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net-timestamp: bpf extension to equip applications transparently #8418

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Pull request for series with
subject: net-timestamp: bpf extension to equip applications transparently
version: 7
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755

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Upstream branch: 0fc5ddd
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755
version: 7

@kernel-patches-daemon-bpf
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Upstream branch: c03320a
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755
version: 7

@kernel-patches-daemon-bpf
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Upstream branch: c03320a
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755
version: 7

@kernel-patches-daemon-bpf
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Upstream branch: 57e71f8
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755
version: 7

@JasonXing
net-timestamp: add support for bpf_setsockopt()
d79f442 
Users can write the following code to enable the bpf extension:
bpf_setsockopt(skops, SOL_SOCKET, SK_BPF_CB_FLAGS, &flags, sizeof(flags));

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: prepare for timestamping callbacks use
bacc378 
Later, I would introduce four callback points to report information
to user space based on this patch.

As to skb initialization here, people can follow these three steps
as below to fetch the shared info from the exported skb in the bpf
prog:
1. skops_kern = bpf_cast_to_kern_ctx(skops);
2. skb = skops_kern->skb;
3. shinfo = bpf_core_cast(skb->head + skb->end, struct skb_shared_info);

More details can be seen in the last selftest patch of the series.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
bpf: stop unsafely accessing TCP fields in bpf callbacks
405901c 
The "allow_tcp_access" flag is added to indicate that the callback
site has a tcp_sock locked.

Applying the new member allow_tcp_access in the existing callbacks
where is_fullsock is set to 1 can help us stop UDP socket accessing
struct tcp_sock and stop TCP socket without sk lock protecting does
the similar thing, or else it could be catastrophe leading to panic.

To keep it simple, instead of distinguishing between read and write
access, we disallow all read/write access to the tcp_sock through
the older bpf_sock_ops ctx. The new timestamping callbacks can use
newer helpers to read everything from a sk (e.g. bpf_core_cast), so
nothing is lost.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
bpf: stop calling some sock_op BPF CALLs in new timestamping callbacks
8a532b7 
Simply disallow calling bpf_sock_ops_setsockopt/getsockopt,
bpf_sock_ops_cb_flags_set, and the bpf_sock_ops_load_hdr_opt for
the new timestamping callbacks for the safety consideration.

Besides, In the next round, we will support the UDP proto for
SO_TIMESTAMPING bpf extension, so we need to ensure there is no
safety problem, which is usually caused by UDP socket trying to
access TCP fields.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: prepare for isolating two modes of SO_TIMESTAMPING
c0b8110 
No functional changes here. I add skb_enable_app_tstamp() to test
if the orig_skb matches the usage of application SO_TIMESTAMPING
and skb_sw_tstamp_tx() to distinguish the software and hardware
timestamp when tsflag is SCM_TSTAMP_SND.

Also, I deliberately distinguish the the software and hardware
SCM_TSTAMP_SND timestamp by passing 'sw' parameter in order to
avoid such a case where hardware may go wrong and pass a NULL
hwstamps, which is even though unlikely to happen. If it really
happens, bpf prog will finally consider it as a software timestamp.
It will be hardly recognized. Let's make the timestamping part
more robust.

After this patch, I will soon add checks about bpf SO_TIMESTAMPING.
In this way, we can support two modes parallelly.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: support SCM_TSTAMP_SCHED for bpf extension
81bde0c 
Introducing SKBTX_BPF is used as an indicator telling us whether
the skb should be traced by the bpf prog.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: support sw SCM_TSTAMP_SND for bpf extension
b40014c 
Support SCM_TSTAMP_SND case. Then we will get the software
timestamp when the driver is about to send the skb. Later, I
will support the hardware timestamp.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: support hw SCM_TSTAMP_SND for bpf extension
c0fc45d 
In this patch, we finish the hardware part. Then bpf program can
fetch the hwstamp from skb directly.

To avoid changing so many callers using SKBTX_HW_TSTAMP from drivers,
use this simple modification like this patch does to support printing
hardware timestamp.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: support SCM_TSTAMP_ACK for bpf extension
be71fd0 
Handle the ACK timestamp case. Actually testing SKBTX_BPF flag
can work, but we need to Introduce a new txstamp_ack_bpf to avoid
cache line misses in tcp_ack_tstamp(). To be more specific, in most
cases, normal flows would not access skb_shinfo as txstamp_ack
is zero, so that this function won't appear in the hot spot lists.
Introducing a new member txstamp_ack_bpf works similarly.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: make TCP tx timestamp bpf extension work
1558fe9 
Make partial of the feature work finally. After this, user can
fully use the bpf prog to trace the tx path for TCP type.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: add a new callback in tcp_tx_timestamp()
209a900 
Introduce the callback to correlate tcp_sendmsg timestamp with other
points, like SND/SW/ACK. We can let bpf trace the beginning of
tcp_sendmsg_locked() and fetch the socket addr, so that in
tcp_tx_timestamp() we can correlate the tskey with the socket addr.
It is accurate since they are under the protect of socket lock.
More details can be found in the selftest.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
net-timestamp: introduce cgroup lock to avoid affecting non-bpf cases
b057bc8 
Introducing the lock to avoid affecting the applications which
are not using timestamping bpf feature.

Signed-off-by: Jason Xing <[email protected]>
@JasonXing
bpf: add simple bpf tests in the tx path for so_timestamping feature
a399c5f 
Only check if we pass those three key points after we enable the
bpf extension for so_timestamping. During each point, we can choose
whether to print the current timestamp.

Signed-off-by: Jason Xing <[email protected]>
@kernel-patches-daemon-bpf
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Upstream branch: 9af5c78
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=928755
version: 7

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