diff options
| author | Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de> | 2014-05-14 19:43:06 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-05-15 23:51:42 +0400 |
| commit | c3a6114f31600b94ee10ebf62e4d493b401ade87 (patch) | |
| tree | a854819cfede389764da13bcc0d7670e1f1e964f /net/ieee802154 | |
| parent | 9dbccc30f3306114e1ca4a89da69be6d5f675782 (diff) | |
| download | linux-c3a6114f31600b94ee10ebf62e4d493b401ade87.tar.xz | |
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>
Diffstat (limited to 'net/ieee802154')
| -rw-r--r-- | net/ieee802154/header_ops.c | 52 |
1 files changed, 45 insertions, 7 deletions
diff --git a/net/ieee802154/header_ops.c b/net/ieee802154/header_ops.c index bed42a48408c..c09294e39ca6 100644 --- a/net/ieee802154/header_ops.c +++ b/net/ieee802154/header_ops.c @@ -195,15 +195,16 @@ ieee802154_hdr_get_sechdr(const u8 *buf, struct ieee802154_sechdr *hdr) 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) { - switch (IEEE802154_SCF_KEY_ID_MODE(sc)) { - case IEEE802154_SCF_KEY_IMPLICIT: return 5; - case IEEE802154_SCF_KEY_INDEX: return 6; - case IEEE802154_SCF_KEY_SHORT_INDEX: return 10; - case IEEE802154_SCF_KEY_HW_INDEX: return 14; - default: return -EINVAL; - } + return ieee802154_sechdr_lengths[IEEE802154_SCF_KEY_ID_MODE(sc)]; } static int ieee802154_hdr_minlen(const struct ieee802154_hdr *hdr) @@ -285,3 +286,40 @@ ieee802154_hdr_peek_addrs(const struct sk_buff *skb, struct ieee802154_hdr *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); |