bpf: Support narrow loads from bpf_sock_addr.user_port

bpf_sock_addr.user_port supports only 4-byte load and it leads to ugly code in BPF programs, like: volatile __u32 user_port = ctx->user_port; __u16 port = bpf_ntohs(user_port); Since otherwise clang may optimize the load to be 2-byte and it's rejected by verifier. Add support for 1- and 2-byte loads same way as it's supported for other fields in bpf_sock_addr like user_ip4, msg_src_ip4, etc.

Andrey Ignatov committed 6 years ago

Commit 7aebfa11 parent 6a098153 files · +9 −10Browse files

Unified · Split

3 files

include/uapi/linux/bpf.h +1 −1
net/core/filter.c +7 −8
tools/include/uapi/linux/bpf.h +1 −1

include/uapi/linux/bpf.h+1−1

@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { · 3727 unmodified lines
3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.	3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.
3729	* Stored in network byte order.	3729	* Stored in network byte order.
3730	*/	3730	*/
3731	__u32 user_port; /* Allows 4-byte read and write.	3731	__u32 user_port; /* Allows 1,2,4-byte read and 4-byte write.
3732	* Stored in network byte order	3732	* Stored in network byte order
3733	*/	3733	*/
3734	__u32 family; /* Allows 4-byte read, but no write */	3734	__u32 family; /* Allows 4-byte read, but no write */

net/core/filter.c+7−8

 	case bpf_ctx_range(struct bpf_sock_addr, msg_src_ip4):
 	case bpf_ctx_range_till(struct bpf_sock_addr, msg_src_ip6[0],
 				msg_src_ip6[3]):
+	case bpf_ctx_range(struct bpf_sock_addr, user_port):
 		if (type == BPF_READ) {
 			bpf_ctx_record_field_size(info, size_default);
 				return false;
 		}
 		break;
-	case bpf_ctx_range(struct bpf_sock_addr, user_port):
-		if (size != size_default)
-			return false;
-		break;
 	case offsetof(struct bpf_sock_addr, sk):
 		if (type != BPF_READ)
 			return false;
 					struct bpf_insn *insn_buf,
 					struct bpf_prog *prog, u32 *target_size)
 {
+	int off, port_size = sizeof_field(struct sockaddr_in6, sin6_port);
 	struct bpf_insn *insn = insn_buf;
-	int off;
 	switch (si->off) {
 	case offsetof(struct bpf_sock_addr, user_family):
 			     offsetof(struct sockaddr_in6, sin6_port));
 		BUILD_BUG_ON(sizeof_field(struct sockaddr_in, sin_port) !=
 			     sizeof_field(struct sockaddr_in6, sin6_port));
-		SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD(struct bpf_sock_addr_kern,
+		/* Account for sin6_port being smaller than user_port. */
-						     struct sockaddr_in6, uaddr,
+		port_size = min(port_size, BPF_LDST_BYTES(si));
-						     sin6_port, tmp_reg);
+		SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD_SIZE_OFF(
+			struct bpf_sock_addr_kern, struct sockaddr_in6, uaddr,
+			sin6_port, bytes_to_bpf_size(port_size), 0, tmp_reg);
 		break;
 	case offsetof(struct bpf_sock_addr, family):

tools/include/uapi/linux/bpf.h+1−1

@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { · 3727 unmodified lines
3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.	3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.
3729	* Stored in network byte order.	3729	* Stored in network byte order.
3730	*/	3730	*/
3731	__u32 user_port; /* Allows 4-byte read and write.	3731	__u32 user_port; /* Allows 1,2,4-byte read and 4-byte write.
3732	* Stored in network byte order	3732	* Stored in network byte order
3733	*/	3733	*/
3734	__u32 family; /* Allows 4-byte read, but no write */	3734	__u32 family; /* Allows 4-byte read, but no write */

bpf: Support narrow loads from bpf_sock_addr.user_port

Keyboard shortcuts

General

Issues and pull requests

Issues, pull requests and Inbox

Repository code