Commit 3b5d4ddf authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann
Browse files

bpf: net: Remove TC_AT_INGRESS_OFFSET and SKB_MONO_DELIVERY_TIME_OFFSET macro 

This patch removes the TC_AT_INGRESS_OFFSET and
SKB_MONO_DELIVERY_TIME_OFFSET macros.  Instead, PKT_VLAN_PRESENT_OFFSET
is used because all of them are at the same offset.  Comment is added to
make it clear that changing the position of tc_at_ingress or
mono_delivery_time will require to adjust the defined macros.

The earlier discussion can be found here:
https://lore.kernel.org/bpf/419d994e-ff61-7c11-0ec7-11fefcb0186e@iogearbox.net/



Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220309090450.3710955-1-kafai@fb.com
parent 743bec1b

include/linux/skbuff.h

+5 −5
Original line number Diff line number Diff line
@@ -960,10 +960,10 @@ struct sk_buff { 
	__u8			csum_complete_sw:1;

	__u8			csum_level:2;

	__u8			dst_pending_confirm:1;

	__u8			mono_delivery_time:1;

	__u8			mono_delivery_time:1;	/* See SKB_MONO_DELIVERY_TIME_MASK */

#ifdef CONFIG_NET_CLS_ACT

	__u8			tc_skip_classify:1;

	__u8			tc_at_ingress:1;

	__u8			tc_at_ingress:1;	/* See TC_AT_INGRESS_MASK */

#endif

#ifdef CONFIG_IPV6_NDISC_NODETYPE

	__u8			ndisc_nodetype:2;
@@ -1062,7 +1062,9 @@ struct sk_buff { 
#endif

#define PKT_TYPE_OFFSET		offsetof(struct sk_buff, __pkt_type_offset)



/* if you move pkt_vlan_present around you also must adapt these constants */

/* if you move pkt_vlan_present, tc_at_ingress, or mono_delivery_time

 * around, you also must adapt these constants.

 */

#ifdef __BIG_ENDIAN_BITFIELD

#define PKT_VLAN_PRESENT_BIT	7

#define TC_AT_INGRESS_MASK		(1 << 0)
@@ -1073,8 +1075,6 @@ struct sk_buff { 
#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__

/*

net/core/filter.c

+7 −7
Original line number Diff line number Diff line
@@ -8896,7 +8896,7 @@ static struct bpf_insn *bpf_convert_dtime_type_read(const struct bpf_insn *si, 
	__u8 tmp_reg = BPF_REG_AX;



	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,

			      SKB_MONO_DELIVERY_TIME_OFFSET);

			      PKT_VLAN_PRESENT_OFFSET);

	*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,

				SKB_MONO_DELIVERY_TIME_MASK);

	*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
@@ -8912,7 +8912,7 @@ static struct bpf_insn *bpf_convert_dtime_type_read(const struct bpf_insn *si, 
	*insn++ = BPF_JMP_A(IS_ENABLED(CONFIG_NET_CLS_ACT) ? 6 : 1);



#ifdef CONFIG_NET_CLS_ACT

	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);

	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);

	*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);

	*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);

	/* At ingress, value_reg = 0 */
@@ -8959,14 +8959,14 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog, 
	if (!prog->delivery_time_access) {

		__u8 tmp_reg = BPF_REG_AX;



		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);

		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);

		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);

		*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 5);

		/* @ingress, read __sk_buff->tstamp as the (rcv) timestamp,

		 * so check the skb->mono_delivery_time.

		 */

		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,

				      SKB_MONO_DELIVERY_TIME_OFFSET);

				      PKT_VLAN_PRESENT_OFFSET);

		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,

					SKB_MONO_DELIVERY_TIME_MASK);

		*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
@@ -8992,18 +8992,18 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog, 
	if (!prog->delivery_time_access) {

		__u8 tmp_reg = BPF_REG_AX;



		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);

		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);

		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);

		*insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3);

		/* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.

		 * Clear the skb->mono_delivery_time.

		 */

		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,

				      SKB_MONO_DELIVERY_TIME_OFFSET);

				      PKT_VLAN_PRESENT_OFFSET);

		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,

					~SKB_MONO_DELIVERY_TIME_MASK);

		*insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg,

				      SKB_MONO_DELIVERY_TIME_OFFSET);

				      PKT_VLAN_PRESENT_OFFSET);

	}

#endif