tools: ynl: user space helpers

Add "fixed" part of the user space Netlink Spec-based library.
This will get linked with the protocol implementations to form
a full API.
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/userspace-api/netlink/intro-specs.rst

@@ -78,3 +78,82 @@ to see other examples.
 The code generation itself is performed by ``tools/net/ynl/ynl-gen-c.py``
 but it takes a few arguments so calling it directly for each file
 quickly becomes tedious.
+
+YNL lib
+=======
+
+``tools/net/ynl/lib/`` contains an implementation of a C library
+(based on libmnl) which integrates with code generated by
+``tools/net/ynl/ynl-gen-c.py`` to create easy to use netlink wrappers.
+
+YNL basics
+----------
+
+The YNL library consists of two parts - the generic code (functions
+prefix by ``ynl_``) and per-family auto-generated code (prefixed
+with the name of the family).
+
+To create a YNL socket call ynl_sock_create() passing the family
+struct (family structs are exported by the auto-generated code).
+ynl_sock_destroy() closes the socket.
+
+YNL requests
+------------
+
+Steps for issuing YNL requests are best explained on an example.
+All the functions and types in this example come from the auto-generated
+code (for the netdev family in this case):
+
+.. code-block:: c
+
+   // 0. Request and response pointers
+   struct netdev_dev_get_req *req;
+   struct netdev_dev_get_rsp *d;
+
+   // 1. Allocate a request
+   req = netdev_dev_get_req_alloc();
+   // 2. Set request parameters (as needed)
+   netdev_dev_get_req_set_ifindex(req, ifindex);
+
+   // 3. Issues the request
+   d = netdev_dev_get(ys, req);
+   // 4. Free the request arguments
+   netdev_dev_get_req_free(req);
+   // 5. Error check (the return value from step 3)
+   if (!d) {
+	// 6. Print the YNL-generated error
+	fprintf(stderr, "YNL: %s\n", ys->err.msg);
+        return -1;
+   }
+
+   // ... do stuff with the response @d
+
+   // 7. Free response
+   netdev_dev_get_rsp_free(d);
+
+YNL dumps
+---------
+
+Performing dumps follows similar pattern as requests.
+Dumps return a list of objects terminated by a special marker,
+or NULL on error. Use ``ynl_dump_foreach()`` to iterate over
+the result.
+
+YNL notifications
+-----------------
+
+YNL lib supports using the same socket for notifications and
+requests. In case notifications arrive during processing of a request
+they are queued internally and can be retrieved at a later time.
+
+To subscribed to notifications use ``ynl_subscribe()``.
+The notifications have to be read out from the socket,
+``ynl_socket_get_fd()`` returns the underlying socket fd which can
+be plugged into appropriate asynchronous IO API like ``poll``,
+or ``select``.
+
+Notifications can be retrieved using ``ynl_ntf_dequeue()`` and have
+to be freed using ``ynl_ntf_free()``. Since we don't know the notification
+type upfront the notifications are returned as ``struct ynl_ntf_base_type *``
+and user is expected to cast them to the appropriate full type based
+on the ``cmd`` member.

tools/net/ynl/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+SUBDIRS = lib generated samples
+
+all: $(SUBDIRS)
+
+$(SUBDIRS):
+	@if [ -f "$@/Makefile" ] ; then \
+		$(MAKE) -C $@ ; \
+	fi
+
+clean hardclean:
+	@for dir in $(SUBDIRS) ; do \
+		if [ -f "$$dir/Makefile" ] ; then \
+			$(MAKE) -C $$dir $@; \
+		fi \
+	done
+
+.PHONY: clean all $(SUBDIRS)

tools/net/ynl/generated/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+CC=gcc
+CFLAGS=-std=gnu11 -O2 -W -Wall -Wextra -Wno-unused-parameter -Wshadow \
+	-I../lib/
+ifeq ("$(DEBUG)","1")
+  CFLAGS += -g -fsanitize=address -fsanitize=leak -static-libasan
+endif
+
+TOOL:=../ynl-gen-c.py
+
+GENS:=
+SRCS=$(patsubst %,%-user.c,${GENS})
+HDRS=$(patsubst %,%-user.h,${GENS})
+OBJS=$(patsubst %,%-user.o,${GENS})
+
+all: protos.a $(HDRS) $(SRCS) $(KHDRS) $(KSRCS) $(UAPI) regen
+
+protos.a: $(OBJS)
+	@echo -e "\tAR $@"
+	@ar rcs $@ $(OBJS)
+
+%-user.h: ../../../../Documentation/netlink/specs/%.yaml $(TOOL)
