Merge branch 'tools-ynl-gen-support-sub-messages-and-rt-link'

Jakub Kicinski says:

====================
tools: ynl-gen: support sub-messages and rt-link

Sub-messages are how we express "polymorphism" in YNL. Donald added
the support to specs and Python a while back, support them in C, too.
Sub-message is a nest, but the interpretation of the attribute types
within that nest depends on a value of another attribute. For example
in rt-link the "kind" attribute contains the link type (veth, bonding,
etc.) and based on that the right enum has to be applied to interpret
link-specific attributes.

The last message is probably the most interesting to look at, as it
adds a fairly advanced sample.

This patch only contains enough support for rtnetlink, we will need
a little more complexity to support TC, where sub-messages may contain
fixed headers, and where the selector may be in a different nest than
the submessage.
====================

Link: https://patch.msgid.link/20250515231650.1325372-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/rt-link.yaml

@@ -594,6 +594,7 @@ definitions:
         name: reasm-overlaps
   - name: br-boolopt-multi
     type: struct
+    header: linux/if_bridge.h
     members:
       -
         name: optval
@@ -826,6 +827,8 @@ definitions:
       - name: default
   -
     name: ovpn-mode
+    enum-name: ovpn-mode
+    name-prefix: ovpn-mode
     type: enum
     entries:
       - p2p
@@ -2195,6 +2198,7 @@ attribute-sets:
         type: u16
   -
     name: linkinfo-ovpn-attrs
+    name-prefix: ifla-ovpn-
     attributes:
       -
         name: mode

tools/net/ynl/Makefile.deps

@@ -33,5 +33,9 @@ CFLAGS_ovs_flow:=$(call get_hdr_inc,__LINUX_OPENVSWITCH_H,openvswitch.h)
 CFLAGS_ovs_vport:=$(call get_hdr_inc,__LINUX_OPENVSWITCH_H,openvswitch.h)
 CFLAGS_rt-addr:=$(call get_hdr_inc,__LINUX_RTNETLINK_H,rtnetlink.h) \
 	$(call get_hdr_inc,__LINUX_IF_ADDR_H,if_addr.h)
+CFLAGS_rt-link:=$(call get_hdr_inc,__LINUX_RTNETLINK_H,rtnetlink.h) \
+	$(call get_hdr_inc,_LINUX_IF_LINK_H,if_link.h)
+CFLAGS_rt-neigh:=$(call get_hdr_inc,__LINUX_RTNETLINK_H,rtnetlink.h)
 CFLAGS_rt-route:=$(call get_hdr_inc,__LINUX_RTNETLINK_H,rtnetlink.h)
+CFLAGS_rt-rule:=$(call get_hdr_inc,__LINUX_FIB_RULES_H,fib_rules.h)
 CFLAGS_tcp_metrics:=$(call get_hdr_inc,_LINUX_TCP_METRICS_H,tcp_metrics.h)

tools/net/ynl/generated/Makefile

@@ -22,10 +22,9 @@ TOOL:=../pyynl/ynl_gen_c.py
 TOOL_RST:=../pyynl/ynl_gen_rst.py
 
 SPECS_DIR:=../../../../Documentation/netlink/specs
-GENS_PATHS=$(shell grep -nrI --files-without-match \
-		'protocol: netlink' \
-		$(SPECS_DIR))
-GENS=$(patsubst $(SPECS_DIR)/%.yaml,%,${GENS_PATHS}) rt-addr rt-route
+SPECS_PATHS=$(wildcard $(SPECS_DIR)/*.yaml)
+GENS_UNSUP=conntrack nftables tc
+GENS=$(filter-out ${GENS_UNSUP},$(patsubst $(SPECS_DIR)/%.yaml,%,${SPECS_PATHS}))
 SRCS=$(patsubst %,%-user.c,${GENS})
 HDRS=$(patsubst %,%-user.h,${GENS})
 OBJS=$(patsubst %,%-user.o,${GENS})

tools/net/ynl/lib/ynl-priv.h

@@ -25,6 +25,7 @@ enum ynl_policy_type {
 	YNL_PT_UINT,
 	YNL_PT_NUL_STR,
 	YNL_PT_BITFIELD32,
+	YNL_PT_SUBMSG,
 };
 
 enum ynl_parse_result {
@@ -42,7 +43,10 @@ typedef int (*ynl_parse_cb_t)(const struct nlmsghdr *nlh,
 			      struct ynl_parse_arg *yarg);
 
 struct ynl_policy_attr {
-	enum ynl_policy_type type;
+	enum ynl_policy_type type:8;
+	__u8 is_submsg:1;
+	__u8 is_selector:1;
+	__u16 selector_type;
 	unsigned int len;
 	const char *name;
 	const struct ynl_policy_nest *nest;
@@ -103,6 +107,8 @@ 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_submsg_failed(struct ynl_parse_arg *yarg, const char *field_name,
+		      const char *sel_name);
 
