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linux/net/6lowpan/nhc_udp.c
Alexander Aring 31264f9563 net: 6lowpan: use array for find nhc id
This patch will remove the complete overengineered and overthinking rb data
structure for looking up the nhc by nhcid. Instead we using the existing
nhc next header array and iterate over it. It works now for 1 byte values
only. However there are only 1 byte nhc id values currently
supported and IANA also does not specify large than 1 byte values yet.
If there are 2 byte values for nhc ids specified we can revisit this
data structure and add support for it.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Link: https://lore.kernel.org/r/20220428030534.3220410-3-aahringo@redhat.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
2022-06-09 21:53:28 +02:00

177 lines
5.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 6LoWPAN IPv6 UDP compression according to RFC6282
*
* Authors:
* Alexander Aring <aar@pengutronix.de>
*
* Original written by:
* Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
* Jon Smirl <jonsmirl@gmail.com>
*/
#include "nhc.h"
#define LOWPAN_NHC_UDP_MASK 0xF8
#define LOWPAN_NHC_UDP_ID 0xF0
#define LOWPAN_NHC_UDP_4BIT_PORT 0xF0B0
#define LOWPAN_NHC_UDP_4BIT_MASK 0xFFF0
#define LOWPAN_NHC_UDP_8BIT_PORT 0xF000
#define LOWPAN_NHC_UDP_8BIT_MASK 0xFF00
/* values for port compression, _with checksum_ ie bit 5 set to 0 */
/* all inline */
#define LOWPAN_NHC_UDP_CS_P_00 0xF0
/* source 16bit inline, dest = 0xF0 + 8 bit inline */
#define LOWPAN_NHC_UDP_CS_P_01 0xF1
/* source = 0xF0 + 8bit inline, dest = 16 bit inline */
#define LOWPAN_NHC_UDP_CS_P_10 0xF2
/* source & dest = 0xF0B + 4bit inline */
#define LOWPAN_NHC_UDP_CS_P_11 0xF3
/* checksum elided */
#define LOWPAN_NHC_UDP_CS_C 0x04
static int udp_uncompress(struct sk_buff *skb, size_t needed)
{
u8 tmp = 0, val = 0;
struct udphdr uh;
bool fail;
int err;
fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));
pr_debug("UDP header uncompression\n");
switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
case LOWPAN_NHC_UDP_CS_P_00:
fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
break;
case LOWPAN_NHC_UDP_CS_P_01:
fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
uh.dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
break;
case LOWPAN_NHC_UDP_CS_P_10:
fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
uh.source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
break;
case LOWPAN_NHC_UDP_CS_P_11:
fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
uh.source = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val >> 4));
uh.dest = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val & 0x0f));
break;
default:
BUG();
}
pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
ntohs(uh.source), ntohs(uh.dest));
/* checksum */
if (tmp & LOWPAN_NHC_UDP_CS_C) {
pr_debug_ratelimited("checksum elided currently not supported\n");
fail = true;
} else {
fail |= lowpan_fetch_skb(skb, &uh.check, sizeof(uh.check));
}
if (fail)
return -EINVAL;
/* UDP length needs to be inferred from the lower layers
* here, we obtain the hint from the remaining size of the
* frame
*/
switch (lowpan_dev(skb->dev)->lltype) {
case LOWPAN_LLTYPE_IEEE802154:
if (lowpan_802154_cb(skb)->d_size)
uh.len = htons(lowpan_802154_cb(skb)->d_size -
sizeof(struct ipv6hdr));
else
uh.len = htons(skb->len + sizeof(struct udphdr));
break;
default:
uh.len = htons(skb->len + sizeof(struct udphdr));
break;
}
pr_debug("uncompressed UDP length: src = %d", ntohs(uh.len));
/* replace the compressed UDP head by the uncompressed UDP
* header
*/
err = skb_cow(skb, needed);
if (unlikely(err))
return err;
skb_push(skb, sizeof(struct udphdr));
skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
return 0;
}
static int udp_compress(struct sk_buff *skb, u8 **hc_ptr)
{
const struct udphdr *uh = udp_hdr(skb);
u8 tmp;
if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
LOWPAN_NHC_UDP_4BIT_PORT) &&
((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
LOWPAN_NHC_UDP_4BIT_PORT)) {
pr_debug("UDP header: both ports compression to 4 bits\n");
/* compression value */
tmp = LOWPAN_NHC_UDP_CS_P_11;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
/* source and destination port */
tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
} else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
LOWPAN_NHC_UDP_8BIT_PORT) {
pr_debug("UDP header: remove 8 bits of dest\n");
/* compression value */
tmp = LOWPAN_NHC_UDP_CS_P_01;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
/* source port */
lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
/* destination port */
tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
} else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
LOWPAN_NHC_UDP_8BIT_PORT) {
pr_debug("UDP header: remove 8 bits of source\n");
/* compression value */
tmp = LOWPAN_NHC_UDP_CS_P_10;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
/* source port */
tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
/* destination port */
lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
} else {
pr_debug("UDP header: can't compress\n");
/* compression value */
tmp = LOWPAN_NHC_UDP_CS_P_00;
lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
/* source port */
lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
/* destination port */
lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
}
/* checksum is always inline */
lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));
return 0;
}
LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
LOWPAN_NHC_UDP_ID, LOWPAN_NHC_UDP_MASK, udp_uncompress, udp_compress);
module_lowpan_nhc(nhc_udp);
MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");
MODULE_LICENSE("GPL");