+	@echo -e "\tGEN $@"
+	@$(TOOL) --mode user --header --spec $< > $@
+
+%-user.c: ../../../../Documentation/netlink/specs/%.yaml $(TOOL)
+	@echo -e "\tGEN $@"
+	@$(TOOL) --mode user --source --spec $< > $@
+
+%-user.o: %-user.c %-user.h
+	@echo -e "\tCC $@"
+	@$(COMPILE.c) -c -o $@ $<
+
+clean:
+	rm -f *.o
+
+hardclean: clean
+	rm -f *.c *.h *.a
+
+regen:
+	@../ynl-regen.sh
+
+.PHONY: all clean hardclean regen
+.DEFAULT_GOAL: all

tools/net/ynl/lib/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+CC=gcc
+CFLAGS=-std=gnu11 -O2 -W -Wall -Wextra -Wno-unused-parameter -Wshadow
+ifeq ("$(DEBUG)","1")
+  CFLAGS += -g -fsanitize=address -fsanitize=leak -static-libasan
+endif
+
+SRCS=$(wildcard *.c)
+OBJS=$(patsubst %.c,%.o,${SRCS})
+
+include $(wildcard *.d)
+
+all: ynl.a
+
+ynl.a: $(OBJS)
+	ar rcs $@ $(OBJS)
+clean:
+	rm -f *.o *.d *~
+
+hardclean: clean
+	rm -f *.a
+
+%.o: %.c
+	$(COMPILE.c) -MMD -c -o $@ $<
+
+.PHONY: all clean
+.DEFAULT_GOAL=all

tools/net/ynl/lib/ynl.c

+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+#include <errno.h>
+#include <poll.h>
+#include <string.h>
+#include <stdlib.h>
+#include <linux/types.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/genetlink.h>
+
+#include "ynl.h"
+
+#define ARRAY_SIZE(arr)		(sizeof(arr) / sizeof(*arr))
+
+#define __yerr_msg(yse, _msg...)					\
+	({								\
+		struct ynl_error *_yse = (yse);				\
+									\
+		if (_yse) {						\
+			snprintf(_yse->msg, sizeof(_yse->msg) - 1,  _msg); \
+			_yse->msg[sizeof(_yse->msg) - 1] = 0;		\
+		}							\
+	})
+
+#define __yerr_code(yse, _code...)		\
+	({					\
+		struct ynl_error *_yse = (yse);	\
+						\
+		if (_yse) {			\
+			_yse->code = _code;	\
+		}				\
+	})
+
+#define __yerr(yse, _code, _msg...)		\
+	({					\
+		__yerr_msg(yse, _msg);		\
+		__yerr_code(yse, _code);	\
+	})
+
+#define __perr(yse, _msg)		__yerr(yse, errno, _msg)
+
+#define yerr_msg(_ys, _msg...)		__yerr_msg(&(_ys)->err, _msg)
+#define yerr(_ys, _code, _msg...)	__yerr(&(_ys)->err, _code, _msg)
+#define perr(_ys, _msg)			__yerr(&(_ys)->err, errno, _msg)
+
+/* -- Netlink boiler plate */
+static int
+ynl_err_walk_report_one(struct ynl_policy_nest *policy, unsigned int type,
+			char *str, int str_sz, int *n)
+{
+	if (!policy) {
+		if (*n < str_sz)
+			*n += snprintf(str, str_sz, "!policy");
+		return 1;
+	}
+
+	if (type > policy->max_attr) {
+		if (*n < str_sz)
+			*n += snprintf(str, str_sz, "!oob");
+		return 1;
+	}
+
+	if (!policy->table[type].name) {
+		if (*n < str_sz)
+			*n += snprintf(str, str_sz, "!name");
+		return 1;
+	}
+
+	if (*n < str_sz)
+		*n += snprintf(str, str_sz - *n,
+			       ".%s", policy->table[type].name);
+	return 0;
+}
+
+static int
+ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
+	     struct ynl_policy_nest *policy, char *str, int str_sz,
+	     struct ynl_policy_nest **nest_pol)
+{
+	unsigned int astart_off, aend_off;
+	const struct nlattr *attr;
+	unsigned int data_len;
+	unsigned int type;
+	bool found = false;
+	int n = 0;
+
+	if (!policy) {
+		if (n < str_sz)
+			n += snprintf(str, str_sz, "!policy");
+		return n;
+	}
+
+	data_len = end - start;
+
+	mnl_attr_for_each_payload(start, data_len) {
+		astart_off = (char *)attr - (char *)start;
+		aend_off = astart_off + mnl_attr_get_payload_len(attr);
+		if (aend_off <= off)
+			continue;
+
+		found = true;
+		break;
+	}
+	if (!found)
+		return 0;
+
+	off -= astart_off;
+
+	type = mnl_attr_get_type(attr);
+
+	if (ynl_err_walk_report_one(policy, type, str, str_sz, &n))
+		return n;
+
+	if (!off) {
+		if (nest_pol)
+			*nest_pol = policy->table[type].nest;
+		return n;
+	}
+
+	if (!policy->table[type].nest) {
+		if (n < str_sz)
+			n += snprintf(str, str_sz, "!nest");
+		return n;
+	}
+
+	off -= sizeof(struct nlattr);
+	start =  mnl_attr_get_payload(attr);
+	end = start + mnl_attr_get_payload_len(attr);
+
+	return n + ynl_err_walk(ys, start, end, off, policy->table[type].nest,
+				&str[n], str_sz - n, nest_pol);
+}