 /* YNL specific helpers used by the auto-generated code */
 

tools/net/ynl/lib/ynl.c

@@ -45,8 +45,39 @@
 #define perr(_ys, _msg)			__yerr(&(_ys)->err, errno, _msg)
 
 /* -- Netlink boiler plate */
+static bool
+ynl_err_walk_is_sel(const struct ynl_policy_nest *policy,
+		    const struct nlattr *attr)
+{
+	unsigned int type = ynl_attr_type(attr);
+
+	return policy && type <= policy->max_attr &&
+		policy->table[type].is_selector;
+}
+
+static const struct ynl_policy_nest *
+ynl_err_walk_sel_policy(const struct ynl_policy_attr *policy_attr,
+			const struct nlattr *selector)
+{
+	const struct ynl_policy_nest *policy = policy_attr->nest;
+	const char *sel;
+	unsigned int i;
+
+	if (!policy_attr->is_submsg)
+		return policy;
+
+	sel = ynl_attr_get_str(selector);
+	for (i = 0; i <= policy->max_attr; i++) {
+		if (!strcmp(sel, policy->table[i].name))
+			return policy->table[i].nest;
+	}
+
+	return NULL;
+}
+
 static int
-ynl_err_walk_report_one(const struct ynl_policy_nest *policy, unsigned int type,
+ynl_err_walk_report_one(const struct ynl_policy_nest *policy,
+			const struct nlattr *selector, unsigned int type,
 			char *str, int str_sz, int *n)
 {
 	if (!policy) {
@@ -67,9 +98,34 @@ ynl_err_walk_report_one(const struct ynl_policy_nest *policy, unsigned int type,
 		return 1;
 	}
 
-	if (*n < str_sz)
-		*n += snprintf(str, str_sz - *n,
-			       ".%s", policy->table[type].name);
+	if (*n < str_sz) {
+		int sz;
+
+		sz = snprintf(str, str_sz - *n,
+			      ".%s", policy->table[type].name);
+		*n += sz;
+		str += sz;
+	}
+
+	if (policy->table[type].is_submsg) {
+		if (!selector) {
+			if (*n < str_sz)
+				*n += snprintf(str, str_sz, "(!selector)");
+			return 1;
+		}
+
+		if (ynl_attr_type(selector) !=
+		    policy->table[type].selector_type) {
+			if (*n < str_sz)
+				*n += snprintf(str, str_sz, "(!=selector)");
+			return 1;
+		}
+
+		if (*n < str_sz)
+			*n += snprintf(str, str_sz - *n, "(%s)",
+				       ynl_attr_get_str(selector));
+	}
+
 	return 0;
 }
 
@@ -78,6 +134,8 @@ ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
 	     const struct ynl_policy_nest *policy, char *str, int str_sz,
 	     const struct ynl_policy_nest **nest_pol)
 {
+	const struct ynl_policy_nest *next_pol;
+	const struct nlattr *selector = NULL;
 	unsigned int astart_off, aend_off;
 	const struct nlattr *attr;
 	unsigned int data_len;
@@ -96,6 +154,10 @@ ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
 	ynl_attr_for_each_payload(start, data_len, attr) {
 		astart_off = (char *)attr - (char *)start;
 		aend_off = (char *)ynl_attr_data_end(attr) - (char *)start;
+
+		if (ynl_err_walk_is_sel(policy, attr))
+			selector = attr;
+
 		if (aend_off <= off)
 			continue;
 
@@ -109,16 +171,20 @@ ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
 
 	type = ynl_attr_type(attr);
 
