On 2/8/25 2:32 AM, Jason Xing wrote:
Use __bpf_kfunc feature to allow bpf prog dynamically and selectively
s/Use/Add/
Remove "dynamically". A kfunc can only be called dynamically at runtime.
Like:
"Add the bpf_sock_ops_enable_tx_tstamp kfunc to allow BPF programs to
selectively enable TX timestamping on a skb during tcp_sendmsg..."
to sample/track the skb. For example, the bpf prog will limit tracking
X numbers of packets and then will stop there instead of tracing
all the sendmsgs of matched flow all along.
> > Signed-off-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
---
kernel/bpf/btf.c | 1 +
net/core/filter.c | 27 ++++++++++++++++++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 8396ce1d0fba..a65e2eeffb88 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8535,6 +8535,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
case BPF_PROG_TYPE_CGROUP_SOCKOPT:
case BPF_PROG_TYPE_CGROUP_SYSCTL:
+ case BPF_PROG_TYPE_SOCK_OPS:
return BTF_KFUNC_HOOK_CGROUP;
case BPF_PROG_TYPE_SCHED_ACT:
return BTF_KFUNC_HOOK_SCHED_ACT;
diff --git a/net/core/filter.c b/net/core/filter.c
index 7f56d0bbeb00..db20a947e757 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -12102,6 +12102,21 @@ __bpf_kfunc int bpf_sk_assign_tcp_reqsk(struct __sk_buff *s, struct sock *sk,
#endif
}
+__bpf_kfunc int bpf_sock_ops_enable_tx_tstamp(struct bpf_sock_ops_kern *skops)
I am ok to always enable txstamp_ack here. Please still add a second "u64 flags"
argument such that future disable/enable is still possible.
+{
+ struct sk_buff *skb;
+
+ if (skops->op != BPF_SOCK_OPS_TS_SND_CB)
> + return -EOPNOTSUPP;> +
+ skb = skops->skb;
+ TCP_SKB_CB(skb)->txstamp_ack = 2;
Willem (thanks!) has already mentioned there is a bug.
This also brought up that a test is missing: the bpf timestamping and user
space's SO_TIMESTAMPING can work without interfering others. The current test
only has SK_BPF_CB_TX_TIMESTAMPING on. A test is needed when both
SK_BPF_CB_TX_TIMESTAMPING and the user space's SO_TIMESTAMPING are on. The
expectation is both of them will work together.
+ skb_shinfo(skb)->tx_flags |= SKBTX_BPF;
+ skb_shinfo(skb)->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
+
+ return 0;
+}
+
__bpf_kfunc_end_defs();
int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
@@ -12135,6 +12150,10 @@ BTF_KFUNCS_START(bpf_kfunc_check_set_tcp_reqsk)
BTF_ID_FLAGS(func, bpf_sk_assign_tcp_reqsk, KF_TRUSTED_ARGS)
BTF_KFUNCS_END(bpf_kfunc_check_set_tcp_reqsk)
+BTF_KFUNCS_START(bpf_kfunc_check_set_sock_ops)
+BTF_ID_FLAGS(func, bpf_sock_ops_enable_tx_tstamp, KF_TRUSTED_ARGS)
+BTF_KFUNCS_END(bpf_kfunc_check_set_sock_ops)
+
static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
.owner = THIS_MODULE,
.set = &bpf_kfunc_check_set_skb,
@@ -12155,6 +12174,11 @@ static const struct btf_kfunc_id_set bpf_kfunc_set_tcp_reqsk = {
.set = &bpf_kfunc_check_set_tcp_reqsk,
};
+static const struct btf_kfunc_id_set bpf_kfunc_set_sock_ops = {
+ .owner = THIS_MODULE,
+ .set = &bpf_kfunc_check_set_sock_ops,
+};
+
static int __init bpf_kfunc_init(void)
{
int ret;
@@ -12173,7 +12197,8 @@ static int __init bpf_kfunc_init(void)
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
&bpf_kfunc_set_sock_addr);
- return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_tcp_reqsk);
+ ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_tcp_reqsk);
+ return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SOCK_OPS, &bpf_kfunc_set_sock_ops);
}
late_initcall(bpf_kfunc_init);