+
+#define NLMSGERR_ATTR_MISS_TYPE (NLMSGERR_ATTR_POLICY + 1)
+#define NLMSGERR_ATTR_MISS_NEST (NLMSGERR_ATTR_POLICY + 2)
+#define NLMSGERR_ATTR_MAX (NLMSGERR_ATTR_MAX + 2)
+
+static int
+ynl_ext_ack_check(struct ynl_sock *ys, const struct nlmsghdr *nlh,
+		  unsigned int hlen)
+{
+	const struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
+	char miss_attr[sizeof(ys->err.msg)];
+	char bad_attr[sizeof(ys->err.msg)];
+	const struct nlattr *attr;
+	const char *str = NULL;
+
+	if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
+		return MNL_CB_OK;
+
+	mnl_attr_for_each(attr, nlh, hlen) {
+		unsigned int len, type;
+
+		len = mnl_attr_get_payload_len(attr);
+		type = mnl_attr_get_type(attr);
+
+		if (type > NLMSGERR_ATTR_MAX)
+			continue;
+
+		tb[type] = attr;
+
+		switch (type) {
+		case NLMSGERR_ATTR_OFFS:
+		case NLMSGERR_ATTR_MISS_TYPE:
+		case NLMSGERR_ATTR_MISS_NEST:
+			if (len != sizeof(__u32))
+				return MNL_CB_ERROR;
+			break;
+		case NLMSGERR_ATTR_MSG:
+			str = mnl_attr_get_payload(attr);
+			if (str[len - 1])
+				return MNL_CB_ERROR;
+			break;
+		default:
+			break;
+		}
+	}
+
+	bad_attr[0] = '\0';
+	miss_attr[0] = '\0';
+
+	if (tb[NLMSGERR_ATTR_OFFS]) {
+		unsigned int n, off;
+		void *start, *end;
+
+		ys->err.attr_offs = mnl_attr_get_u32(tb[NLMSGERR_ATTR_OFFS]);
+
+		n = snprintf(bad_attr, sizeof(bad_attr), "%sbad attribute: ",
+			     str ? " (" : "");
+
+		start = mnl_nlmsg_get_payload_offset(ys->nlh,
+						     sizeof(struct genlmsghdr));
+		end = mnl_nlmsg_get_payload_tail(ys->nlh);
+
+		off = ys->err.attr_offs;
+		off -= sizeof(struct nlmsghdr);
+		off -= sizeof(struct genlmsghdr);
+
+		n += ynl_err_walk(ys, start, end, off, ys->req_policy,
+				  &bad_attr[n], sizeof(bad_attr) - n, NULL);
+
+		if (n >= sizeof(bad_attr))
+			n = sizeof(bad_attr) - 1;
+		bad_attr[n] = '\0';
+	}
+	if (tb[NLMSGERR_ATTR_MISS_TYPE]) {
+		struct ynl_policy_nest *nest_pol = NULL;
+		unsigned int n, off, type;
+		void *start, *end;
+		int n2;
+
+		type = mnl_attr_get_u32(tb[NLMSGERR_ATTR_MISS_TYPE]);
+
+		n = snprintf(miss_attr, sizeof(miss_attr), "%smissing attribute: ",
+			     bad_attr[0] ? ", " : (str ? " (" : ""));
+
+		start = mnl_nlmsg_get_payload_offset(ys->nlh,
+						     sizeof(struct genlmsghdr));
+		end = mnl_nlmsg_get_payload_tail(ys->nlh);
+
+		nest_pol = ys->req_policy;
+		if (tb[NLMSGERR_ATTR_MISS_NEST]) {
+			off = mnl_attr_get_u32(tb[NLMSGERR_ATTR_MISS_NEST]);
+			off -= sizeof(struct nlmsghdr);
+			off -= sizeof(struct genlmsghdr);
+
+			n += ynl_err_walk(ys, start, end, off, ys->req_policy,
+					  &miss_attr[n], sizeof(miss_attr) - n,
+					  &nest_pol);
+		}
+
+		n2 = 0;
+		ynl_err_walk_report_one(nest_pol, type, &miss_attr[n],
+					sizeof(miss_attr) - n, &n2);
+		n += n2;
+
+		if (n >= sizeof(miss_attr))
+			n = sizeof(miss_attr) - 1;
+		miss_attr[n] = '\0';
+	}
+
+	/* Implicitly depend on ys->err.code already set */
+	if (str)
+		yerr_msg(ys, "Kernel %s: '%s'%s%s%s",
+			 ys->err.code ? "error" : "warning",
+			 str, bad_attr, miss_attr,
+			 bad_attr[0] || miss_attr[0] ? ")" : "");
+	else if (bad_attr[0] || miss_attr[0])
+		yerr_msg(ys, "Kernel %s: %s%s",
+			 ys->err.code ? "error" : "warning",
+			 bad_attr, miss_attr);
+
+	return MNL_CB_OK;
+}
+
+static int ynl_cb_error(const struct nlmsghdr *nlh, void *data)
+{
+	const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
+	struct ynl_parse_arg *yarg = data;
+	unsigned int hlen;
+	int code;
+
+	code = err->error >= 0 ? err->error : -err->error;
+	yarg->ys->err.code = code;
+	errno = code;
+
+	hlen = sizeof(*err);
+	if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
+		hlen += mnl_nlmsg_get_payload_len(&err->msg);
+
+	ynl_ext_ack_check(yarg->ys, nlh, hlen);
+
+	return code ? MNL_CB_ERROR : MNL_CB_STOP;
+}
+
+static int ynl_cb_done(const struct nlmsghdr *nlh, void *data)
+{
+	struct ynl_parse_arg *yarg = data;
+	int err;
+
+	err = *(int *)NLMSG_DATA(nlh);
+	if (err < 0) {
+		yarg->ys->err.code = -err;