-	if (ynl_err_walk_report_one(policy, type, str, str_sz, &n))
+	if (ynl_err_walk_report_one(policy, selector, type, str, str_sz, &n))
+		return n;
+
+	next_pol = ynl_err_walk_sel_policy(&policy->table[type], selector);
+	if (!next_pol)
 		return n;
 
 	if (!off) {
 		if (nest_pol)
-			*nest_pol = policy->table[type].nest;
+			*nest_pol = next_pol;
 		return n;
 	}
 
-	if (!policy->table[type].nest) {
+	if (!next_pol) {
 		if (n < str_sz)
 			n += snprintf(str, str_sz, "!nest");
 		return n;
@@ -128,7 +194,7 @@ ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
 	start =  ynl_attr_data(attr);
 	end = start + ynl_attr_data_len(attr);
 
-	return n + ynl_err_walk(ys, start, end, off, policy->table[type].nest,
+	return n + ynl_err_walk(ys, start, end, off, next_pol,
 				&str[n], str_sz - n, nest_pol);
 }
 
@@ -231,7 +297,7 @@ ynl_ext_ack_check(struct ynl_sock *ys, const struct nlmsghdr *nlh,
 		}
 
 		n2 = 0;
-		ynl_err_walk_report_one(nest_pol, type, &miss_attr[n],
+		ynl_err_walk_report_one(nest_pol, NULL, type, &miss_attr[n],
 					sizeof(miss_attr) - n, &n2);
 		n += n2;
 
@@ -384,6 +450,15 @@ int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr)
 	return 0;
 }
 
+int ynl_submsg_failed(struct ynl_parse_arg *yarg, const char *field_name,
+		      const char *sel_name)
+{
+	yerr(yarg->ys, YNL_ERROR_SUBMSG_KEY,
+	     "Parsing error: Sub-message key not set (msg %s, key %s)",
+	     field_name, sel_name);
+	return YNL_PARSE_CB_ERROR;
+}
+
 /* Generic code */
 
 static void ynl_err_reset(struct ynl_sock *ys)

tools/net/ynl/lib/ynl.h

@@ -23,6 +23,7 @@ enum ynl_error_code {
 	YNL_ERROR_INV_RESP,
 	YNL_ERROR_INPUT_INVALID,
 	YNL_ERROR_INPUT_TOO_BIG,
+	YNL_ERROR_SUBMSG_KEY,
 };
 
 /**

tools/net/ynl/pyynl/lib/__init__.py

@@ -1,8 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 
 from .nlspec import SpecAttr, SpecAttrSet, SpecEnumEntry, SpecEnumSet, \
-    SpecFamily, SpecOperation
+    SpecFamily, SpecOperation, SpecSubMessage, SpecSubMessageFormat
 from .ynl import YnlFamily, Netlink, NlError
 
 __all__ = ["SpecAttr", "SpecAttrSet", "SpecEnumEntry", "SpecEnumSet",
-           "SpecFamily", "SpecOperation", "YnlFamily", "Netlink", "NlError"]
+           "SpecFamily", "SpecOperation", "SpecSubMessage", "SpecSubMessageFormat",
+           "YnlFamily", "Netlink", "NlError"]

tools/net/ynl/pyynl/ynl_gen_c.py

@@ -14,6 +14,7 @@ import yaml
 
 sys.path.append(pathlib.Path(__file__).resolve().parent.as_posix())
 from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, SpecEnumEntry
+from lib import SpecSubMessage, SpecSubMessageFormat
 
 
 def c_upper(name):
@@ -56,11 +57,20 @@ class Type(SpecAttr):
         self.request = False
         self.reply = False
 
+        self.is_selector = False
+
         if 'len' in attr:
             self.len = attr['len']
 
         if 'nested-attributes' in attr:
-            self.nested_attrs = attr['nested-attributes']
+            nested = attr['nested-attributes']
+        elif 'sub-message' in attr:
+            nested = attr['sub-message']
+        else:
+            nested = None
+
+        if nested:
+            self.nested_attrs = nested
             if self.nested_attrs == family.name:
                 self.nested_render_name = c_lower(f"{family.ident_name}")
             else:
@@ -119,7 +129,9 @@ class Type(SpecAttr):
         return c_upper(value)
 
