[PATCH net-next 3/8] tools: ynl-gen: support fixed headers in genetlink

[Jakub Kicinski <kuba@kernel.org>]

Support genetlink families using simple fixed headers.
Assume fixed header is identical for all ops of the family for now.

Fixed headers are added to the request and reply structs as a _hdr
member, and copied to/from netlink messages appropriately.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/net/ynl/lib/ynl.c    |  8 +++----
 tools/net/ynl/lib/ynl.h    |  1 +
 tools/net/ynl/ynl-gen-c.py | 44 ++++++++++++++++++++++++++++++++++----
 3 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/tools/net/ynl/lib/ynl.c b/tools/net/ynl/lib/ynl.c
index 587286de10b5..c82a7f41b31c 100644
--- a/tools/net/ynl/lib/ynl.c
+++ b/tools/net/ynl/lib/ynl.c
@@ -191,12 +191,12 @@ ynl_ext_ack_check(struct ynl_sock *ys, const struct nlmsghdr *nlh,
 			     str ? " (" : "");
 
 		start = mnl_nlmsg_get_payload_offset(ys->nlh,
-						     sizeof(struct genlmsghdr));
+						     ys->family->hdr_len);
 		end = mnl_nlmsg_get_payload_tail(ys->nlh);
 
 		off = ys->err.attr_offs;
 		off -= sizeof(struct nlmsghdr);
-		off -= sizeof(struct genlmsghdr);
+		off -= ys->family->hdr_len;
 
 		n += ynl_err_walk(ys, start, end, off, ys->req_policy,
 				  &bad_attr[n], sizeof(bad_attr) - n, NULL);
@@ -217,14 +217,14 @@ ynl_ext_ack_check(struct ynl_sock *ys, const struct nlmsghdr *nlh,
 			     bad_attr[0] ? ", " : (str ? " (" : ""));
 
 		start = mnl_nlmsg_get_payload_offset(ys->nlh,
-						     sizeof(struct genlmsghdr));
+						     ys->family->hdr_len);
 		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);
+			off -= ys->family->hdr_len;
 
 			n += ynl_err_walk(ys, start, end, off, ys->req_policy,
 					  &miss_attr[n], sizeof(miss_attr) - n,
diff --git a/tools/net/ynl/lib/ynl.h b/tools/net/ynl/lib/ynl.h
index 5de580b992b8..ce77a6d76ce0 100644
--- a/tools/net/ynl/lib/ynl.h
+++ b/tools/net/ynl/lib/ynl.h
@@ -44,6 +44,7 @@ struct ynl_error {
 struct ynl_family {
 /* private: */
 	const char *name;
+	size_t hdr_len;
 	const struct ynl_ntf_info *ntf_info;
 	unsigned int ntf_info_size;
 };
diff --git a/tools/net/ynl/ynl-gen-c.py b/tools/net/ynl/ynl-gen-c.py
index ab009d0f9db5..70e2c41e5bd6 100755
--- a/tools/net/ynl/ynl-gen-c.py
+++ b/tools/net/ynl/ynl-gen-c.py
@@ -1124,6 +1124,10 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
         self.op_mode = op_mode
         self.op = op
 
+        self.fixed_hdr = None
+        if op and op.fixed_header:
+            self.fixed_hdr = 'struct ' + c_lower(op.fixed_header)
+
         # 'do' and 'dump' response parsing is identical
         self.type_consistent = True
         if op_mode != 'do' and 'dump' in op:
@@ -1570,7 +1574,9 @@ _C_KW = {
     if struct.nested:
         iter_line = "mnl_attr_for_each_nested(attr, nested)"
     else:
-        iter_line = "mnl_attr_for_each(attr, nlh, sizeof(struct genlmsghdr))"
+        if ri.fixed_hdr:
+            local_vars += ['void *hdr;']
+        iter_line = "mnl_attr_for_each(attr, nlh, yarg->ys->family->hdr_len)"
 
     array_nests = set()
     multi_attrs = set()
@@ -1603,6 +1609,9 @@ _C_KW = {
     for arg in struct.inherited:
         ri.cw.p(f'dst->{arg} = {arg};')
 
