sync with latest libbpf repo

sync with latest libbpf repo upto the following commit:
  libbpf/libbpf@8687395

Signed-off-by: Yonghong Song <yhs@fb.com>

docs/kernel-versions.md

@@ -267,6 +267,7 @@ Helper | Kernel version | License | Commit |
 `BPF_FUNC_tail_call()` | 4.2 |  | [`04fd61ab36ec`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=04fd61ab36ec065e194ab5e74ae34a5240d992bb)
 `BPF_FUNC_tcp_check_syncookie()` | 5.2 |  | [`399040847084`](https://kernel.googlesource.com/pub/scm/linux/kernel/git/davem/net-next/+/399040847084a69f345e0a52fd62f04654e0fce3)
 `BPF_FUNC_tcp_gen_syncookie()` | 5.3 |  | [`70d66244317e`](https://github.com/torvalds/linux/commit/70d66244317e958092e9c971b08dd5b7fd29d9cb#diff-05da4bf36c7fbcd176254e1615d98b28)
+`BPF_FUNC_tcp_send_ack()` | 5.5 | | [`206057fe020a`](https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=206057fe020ac5c037d5e2dd6562a9bd216ec765)
 `BPF_FUNC_tcp_sock()` | 5.1 |  | [`655a51e536c0`](https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=655a51e536c09d15ffa3603b1b6fce2b45b85a1f)
 `BPF_FUNC_trace_printk()` | 4.1 | GPL | [`9c959c863f82`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9c959c863f8217a2ff3d7c296e8223654d240569)
 `BPF_FUNC_xdp_adjust_head()` | 4.10 |  | [`17bedab27231`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17bedab2723145d17b14084430743549e6943d03)

introspection/bps.c

@@ -43,6 +43,7 @@ static const char * const prog_type_strings[] = {
   [BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE] = "raw_tracepoint_writable",
   [BPF_PROG_TYPE_CGROUP_SOCKOPT] = "cgroup_sockopt",
   [BPF_PROG_TYPE_TRACING] = "tracing",
+  [BPF_PROG_TYPE_STRUCT_OPS] = "struct_ops",
 };
 
 static const char * const map_type_strings[] = {
@@ -71,6 +72,7 @@ static const char * const map_type_strings[] = {
   [BPF_MAP_TYPE_STACK] = "stack",
   [BPF_MAP_TYPE_SK_STORAGE] = "sk_storage",
   [BPF_MAP_TYPE_DEVMAP_HASH] = "devmap_hash",
+  [BPF_MAP_TYPE_STRUCT_OPS] = "struct_ops",
 };
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

src/cc/compat/linux/virtual_bpf.h

@@ -137,6 +137,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_STACK,
 	BPF_MAP_TYPE_SK_STORAGE,
 	BPF_MAP_TYPE_DEVMAP_HASH,
+	BPF_MAP_TYPE_STRUCT_OPS,
 };
 
 /* Note that tracing related programs such as
@@ -175,6 +176,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
 	BPF_PROG_TYPE_CGROUP_SOCKOPT,
 	BPF_PROG_TYPE_TRACING,
+	BPF_PROG_TYPE_STRUCT_OPS,
 };
 
 enum bpf_attach_type {
@@ -232,6 +234,11 @@ enum bpf_attach_type {
  * When children program makes decision (like picking TCP CA or sock bind)
  * parent program has a chance to override it.
  *
+ * With BPF_F_ALLOW_MULTI a new program is added to the end of the list of
+ * programs for a cgroup. Though it's possible to replace an old program at
+ * any position by also specifying BPF_F_REPLACE flag and position itself in
+ * replace_bpf_fd attribute. Old program at this position will be released.
+ *
  * A cgroup with MULTI or OVERRIDE flag allows any attach flags in sub-cgroups.
  * A cgroup with NONE doesn't allow any programs in sub-cgroups.
  * Ex1:
@@ -250,6 +257,7 @@ enum bpf_attach_type {
  */
 #define BPF_F_ALLOW_OVERRIDE	(1U << 0)
 #define BPF_F_ALLOW_MULTI	(1U << 1)
+#define BPF_F_REPLACE		(1U << 2)
 
 /* If BPF_F_STRICT_ALIGNMENT is used in BPF_PROG_LOAD command, the
  * verifier will perform strict alignment checking as if the kernel
@@ -352,7 +360,12 @@ enum bpf_attach_type {
 /* Enable memory-mapping BPF map */
 #define BPF_F_MMAPABLE		(1U << 10)
 
-/* flags for BPF_PROG_QUERY */
+/* Flags for BPF_PROG_QUERY. */
+
+/* Query effective (directly attached + inherited from ancestor cgroups)
+ * programs that will be executed for events within a cgroup.
+ * attach_flags with this flag are returned only for directly attached programs.
+ */
 #define BPF_F_QUERY_EFFECTIVE	(1U << 0)
 
 enum bpf_stack_build_id_status {
@@ -392,6 +405,10 @@ union bpf_attr {
 		__u32	btf_fd;		/* fd pointing to a BTF type data */
 		__u32	btf_key_type_id;	/* BTF type_id of the key */
 		__u32	btf_value_type_id;	/* BTF type_id of the value */
+		__u32	btf_vmlinux_value_type_id;/* BTF type_id of a kernel-
+						   * struct stored as the
+						   * map value
+						   */
 	};
 
 	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
@@ -443,6 +460,10 @@ union bpf_attr {
 		__u32		attach_bpf_fd;	/* eBPF program to attach */
 		__u32		attach_type;
 		__u32		attach_flags;
+		__u32		replace_bpf_fd;	/* previously attached eBPF
+						 * program to replace if
+						 * BPF_F_REPLACE is used
+						 */
 	};
 
 	struct { /* anonymous struct used by BPF_PROG_TEST_RUN command */
@@ -2822,6 +2843,14 @@ union bpf_attr {
  * 	Return
  * 		On success, the strictly positive length of the string,	including
  * 		the trailing NUL character. On error, a negative value.
+ *
+ * int bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
+ *	Description
+ *		Send out a tcp-ack. *tp* is the in-kernel struct tcp_sock.
+ *		*rcv_nxt* is the ack_seq to be sent out.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2939,7 +2968,8 @@ union bpf_attr {
 	FN(probe_read_user),		\
 	FN(probe_read_kernel),		\
 	FN(probe_read_user_str),	\
-	FN(probe_read_kernel_str),
+	FN(probe_read_kernel_str),	\
+	FN(tcp_send_ack),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3340,7 +3370,7 @@ struct bpf_map_info {
 	__u32 map_flags;
 	char  name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u32 :32;
+	__u32 btf_vmlinux_value_type_id;
 	__u64 netns_dev;
 	__u64 netns_ino;
 	__u32 btf_id;

src/cc/libbpf.c

@@ -213,6 +213,7 @@ static struct bpf_helper helpers[] = {
   {"probe_read_kernel", "5.5"},
   {"probe_read_user_str", "5.5"},
   {"probe_read_kernel_str", "5.5"},
+  {"tcp_send_ack", "5.5"},
 };
 
 static uint64_t ptr_to_u64(void *ptr)