Commit 0939a418 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

tools: ynl: submsg: reverse parse / error reporting 



Reverse parsing lets YNL convert bad and missing attr pointers
from extack into a string like "missing attribute nest1.nest2.attr_name".
It's a feature that's unique to YNL C AFAIU (even the Python YNL
can't do nested reverse parsing). Add support for reverse-parsing
of sub-messages.

To simplify the logic and the code annotate the type policies
with extra metadata. Mark the selectors and the messages with
the information we need. We assume that key / selector always
precedes the sub-message while parsing (and also if there are
multiple sub-messages like in rt-link they are interleaved
selector 1 ... submsg 1 ... selector 2 .. submsg 2, not
selector 1 ... selector 2 ... submsg 1 ... submsg 2).

The rt-link sample in a subsequent changes shows reverse parsing
of sub-messages in action.

Reviewed-by: default avatarDonald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250515231650.1325372-8-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b9e03e26

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

+4 −1
Original line number Diff line number Diff line
@@ -43,7 +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;

tools/net/ynl/lib/ynl.c

+75 −9
Original line number Diff line number Diff line
@@ -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,

	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;

tools/net/ynl/pyynl/ynl_gen_c.py

+28 −1
Original line number Diff line number Diff line
@@ -57,6 +57,8 @@ class Type(SpecAttr): 
        self.request = False

        self.reply = False



        self.is_selector = False



        if 'len' in attr:

            self.len = attr['len']
@@ -484,7 +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:
@@ -878,6 +883,16 @@ class TypeNestTypeValue(Type): 




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})',
@@ -890,6 +905,18 @@ class TypeSubMessage(TypeNest): 
        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, submsg=None):