     def resolve(self):
-        if 'name-prefix' in self.attr:
+        if 'parent-sub-message' in self.attr:
+            enum_name = self.attr['parent-sub-message'].enum_name
+        elif 'name-prefix' in self.attr:
             enum_name = f"{self.attr['name-prefix']}{self.name}"
         else:
             enum_name = f"{self.attr_set.name_prefix}{self.name}"
@@ -474,7 +486,10 @@ class TypeString(Type):
         ri.cw.p(f"char *{self.c_name};")
 
     def _attr_typol(self):
-        return f'.type = YNL_PT_NUL_STR, '
+        typol = f'.type = YNL_PT_NUL_STR, '
+        if self.is_selector:
+            typol += '.is_selector = 1, '
+        return typol
 
     def _attr_policy(self, policy):
         if 'exact-len' in self.checks:
@@ -867,14 +882,51 @@ class TypeNestTypeValue(Type):
         return get_lines, init_lines, local_vars
 
 
+class TypeSubMessage(TypeNest):
+    def __init__(self, family, attr_set, attr, value):
+        super().__init__(family, attr_set, attr, value)
+
+        self.selector = Selector(attr, attr_set)
+
+    def _attr_typol(self):
+        typol = f'.type = YNL_PT_NEST, .nest = &{self.nested_render_name}_nest, '
+        typol += f'.is_submsg = 1, .selector_type = {self.attr_set[self["selector"]].value} '
+        return typol
+
+    def _attr_get(self, ri, var):
+        sel = c_lower(self['selector'])
+        get_lines = [f'if (!{var}->{sel})',
+                     f'return ynl_submsg_failed(yarg, "%s", "%s");' %
+                        (self.name, self['selector']),
+                    f"if ({self.nested_render_name}_parse(&parg, {var}->{sel}, attr))",
+                     "return YNL_PARSE_CB_ERROR;"]
+        init_lines = [f"parg.rsp_policy = &{self.nested_render_name}_nest;",
+                      f"parg.data = &{var}->{self.c_name};"]
+        return get_lines, init_lines, None
+
+
+class Selector:
+    def __init__(self, msg_attr, attr_set):
+        self.name = msg_attr["selector"]
+
+        if self.name in attr_set:
+            self.attr = attr_set[self.name]
+            self.attr.is_selector = True
+            self._external = False
+        else:
+            raise Exception("Passing selectors from external nests not supported")
+
+
 class Struct:
-    def __init__(self, family, space_name, type_list=None, inherited=None):
+    def __init__(self, family, space_name, type_list=None,
+                 inherited=None, submsg=None):
         self.family = family
         self.space_name = space_name
         self.attr_set = family.attr_sets[space_name]
         # Use list to catch comparisons with empty sets
         self._inherited = inherited if inherited is not None else []
         self.inherited = []
+        self.submsg = submsg
 
         self.nested = type_list is None
         if family.name == c_lower(space_name):
@@ -1047,6 +1099,8 @@ class AttrSet(SpecAttrSet):
                 raise Exception(f'new_attr: unsupported sub-type {elem["sub-type"]}')
         elif elem['type'] == 'nest-type-value':
             t = TypeNestTypeValue(self.family, self, elem, value)
+        elif elem['type'] == 'sub-message':
+            t = TypeSubMessage(self.family, self, elem, value)
         else:
             raise Exception(f"No typed class for type {elem['type']}")
 
@@ -1091,6 +1145,16 @@ class Operation(SpecOperation):
         self.has_ntf = True
 
 
+class SubMessage(SpecSubMessage):
+    def __init__(self, family, yaml):
+        super().__init__(family, yaml)
+
+        self.render_name = c_lower(family.ident_name + '-' + yaml['name'])
+
+    def resolve(self):
+        self.resolve_up(super())
+
+
 class Family(SpecFamily):
     def __init__(self, file_name, exclude_ops):
         # Added by resolve:
@@ -1173,6 +1237,9 @@ class Family(SpecFamily):
     def new_operation(self, elem, req_value, rsp_value):
         return Operation(self, elem, req_value, rsp_value)
 
+    def new_sub_message(self, elem):
+        return SubMessage(self, elem)
+
     def is_classic(self):
         return self.proto == 'netlink-raw'
 
