tools: ynl: support creating non-genl sockets

Classic netlink has static family IDs specified in YAML,
there is no family name -> ID lookup. Support providing
the ID info to the library via the generated struct and
make library use it. Since NETLINK_ROUTE is ID 0 we need
an extra boolean to indicate classic_id is to be used.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250410014658.782120-8-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/lib/ynl.c

@@ -663,6 +663,7 @@ ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
 	struct sockaddr_nl addr;
 	struct ynl_sock *ys;
 	socklen_t addrlen;
+	int sock_type;
 	int one = 1;
 
 	ys = malloc(sizeof(*ys) + 2 * YNL_SOCKET_BUFFER_SIZE);
@@ -675,7 +676,9 @@ ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
 	ys->rx_buf = &ys->raw_buf[YNL_SOCKET_BUFFER_SIZE];
 	ys->ntf_last_next = &ys->ntf_first;
 
-	ys->socket = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
+	sock_type = yf->is_classic ? yf->classic_id : NETLINK_GENERIC;
+
+	ys->socket = socket(AF_NETLINK, SOCK_RAW, sock_type);
 	if (ys->socket < 0) {
 		__perr(yse, "failed to create a netlink socket");
 		goto err_free_sock;
@@ -708,8 +711,9 @@ ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
 	ys->portid = addr.nl_pid;
 	ys->seq = random();
 
-
-	if (ynl_sock_read_family(ys, yf->name)) {
+	if (yf->is_classic) {
+		ys->family_id = yf->classic_id;
+	} else if (ynl_sock_read_family(ys, yf->name)) {
 		if (yse)
 			memcpy(yse, &ys->err, sizeof(*yse));
 		goto err_close_sock;
@@ -791,13 +795,21 @@ 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;
+	__u32 cmd;
 	int ret;
 
-	gehdr = ynl_nlmsg_data(nlh);
-	if (gehdr->cmd >= ys->family->ntf_info_size)
+	if (ys->family->is_classic) {
+		cmd = nlh->nlmsg_type;
+	} else {
+		struct genlmsghdr *gehdr;
+
+		gehdr = ynl_nlmsg_data(nlh);
+		cmd = gehdr->cmd;
+	}
+
+	if (cmd >= ys->family->ntf_info_size)
 		return YNL_PARSE_CB_ERROR;
-	info = &ys->family->ntf_info[gehdr->cmd];
+	info = &ys->family->ntf_info[cmd];
 	if (!info->cb)
 		return YNL_PARSE_CB_ERROR;
 
@@ -811,7 +823,7 @@ static int ynl_ntf_parse(struct ynl_sock *ys, const struct nlmsghdr *nlh)
 		goto err_free;
 
 	rsp->family = nlh->nlmsg_type;
-	rsp->cmd = gehdr->cmd;
+	rsp->cmd = cmd;
 
 	*ys->ntf_last_next = rsp;
 	ys->ntf_last_next = &rsp->next;
@@ -863,18 +875,23 @@ int ynl_error_parse(struct ynl_parse_arg *yarg, const char *msg)
 static int
 ynl_check_alien(struct ynl_sock *ys, const struct nlmsghdr *nlh, __u32 rsp_cmd)
 {
-	struct genlmsghdr *gehdr;
+	if (ys->family->is_classic) {
+		if (nlh->nlmsg_type != rsp_cmd)
+			return ynl_ntf_parse(ys, nlh);
+	} else {
+		struct genlmsghdr *gehdr;
 
-	if (ynl_nlmsg_data_len(nlh) < sizeof(*gehdr)) {
-		yerr(ys, YNL_ERROR_INV_RESP,
-		     "Kernel responded with truncated message");
-		return -1;
+		if (ynl_nlmsg_data_len(nlh) < sizeof(*gehdr)) {
+			yerr(ys, YNL_ERROR_INV_RESP,
+			     "Kernel responded with truncated message");
+			return -1;
+		}
+
+		gehdr = ynl_nlmsg_data(nlh);
+		if (gehdr->cmd != rsp_cmd)
+			return ynl_ntf_parse(ys, nlh);
 	}
 
-	gehdr = ynl_nlmsg_data(nlh);
-	if (gehdr->cmd != rsp_cmd)
-		return ynl_ntf_parse(ys, nlh);
-
 	return 0;
 }
 

tools/net/ynl/lib/ynl.h

@@ -2,6 +2,7 @@
 #ifndef __YNL_C_H
 #define __YNL_C_H 1
 
+#include <stdbool.h>
 #include <stddef.h>
 #include <linux/genetlink.h>
 #include <linux/types.h>
@@ -48,6 +49,8 @@ struct ynl_family {
 /* private: */
 	const char *name;
 	size_t hdr_len;
+	bool is_classic;
+	__u16 classic_id;
 	const struct ynl_ntf_info *ntf_info;
 	unsigned int ntf_info_size;
 };

tools/net/ynl/pyynl/ynl_gen_c.py

@@ -971,9 +971,6 @@ class Family(SpecFamily):
     def resolve(self):
         self.resolve_up(super())
 
-        if self.yaml.get('protocol', 'genetlink') not in {'genetlink', 'genetlink-c', 'genetlink-legacy'}:
-            raise Exception("Codegen only supported for genetlink")
-
         self.c_name = c_lower(self.ident_name)
         if 'name-prefix' in self.yaml['operations']:
             self.op_prefix = c_upper(self.yaml['operations']['name-prefix'])
@@ -1020,6 +1017,9 @@ class Family(SpecFamily):
     def new_operation(self, elem, req_value, rsp_value):
         return Operation(self, elem, req_value, rsp_value)
 
+    def is_classic(self):
+        return self.proto == 'netlink-raw'
+
     def _mark_notify(self):
         for op in self.msgs.values():
             if 'notify' in op:
@@ -2730,6 +2730,9 @@ def render_user_family(family, cw, prototype):
 
     cw.block_start(f'{symbol} = ')
     cw.p(f'.name\t\t= "{family.c_name}",')
+    if family.is_classic():
+        cw.p(f'.is_classic\t= true,')
+        cw.p(f'.classic_id\t= {family.get("protonum")},')
     if family.fixed_header:
         cw.p(f'.hdr_len\t= sizeof(struct genlmsghdr) + sizeof(struct {c_lower(family.fixed_header)}),')
     else: