bpf: expose is_mptcp flag to bpf_tcp_sock

.travis.yml

@@ -0,0 +1,33 @@
+sudo: required
+language: bash
+dist: bionic
+services:
+ - docker
+
+env:
+ global:
+ - PROJECT_NAME='libbpf'
+ - AUTHOR_EMAIL="$(git log -1 --pretty=\"%aE\")"
+ - REPO_ROOT="$TRAVIS_BUILD_DIR"
+ - CI_ROOT="$REPO_ROOT/travis-ci"
+ - VMTEST_ROOT="$CI_ROOT/vmtest"
+
+addons:
+ apt:
+ packages:
+ - qemu-kvm
+ - zstd
+ - binutils-dev
+ - elfutils
+ - libcap-dev
+ - libelf-dev
+ - libdw-dev
+ - python3-docutils
+
+jobs:
+ include:
+ - stage: Builds & Tests
+ name: Kernel LATEST + selftests
+ language: bash
+ env: KERNEL=LATEST
+ script: $CI_ROOT/vmtest/run_vmtest.sh || travis_terminate 1

include/linux/bpf.h

@@ -305,6 +305,7 @@ enum bpf_return_type {
 RET_PTR_TO_SOCK_COMMON_OR_NULL,	/* returns a pointer to a sock_common or NULL */
 RET_PTR_TO_ALLOC_MEM_OR_NULL,	/* returns a pointer to dynamically allocated memory or NULL */
 RET_PTR_TO_BTF_ID_OR_NULL,	/* returns a pointer to a btf_id or NULL */
+RET_PTR_TO_MPTCP_SOCK_OR_NULL,	/* returns a pointer to mptcp_sock or NULL */
 };
 
 /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
@@ -385,6 +386,8 @@ enum bpf_reg_type {
 PTR_TO_RDONLY_BUF_OR_NULL, /* reg points to a readonly buffer or NULL */
 PTR_TO_RDWR_BUF, /* reg points to a read/write buffer */
 PTR_TO_RDWR_BUF_OR_NULL, /* reg points to a read/write buffer or NULL */
+PTR_TO_MPTCP_SOCK, /* reg points to struct mptcp_sock */
+PTR_TO_MPTCP_SOCK_OR_NULL, /* reg points to struct mptcp_sock or NULL */
 };
 
 /* The information passed from prog-specific *_is_valid_access
@@ -1785,6 +1788,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
 extern const struct bpf_func_proto bpf_copy_from_user_proto;
+extern const struct bpf_func_proto bpf_mptcp_sock_proto;
 
 const struct bpf_func_proto *bpf_tracing_func_proto(
 enum bpf_func_id func_id, const struct bpf_prog *prog);
@@ -1841,6 +1845,35 @@ struct sk_reuseport_kern {
 u32 reuseport_id;
 bool bind_inany;
 };
+
+#ifdef CONFIG_MPTCP
+bool bpf_mptcp_sock_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ struct bpf_insn_access_aux *info);
+
+u32 bpf_mptcp_sock_convert_ctx_access(enum bpf_access_type type,
+ const struct bpf_insn *si,
+ struct bpf_insn *insn_buf,
+ struct bpf_prog *prog,
+ u32 *target_size);
+#else /* CONFIG_MPTCP */
+static inline bool bpf_mptcp_sock_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ struct bpf_insn_access_aux *info)
+{
+return false;
+}
+
+static inline u32 bpf_mptcp_sock_convert_ctx_access(enum bpf_access_type type,
+ const struct bpf_insn *si,
+ struct bpf_insn *insn_buf,
+ struct bpf_prog *prog,
+ u32 *target_size)
+{
+return 0;
+}
+#endif /* CONFIG_MPTCP */
+
 bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
  struct bpf_insn_access_aux *info);
 

include/uapi/linux/bpf.h

@@ -3579,6 +3579,15 @@ union bpf_attr {
  *	the data in *dst*. This is a wrapper of **copy_from_user**\ ().
  *	Return
  *	0 on success, or a negative error in case of failure.
+ *
+ * struct bpf_mptcp_sock *bpf_mptcp_sock(struct bpf_sock *sk)
+ *	Description
+ *	This helper gets a **struct bpf_mptcp_sock** pointer from a
+ *	**struct bpf_sock** pointer.
+ *	Return
+ *	A **struct bpf_mptcp_sock** pointer on success, or **NULL** in
+ *	case of failure.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)	\
 FN(unspec),	\
@@ -3730,6 +3739,7 @@ union bpf_attr {
 FN(inode_storage_delete),	\
 FN(d_path),	\
 FN(copy_from_user),	\
+FN(mptcp_sock),	\
 /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4060,6 +4070,11 @@ struct bpf_tcp_sock {
 __u32 delivered;	/* Total data packets delivered incl. rexmits */
 __u32 delivered_ce;	/* Like the above but only ECE marked packets */
 __u32 icsk_retransmits;	/* Number of unrecovered [RTO] timeouts */
+__u32 is_mptcp;	/* Is MPTCP subflow? */
+};
+
+struct bpf_mptcp_sock {
+__u32 token;	/* msk token */
 };
 
 struct bpf_sock_tuple {

kernel/bpf/verifier.c

@@ -392,13 +392,15 @@ static bool type_is_sk_pointer(enum bpf_reg_type type)
 return type == PTR_TO_SOCKET ||
 type == PTR_TO_SOCK_COMMON ||
 type == PTR_TO_TCP_SOCK ||
+type == PTR_TO_MPTCP_SOCK ||
 type == PTR_TO_XDP_SOCK;
 }
 
 static bool reg_type_not_null(enum bpf_reg_type type)
 {
 return type == PTR_TO_SOCKET ||
 type == PTR_TO_TCP_SOCK ||
+type == PTR_TO_MPTCP_SOCK ||
 type == PTR_TO_MAP_VALUE ||
 type == PTR_TO_SOCK_COMMON;
 }
@@ -409,6 +411,7 @@ static bool reg_type_may_be_null(enum bpf_reg_type type)
  type == PTR_TO_SOCKET_OR_NULL ||
  type == PTR_TO_SOCK_COMMON_OR_NULL ||
  type == PTR_TO_TCP_SOCK_OR_NULL ||
+ type == PTR_TO_MPTCP_SOCK_OR_NULL ||
  type == PTR_TO_BTF_ID_OR_NULL ||
  type == PTR_TO_MEM_OR_NULL ||
  type == PTR_TO_RDONLY_BUF_OR_NULL ||
@@ -427,6 +430,8 @@ static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
 type == PTR_TO_SOCKET_OR_NULL ||
 type == PTR_TO_TCP_SOCK ||
 type == PTR_TO_TCP_SOCK_OR_NULL ||
+type == PTR_TO_MPTCP_SOCK ||
+type == PTR_TO_MPTCP_SOCK_OR_NULL ||
 type == PTR_TO_MEM ||
 type == PTR_TO_MEM_OR_NULL;
 }
@@ -500,6 +505,8 @@ static const char * const reg_type_str[] = {
 [PTR_TO_SOCK_COMMON_OR_NULL] = "sock_common_or_null",
 [PTR_TO_TCP_SOCK]	= "tcp_sock",
 [PTR_TO_TCP_SOCK_OR_NULL] = "tcp_sock_or_null",
+[PTR_TO_MPTCP_SOCK]	= "mptcp_sock",
+[PTR_TO_MPTCP_SOCK_OR_NULL] = "mptcp_sock_or_null",
 [PTR_TO_TP_BUFFER]	= "tp_buffer",
 [PTR_TO_XDP_SOCK]	= "xdp_sock",
 [PTR_TO_BTF_ID]	= "ptr_",
@@ -2177,6 +2184,8 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
 case PTR_TO_SOCK_COMMON_OR_NULL:
 case PTR_TO_TCP_SOCK:
 case PTR_TO_TCP_SOCK_OR_NULL:
+case PTR_TO_MPTCP_SOCK:
+case PTR_TO_MPTCP_SOCK_OR_NULL:
 case PTR_TO_XDP_SOCK:
 case PTR_TO_BTF_ID:
 case PTR_TO_BTF_ID_OR_NULL:
@@ -2786,6 +2795,9 @@ static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
 case PTR_TO_TCP_SOCK:
 valid = bpf_tcp_sock_is_valid_access(off, size, t, &info);
 break;
+case PTR_TO_MPTCP_SOCK:
+valid = bpf_mptcp_sock_is_valid_access(off, size, t, &info);
+break;
 case PTR_TO_XDP_SOCK:
 valid = bpf_xdp_sock_is_valid_access(off, size, t, &info);
 break;
@@ -2944,6 +2956,9 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
 case PTR_TO_TCP_SOCK:
 pointer_desc = "tcp_sock ";
 break;
+case PTR_TO_MPTCP_SOCK:
+pointer_desc = "mptcp_sock ";
+break;
 case PTR_TO_XDP_SOCK:
 pointer_desc = "xdp_sock ";
 break;
@@ -4997,6 +5012,10 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 mark_reg_known_zero(env, regs, BPF_REG_0);
 regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
 regs[BPF_REG_0].id = ++env->id_gen;
+} else if (fn->ret_type == RET_PTR_TO_MPTCP_SOCK_OR_NULL) {
+mark_reg_known_zero(env, regs, BPF_REG_0);
+regs[BPF_REG_0].type = PTR_TO_MPTCP_SOCK_OR_NULL;
+regs[BPF_REG_0].id = ++env->id_gen;
 } else if (fn->ret_type == RET_PTR_TO_ALLOC_MEM_OR_NULL) {
 mark_reg_known_zero(env, regs, BPF_REG_0);
 regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
@@ -5328,6 +5347,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 case PTR_TO_SOCK_COMMON_OR_NULL:
 case PTR_TO_TCP_SOCK:
 case PTR_TO_TCP_SOCK_OR_NULL:
+case PTR_TO_MPTCP_SOCK:
+case PTR_TO_MPTCP_SOCK_OR_NULL:
 case PTR_TO_XDP_SOCK:
 verbose(env, "R%d pointer arithmetic on %s prohibited\n",
 dst, reg_type_str[ptr_reg->type]);
@@ -7048,6 +7069,8 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
 reg->type = PTR_TO_SOCK_COMMON;
 } else if (reg->type == PTR_TO_TCP_SOCK_OR_NULL) {
 reg->type = PTR_TO_TCP_SOCK;
+} else if (reg->type == PTR_TO_MPTCP_SOCK_OR_NULL) {
+reg->type = PTR_TO_MPTCP_SOCK;
 } else if (reg->type == PTR_TO_BTF_ID_OR_NULL) {
 reg->type = PTR_TO_BTF_ID;
 } else if (reg->type == PTR_TO_MEM_OR_NULL) {
@@ -8411,6 +8434,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
 case PTR_TO_SOCK_COMMON_OR_NULL:
 case PTR_TO_TCP_SOCK:
 case PTR_TO_TCP_SOCK_OR_NULL:
+case PTR_TO_MPTCP_SOCK:
+case PTR_TO_MPTCP_SOCK_OR_NULL:
 case PTR_TO_XDP_SOCK:
 /* Only valid matches are exact, which memcmp() above
  * would have accepted
@@ -8938,6 +8963,8 @@ static bool reg_type_mismatch_ok(enum bpf_reg_type type)
 case PTR_TO_SOCK_COMMON_OR_NULL:
 case PTR_TO_TCP_SOCK:
 case PTR_TO_TCP_SOCK_OR_NULL:
+case PTR_TO_MPTCP_SOCK:
+case PTR_TO_MPTCP_SOCK_OR_NULL:
 case PTR_TO_XDP_SOCK:
 case PTR_TO_BTF_ID:
 case PTR_TO_BTF_ID_OR_NULL:
@@ -10076,6 +10103,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 case PTR_TO_TCP_SOCK:
 convert_ctx_access = bpf_tcp_sock_convert_ctx_access;
 break;
+case PTR_TO_MPTCP_SOCK:
+convert_ctx_access = bpf_mptcp_sock_convert_ctx_access;
+break;
 case PTR_TO_XDP_SOCK:
 convert_ctx_access = bpf_xdp_sock_convert_ctx_access;
 break;

net/core/filter.c

@@ -5837,7 +5837,7 @@ bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
  struct bpf_insn_access_aux *info)
 {
 if (off < 0 || off >= offsetofend(struct bpf_tcp_sock,
- icsk_retransmits))
+ is_mptcp))
 return false;
 
 if (off % size != 0)
@@ -5971,6 +5971,13 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
 case offsetof(struct bpf_tcp_sock, icsk_retransmits):
 BPF_INET_SOCK_GET_COMMON(icsk_retransmits);
 break;
+case offsetof(struct bpf_tcp_sock, is_mptcp):
+#ifdef CONFIG_MPTCP
+BPF_TCP_SOCK_GET_COMMON(is_mptcp);
+#else
+*insn++ = BPF_MOV32_IMM(si->dst_reg, 0);
+#endif
+break;
 }
 
 return insn - insn_buf;
@@ -6883,6 +6890,10 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 case BPF_FUNC_tcp_sock:
 return &bpf_tcp_sock_proto;
 #endif /* CONFIG_INET */
+#ifdef CONFIG_MPTCP
+case BPF_FUNC_mptcp_sock:
+return &bpf_mptcp_sock_proto;
+#endif /* CONFIG_MPTCP */
 default:
 return bpf_base_func_proto(func_id);
 }

net/mptcp/Makefile

@@ -10,3 +10,5 @@ obj-$(CONFIG_INET_MPTCP_DIAG) += mptcp_diag.o
 mptcp_crypto_test-objs := crypto_test.o
 mptcp_token_test-objs := token_test.o
 obj-$(CONFIG_MPTCP_KUNIT_TESTS) += mptcp_crypto_test.o mptcp_token_test.o
+
+obj-$(CONFIG_BPF) += bpf.o

net/mptcp/bpf.c

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2020, Tessares SA.
+ *
+ * Author: Nicolas Rybowski <nicolas.rybowski@tessares.net>
+ *
+ */
+
+#include <linux/bpf.h>
+
+#include "protocol.h"
+
+bool bpf_mptcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
+ struct bpf_insn_access_aux *info)
+{
+if (off < 0 || off >= offsetofend(struct bpf_mptcp_sock, token))
+return false;
+
+if (off % size != 0)
+return false;
+
+switch (off) {
+default:
+return size == sizeof(__u32);
+}
+}
+
+u32 bpf_mptcp_sock_convert_ctx_access(enum bpf_access_type type,
+ const struct bpf_insn *si,
+ struct bpf_insn *insn_buf,
+ struct bpf_prog *prog, u32 *target_size)
+{
+struct bpf_insn *insn = insn_buf;
+
+#define BPF_MPTCP_SOCK_GET_COMMON(FIELD)	\
+do {	\
+BUILD_BUG_ON(sizeof_field(struct mptcp_sock, FIELD) >	\
+sizeof_field(struct bpf_mptcp_sock, FIELD));	\
+*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct mptcp_sock, FIELD),	\
+si->dst_reg, si->src_reg,	\
+offsetof(struct mptcp_sock, FIELD));	\
+} while (0)
+
+if (insn > insn_buf)
+return insn - insn_buf;
+
+switch (si->off) {
+case offsetof(struct bpf_mptcp_sock, token):
+BPF_MPTCP_SOCK_GET_COMMON(token);
+break;
+}
+
+return insn - insn_buf;
+}
+
+BPF_CALL_1(bpf_mptcp_sock, struct sock *, sk)
+{
+if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk)) {
+struct mptcp_subflow_context *mptcp_sfc = mptcp_subflow_ctx(sk);
+
+return (unsigned long)mptcp_sfc->conn;
+}
+return (unsigned long)NULL;
+}
+
+const struct bpf_func_proto bpf_mptcp_sock_proto = {
+.func = bpf_mptcp_sock,
+.gpl_only = false,
+.ret_type = RET_PTR_TO_MPTCP_SOCK_OR_NULL,
+.arg1_type = ARG_PTR_TO_SOCK_COMMON,
+};