+		errno = -err;
+
+		ynl_ext_ack_check(yarg->ys, nlh, sizeof(int));
+
+		return MNL_CB_ERROR;
+	}
+	return MNL_CB_STOP;
+}
+
+static int ynl_cb_noop(const struct nlmsghdr *nlh, void *data)
+{
+	return MNL_CB_OK;
+}
+
+mnl_cb_t ynl_cb_array[NLMSG_MIN_TYPE] = {
+	[NLMSG_NOOP]	= ynl_cb_noop,
+	[NLMSG_ERROR]	= ynl_cb_error,
+	[NLMSG_DONE]	= ynl_cb_done,
+	[NLMSG_OVERRUN]	= ynl_cb_noop,
+};
+
+/* Attribute validation */
+
+int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr)
+{
+	struct ynl_policy_attr *policy;
+	unsigned int type, len;
+	unsigned char *data;
+
+	data = mnl_attr_get_payload(attr);
+	len = mnl_attr_get_payload_len(attr);
+	type = mnl_attr_get_type(attr);
+	if (type > yarg->rsp_policy->max_attr) {
+		yerr(yarg->ys, YNL_ERROR_INTERNAL,
+		     "Internal error, validating unknown attribute");
+		return -1;
+	}
+
+	policy = &yarg->rsp_policy->table[type];
+
+	switch (policy->type) {
+	case YNL_PT_REJECT:
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Rejected attribute (%s)", policy->name);
+		return -1;
+	case YNL_PT_IGNORE:
+		break;
+	case YNL_PT_U8:
+		if (len == sizeof(__u8))
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (u8 %s)", policy->name);
+		return -1;
+	case YNL_PT_U16:
+		if (len == sizeof(__u16))
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (u16 %s)", policy->name);
+		return -1;
+	case YNL_PT_U32:
+		if (len == sizeof(__u32))
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (u32 %s)", policy->name);
+		return -1;
+	case YNL_PT_U64:
+		if (len == sizeof(__u64))
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (u64 %s)", policy->name);
+		return -1;
+	case YNL_PT_FLAG:
+		/* Let flags grow into real attrs, why not.. */
+		break;
+	case YNL_PT_NEST:
+		if (!len || len >= sizeof(*attr))
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (nest %s)", policy->name);
+		return -1;
+	case YNL_PT_BINARY:
+		if (!policy->len || len == policy->len)
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (binary %s)", policy->name);
+		return -1;
+	case YNL_PT_NUL_STR:
+		if ((!policy->len || len <= policy->len) && !data[len - 1])
+			break;
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (string %s)", policy->name);
+		return -1;
+	default:
+		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
+		     "Invalid attribute (unknown %s)", policy->name);
+		return -1;
+	}
+
+	return 0;
+}
+
+/* Generic code */
+
+static void ynl_err_reset(struct ynl_sock *ys)
+{
+	ys->err.code = 0;
+	ys->err.attr_offs = 0;
+	ys->err.msg[0] = 0;
+}
+
+struct nlmsghdr *ynl_msg_start(struct ynl_sock *ys, __u32 id, __u16 flags)
+{
+	struct nlmsghdr *nlh;
+
+	ynl_err_reset(ys);
+
+	nlh = ys->nlh = mnl_nlmsg_put_header(ys->tx_buf);
+	nlh->nlmsg_type	= id;
+	nlh->nlmsg_flags = flags;
+	nlh->nlmsg_seq = ++ys->seq;
+
+	return nlh;
+}
+
+struct nlmsghdr *
+ynl_gemsg_start(struct ynl_sock *ys, __u32 id, __u16 flags,
+		__u8 cmd, __u8 version)
+{
+	struct genlmsghdr gehdr;
+	struct nlmsghdr *nlh;
+	void *data;
+
+	nlh = ynl_msg_start(ys, id, flags);
+
+	memset(&gehdr, 0, sizeof(gehdr));
+	gehdr.cmd = cmd;
+	gehdr.version = version;
+
+	data = mnl_nlmsg_put_extra_header(nlh, sizeof(gehdr));
+	memcpy(data, &gehdr, sizeof(gehdr));
+
+	return nlh;
+}
+
+void ynl_msg_start_req(struct ynl_sock *ys, __u32 id)
+{
+	ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK);
+}
+
+void ynl_msg_start_dump(struct ynl_sock *ys, __u32 id)
+{
+	ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);
+}
+
+struct nlmsghdr *
+ynl_gemsg_start_req(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version)
+{
+	return ynl_gemsg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK, cmd, version);
+}
+
+struct nlmsghdr *
+ynl_gemsg_start_dump(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version)
+{
+	return ynl_gemsg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP,
+			       cmd, version);
+}
+
+int ynl_recv_ack(struct ynl_sock *ys, int ret)
+{
+	if (!ret) {
+		yerr(ys, YNL_ERROR_EXPECT_ACK,