@@ -1225,20 +1292,70 @@ class Family(SpecFamily):
             for _, spec in self.attr_sets[name].items():
                 if 'nested-attributes' in spec:
                     nested = spec['nested-attributes']
-                    # If the unknown nest we hit is recursive it's fine, it'll be a pointer
-                    if self.pure_nested_structs[nested].recursive:
-                        continue
-                    if nested not in pns_key_seen:
-                        # Dicts are sorted, this will make struct last
-                        struct = self.pure_nested_structs.pop(name)
-                        self.pure_nested_structs[name] = struct
-                        finished = False
-                        break
+                elif 'sub-message' in spec:
+                    nested = spec.sub_message
+                else:
+                    continue
+
+                # If the unknown nest we hit is recursive it's fine, it'll be a pointer
+                if self.pure_nested_structs[nested].recursive:
+                    continue
+                if nested not in pns_key_seen:
+                    # Dicts are sorted, this will make struct last
+                    struct = self.pure_nested_structs.pop(name)
+                    self.pure_nested_structs[name] = struct
+                    finished = False
+                    break
             if finished:
                 pns_key_seen.add(name)
             else:
                 pns_key_list.append(name)
 
+    def _load_nested_set_nest(self, spec):
+        inherit = set()
+        nested = spec['nested-attributes']
+        if nested not in self.root_sets:
+            if nested not in self.pure_nested_structs:
+                self.pure_nested_structs[nested] = Struct(self, nested, inherited=inherit)
+        else:
+            raise Exception(f'Using attr set as root and nested not supported - {nested}')
+
+        if 'type-value' in spec:
+            if nested in self.root_sets:
+                raise Exception("Inheriting members to a space used as root not supported")
+            inherit.update(set(spec['type-value']))
+        elif spec['type'] == 'indexed-array':
+            inherit.add('idx')
+        self.pure_nested_structs[nested].set_inherited(inherit)
+
+        return nested
+
+    def _load_nested_set_submsg(self, spec):
+        # Fake the struct type for the sub-message itself
+        # its not a attr_set but codegen wants attr_sets.
+        submsg = self.sub_msgs[spec["sub-message"]]
+        nested = submsg.name
+
+        attrs = []
+        for name, fmt in submsg.formats.items():
+            attrs.append({
+                "name": name,
+                "type": "nest",
+                "parent-sub-message": spec,
+                "nested-attributes": fmt['attribute-set']
+            })
+
+        self.attr_sets[nested] = AttrSet(self, {
+            "name": nested,
+            "name-pfx": self.name + '-' + spec.name + '-',
+            "attributes": attrs
+        })
+
+        if nested not in self.pure_nested_structs:
+            self.pure_nested_structs[nested] = Struct(self, nested, submsg=submsg)
+
+        return nested
+
     def _load_nested_sets(self):
         attr_set_queue = list(self.root_sets.keys())
         attr_set_seen = set(self.root_sets.keys())
@@ -1246,37 +1363,32 @@ class Family(SpecFamily):
         while len(attr_set_queue):
             a_set = attr_set_queue.pop(0)
             for attr, spec in self.attr_sets[a_set].items():
-                if 'nested-attributes' not in spec:
+                if 'nested-attributes' in spec:
+                    nested = self._load_nested_set_nest(spec)
+                elif 'sub-message' in spec:
+                    nested = self._load_nested_set_submsg(spec)
+                else:
                     continue
 
-                nested = spec['nested-attributes']
                 if nested not in attr_set_seen:
                     attr_set_queue.append(nested)
                     attr_set_seen.add(nested)
 
