tx_timestamp(skb, sk, tstype);
}
EXPORT_SYMBOL_GPL(__skb_tstamp_tx);