+		     "Expecting an ACK but nothing received");
+		return -1;
+	}
+
+	ret = mnl_socket_recvfrom(ys->sock, ys->rx_buf, MNL_SOCKET_BUFFER_SIZE);
+	if (ret < 0) {
+		perr(ys, "Socket receive failed");
+		return ret;
+	}
+	return mnl_cb_run(ys->rx_buf, ret, ys->seq, ys->portid,
+			  ynl_cb_null, ys);
+}
+
+int ynl_cb_null(const struct nlmsghdr *nlh, void *data)
+{
+	struct ynl_parse_arg *yarg = data;
+
+	yerr(yarg->ys, YNL_ERROR_UNEXPECT_MSG,
+	     "Received a message when none were expected");
+
+	return MNL_CB_ERROR;
+}
+
+/* Init/fini and genetlink boiler plate */
+static int
+ynl_get_family_info_mcast(struct ynl_sock *ys, const struct nlattr *mcasts)
+{
+	const struct nlattr *entry, *attr;
+	unsigned int i;
+
+	mnl_attr_for_each_nested(attr, mcasts)
+		ys->n_mcast_groups++;
+
+	if (!ys->n_mcast_groups)
+		return 0;
+
+	ys->mcast_groups = calloc(ys->n_mcast_groups,
+				  sizeof(*ys->mcast_groups));
+	if (!ys->mcast_groups)
+		return MNL_CB_ERROR;
+
+	i = 0;
+	mnl_attr_for_each_nested(entry, mcasts) {
+		mnl_attr_for_each_nested(attr, entry) {
+			if (mnl_attr_get_type(attr) == CTRL_ATTR_MCAST_GRP_ID)
+				ys->mcast_groups[i].id = mnl_attr_get_u32(attr);
+			if (mnl_attr_get_type(attr) == CTRL_ATTR_MCAST_GRP_NAME) {
+				strncpy(ys->mcast_groups[i].name,
+					mnl_attr_get_str(attr),
+					GENL_NAMSIZ - 1);
+				ys->mcast_groups[i].name[GENL_NAMSIZ - 1] = 0;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int ynl_get_family_info_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct ynl_parse_arg *yarg = data;
+	struct ynl_sock *ys = yarg->ys;
+	const struct nlattr *attr;
+	bool found_id = true;
+
+	mnl_attr_for_each(attr, nlh, sizeof(struct genlmsghdr)) {
+		if (mnl_attr_get_type(attr) == CTRL_ATTR_MCAST_GROUPS)
+			if (ynl_get_family_info_mcast(ys, attr))
+				return MNL_CB_ERROR;
+
+		if (mnl_attr_get_type(attr) != CTRL_ATTR_FAMILY_ID)
+			continue;
+
+		if (mnl_attr_get_payload_len(attr) != sizeof(__u16)) {
+			yerr(ys, YNL_ERROR_ATTR_INVALID, "Invalid family ID");
+			return MNL_CB_ERROR;
+		}
+
+		ys->family_id = mnl_attr_get_u16(attr);
+		found_id = true;
+	}
+
+	if (!found_id) {
+		yerr(ys, YNL_ERROR_ATTR_MISSING, "Family ID missing");
+		return MNL_CB_ERROR;
+	}
+	return MNL_CB_OK;
+}
+
+static int ynl_sock_read_family(struct ynl_sock *ys, const char *family_name)
+{
+	struct ynl_parse_arg yarg = { .ys = ys, };
+	struct nlmsghdr *nlh;
+	int err;
+
+	nlh = ynl_gemsg_start_req(ys, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, 1);
+	mnl_attr_put_strz(nlh, CTRL_ATTR_FAMILY_NAME, family_name);
+
+	err = mnl_socket_sendto(ys->sock, nlh, nlh->nlmsg_len);
+	if (err < 0) {
+		perr(ys, "failed to request socket family info");
+		return err;
+	}
+
+	err = mnl_socket_recvfrom(ys->sock, ys->rx_buf, MNL_SOCKET_BUFFER_SIZE);
+	if (err <= 0) {
+		perr(ys, "failed to receive the socket family info");
+		return err;
+	}
+	err = mnl_cb_run2(ys->rx_buf, err, ys->seq, ys->portid,
+			  ynl_get_family_info_cb, &yarg,
+			  ynl_cb_array, ARRAY_SIZE(ynl_cb_array));
+	if (err < 0) {
+		free(ys->mcast_groups);
+		perr(ys, "failed to receive the socket family info - no such family?");
+		return err;
+	}
+
+	return ynl_recv_ack(ys, err);
+}
+
+struct ynl_sock *
+ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
+{
+	struct ynl_sock *ys;
+	int one = 1;
+
+	ys = malloc(sizeof(*ys) + 2 * MNL_SOCKET_BUFFER_SIZE);
+	if (!ys)
+		return NULL;
+	memset(ys, 0, sizeof(*ys));
+
+	ys->family = yf;
+	ys->tx_buf = &ys->raw_buf[0];
+	ys->rx_buf = &ys->raw_buf[MNL_SOCKET_BUFFER_SIZE];
+	ys->ntf_last_next = &ys->ntf_first;
+
+	ys->sock = mnl_socket_open(NETLINK_GENERIC);
+	if (!ys->sock) {
+		__perr(yse, "failed to create a netlink socket");
+		goto err_free_sock;
+	}
+
+	if (mnl_socket_setsockopt(ys->sock, NETLINK_CAP_ACK,
+				  &one, sizeof(one))) {
+		__perr(yse, "failed to enable netlink ACK");
+		goto err_close_sock;
+	}
+	if (mnl_socket_setsockopt(ys->sock, NETLINK_EXT_ACK,
+				  &one, sizeof(one))) {
