BpfClassic.h - more helpers

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie0eb8895c2d887b71ba886735ad106c1118ebeac

staticlibs/native/bpf_headers/include/bpf/BpfClassic.h

@@ -108,3 +108,55 @@
 	  _Static_assert(field_sizeof(struct ipv6hdr, field) == 4, "field of wrong size"); \
 	  offsetof(ipv6hdr, field); \
 	}))
+
+// Load the length of the IPv4 header into X index register.
+// ie. X := 4 * IPv4.IHL, where IPv4.IHL is the bottom nibble
+// of the first byte of the IPv4 (aka network layer) header.
+#define BPF_LOADX_NET_RELATIVE_IPV4_HLEN \
+    BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, (__u32)SKF_NET_OFF)
+
+// Blindly assumes no IPv6 extension headers, just does X := 40
+// You may later adjust this as you parse through IPv6 ext hdrs.
+#define BPF_LOADX_CONSTANT_IPV6_HLEN \
+    BPF_STMT(BPF_LDX | BPF_W | BPF_IMM, sizeof(struct ipv6hdr))
+
+// NOTE: all the following require X to be setup correctly (v4: 20+, v6: 40+)
+
+// 8-bit load from L4 (TCP/UDP/...) header
+#define BPF_LOAD_NETX_RELATIVE_L4_U8(ofs) \
+    BPF_STMT(BPF_LD | BPF_B | BPF_IND, (__u32)SKF_NET_OFF + (ofs))
+
+// Big/Network Endian 16-bit load from L4 (TCP/UDP/...) header
+#define BPF_LOAD_NETX_RELATIVE_L4_BE16(ofs) \
+    BPF_STMT(BPF_LD | BPF_H | BPF_IND, (__u32)SKF_NET_OFF + (ofs))
+
+// Big/Network Endian 32-bit load from L4 (TCP/UDP/...) header
+#define BPF_LOAD_NETX_RELATIVE_L4_BE32(ofs) \
+    BPF_STMT(BPF_LD | BPF_W | BPF_IND, (__u32)SKF_NET_OFF + (ofs))
+
+// Both ICMPv4 and ICMPv6 start with u8 type, u8 code
+#define BPF_LOAD_NETX_RELATIVE_ICMP_TYPE BPF_LOAD_NETX_RELATIVE_L4_U8(0)
+#define BPF_LOAD_NETX_RELATIVE_ICMP_CODE BPF_LOAD_NETX_RELATIVE_L4_U8(1)
+
+// IPv6 extension headers (HOPOPTS, DSTOPS, FRAG) begin with a u8 nexthdr
+#define BPF_LOAD_NETX_RELATIVE_V6EXTHDR_NEXTHDR BPF_LOAD_NETX_RELATIVE_L4_U8(0)
+
+// IPv6 fragment header is always exactly 8 bytes long
+#define BPF_LOAD_CONSTANT_V6FRAGHDR_LEN \
+    BPF_STMT(BPF_LD | BPF_IMM, 8)
+
+// HOPOPTS/DSTOPS follow up with 'u8 len', counting 8 byte units, (0->8, 1->16)
+// *THREE* instructions
+#define BPF3_LOAD_NETX_RELATIVE_V6EXTHDR_LEN \
+    BPF_LOAD_NETX_RELATIVE_L4_U8(1) \
+    BPF_STMT(BPF_ALU | BPF_ADD | BPF_K, 1) \
+    BPF_STMT(BPF_ALU | BPF_LSH | BPF_K, 3)
+
+// *TWO* instructions: A += X; X := A
+#define BPF2_ADD_A_TO_X \
+    BPF_STMT(BPF_ALU | BPF_ADD | BPF_X, 0) \
+    BPF_STMT(BPF_MISC | BPF_TAX, 0)
+
+// UDP/UDPLITE/TCP/SCTP/DCCP all start with be16 srcport, dstport
+#define BPF_LOAD_NETX_RELATIVE_SRC_PORT BPF_LOAD_NETX_RELATIVE_L4_BE16(0)
+#define BPF_LOAD_NETX_RELATIVE_DST_PORT BPF_LOAD_NETX_RELATIVE_L4_BE16(2)