-                inherit = set()
-                if nested not in self.root_sets:
-                    if nested not in self.pure_nested_structs:
-                        self.pure_nested_structs[nested] = Struct(self, nested, inherited=inherit)
-                else:
-                    raise Exception(f'Using attr set as root and nested not supported - {nested}')
-
-                if 'type-value' in spec:
-                    if nested in self.root_sets:
-                        raise Exception("Inheriting members to a space used as root not supported")
-                    inherit.update(set(spec['type-value']))
-                elif spec['type'] == 'indexed-array':
-                    inherit.add('idx')
-                self.pure_nested_structs[nested].set_inherited(inherit)
-
         for root_set, rs_members in self.root_sets.items():
             for attr, spec in self.attr_sets[root_set].items():
                 if 'nested-attributes' in spec:
                     nested = spec['nested-attributes']
+                elif 'sub-message' in spec:
+                    nested = spec.sub_message
+                else:
+                    nested = None
+
+                if nested:
                     if attr in rs_members['request']:
                         self.pure_nested_structs[nested].request = True
                     if attr in rs_members['reply']:
                         self.pure_nested_structs[nested].reply = True
+
                     if spec.is_multi_val():
                         child = self.pure_nested_structs.get(nested)
                         child.in_multi_val = True
@@ -1286,20 +1398,26 @@ class Family(SpecFamily):
         # Propagate the request / reply / recursive
         for attr_set, struct in reversed(self.pure_nested_structs.items()):
             for _, spec in self.attr_sets[attr_set].items():
-                if 'nested-attributes' in spec:
-                    child_name = spec['nested-attributes']
-                    struct.child_nests.add(child_name)
-                    child = self.pure_nested_structs.get(child_name)
-                    if child:
-                        if not child.recursive:
-                            struct.child_nests.update(child.child_nests)
-                        child.request |= struct.request
-                        child.reply |= struct.reply
-                        if spec.is_multi_val():
-                            child.in_multi_val = True
                 if attr_set in struct.child_nests:
                     struct.recursive = True
 
+                if 'nested-attributes' in spec:
+                    child_name = spec['nested-attributes']
+                elif 'sub-message' in spec:
+                    child_name = spec.sub_message
+                else:
+                    continue
+
+                struct.child_nests.add(child_name)
+                child = self.pure_nested_structs.get(child_name)
+                if child:
+                    if not child.recursive:
+                        struct.child_nests.update(child.child_nests)
+                    child.request |= struct.request
+                    child.reply |= struct.reply
+                    if spec.is_multi_val():
+                        child.in_multi_val = True
+
         self._sort_pure_types()
 
     def _load_attr_use(self):
@@ -1736,11 +1854,34 @@ def print_dump_prototype(ri):
     print_prototype(ri, "request")
 
 
+def put_typol_submsg(cw, struct):
+    cw.block_start(line=f'const struct ynl_policy_attr {struct.render_name}_policy[] =')
+
+    i = 0
+    for name, arg in struct.member_list():
+        cw.p('[%d] = { .type = YNL_PT_SUBMSG, .name = "%s", .nest = &%s_nest, },' %
+             (i, name, arg.nested_render_name))
+        i += 1
+
+    cw.block_end(line=';')
+    cw.nl()
+
+    cw.block_start(line=f'const struct ynl_policy_nest {struct.render_name}_nest =')
+    cw.p(f'.max_attr = {i - 1},')
+    cw.p(f'.table = {struct.render_name}_policy,')
+    cw.block_end(line=';')
+    cw.nl()
+
+
 def put_typol_fwd(cw, struct):
     cw.p(f'extern const struct ynl_policy_nest {struct.render_name}_nest;')
 
 
 def put_typol(cw, struct):
+    if struct.submsg:
+        put_typol_submsg(cw, struct)
+        return
+
     type_max = struct.attr_set.max_name
     cw.block_start(line=f'const struct ynl_policy_attr {struct.render_name}_policy[{type_max} + 1] =')
 
@@ -1826,8 +1967,9 @@ def put_req_nested(ri, struct):
     local_vars = []
     init_lines = []
 
-    local_vars.append('struct nlattr *nest;')
-    init_lines.append("nest = ynl_attr_nest_start(nlh, attr_type);")
+    if struct.submsg is None:
+        local_vars.append('struct nlattr *nest;')
+        init_lines.append("nest = ynl_attr_nest_start(nlh, attr_type);")
 
     has_anest = False
     has_count = False
@@ -1849,7 +1991,8 @@ def put_req_nested(ri, struct):
     for _, arg in struct.member_list():
         arg.attr_put(ri, "obj")
 
-    ri.cw.p("ynl_attr_nest_end(nlh, nest);")
+    if struct.submsg is None:
+        ri.cw.p("ynl_attr_nest_end(nlh, nest);")
 
     ri.cw.nl()
     ri.cw.p('return 0;')
@@ -1886,6 +2029,7 @@ def _multi_parse(ri, struct, init_lines, local_vars):
         if 'multi-attr' in aspec:
             multi_attrs.add(arg)
         needs_parg |= 'nested-attributes' in aspec
+        needs_parg |= 'sub-message' in aspec
     if array_nests or multi_attrs:
         local_vars.append('int i;')
     if needs_parg:
@@ -2004,9 +2148,43 @@ def _multi_parse(ri, struct, init_lines, local_vars):
     ri.cw.nl()
 