+		__perr(yse, "failed to enable netlink ext ACK");
+		goto err_close_sock;
+	}
+
+	ys->seq = random();
+	ys->portid = mnl_socket_get_portid(ys->sock);
+
+	if (ynl_sock_read_family(ys, yf->name)) {
+		if (yse)
+			memcpy(yse, &ys->err, sizeof(*yse));
+		goto err_close_sock;
+	}
+
+	return ys;
+
+err_close_sock:
+	mnl_socket_close(ys->sock);
+err_free_sock:
+	free(ys);
+	return NULL;
+}
+
+void ynl_sock_destroy(struct ynl_sock *ys)
+{
+	struct ynl_ntf_base_type *ntf;
+
+	mnl_socket_close(ys->sock);
+	while ((ntf = ynl_ntf_dequeue(ys)))
+		ynl_ntf_free(ntf);
+	free(ys->mcast_groups);
+	free(ys);
+}
+
+/* YNL multicast handling */
+
+void ynl_ntf_free(struct ynl_ntf_base_type *ntf)
+{
+	ntf->free(ntf);
+}
+
+int ynl_subscribe(struct ynl_sock *ys, const char *grp_name)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < ys->n_mcast_groups; i++)
+		if (!strcmp(ys->mcast_groups[i].name, grp_name))
+			break;
+	if (i == ys->n_mcast_groups) {
+		yerr(ys, ENOENT, "Multicast group '%s' not found", grp_name);
+		return -1;
+	}
+
+	err = mnl_socket_setsockopt(ys->sock, NETLINK_ADD_MEMBERSHIP,
+				    &ys->mcast_groups[i].id,
+				    sizeof(ys->mcast_groups[i].id));
+	if (err < 0) {
+		perr(ys, "Subscribing to multicast group failed");
+		return -1;
+	}
+
+	return 0;
+}
+
+int ynl_socket_get_fd(struct ynl_sock *ys)
+{
+	return mnl_socket_get_fd(ys->sock);
+}
+
+struct ynl_ntf_base_type *ynl_ntf_dequeue(struct ynl_sock *ys)
+{
+	struct ynl_ntf_base_type *ntf;
+
+	if (!ynl_has_ntf(ys))
+		return NULL;
+
+	ntf = ys->ntf_first;
+	ys->ntf_first = ntf->next;
+	if (ys->ntf_last_next == &ntf->next)
+		ys->ntf_last_next = &ys->ntf_first;
+
+	return ntf;
+}
+
+static int ynl_ntf_parse(struct ynl_sock *ys, const struct nlmsghdr *nlh)
+{
+	struct ynl_parse_arg yarg = { .ys = ys, };
+	const struct ynl_ntf_info *info;
+	struct ynl_ntf_base_type *rsp;
+	struct genlmsghdr *gehdr;
+	int ret;
+
+	gehdr = mnl_nlmsg_get_payload(nlh);
+	if (gehdr->cmd >= ys->family->ntf_info_size)
+		return MNL_CB_ERROR;
+	info = &ys->family->ntf_info[gehdr->cmd];
+	if (!info->cb)
+		return MNL_CB_ERROR;
+
+	rsp = calloc(1, info->alloc_sz);
+	rsp->free = info->free;
+	yarg.data = rsp->data;
+	yarg.rsp_policy = info->policy;
+
+	ret = info->cb(nlh, &yarg);
+	if (ret <= MNL_CB_STOP)
+		goto err_free;
+
+	rsp->family = nlh->nlmsg_type;
+	rsp->cmd = gehdr->cmd;
+
+	*ys->ntf_last_next = rsp;
+	ys->ntf_last_next = &rsp->next;
+
+	return MNL_CB_OK;
+
+err_free:
+	info->free(rsp);
+	return MNL_CB_ERROR;
+}
+
+static int ynl_ntf_trampoline(const struct nlmsghdr *nlh, void *data)
+{
+	return ynl_ntf_parse((struct ynl_sock *)data, nlh);
+}
+
+int ynl_ntf_check(struct ynl_sock *ys)
+{
+	ssize_t len;
+	int err;
+
+	do {
+		/* libmnl doesn't let us pass flags to the recv to make
+		 * it non-blocking so we need to poll() or peek() :|
+		 */
+		struct pollfd pfd = { };
+
+		pfd.fd = mnl_socket_get_fd(ys->sock);
+		pfd.events = POLLIN;
+		err = poll(&pfd, 1, 1);
+		if (err < 1)
+			return err;
+
+		len = mnl_socket_recvfrom(ys->sock, ys->rx_buf,
+					  MNL_SOCKET_BUFFER_SIZE);
+		if (len < 0)
+			return len;
+
+		err = mnl_cb_run2(ys->rx_buf, len, ys->seq, ys->portid,
+				  ynl_ntf_trampoline, ys,
+				  ynl_cb_array, NLMSG_MIN_TYPE);
+		if (err < 0)
+			return err;
+	} while (err > 0);
+
+	return 0;
+}
+
+/* YNL specific helpers used by the auto-generated code */
+
+struct ynl_dump_list_type *YNL_LIST_END = (void *)(0xb4d123);
+
+void ynl_error_unknown_notification(struct ynl_sock *ys, __u8 cmd)
+{
+	yerr(ys, YNL_ERROR_UNKNOWN_NTF,
+	     "Unknown notification message type '%d'", cmd);
+}
+
+int ynl_error_parse(struct ynl_parse_arg *yarg, const char *msg)
+{
+	yerr(yarg->ys, YNL_ERROR_INV_RESP, "Error parsing response: %s", msg);
+	return MNL_CB_ERROR;
+}
+
+static int
+ynl_check_alien(struct ynl_sock *ys, const struct nlmsghdr *nlh, __u32 rsp_cmd)
+{
+	struct genlmsghdr *gehdr;
+
+	if (mnl_nlmsg_get_payload_len(nlh) < sizeof(*gehdr)) {
+		yerr(ys, YNL_ERROR_INV_RESP,
