diff options
author | Martin KaFai Lau | 2022-03-02 11:56:28 -0800 |
---|---|---|
committer | David S. Miller | 2022-03-03 14:38:48 +0000 |
commit | 7449197d600d30d038b1ce6285ab4747096eac7f (patch) | |
tree | db9b98b78d4502e54adf2c3cbfc79536f28c1c09 /include | |
parent | cd14e9b7b8d312dfbf75ce1f78552902e51b9045 (diff) |
bpf: Keep the (rcv) timestamp behavior for the existing tc-bpf@ingress
The current tc-bpf@ingress reads and writes the __sk_buff->tstamp
as a (rcv) timestamp which currently could either be 0 (not available)
or ktime_get_real(). This patch is to backward compatible with the
(rcv) timestamp expectation at ingress. If the skb->tstamp has
the delivery_time, the bpf insn rewrite will read 0 for tc-bpf
running at ingress as it is not available. When writing at ingress,
it will also clear the skb->mono_delivery_time bit.
/* BPF_READ: a = __sk_buff->tstamp */
if (!skb->tc_at_ingress || !skb->mono_delivery_time)
a = skb->tstamp;
else
a = 0
/* BPF_WRITE: __sk_buff->tstamp = a */
if (skb->tc_at_ingress)
skb->mono_delivery_time = 0;
skb->tstamp = a;
[ A note on the BPF_CGROUP_INET_INGRESS which can also access
skb->tstamp. At that point, the skb is delivered locally
and skb_clear_delivery_time() has already been done,
so the skb->tstamp will only have the (rcv) timestamp. ]
If the tc-bpf@egress writes 0 to skb->tstamp, the skb->mono_delivery_time
has to be cleared also. It could be done together during
convert_ctx_access(). However, the latter patch will also expose
the skb->mono_delivery_time bit as __sk_buff->delivery_time_type.
Changing the delivery_time_type in the background may surprise
the user, e.g. the 2nd read on __sk_buff->delivery_time_type
may need a READ_ONCE() to avoid compiler optimization. Thus,
in expecting the needs in the latter patch, this patch does a
check on !skb->tstamp after running the tc-bpf and clears the
skb->mono_delivery_time bit if needed. The earlier discussion
on v4 [0].
The bpf insn rewrite requires the skb's mono_delivery_time bit and
tc_at_ingress bit. They are moved up in sk_buff so that bpf rewrite
can be done at a fixed offset. tc_skip_classify is moved together with
tc_at_ingress. To get one bit for mono_delivery_time, csum_not_inet is
moved down and this bit is currently used by sctp.
[0]: https://lore.kernel.org/bpf/20220217015043.khqwqklx45c4m4se@kafai-mbp.dhcp.thefacebook.com/
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/skbuff.h | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 4b5b926a81f2..5445860e1ba6 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -941,8 +941,12 @@ struct sk_buff { __u8 vlan_present:1; /* See PKT_VLAN_PRESENT_BIT */ __u8 csum_complete_sw:1; __u8 csum_level:2; - __u8 csum_not_inet:1; __u8 dst_pending_confirm:1; + __u8 mono_delivery_time:1; +#ifdef CONFIG_NET_CLS_ACT + __u8 tc_skip_classify:1; + __u8 tc_at_ingress:1; +#endif #ifdef CONFIG_IPV6_NDISC_NODETYPE __u8 ndisc_nodetype:2; #endif @@ -954,10 +958,6 @@ struct sk_buff { __u8 offload_fwd_mark:1; __u8 offload_l3_fwd_mark:1; #endif -#ifdef CONFIG_NET_CLS_ACT - __u8 tc_skip_classify:1; - __u8 tc_at_ingress:1; -#endif __u8 redirected:1; #ifdef CONFIG_NET_REDIRECT __u8 from_ingress:1; @@ -969,7 +969,7 @@ struct sk_buff { __u8 decrypted:1; #endif __u8 slow_gro:1; - __u8 mono_delivery_time:1; + __u8 csum_not_inet:1; #ifdef CONFIG_NET_SCHED __u16 tc_index; /* traffic control index */ @@ -1047,10 +1047,16 @@ struct sk_buff { /* if you move pkt_vlan_present around you also must adapt these constants */ #ifdef __BIG_ENDIAN_BITFIELD #define PKT_VLAN_PRESENT_BIT 7 +#define TC_AT_INGRESS_MASK (1 << 0) +#define SKB_MONO_DELIVERY_TIME_MASK (1 << 2) #else #define PKT_VLAN_PRESENT_BIT 0 +#define TC_AT_INGRESS_MASK (1 << 7) +#define SKB_MONO_DELIVERY_TIME_MASK (1 << 5) #endif #define PKT_VLAN_PRESENT_OFFSET offsetof(struct sk_buff, __pkt_vlan_present_offset) +#define TC_AT_INGRESS_OFFSET offsetof(struct sk_buff, __pkt_vlan_present_offset) +#define SKB_MONO_DELIVERY_TIME_OFFSET offsetof(struct sk_buff, __pkt_vlan_present_offset) #ifdef __KERNEL__ /* |