 
+def parse_rsp_submsg(ri, struct):
+    parse_rsp_nested_prototype(ri, struct, suffix='')
+
+    var = 'dst'
+
+    ri.cw.block_start()
+    ri.cw.write_func_lvar(['const struct nlattr *attr = nested;',
+                          f'{struct.ptr_name}{var} = yarg->data;',
+                          'struct ynl_parse_arg parg;'])
+
+    ri.cw.p('parg.ys = yarg->ys;')
+    ri.cw.nl()
+
+    first = True
+    for name, arg in struct.member_list():
+        kw = 'if' if first else 'else if'
+        first = False
+
+        ri.cw.block_start(line=f'{kw} (!strcmp(sel, "{name}"))')
+        get_lines, init_lines, _ = arg._attr_get(ri, var)
+        for line in init_lines:
+            ri.cw.p(line)
+        for line in get_lines:
+            ri.cw.p(line)
+        if arg.presence_type() == 'present':
+            ri.cw.p(f"{var}->_present.{arg.c_name} = 1;")
+        ri.cw.block_end()
+    ri.cw.p('return 0;')
+    ri.cw.block_end()
+    ri.cw.nl()
+
+
 def parse_rsp_nested_prototype(ri, struct, suffix=';'):
     func_args = ['struct ynl_parse_arg *yarg',
                  'const struct nlattr *nested']
+    if struct.submsg:
+        func_args.insert(1, 'const char *sel')
     for arg in struct.inherited:
         func_args.append('__u32 ' + arg)
 
@@ -2015,6 +2193,9 @@ def parse_rsp_nested_prototype(ri, struct, suffix=';'):
 
 
 def parse_rsp_nested(ri, struct):
+    if struct.submsg:
+        return parse_rsp_submsg(ri, struct)
+
     parse_rsp_nested_prototype(ri, struct, suffix='')
 
     local_vars = ['const struct nlattr *attr;',
@@ -3302,8 +3483,7 @@ def main():
                     has_recursive_nests = True
             if has_recursive_nests:
                 cw.nl()
-            for name in parsed.pure_nested_structs:
-                struct = Struct(parsed, name)
+            for struct in parsed.pure_nested_structs.values():
                 put_typol(cw, struct)
             for name in parsed.root_sets:
                 struct = Struct(parsed, name)