+		     "Kernel responded with truncated message");
+		return -1;
+	}
+
+	gehdr = mnl_nlmsg_get_payload(nlh);
+	if (gehdr->cmd != rsp_cmd)
+		return ynl_ntf_parse(ys, nlh);
+
+	return 0;
+}
+
+static int ynl_req_trampoline(const struct nlmsghdr *nlh, void *data)
+{
+	struct ynl_req_state *yrs = data;
+	int ret;
+
+	ret = ynl_check_alien(yrs->yarg.ys, nlh, yrs->rsp_cmd);
+	if (ret)
+		return ret < 0 ? MNL_CB_ERROR : MNL_CB_OK;
+
+	return yrs->cb(nlh, &yrs->yarg);
+}
+
+int ynl_exec(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
+	     struct ynl_req_state *yrs)
+{
+	ssize_t len;
+	int err;
+
+	err = mnl_socket_sendto(ys->sock, req_nlh, req_nlh->nlmsg_len);
+	if (err < 0)
+		return err;
+
+	do {
+		len = mnl_socket_recvfrom(ys->sock, ys->rx_buf,
+					  MNL_SOCKET_BUFFER_SIZE);
+		if (len < 0)
+			return len;
+
+		err = mnl_cb_run2(ys->rx_buf, len, ys->seq, ys->portid,
+				  ynl_req_trampoline, yrs,
+				  ynl_cb_array, NLMSG_MIN_TYPE);
+		if (err < 0)
+			return err;
+	} while (err > 0);
+
+	return 0;
+}
+
+static int ynl_dump_trampoline(const struct nlmsghdr *nlh, void *data)
+{
+	struct ynl_dump_state *ds = data;
+	struct ynl_dump_list_type *obj;
+	struct ynl_parse_arg yarg = {};
+	int ret;
+
+	ret = ynl_check_alien(ds->ys, nlh, ds->rsp_cmd);
+	if (ret)
+		return ret < 0 ? MNL_CB_ERROR : MNL_CB_OK;
+
+	obj = calloc(1, ds->alloc_sz);
+	if (!obj)
+		return MNL_CB_ERROR;
+
+	if (!ds->first)
+		ds->first = obj;
+	if (ds->last)
+		ds->last->next = obj;
+	ds->last = obj;
+
+	yarg.ys = ds->ys;
+	yarg.rsp_policy = ds->rsp_policy;
+	yarg.data = &obj->data;
+
+	return ds->cb(nlh, &yarg);
+}
+
+static void *ynl_dump_end(struct ynl_dump_state *ds)
+{
+	if (!ds->first)
+		return YNL_LIST_END;
+
+	ds->last->next = YNL_LIST_END;
+	return ds->first;
+}
+
+int ynl_exec_dump(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
+		  struct ynl_dump_state *yds)
+{
+	ssize_t len;
+	int err;
+
+	err = mnl_socket_sendto(ys->sock, req_nlh, req_nlh->nlmsg_len);
+	if (err < 0)
+		return err;
+
+	do {
+		len = mnl_socket_recvfrom(ys->sock, ys->rx_buf,
+					  MNL_SOCKET_BUFFER_SIZE);
+		if (len < 0)
+			goto err_close_list;
+
+		err = mnl_cb_run2(ys->rx_buf, len, ys->seq, ys->portid,
+				  ynl_dump_trampoline, yds,
+				  ynl_cb_array, NLMSG_MIN_TYPE);
+		if (err < 0)
+			goto err_close_list;
+	} while (err > 0);
+
+	yds->first = ynl_dump_end(yds);
+	return 0;
+
+err_close_list:
+	yds->first = ynl_dump_end(yds);
+	return -1;
+}

tools/net/ynl/lib/ynl.h

+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+#ifndef __YNL_C_H
+#define __YNL_C_H 1
+
+#include <stddef.h>
+#include <libmnl/libmnl.h>
+#include <linux/genetlink.h>
+#include <linux/types.h>
+
+struct mnl_socket;
+struct nlmsghdr;
+
+/*
+ * User facing code
+ */
+
+struct ynl_ntf_base_type;
+struct ynl_ntf_info;
+struct ynl_sock;
+
+enum ynl_error_code {
+	YNL_ERROR_NONE = 0,
+	__YNL_ERRNO_END = 4096,
+	YNL_ERROR_INTERNAL,
+	YNL_ERROR_EXPECT_ACK,
+	YNL_ERROR_EXPECT_MSG,
+	YNL_ERROR_UNEXPECT_MSG,
+	YNL_ERROR_ATTR_MISSING,
+	YNL_ERROR_ATTR_INVALID,
+	YNL_ERROR_UNKNOWN_NTF,
+	YNL_ERROR_INV_RESP,
+};
+
+/**
+ * struct ynl_error - error encountered by YNL
+ * @code:	errno (low values) or YNL error code (enum ynl_error_code)
+ * @attr_offs:	offset of bad attribute (for very advanced users)
+ * @msg:	error message
+ *
+ * Error information for when YNL operations fail.
+ * Users should interact with the err member of struct ynl_sock directly.
+ * The main exception to that rule is ynl_sock_create().
+ */
+struct ynl_error {
+	enum ynl_error_code code;
+	unsigned int attr_offs;
+	char msg[512];
+};
+
+/**
+ * struct ynl_family - YNL family info
+ * Family description generated by codegen. Pass to ynl_sock_create().
+ */
+struct ynl_family {
+/* private: */
+	const char *name;
+	const struct ynl_ntf_info *ntf_info;
+	unsigned int ntf_info_size;
+};
+
+/**
+ * struct ynl_sock - YNL wrapped netlink socket
+ * @err: YNL error descriptor, cleared on every request.