+    if ri.fixed_hdr:
+        ri.cw.p('hdr = mnl_nlmsg_get_payload_offset(nlh, sizeof(struct genlmsghdr));')
+        ri.cw.p(f"memcpy(&dst->_hdr, hdr, sizeof({ri.fixed_hdr}));")
     for anest in sorted(all_multi):
         aspec = struct[anest]
         ri.cw.p(f"if (dst->{aspec.c_name})")
@@ -1723,6 +1732,10 @@ _C_KW = {
         ret_err = 'NULL'
         local_vars += [f'{type_name(ri, rdir(direction))} *rsp;']
 
+    if ri.fixed_hdr:
+        local_vars += ['size_t hdr_len;',
+                       'void *hdr;']
+
     print_prototype(ri, direction, terminate=False)
     ri.cw.block_start()
     ri.cw.write_func_lvar(local_vars)
@@ -1733,6 +1746,13 @@ _C_KW = {
     if 'reply' in ri.op[ri.op_mode]:
         ri.cw.p(f"yrs.yarg.rsp_policy = &{ri.struct['reply'].render_name}_nest;")
     ri.cw.nl()
+
+    if ri.fixed_hdr:
+        ri.cw.p("hdr_len = sizeof(req->_hdr);")
+        ri.cw.p("hdr = mnl_nlmsg_put_extra_header(nlh, hdr_len);")
+        ri.cw.p("memcpy(hdr, &req->_hdr, hdr_len);")
+        ri.cw.nl()
+
     for _, attr in ri.struct["request"].member_list():
         attr.attr_put(ri, "req")
     ri.cw.nl()
@@ -1773,9 +1793,11 @@ _C_KW = {
                   'struct nlmsghdr *nlh;',
                   'int err;']
 
-    for var in local_vars:
-        ri.cw.p(f'{var}')
-    ri.cw.nl()
+    if ri.fixed_hdr:
+        local_vars += ['size_t hdr_len;',
+                       'void *hdr;']
+
+    ri.cw.write_func_lvar(local_vars)
 
     ri.cw.p('yds.ys = ys;')
     ri.cw.p(f"yds.alloc_sz = sizeof({type_name(ri, rdir(direction))});")
@@ -1788,6 +1810,12 @@ _C_KW = {
     ri.cw.nl()
     ri.cw.p(f"nlh = ynl_gemsg_start_dump(ys, {ri.nl.get_family_id()}, {ri.op.enum_name}, 1);")
 
+    if ri.fixed_hdr:
+        ri.cw.p("hdr_len = sizeof(req->_hdr);")
+        ri.cw.p("hdr = mnl_nlmsg_put_extra_header(nlh, hdr_len);")
+        ri.cw.p("memcpy(hdr, &req->_hdr, hdr_len);")
+        ri.cw.nl()
+
     if "request" in ri.op[ri.op_mode]:
         ri.cw.p(f"ys->req_policy = &{ri.struct['request'].render_name}_nest;")
         ri.cw.nl()
@@ -1845,6 +1873,10 @@ _C_KW = {
 
     ri.cw.block_start(line=f"struct {ri.family.c_name}{suffix}")
 
+    if ri.fixed_hdr:
+        ri.cw.p(ri.fixed_hdr + ' _hdr;')
+        ri.cw.nl()
+
     meta_started = False
     for _, attr in struct.member_list():
         for type_filter in ['len', 'bit']:
@@ -2482,6 +2514,10 @@ _C_KW = {
 
     cw.block_start(f'{symbol} = ')
     cw.p(f'.name\t\t= "{family.c_name}",')
+    if family.fixed_header:
+        cw.p(f'.hdr_len\t= sizeof(struct genlmsghdr) + sizeof(struct {c_lower(family.fixed_header)}),')
+    else:
+        cw.p('.hdr_len\t= sizeof(struct genlmsghdr),')
     if family.ntfs:
         cw.p(f".ntf_info\t= {family['name']}_ntf_info,")
         cw.p(f".ntf_info_size\t= MNL_ARRAY_SIZE({family['name']}_ntf_info),")
-- 
2.43.0