Merge branch 'tcp-tcstamp_ack-frag-coalesce'

Martin KaFai Lau says:

====================
tcp: Handle txstamp_ack when fragmenting/coalescing skbs

This patchset is to handle the txstamp-ack bit when
fragmenting/coalescing skbs.

The second patch depends on the recently posted series
for the net branch:
"tcp: Merge timestamp info when coalescing skbs"

A BPF prog is used to kprobe to sock_queue_err_skb()
and print out the value of serr->ee.ee_data.  The BPF
prog (run-able from bcc) is attached here:

BPF prog used for testing:
~~~~~

from __future__ import print_function
from bcc import BPF

bpf_text = """

int trace_err_skb(struct pt_regs *ctx)
{
	struct sk_buff *skb = (struct sk_buff *)ctx->si;
	struct sock *sk = (struct sock *)ctx->di;
	struct sock_exterr_skb *serr;
	u32 ee_data = 0;

	if (!sk || !skb)
		return 0;

	serr = SKB_EXT_ERR(skb);
	bpf_probe_read(&ee_data, sizeof(ee_data), &serr->ee.ee_data);
	bpf_trace_printk("ee_data:%u\\n", ee_data);

	return 0;
};
"""

b = BPF(text=bpf_text)
b.attach_kprobe(event="sock_queue_err_skb", fn_name="trace_err_skb")
print("Attached to kprobe")
b.trace_print()
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_output.c

@@ -1123,6 +1123,8 @@ static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
 		shinfo->tx_flags &= ~tsflags;
 		shinfo2->tx_flags |= tsflags;
 		swap(shinfo->tskey, shinfo2->tskey);
+		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
+		TCP_SKB_CB(skb)->txstamp_ack = 0;
 	}
 }
 
@@ -2452,6 +2454,8 @@ void tcp_skb_collapse_tstamp(struct sk_buff *skb,
 
 		shinfo->tx_flags |= tsflags;
 		shinfo->tskey = next_shinfo->tskey;
+		TCP_SKB_CB(skb)->txstamp_ack |=
+			TCP_SKB_CB(next_skb)->txstamp_ack;
 	}
 }