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Merge branch 'tcp-coalesce-merge-timestamps'

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Martin KaFai Lau says:

====================
tcp: Merge timestamp info when coalescing skbs

This series is separated from the RFC series related to
tcp_sendmsg(MSG_EOR) and it is targeting for the net branch.
This patchset is focusing on fixing cases where TCP
timestamp could be lost after 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>
This commit is contained in:
David S. Miller
2016-04-21 14:40:56 -04:00
parent 3fa88c51c7 cfea5a688e
commit 5bec11cf44
3 changed files with 19 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/tcp.h
View File

@@ -552,6 +552,8 @@ void tcp_send_ack(struct sock *sk);
void tcp_send_delayed_ack(struct sock *sk);
void tcp_send_loss_probe(struct sock *sk);
bool tcp_schedule_loss_probe(struct sock *sk);
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
const struct sk_buff *next_skb);
/* tcp_input.c */
void tcp_resume_early_retransmit(struct sock *sk);

1
net/ipv4/tcp_input.c
View File

@@ -1309,6 +1309,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
if (skb == tcp_highest_sack(sk))
tcp_advance_highest_sack(sk, skb);
tcp_skb_collapse_tstamp(prev, skb);
tcp_unlink_write_queue(skb, sk);
sk_wmem_free_skb(sk, skb);

16
net/ipv4/tcp_output.c
View File

@@ -2441,6 +2441,20 @@ u32 __tcp_select_window(struct sock *sk)
return window;
}
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
const struct sk_buff *next_skb)
{
const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb);
u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
if (unlikely(tsflags)) {
struct skb_shared_info *shinfo = skb_shinfo(skb);
shinfo->tx_flags |= tsflags;
shinfo->tskey = next_shinfo->tskey;
}
}
/* Collapses two adjacent SKB's during retransmission. */
static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
{
@@ -2484,6 +2498,8 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
tcp_skb_collapse_tstamp(skb, next_skb);
sk_wmem_free_skb(sk, next_skb);
}