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