+ */
+struct ynl_sock {
+	struct ynl_error err;
+
+/* private: */
+	const struct ynl_family *family;
+	struct mnl_socket *sock;
+	__u32 seq;
+	__u32 portid;
+	__u16 family_id;
+
+	unsigned int n_mcast_groups;
+	struct {
+		unsigned int id;
+		char name[GENL_NAMSIZ];
+	} *mcast_groups;
+
+	struct ynl_ntf_base_type *ntf_first;
+	struct ynl_ntf_base_type **ntf_last_next;
+
+	struct nlmsghdr *nlh;
+	struct ynl_policy_nest *req_policy;
+	unsigned char *tx_buf;
+	unsigned char *rx_buf;
+	unsigned char raw_buf[];
+};
+
+struct ynl_sock *
+ynl_sock_create(const struct ynl_family *yf, struct ynl_error *e);
+void ynl_sock_destroy(struct ynl_sock *ys);
+
+#define ynl_dump_foreach(dump, iter)					\
+	for (typeof(dump->obj) *iter = &dump->obj;			\
+	     !ynl_dump_obj_is_last(iter);				\
+	     iter = ynl_dump_obj_next(iter))
+
+int ynl_subscribe(struct ynl_sock *ys, const char *grp_name);
+int ynl_socket_get_fd(struct ynl_sock *ys);
+int ynl_ntf_check(struct ynl_sock *ys);
+
+/**
+ * ynl_has_ntf() - check if socket has *parsed* notifications
+ * @ys: active YNL socket
+ *
+ * Note that this does not take into account notifications sitting
+ * in netlink socket, just the notifications which have already been
+ * read and parsed (e.g. during a ynl_ntf_check() call).
+ */
+static inline bool ynl_has_ntf(struct ynl_sock *ys)
+{
+	return ys->ntf_last_next != &ys->ntf_first;
+}
+struct ynl_ntf_base_type *ynl_ntf_dequeue(struct ynl_sock *ys);
+
+void ynl_ntf_free(struct ynl_ntf_base_type *ntf);
+
+/*
+ * YNL internals / low level stuff
+ */
+
+/* Generic mnl helper code */
+
+enum ynl_policy_type {
+	YNL_PT_REJECT = 1,
+	YNL_PT_IGNORE,
+	YNL_PT_NEST,
+	YNL_PT_FLAG,
+	YNL_PT_BINARY,
+	YNL_PT_U8,
+	YNL_PT_U16,
+	YNL_PT_U32,
+	YNL_PT_U64,
+	YNL_PT_NUL_STR,
+};
+
+struct ynl_policy_attr {
+	enum ynl_policy_type type;
+	unsigned int len;
+	const char *name;
+	struct ynl_policy_nest *nest;
+};
+
+struct ynl_policy_nest {
+	unsigned int max_attr;
+	struct ynl_policy_attr *table;
+};
+
+struct ynl_parse_arg {
+	struct ynl_sock *ys;
+	struct ynl_policy_nest *rsp_policy;
+	void *data;
+};
+
+struct ynl_dump_list_type {
+	struct ynl_dump_list_type *next;
+	unsigned char data[] __attribute__ ((aligned (8)));
+};
+extern struct ynl_dump_list_type *YNL_LIST_END;
+
+static inline bool ynl_dump_obj_is_last(void *obj)
+{
+	unsigned long uptr = (unsigned long)obj;
+
+	uptr -= offsetof(struct ynl_dump_list_type, data);
+	return uptr == (unsigned long)YNL_LIST_END;
+}
+
+static inline void *ynl_dump_obj_next(void *obj)
+{
+	unsigned long uptr = (unsigned long)obj;
+	struct ynl_dump_list_type *list;
+
+	uptr -= offsetof(struct ynl_dump_list_type, data);
+	list = (void *)uptr;
+	uptr = (unsigned long)list->next;
+	uptr += offsetof(struct ynl_dump_list_type, data);
+
+	return (void *)uptr;
+}
+
+struct ynl_ntf_base_type {
+	__u16 family;
+	__u8 cmd;
+	struct ynl_ntf_base_type *next;
+	void (*free)(struct ynl_ntf_base_type *ntf);
+	unsigned char data[] __attribute__ ((aligned (8)));
+};
+
+extern mnl_cb_t ynl_cb_array[NLMSG_MIN_TYPE];
+
+struct nlmsghdr *
+ynl_gemsg_start_req(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version);
+struct nlmsghdr *
+ynl_gemsg_start_dump(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version);
+
+int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr);
+
+int ynl_recv_ack(struct ynl_sock *ys, int ret);
+int ynl_cb_null(const struct nlmsghdr *nlh, void *data);
+
+/* YNL specific helpers used by the auto-generated code */
+
+struct ynl_req_state {
+	struct ynl_parse_arg yarg;
+	mnl_cb_t cb;
+	__u32 rsp_cmd;
+};
+
+struct ynl_dump_state {
+	struct ynl_sock *ys;
+	struct ynl_policy_nest *rsp_policy;
+	void *first;
+	struct ynl_dump_list_type *last;
+	size_t alloc_sz;
+	mnl_cb_t cb;
+	__u32 rsp_cmd;
+};
+
+struct ynl_ntf_info {
+	struct ynl_policy_nest *policy;
+	mnl_cb_t cb;
+	size_t alloc_sz;
+	void (*free)(struct ynl_ntf_base_type *ntf);
+};
+
+int ynl_exec(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
+	     struct ynl_req_state *yrs);
+int ynl_exec_dump(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
+		  struct ynl_dump_state *yds);
+
+void ynl_error_unknown_notification(struct ynl_sock *ys, __u8 cmd);
+int ynl_error_parse(struct ynl_parse_arg *yarg, const char *msg);
+
+#endif

tools/net/ynl/ynl-regen.sh

@@ -14,7 +14,7 @@ done
 
 KDIR=$(dirname $(dirname $(dirname $(dirname $(realpath $0)))))
 
-files=$(git grep --files-with-matches '^/\* YNL-GEN \(kernel\|uapi\)')
+files=$(git grep --files-with-matches '^/\* YNL-GEN \(kernel\|uapi\|user\)')
 for f in $files; do
     # params:     0       1      2     3
     #         $YAML YNL-GEN kernel $mode