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authorMartin KaFai Lau2022-03-02 11:56:28 -0800
committerDavid S. Miller2022-03-03 14:38:48 +0000
commit7449197d600d30d038b1ce6285ab4747096eac7f (patch)
treedb9b98b78d4502e54adf2c3cbfc79536f28c1c09 /include
parentcd14e9b7b8d312dfbf75ce1f78552902e51b9045 (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.h18
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__
/*