tools/net/ynl/samples/.gitignore

@@ -4,4 +4,5 @@ netdev
 ovs
 page-pool
 rt-addr
+rt-link
 rt-route

tools/net/ynl/samples/rt-link.c

@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <string.h>
+
+#include <ynl.h>
+
+#include <arpa/inet.h>
+#include <net/if.h>
+
+#include "rt-link-user.h"
+
+static void rt_link_print(struct rt_link_getlink_rsp *r)
+{
+	unsigned int i;
+
+	printf("%3d: ", r->_hdr.ifi_index);
+
+	if (r->_len.ifname)
+		printf("%16s: ", r->ifname);
+
+	if (r->_present.mtu)
+		printf("mtu %5d  ", r->mtu);
+
+	if (r->linkinfo._len.kind)
+		printf("kind %-8s  ", r->linkinfo.kind);
+	else
+		printf("     %8s  ", "");
+
+	if (r->prop_list._count.alt_ifname) {
+		printf("altname ");
+		for (i = 0; i < r->prop_list._count.alt_ifname; i++)
+			printf("%s ", r->prop_list.alt_ifname[i]->str);
+		printf(" ");
+	}
+
+	if (r->linkinfo._present.data && r->linkinfo.data._present.netkit) {
+		struct rt_link_linkinfo_netkit_attrs *netkit;
+		const char *name;
+
+		netkit = &r->linkinfo.data.netkit;
+		printf("primary %d  ", netkit->primary);
+
+		name = NULL;
+		if (netkit->_present.policy)
+			name = rt_link_netkit_policy_str(netkit->policy);
+		if (name)
+			printf("policy %s  ", name);
+	}
+
+	printf("\n");
+}
+
+static int rt_link_create_netkit(struct ynl_sock *ys)
+{
+	struct rt_link_getlink_ntf *ntf_gl;
+	struct rt_link_newlink_req *req;
+	struct ynl_ntf_base_type *ntf;
+	int ret;
+
+	req = rt_link_newlink_req_alloc();
+	if (!req) {
+		fprintf(stderr, "Can't alloc req\n");
+		return -1;
+	}
+
+	/* rtnetlink doesn't provide info about the created object.
+	 * It expects us to set the ECHO flag and the dig the info out
+	 * of the notifications...
+	 */
+	rt_link_newlink_req_set_nlflags(req, NLM_F_CREATE | NLM_F_ECHO);
+
+	rt_link_newlink_req_set_linkinfo_kind(req, "netkit");
+
+	/* Test error messages */
+	rt_link_newlink_req_set_linkinfo_data_netkit_policy(req, 10);
+	ret = rt_link_newlink(ys, req);
+	if (ret) {
+		printf("Testing error message for policy being bad:\n\t%s\n", ys->err.msg);
+	} else {
+		fprintf(stderr,	"Warning: unexpected success creating netkit with bad attrs\n");
+		goto created;
+	}
+
+	rt_link_newlink_req_set_linkinfo_data_netkit_policy(req, NETKIT_DROP);
+
+	ret = rt_link_newlink(ys, req);
+created:
+	rt_link_newlink_req_free(req);
+	if (ret) {
+		fprintf(stderr, "YNL: %s\n", ys->err.msg);
+		return -1;
+	}
+
+	if (!ynl_has_ntf(ys)) {
+		fprintf(stderr,
+			"Warning: interface created but received no notification, won't delete the interface\n");
+		return 0;
+	}
+
+	ntf = ynl_ntf_dequeue(ys);
+	if (ntf->cmd !=	RTM_NEWLINK) {
+		fprintf(stderr,
+			"Warning: unexpected notification type, won't delete the interface\n");
+		return 0;
+	}
+	ntf_gl = (void *)ntf;
+	ret = ntf_gl->obj._hdr.ifi_index;
+	ynl_ntf_free(ntf);
+
+	return ret;
+}
+
+static void rt_link_del(struct ynl_sock *ys, int ifindex)
+{
+	struct rt_link_dellink_req *req;
+
+	req = rt_link_dellink_req_alloc();
+	if (!req) {
+		fprintf(stderr, "Can't alloc req\n");
+		return;
+	}
+
+	req->_hdr.ifi_index = ifindex;
+	if (rt_link_dellink(ys, req))
+		fprintf(stderr, "YNL: %s\n", ys->err.msg);
+	else
+		fprintf(stderr,
+			"Trying to delete a Netkit interface (ifindex %d)\n",
+			ifindex);
+
+	rt_link_dellink_req_free(req);
+}
+
+int main(int argc, char **argv)
+{
+	struct rt_link_getlink_req_dump *req;
+	struct rt_link_getlink_list *rsp;
+	struct ynl_error yerr;
+	struct ynl_sock *ys;
+	int created = 0;
+
+	ys = ynl_sock_create(&ynl_rt_link_family, &yerr);
+	if (!ys) {
+		fprintf(stderr, "YNL: %s\n", yerr.msg);
+		return 1;
+	}
+
+	if (argc > 1) {
+		fprintf(stderr, "Trying to create a Netkit interface\n");
+		created = rt_link_create_netkit(ys);
+		if (created < 0)
+			goto err_destroy;
+	}
+
+	req = rt_link_getlink_req_dump_alloc();
+	if (!req)
+		goto err_del_ifc;
+
+	rsp = rt_link_getlink_dump(ys, req);
+	rt_link_getlink_req_dump_free(req);
+	if (!rsp)
+		goto err_close;
+
+	if (ynl_dump_empty(rsp))
+		fprintf(stderr, "Error: no links reported\n");
+	ynl_dump_foreach(rsp, link)
+		rt_link_print(link);
+	rt_link_getlink_list_free(rsp);
+
+	if (created)
+		rt_link_del(ys, created);
+
+	ynl_sock_destroy(ys);
+	return 0;
+
+err_close:
+	fprintf(stderr, "YNL: %s\n", ys->err.msg);
+err_del_ifc:
+	if (created)
+		rt_link_del(ys, created);
+err_destroy:
+	ynl_sock_destroy(ys);
+	return 2;
+}