On 4/10/24 1:25 PM, Abhishek Chauhan (ABC) wrote:
@@ -830,6 +833,9 @@ enum skb_tstamp_type {
* delivery_time in mono clock base (i.e. EDT). Otherwise, the
* skb->tstamp has the (rcv) timestamp at ingress and
* delivery_time at egress.
+ * delivery_time in mono clock base (i.e., EDT) or a clock base chosen
+ * by SO_TXTIME. If zero, skb->tstamp has the (rcv) timestamp at
+ * ingress.
* @napi_id: id of the NAPI struct this skb came from
* @sender_cpu: (aka @napi_id) source CPU in XPS
* @alloc_cpu: CPU which did the skb allocation.
@@ -960,7 +966,7 @@ struct sk_buff {
/* private: */
__u8 __mono_tc_offset[0];
/* public: */
- __u8 tstamp_type:1; /* See SKB_MONO_DELIVERY_TIME_MASK */
+ __u8 tstamp_type:2; /* See SKB_MONO_DELIVERY_TIME_MASK */
#ifdef CONFIG_NET_XGRESS
__u8 tc_at_ingress:1; /* See TC_AT_INGRESS_MASK */
The above "tstamp_type:2" change shifted the tc_at_ingress bit.
TC_AT_INGRESS_MASK needs to be adjusted.
__u8 tc_skip_classify:1;
With pahole, does this have an effect on sk_buff layout?
I think it does and it also impacts BPF testing. Hence in my cover letter i have mentioned that these
changes will impact BPF. My level of expertise is very limited to BPF hence the reason for RFC.
That being said i am actually trying to understand/learn BPF instructions to know things better.
I think we need to also change the offset SKB_MONO_DELIVERY_TIME_MASK and TC_AT_INGRESS_MASK
#ifdef __BIG_ENDIAN_BITFIELD
#define SKB_MONO_DELIVERY_TIME_MASK (1 << 7) //Suspecting changes here too
#define TC_AT_INGRESS_MASK (1 << 6) // and here
#else
#define SKB_MONO_DELIVERY_TIME_MASK (1 << 0)
#define TC_AT_INGRESS_MASK (1 << 1) (this might have to change to 1<<2 )
This should be (1 << 2) now. Similar adjustment for the big endian.
#endif
#define SKB_BF_MONO_TC_OFFSET offsetof(struct sk_buff, __mono_tc_offset)
Also i suspect i change in /selftests/bpf/prog_tests/ctx_rewrite.c
ctx_rewrite.c tests the bpf ctx rewrite code. In this particular case, it tests
the bpf_convert_tstamp_read() and bpf_convert_tstamp_write() generate the
correct bpf instructions.
e.g. "w11 &= 3;" is testing the following in bpf_convert_tstamp_read():
*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK);
The existing "TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK" is 0x3
and it should become 0x5 if my hand counts correctly.
The patch set cannot be applied to the bpf-next:
https://patchwork.kernel.org/project/netdevbpf/patch/20240409210547.3815806-4-quic_abchauha@xxxxxxxxxxx/
, so bpf CI cannot run to reproduce the issue.
