[PATCH net-next 0/2] tcp: Handle txstamp_ack when fragmenting/coalescing skbs

[PATCH net-next 0/2] tcp: Handle txstamp_ack when fragmenting/coalescing skbs

[Martin KaFai Lau]

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:
~~~~~
#!/usr/bin/env python

from __future__ import print_function
from bcc import BPF

bpf_text = """
#include <uapi/linux/ptrace.h>
#include <net/sock.h>
#include <bcc/proto.h>
#include <linux/errqueue.h>

#ifdef memset
#undef memset
#endif

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()

[PATCH net-next 1/2] tcp: Carry txstamp_ack in tcp_fragment_tstamp

[Martin KaFai Lau]

When a tcp skb is sliced into two smaller skbs (e.g. in
tcp_fragment() and tso_fragment()),  it does not carry
the txstamp_ack bit to the newly created skb if it is needed.
The end result is a timestamping event (SCM_TSTAMP_ACK) will
be missing from the sk->sk_error_queue.

This patch carries this bit to the new skb2
in tcp_fragment_tstamp().

BPF Output Before:
~~~~~~
<No output due to missing SCM_TSTAMP_ACK timestamp>

BPF Output After:
~~~~~~
<...>-2050  [000] d.s.   100.928763: : ee_data:14599

Packetdrill Script:
~~~~~~
+0 `sysctl -q -w net.ipv4.tcp_min_tso_segs=10`
+0 `sysctl -q -w net.ipv4.tcp_no_metrics_save=1`
+0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0

0.100 < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 7>
0.100 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7>
0.200 < . 1:1(0) ack 1 win 257
0.200 accept(3, ..., ...) = 4
+0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0

+0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
0.200 write(4, ..., 14600) = 14600
+0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0

0.200 > . 1:7301(7300) ack 1
0.200 > P. 7301:14601(7300) ack 1

0.300 < . 1:1(0) ack 14601 win 257

0.300 close(4) = 0
0.300 > F. 14601:14601(0) ack 1
0.400 < F. 1:1(0) ack 16062 win 257
0.400 > . 14602:14602(0) ack 2

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 net/ipv4/tcp_output.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 96182a2..f7c3bc0 100644
--- a/net/ipv4/tcp_output.c
+++ b/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;
 	}
 }
 
-- 
2.5.1

[PATCH net-next 2/2] tcp: Merge txstamp_ack in tcp_skb_collapse_tstamp

[Martin KaFai Lau]

When collapsing skbs, txstamp_ack also needs to be merged.

Retrans Collapse Test:
~~~~~~
0.200 accept(3, ..., ...) = 4
+0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0

0.200 write(4, ..., 730) = 730
+0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
0.200 write(4, ..., 730) = 730
+0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0
0.200 write(4, ..., 11680) = 11680

0.200 > P. 1:731(730) ack 1
0.200 > P. 731:1461(730) ack 1
0.200 > . 1461:8761(7300) ack 1
0.200 > P. 8761:13141(4380) ack 1

0.300 < . 1:1(0) ack 1 win 257 <sack 1461:2921,nop,nop>
0.300 < . 1:1(0) ack 1 win 257 <sack 1461:4381,nop,nop>
0.300 < . 1:1(0) ack 1 win 257 <sack 1461:5841,nop,nop>
0.300 > P. 1:1461(1460) ack 1
0.400 < . 1:1(0) ack 13141 win 257

BPF Output Before:
~~~~~
<No output due to missing SCM_TSTAMP_ACK timestamp>

BPF Output After:
~~~~~
<...>-2027  [007] d.s.    79.765921: : ee_data:1459

Sacks Collapse Test:
~~~~~
0.200 accept(3, ..., ...) = 4
+0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0

0.200 write(4, ..., 1460) = 1460
+0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
0.200 write(4, ..., 13140) = 13140
+0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0

0.200 > P. 1:1461(1460) ack 1
0.200 > . 1461:8761(7300) ack 1
0.200 > P. 8761:14601(5840) ack 1

0.300 < . 1:1(0) ack 1 win 257 <sack 1461:14601,nop,nop>
0.300 > P. 1:1461(1460) ack 1
0.400 < . 1:1(0) ack 14601 win 257

BPF Output Before:
~~~~~
<No output due to missing SCM_TSTAMP_ACK timestamp>

BPF Output After:
~~~~~
<...>-2049  [007] d.s.    89.185538: : ee_data:14599

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
---
 net/ipv4/tcp_output.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f7c3bc0..a6e4a83 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2454,6 +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;
 	}
 }
 
-- 
2.5.1

Re: [PATCH net-next 1/2] tcp: Carry txstamp_ack in tcp_fragment_tstamp

[Soheil Hassas Yeganeh]

