On 12/7/24 9:38 AM, Jason Xing wrote:
From: Jason Xing <kernelxing@xxxxxxxxxxx>
For now, there are three phases where we are not able to fetch
the right seqno from the skops->skb_data, because:
1) in __dev_queue_xmit(), the skb->data doesn't point to the start
offset in tcp header.
2) in tcp_ack_tstamp(), the skb doesn't have the tcp header.
In the long run, we may add other trace points for bpf extension.
And the shinfo->tskey is always the same value for both bpf and
non-bpf cases. With that said, let's directly use shinfo->tskey
for TCP protocol.
Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
---
net/core/skbuff.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7c59ef501c74..2e13643f791c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5544,7 +5544,7 @@ static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb,
int tstype)
{
struct timespec64 tstamp;
- u32 args[2] = {0, 0};
+ u32 args[3] = {0, 0, 0};
int op;
if (!sk)
@@ -5569,7 +5569,10 @@ static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb,
return;
}
- bpf_skops_tx_timestamping(sk, skb, op, 2, args);
+ if (sk_is_tcp(sk))
+ args[2] = skb_shinfo(skb)->tskey;
Instead of only passing one info "skb_shinfo(skb)->tskey" of a skb, pass the
whole skb ptr to the bpf prog. Take a look at bpf_skops_init_skb. Lets start
with end_offset = 0 for now so that the bpf prog won't use it to read the
skb->data. It can be revisited later.
bpf_skops_init_skb(&sock_ops, skb, 0);
The bpf prog can use bpf_cast_to_kern_ctx() and bpf_core_cast() to get to the
skb_shinfo(skb). Take a look at the md_skb example in type_cast.c.
Then it needs to add a bpf_sock->op check to the existing
bpf_sock_ops_{load,store}_hdr_opt() helpers to ensure these helpers can only be
used by the BPF_SOCK_OPS_PARSE_HDR_OPT_CB, BPF_SOCK_OPS_HDR_OPT_LEN_CB, and
BPF_SOCK_OPS_WRITE_HDR_OPT_CB callback.
btw, how is the ack_skb used for the SCM_TSTAMP_ACK by the user space now?
