Merge branch 'net: skbuff: skb bitfield compaction - bpf'

Jakub Kicinski says:

====================

I'm trying to make more of the sk_buff bits optional.
Move the BPF-accessed bits a little - because they must
be at coding-time-constant offsets they must precede any
optional bit. While at it clean up the naming a bit.

v1: https://lore.kernel.org/all/20230308003159.441580-1-kuba@kernel.org/
====================
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

include/linux/skbuff.h

@@ -944,6 +944,19 @@ struct sk_buff {
 	__u8			ip_summed:2;
 	__u8			ooo_okay:1;
 
+	/* private: */
+	__u8			__mono_tc_offset[0];
+	/* public: */
+	__u8			mono_delivery_time:1;	/* See SKB_MONO_DELIVERY_TIME_MASK */
+#ifdef CONFIG_NET_CLS_ACT
+	__u8			tc_at_ingress:1;	/* See TC_AT_INGRESS_MASK */
+	__u8			tc_skip_classify:1;
+#endif
+	__u8			remcsum_offload:1;
+	__u8			csum_complete_sw:1;
+	__u8			csum_level:2;
+	__u8			dst_pending_confirm:1;
+
 	__u8			l4_hash:1;
 	__u8			sw_hash:1;
 	__u8			wifi_acked_valid:1;
@@ -953,19 +966,6 @@ struct sk_buff {
 	__u8			encapsulation:1;
 	__u8			encap_hdr_csum:1;
 	__u8			csum_valid:1;
-
-	/* private: */
-	__u8			__pkt_vlan_present_offset[0];
-	/* public: */
-	__u8			remcsum_offload:1;
-	__u8			csum_complete_sw:1;
-	__u8			csum_level:2;
-	__u8			dst_pending_confirm: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;	/* See TC_AT_INGRESS_MASK */
-#endif
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
 	__u8			ndisc_nodetype:2;
 #endif
@@ -1072,13 +1072,13 @@ struct sk_buff {
  * around, you also must adapt these constants.
  */
 #ifdef __BIG_ENDIAN_BITFIELD
-#define TC_AT_INGRESS_MASK		(1 << 0)
-#define SKB_MONO_DELIVERY_TIME_MASK	(1 << 2)
+#define SKB_MONO_DELIVERY_TIME_MASK	(1 << 7)
+#define TC_AT_INGRESS_MASK		(1 << 6)
 #else
-#define TC_AT_INGRESS_MASK		(1 << 7)
-#define SKB_MONO_DELIVERY_TIME_MASK	(1 << 5)
+#define SKB_MONO_DELIVERY_TIME_MASK	(1 << 0)
+#define TC_AT_INGRESS_MASK		(1 << 1)
 #endif
-#define PKT_VLAN_PRESENT_OFFSET	offsetof(struct sk_buff, __pkt_vlan_present_offset)
+#define SKB_BF_MONO_TC_OFFSET		offsetof(struct sk_buff, __mono_tc_offset)
 
 #ifdef __KERNEL__
 /*

net/core/filter.c

@@ -9185,7 +9185,7 @@ static struct bpf_insn *bpf_convert_tstamp_type_read(const struct bpf_insn *si,
 	__u8 tmp_reg = BPF_REG_AX;
 
 	*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
-			      PKT_VLAN_PRESENT_OFFSET);
+			      SKB_BF_MONO_TC_OFFSET);
 	*insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg,
 				SKB_MONO_DELIVERY_TIME_MASK, 2);
 	*insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_UNSPEC);
@@ -9232,7 +9232,7 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog,
 		/* AX is needed because src_reg and dst_reg could be the same */
 		__u8 tmp_reg = BPF_REG_AX;
 
-		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);
+		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, SKB_BF_MONO_TC_OFFSET);
 		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
 					TC_AT_INGRESS_MASK | SKB_MONO_DELIVERY_TIME_MASK);
 		*insn++ = BPF_JMP32_IMM(BPF_JNE, tmp_reg,
@@ -9267,14 +9267,14 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
 	if (!prog->tstamp_type_access) {
 		__u8 tmp_reg = BPF_REG_AX;
 
-		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET);
+		*insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, SKB_BF_MONO_TC_OFFSET);
 		/* Writing __sk_buff->tstamp as ingress, goto <clear> */
 		*insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg, TC_AT_INGRESS_MASK, 1);
 		/* goto <store> */
 		*insn++ = BPF_JMP_A(2);
 		/* <clear>: mono_delivery_time */
 		*insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, ~SKB_MONO_DELIVERY_TIME_MASK);
-		*insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, PKT_VLAN_PRESENT_OFFSET);
+		*insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, SKB_BF_MONO_TC_OFFSET);
 	}
 #endif
 

tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c

@@ -68,17 +68,17 @@ static struct test_case test_cases[] = {
 #if defined(__x86_64__) || defined(__aarch64__)
 	{
 		N(SCHED_CLS, struct __sk_buff, tstamp),
-		.read  = "r11 = *(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset);"
-			 "w11 &= 160;"
-			 "if w11 != 0xa0 goto pc+2;"
+		.read  = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
+			 "w11 &= 3;"
+			 "if w11 != 0x3 goto pc+2;"
 			 "$dst = 0;"
 			 "goto pc+1;"
 			 "$dst = *(u64 *)($ctx + sk_buff::tstamp);",
-		.write = "r11 = *(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset);"
-			 "if w11 & 0x80 goto pc+1;"
+		.write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
+			 "if w11 & 0x2 goto pc+1;"
 			 "goto pc+2;"
-			 "w11 &= -33;"
-			 "*(u8 *)($ctx + sk_buff::__pkt_vlan_present_offset) = r11;"
+			 "w11 &= -2;"
+			 "*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
 			 "*(u64 *)($ctx + sk_buff::tstamp) = $src;",
 	},
 #endif