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linux/net/ieee802154/header_ops.c
Phoebe Buckheister c3a6114f31 ieee802154: add definitions for link-layer security and header functions 
When dealing with 802.15.4, one often has to know the maximum payload
size for a given packet. This depends on many factors, one of which is
whether or not a security header is present in the frame. These
definitions and functions provide an easy way for any upper layer to
calculate the maximum payload size for a packet. The first obvious user
for this is 6lowpan, which duplicates this calculation and gets it
partially wrong because it ignores security headers.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-15 15:51:42 -04:00

326 lines
6.8 KiB
C
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/*
* Copyright (C) 2014 Fraunhofer ITWM
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Written by:
* Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
*/
#include <net/mac802154.h>
#include <net/ieee802154.h>
#include <net/ieee802154_netdev.h>
static int
ieee802154_hdr_push_addr(u8 *buf, const struct ieee802154_addr *addr,
bool omit_pan)
{
int pos = 0;
if (addr->mode == IEEE802154_ADDR_NONE)
return 0;
if (!omit_pan) {
memcpy(buf + pos, &addr->pan_id, 2);
pos += 2;
}
switch (addr->mode) {
case IEEE802154_ADDR_SHORT:
memcpy(buf + pos, &addr->short_addr, 2);
pos += 2;
break;
case IEEE802154_ADDR_LONG:
memcpy(buf + pos, &addr->extended_addr, IEEE802154_ADDR_LEN);
pos += IEEE802154_ADDR_LEN;
break;
default:
return -EINVAL;
}
return pos;
}
static int
ieee802154_hdr_push_sechdr(u8 *buf, const struct ieee802154_sechdr *hdr)
{
int pos = 5;
memcpy(buf, hdr, 1);
memcpy(buf + 1, &hdr->frame_counter, 4);
switch (hdr->key_id_mode) {
case IEEE802154_SCF_KEY_IMPLICIT:
return pos;
case IEEE802154_SCF_KEY_INDEX:
break;
case IEEE802154_SCF_KEY_SHORT_INDEX:
memcpy(buf + pos, &hdr->short_src, 4);
pos += 4;
break;
case IEEE802154_SCF_KEY_HW_INDEX:
memcpy(buf + pos, &hdr->extended_src, IEEE802154_ADDR_LEN);
pos += IEEE802154_ADDR_LEN;
break;
}
buf[pos++] = hdr->key_id;
return pos;
}
int
ieee802154_hdr_push(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
{
u8 buf[MAC802154_FRAME_HARD_HEADER_LEN];
int pos = 2;
int rc;
struct ieee802154_hdr_fc fc = hdr->fc;
buf[pos++] = hdr->seq;
fc.dest_addr_mode = hdr->dest.mode;
rc = ieee802154_hdr_push_addr(buf + pos, &hdr->dest, false);
if (rc < 0)
return -EINVAL;
pos += rc;
fc.source_addr_mode = hdr->source.mode;
if (hdr->source.pan_id == hdr->dest.pan_id &&
hdr->dest.mode != IEEE802154_ADDR_NONE)
fc.intra_pan = true;
rc = ieee802154_hdr_push_addr(buf + pos, &hdr->source, fc.intra_pan);
if (rc < 0)
return -EINVAL;
pos += rc;
if (fc.security_enabled) {
fc.version = 1;
rc = ieee802154_hdr_push_sechdr(buf + pos, &hdr->sec);
if (rc < 0)
return -EINVAL;
pos += rc;
}
memcpy(buf, &fc, 2);
memcpy(skb_push(skb, pos), buf, pos);
return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_push);
static int
ieee802154_hdr_get_addr(const u8 *buf, int mode, bool omit_pan,
struct ieee802154_addr *addr)
{
int pos = 0;
addr->mode = mode;
if (mode == IEEE802154_ADDR_NONE)
return 0;
if (!omit_pan) {
memcpy(&addr->pan_id, buf + pos, 2);
pos += 2;
}
if (mode == IEEE802154_ADDR_SHORT) {
memcpy(&addr->short_addr, buf + pos, 2);
return pos + 2;
} else {
memcpy(&addr->extended_addr, buf + pos, IEEE802154_ADDR_LEN);
return pos + IEEE802154_ADDR_LEN;
}
}
static int ieee802154_hdr_addr_len(int mode, bool omit_pan)
{
int pan_len = omit_pan ? 0 : 2;
switch (mode) {
case IEEE802154_ADDR_NONE: return 0;
case IEEE802154_ADDR_SHORT: return 2 + pan_len;
