Re: [PATCH rfc 1/4] net-timestamp: pull headers for SOCK_STREAM

From: Willem de Bruijn <willemb@google.com>
Date: Tue, 25 Nov 2014 12:58:03 -0500

From: Willem de Bruijn <willemb@google.com>

When returning timestamped packets on the error queue, only return
the data that the application initially sent: not the protocol
headers.

This changes the ABI. The TCP interface is new enough that it should
be safe to do so. The UDP interface could be changed analogously with

+  else if (sk->sk_protocol == IPPROTO_UDP)
+    skb_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr));

Tested with Documentation/networking/timestamping/txtimestamp -l 60 -x

Signed-off-by: Willem de Bruijn <willemb@google.com>

What's the harm in exposing the headers?  Either it's harmful, and
therefore doing so for UDP is bad too, or it's harmless and we should
probably leave it alone to not risk breaking anyone.