Subject: [PATCH net-next 0/9] net-timestamp: bpf extension to equip applications transparently

From: Jason Xing <[email-masked]>
Date: Tue, 8 Oct 2024 17:51:00 +0800

From: Jason Xing <[email-masked]>

A few weeks ago, I planned to extend SO_TIMESTMAMPING feature by using
tracepoint to print information (say, tstamp) so that we can
transparently equip applications with this feature and require no
modification in user side.

Later, we discussed at netconf and agreed that we can use bpf for better
extension, which is mainly suggested by John Fastabend and Willem de
Bruijn. Many thanks here! So I post this series to see if we have a
better solution to extend. 

This approach relies on existing SO_TIMESTAMPING feature, for tx path,
users only needs to pass certain flags through bpf program to make sure
the last skb from each sendmsg() has timestamp related controlled flag.
For rx path, we have to use bpf_setsockopt() to set the sk->sk_tsflags
and wait for the moment when recvmsg() is called.

After this series, we could step by step implement more advanced
functions/flags already in SO_TIMESTAMPING feature for bpf extension.

Here is the test output:
1) receive path
iperf3-987305  [008] ...11 179955.200990: bpf_trace_printk: rx: port: 5201:55192, swtimestamp: 1728167973,670426346, hwtimestamp: 0,0
2) xmit path
iperf3-19765   [013] ...11  2021.329602: bpf_trace_printk: tx: port: 47528:5201, key: 1036, timestamp: 1728357067,436678584
iperf3-19765   [013] b..11  2021.329611: bpf_trace_printk: tx: port: 47528:5201, key: 1036, timestamp: 1728357067,436689976
iperf3-19765   [013] ...11  2021.329622: bpf_trace_printk: tx: port: 47528:5201, key: 1036, timestamp: 1728357067,436700739

Here is the full bpf program:
#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include <uapi/linux/net_tstamp.h>

int _version SEC("version") = 1;
char _license[] SEC("license") = "GPL";

# define SO_TIMESTAMPING         37

__section("sockops")
int set_initial_rto(struct bpf_sock_ops *skops)
{
	int op = (int) skops->op;
	u32 sport = 0, dport = 0;
	int rcv_flags;

	switch (op) {
	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
	case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
		rcv_flags = SOF_TIMESTAMPING_RX_SOFTWARE;
		bpf_setsockopt(skops, SOL_SOCKET, SO_TIMESTAMPING, &rcv_flags, sizeof(rcv_flags));
		bpf_sock_ops_cb_flags_set(skops, BPF_SOCK_OPS_RX_TIMESTAMPING_OPT_CB_FLAG);
		break;
	case BPF_SOCK_OPS_TX_TS_OPT_CB:
		skops->reply = SOF_TIMESTAMPING_TX_SCHED|SOF_TIMESTAMPING_TX_ACK|SOF_TIMESTAMPING_TX_SOFTWARE|
		SOF_TIMESTAMPING_OPT_ID|SOF_TIMESTAMPING_OPT_ID_TCP;
		bpf_sock_ops_cb_flags_set(skops, BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG);
		break;
	case BPF_SOCK_OPS_TS_SCHED_OPT_CB:
	case BPF_SOCK_OPS_TS_SW_OPT_CB:
	case BPF_SOCK_OPS_TS_ACK_OPT_CB:
		dport = bpf_ntohl(skops->remote_port);
		sport = skops->local_port;
		bpf_printk("tx: port: %u:%u, key: %u, timestamp: %u,%u\n",
			   sport, dport, skops->args[0], skops->args[1], skops->args[2]);
		break;
	case BPF_SOCK_OPS_TS_RX_OPT_CB:
		dport = bpf_ntohl(skops->remote_port);
		sport = skops->local_port;
		bpf_printk("rx: port: %u:%u, swtimestamp: %u,%u, hwtimestamp: %u,%u\n",
			   sport, dport, skops->args[0], skops->args[1], skops->args[2], skops->args[3]);
		break;
	}
	return 1;
}

Jason Xing (9):
  net-timestamp: add bpf infrastructure to allow exposing more
    information later
  net-timestamp: introduce TS_SCHED_OPT_CB to generate dev xmit
    timestamp
  net-timestamp: introduce TS_SW_OPT_CB to generate driver timestamp
  net-timestamp: introduce TS_ACK_OPT_CB to generate tcp acked timestamp
  net-timestamp: ready to turn on the button to generate tx timestamps
  net-timestamp: add tx OPT_ID_TCP support for bpf case
  net-timestamp: open gate for bpf_setsockopt
  net-timestamp: add bpf framework for rx timestamps
  net-timestamp: add bpf support for rx software/hardware timestamp

 include/linux/tcp.h            |  2 +-
 include/net/tcp.h              | 14 ++++++
 include/uapi/linux/bpf.h       | 36 ++++++++++++++-
 net/core/filter.c              |  3 ++
 net/core/skbuff.c              | 51 +++++++++++++++++++++
 net/ipv4/tcp.c                 | 81 ++++++++++++++++++++++++++++++++--
 tools/include/uapi/linux/bpf.h | 36 ++++++++++++++-
 7 files changed, 217 insertions(+), 6 deletions(-)

-- 
2.37.3