On Wed, Apr 20, 2016 at 1:50 AM, Martin KaFai Lau <kafai@fb.com> wrote:
> When a tcp skb is sliced into two smaller skbs (e.g. in
> tcp_fragment() and tso_fragment()),  it does not carry
> the txstamp_ack bit to the newly created skb if it is needed.
> The end result is a timestamping event (SCM_TSTAMP_ACK) will
> be missing from the sk->sk_error_queue.
>
> This patch carries this bit to the new skb2
> in tcp_fragment_tstamp().
>
> BPF Output Before:
> ~~~~~~
> <No output due to missing SCM_TSTAMP_ACK timestamp>
>
> BPF Output After:
> ~~~~~~
> <...>-2050  [000] d.s.   100.928763: : ee_data:14599
>
> Packetdrill Script:
> ~~~~~~
> +0 `sysctl -q -w net.ipv4.tcp_min_tso_segs=10`
> +0 `sysctl -q -w net.ipv4.tcp_no_metrics_save=1`
> +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> +0 bind(3, ..., ...) = 0
> +0 listen(3, 1) = 0
>
> 0.100 < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 7>
> 0.100 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7>
> 0.200 < . 1:1(0) ack 1 win 257
> 0.200 accept(3, ..., ...) = 4
> +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
>
> +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
> 0.200 write(4, ..., 14600) = 14600
> +0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0
>
> 0.200 > . 1:7301(7300) ack 1
> 0.200 > P. 7301:14601(7300) ack 1
>
> 0.300 < . 1:1(0) ack 14601 win 257
>
> 0.300 close(4) = 0
> 0.300 > F. 14601:14601(0) ack 1
> 0.400 < F. 1:1(0) ack 16062 win 257
> 0.400 > . 14602:14602(0) ack 2
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> Cc: Soheil Hassas Yeganeh <soheil@google.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Tested-by: Soheil Hassas Yeganeh <soheil@google.com>
> ---
>  net/ipv4/tcp_output.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 96182a2..f7c3bc0 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/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;
>         }
>  }
>
> --
> 2.5.1
>

Re: [PATCH net-next 2/2] tcp: Merge txstamp_ack in tcp_skb_collapse_tstamp

[Soheil Hassas Yeganeh]

On Wed, Apr 20, 2016 at 1:50 AM, Martin KaFai Lau <kafai@fb.com> wrote:
> When collapsing skbs, txstamp_ack also needs to be merged.
>
> Retrans Collapse Test:
> ~~~~~~
> 0.200 accept(3, ..., ...) = 4
> +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
>
> 0.200 write(4, ..., 730) = 730
> +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
> 0.200 write(4, ..., 730) = 730
> +0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0
> 0.200 write(4, ..., 11680) = 11680
>
> 0.200 > P. 1:731(730) ack 1
> 0.200 > P. 731:1461(730) ack 1
> 0.200 > . 1461:8761(7300) ack 1
> 0.200 > P. 8761:13141(4380) ack 1
>
> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:2921,nop,nop>
> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:4381,nop,nop>
> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:5841,nop,nop>
> 0.300 > P. 1:1461(1460) ack 1
> 0.400 < . 1:1(0) ack 13141 win 257
>
> BPF Output Before:
> ~~~~~
> <No output due to missing SCM_TSTAMP_ACK timestamp>
>
> BPF Output After:
> ~~~~~
> <...>-2027  [007] d.s.    79.765921: : ee_data:1459
>
> Sacks Collapse Test:
> ~~~~~
> 0.200 accept(3, ..., ...) = 4
> +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
>
> 0.200 write(4, ..., 1460) = 1460
> +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
> 0.200 write(4, ..., 13140) = 13140
> +0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0
>
> 0.200 > P. 1:1461(1460) ack 1
> 0.200 > . 1461:8761(7300) ack 1
> 0.200 > P. 8761:14601(5840) ack 1
>
> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:14601,nop,nop>
> 0.300 > P. 1:1461(1460) ack 1
> 0.400 < . 1:1(0) ack 14601 win 257
>
> BPF Output Before:
> ~~~~~
> <No output due to missing SCM_TSTAMP_ACK timestamp>
>
> BPF Output After:
> ~~~~~
> <...>-2049  [007] d.s.    89.185538: : ee_data:14599
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> Cc: Soheil Hassas Yeganeh <soheil@google.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Tested-by: Soheil Hassas Yeganeh <soheil@google.com>
> ---
>  net/ipv4/tcp_output.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index f7c3bc0..a6e4a83 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2454,6 +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;
>         }
>  }
>
> --
> 2.5.1
>

Re: [PATCH net-next 0/2] tcp: Handle txstamp_ack when fragmenting/coalescing skbs

[David Miller]

From: Martin KaFai Lau <kafai@fb.com>
Date: Tue, 19 Apr 2016 22:50:46 -0700

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

I'll therefore apply this after I do my next merge of net into
net-next, just FYI...

Re: [PATCH net-next 1/2] tcp: Carry txstamp_ack in tcp_fragment_tstamp

[Willem de Bruijn]

On Wed, Apr 20, 2016 at 1:50 AM, Martin KaFai Lau <kafai@fb.com> wrote:
> When a tcp skb is sliced into two smaller skbs (e.g. in
> tcp_fragment() and tso_fragment()),  it does not carry
> the txstamp_ack bit to the newly created skb if it is needed.
> The end result is a timestamping event (SCM_TSTAMP_ACK) will
> be missing from the sk->sk_error_queue.
>
> This patch carries this bit to the new skb2
> in tcp_fragment_tstamp().

> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> Cc: Soheil Hassas Yeganeh <soheil@google.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>

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

Re: [PATCH net-next 0/2] tcp: Handle txstamp_ack when fragmenting/coalescing skbs

[David Miller]

From: Martin KaFai Lau <kafai@fb.com>
Date: Tue, 19 Apr 2016 22:50:46 -0700

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

Series applied, thanks.