case IEEE802154_ADDR_LONG: return IEEE802154_ADDR_LEN + pan_len;
default: return -EINVAL;
}
}
static int
ieee802154_hdr_get_sechdr(const u8 *buf, struct ieee802154_sechdr *hdr)
{
int pos = 5;
memcpy(hdr, buf, 1);
memcpy(&hdr->frame_counter, buf + 1, 4);
switch (hdr->key_id_mode) {
case IEEE802154_SCF_KEY_IMPLICIT:
return pos;
case IEEE802154_SCF_KEY_INDEX:
break;
case IEEE802154_SCF_KEY_SHORT_INDEX:
memcpy(&hdr->short_src, buf + pos, 4);
pos += 4;
break;
case IEEE802154_SCF_KEY_HW_INDEX:
memcpy(&hdr->extended_src, buf + pos, IEEE802154_ADDR_LEN);
pos += IEEE802154_ADDR_LEN;
break;
}
hdr->key_id = buf[pos++];
return pos;
}
static int ieee802154_sechdr_lengths[4] = {
[IEEE802154_SCF_KEY_IMPLICIT] = 5,
[IEEE802154_SCF_KEY_INDEX] = 6,
[IEEE802154_SCF_KEY_SHORT_INDEX] = 10,
[IEEE802154_SCF_KEY_HW_INDEX] = 14,
};
static int ieee802154_hdr_sechdr_len(u8 sc)
{
return ieee802154_sechdr_lengths[IEEE802154_SCF_KEY_ID_MODE(sc)];
}
static int ieee802154_hdr_minlen(const struct ieee802154_hdr *hdr)
{
int dlen, slen;
dlen = ieee802154_hdr_addr_len(hdr->fc.dest_addr_mode, false);
slen = ieee802154_hdr_addr_len(hdr->fc.source_addr_mode,
hdr->fc.intra_pan);
if (slen < 0 || dlen < 0)
return -EINVAL;
return 3 + dlen + slen + hdr->fc.security_enabled;
}
static int
ieee802154_hdr_get_addrs(const u8 *buf, struct ieee802154_hdr *hdr)
{
int pos = 0;
pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.dest_addr_mode,
false, &hdr->dest);
pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.source_addr_mode,
hdr->fc.intra_pan, &hdr->source);
if (hdr->fc.intra_pan)
hdr->source.pan_id = hdr->dest.pan_id;
return pos;
}
int
ieee802154_hdr_pull(struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
int pos = 3, rc;
if (!pskb_may_pull(skb, 3))
return -EINVAL;
memcpy(hdr, skb->data, 3);
rc = ieee802154_hdr_minlen(hdr);
if (rc < 0 || !pskb_may_pull(skb, rc))
return -EINVAL;
pos += ieee802154_hdr_get_addrs(skb->data + pos, hdr);
if (hdr->fc.security_enabled) {
int want = pos + ieee802154_hdr_sechdr_len(skb->data[pos]);
if (!pskb_may_pull(skb, want))
return -EINVAL;
pos += ieee802154_hdr_get_sechdr(skb->data + pos, &hdr->sec);
}
skb_pull(skb, pos);
return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_pull);
int
ieee802154_hdr_peek_addrs(const struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
const u8 *buf = skb_mac_header(skb);
int pos = 3, rc;
if (buf + 3 > skb_tail_pointer(skb))
return -EINVAL;
memcpy(hdr, buf, 3);
rc = ieee802154_hdr_minlen(hdr);
if (rc < 0 || buf + rc > skb_tail_pointer(skb))
return -EINVAL;
pos += ieee802154_hdr_get_addrs(buf + pos, hdr);
return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_peek_addrs);
int
ieee802154_hdr_peek(const struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
const u8 *buf = skb_mac_header(skb);
int pos;
pos = ieee802154_hdr_peek_addrs(skb, hdr);
if (pos < 0)
return -EINVAL;
if (hdr->fc.security_enabled) {
u8 key_id_mode = IEEE802154_SCF_KEY_ID_MODE(*(buf + pos));
int want = pos + ieee802154_sechdr_lengths[key_id_mode];
if (buf + want > skb_tail_pointer(skb))
return -EINVAL;
pos += ieee802154_hdr_get_sechdr(buf + pos, &hdr->sec);
}
return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_peek);
int ieee802154_max_payload(const struct ieee802154_hdr *hdr)
{
int hlen = ieee802154_hdr_minlen(hdr);
if (hdr->fc.security_enabled) {
hlen += ieee802154_sechdr_lengths[hdr->sec.key_id_mode] - 1;
hlen += ieee802154_sechdr_authtag_len(&hdr->sec);
}
return IEEE802154_MTU - hlen - IEEE802154_MFR_SIZE;
}
EXPORT_SYMBOL_GPL(ieee802154_max_payload);
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