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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* em_canid.c Ematch rule to match CAN frames according to their CAN IDs
*
* Idea: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
* Copyright: (c) 2011 Czech Technical University in Prague
* (c) 2011 Volkswagen Group Research
* Authors: Michal Sojka <sojkam1@fel.cvut.cz>
* Pavel Pisa <pisa@cmp.felk.cvut.cz>
* Rostislav Lisovy <lisovy@gmail.cz>
* Funded by: Volkswagen Group Research
*/
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <net/pkt_cls.h>
#include <linux/can.h>
#define EM_CAN_RULES_MAX 500
struct canid_match {
/* For each SFF CAN ID (11 bit) there is one record in this bitfield */
DECLARE_BITMAP(match_sff, (1 << CAN_SFF_ID_BITS));
int rules_count;
int sff_rules_count;
int eff_rules_count;
/*
* Raw rules copied from netlink message; Used for sending
* information to userspace (when 'tc filter show' is invoked)
* AND when matching EFF frames
*/
struct can_filter rules_raw[];
};
/**
* em_canid_get_id() - Extracts Can ID out of the sk_buff structure.
* @skb: buffer to extract Can ID from
*/
static canid_t em_canid_get_id(struct sk_buff *skb)
{
/* CAN ID is stored within the data field */
struct can_frame *cf = (struct can_frame *)skb->data;
return cf->can_id;
}
static void em_canid_sff_match_add(struct canid_match *cm, u32 can_id,
u32 can_mask)
{
int i;
/*
* Limit can_mask and can_id to SFF range to
* protect against write after end of array
*/
can_mask &= CAN_SFF_MASK;
can_id &= can_mask;
/* Single frame */
if (can_mask == CAN_SFF_MASK) {
set_bit(can_id, cm->match_sff);
return;
}
/* All frames */
if (can_mask == 0) {
bitmap_fill(cm->match_sff, (1 << CAN_SFF_ID_BITS));
return;
}
/*
* Individual frame filter.
* Add record (set bit to 1) for each ID that
* conforms particular rule
*/
for (i = 0; i < (1 << CAN_SFF_ID_BITS); i++) {
if ((i & can_mask) == can_id)
set_bit(i, cm->match_sff);
}
}
static inline struct canid_match *em_canid_priv(struct tcf_ematch *m)
{
return (struct canid_match *)m->data;
}
static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m,
struct tcf_pkt_info *info)
{
struct canid_match *cm = em_canid_priv(m);
canid_t can_id;
int match = 0;
int i;
const struct can_filter *lp;
can_id = em_canid_get_id(skb);
if (can_id & CAN_EFF_FLAG) {
for (i = 0, lp = cm->rules_raw;
i < cm->eff_rules_count; i++, lp++) {
if (!(((lp->can_id ^ can_id) & lp->can_mask))) {
match = 1;
break;
}
}
} else { /* SFF */
can_id &= CAN_SFF_MASK;
match = (test_bit(can_id, cm->match_sff) ? 1 : 0);
}
return match;
}
static int em_canid_change(struct net *net, void *data, int len,
struct tcf_ematch *m)
{
struct can_filter *conf = data; /* Array with rules */
struct canid_match *cm;
int i;
if (!len)
return -EINVAL;
if (len % sizeof(struct can_filter))
return -EINVAL;
if (len > sizeof(struct can_filter) * EM_CAN_RULES_MAX)
return -EINVAL;
cm = kzalloc(sizeof(struct canid_match) + len, GFP_KERNEL);
if (!cm)
return -ENOMEM;
cm->rules_count = len / sizeof(struct can_filter);
/*
* We need two for() loops for copying rules into two contiguous
* areas in rules_raw to process all eff rules with a simple loop.
* NB: The configuration interface supports sff and eff rules.
* We do not support filters here that match for the same can_id
* provided in a SFF and EFF frame (e.g. 0x123 / 0x80000123).
* For this (unusual case) two filters have to be specified. The
* SFF/EFF separation is done with the CAN_EFF_FLAG in the can_id.
*/
/* Fill rules_raw with EFF rules first */
for (i = 0; i < cm->rules_count; i++) {
if (conf[i].can_id & CAN_EFF_FLAG) {
memcpy(cm->rules_raw + cm->eff_rules_count,
&conf[i],
sizeof(struct can_filter));
cm->eff_rules_count++;
}
}
/* append SFF frame rules */
for (i = 0; i < cm->rules_count; i++) {
if (!(conf[i].can_id & CAN_EFF_FLAG)) {
memcpy(cm->rules_raw
+ cm->eff_rules_count
+ cm->sff_rules_count,
&conf[i], sizeof(struct can_filter));
cm->sff_rules_count++;
em_canid_sff_match_add(cm,
conf[i].can_id, conf[i].can_mask);
}
}
m->datalen = sizeof(struct canid_match) + len;
m->data = (unsigned long)cm;
return 0;
}
static void em_canid_destroy(struct tcf_ematch *m)
{
struct canid_match *cm = em_canid_priv(m);
kfree(cm);
}
static int em_canid_dump(struct sk_buff *skb, struct tcf_ematch *m)
{
struct canid_match *cm = em_canid_priv(m);
/*
* When configuring this ematch 'rules_count' is set not to exceed
* 'rules_raw' array size
*/
if (nla_put_nohdr(skb, sizeof(struct can_filter) * cm->rules_count,
&cm->rules_raw) < 0)
return -EMSGSIZE;
return 0;
}
static struct tcf_ematch_ops em_canid_ops = {
.kind = TCF_EM_CANID,
.change = em_canid_change,
.match = em_canid_match,
.destroy = em_canid_destroy,
.dump = em_canid_dump,
.owner = THIS_MODULE,
.link = LIST_HEAD_INIT(em_canid_ops.link)
};
static int __init init_em_canid(void)
{
return tcf_em_register(&em_canid_ops);
}
static void __exit exit_em_canid(void)
{
tcf_em_unregister(&em_canid_ops);
}
MODULE_DESCRIPTION("ematch classifier to match CAN IDs embedded in skb CAN frames");
MODULE_LICENSE("GPL");
module_init(init_em_canid);
module_exit(exit_em_canid);
MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID);
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