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6lowpan: rework tc and flow label handling

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This patch reworks the handling of compression/decompression of traffic
class and flow label handling. The current method is hard to understand,
also doesn't checks if we can read the buffer from skb length.

I tried to put the shifting operations into static inline functions and
comment each steps which I did there to make it hopefully somewhat more
readable. The big mess to deal with that is the that the ipv6 header
bring the order "DSCP + ECN" but iphc uses "ECN + DSCP". Additional the
DCSP + ECN bits are splitted in ipv6_hdr inside the priority and
flow_lbl[0] fields.

I tested these compressions by using fakelb 802.15.4 driver and
manipulate the tc and flow label fields manually in function
"__ip6_local_out" before the skb will be send to lower layers. Then I
looked up the tc and flow label fields in wireshark on a wpan and lowpan
interface.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Alexander Aring 2015-10-20 08:31:25 +02:00 committed by Marcel Holtmann
parent c8a3e7eb98
commit b5af9bdbfe
1 changed files with 205 additions and 85 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

290
net/6lowpan/iphc.c
View File

@ -346,6 +346,108 @@ static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
return 0;
}
/* get the ecn values from iphc tf format and set it to ipv6hdr */
static inline void lowpan_iphc_tf_set_ecn(struct ipv6hdr *hdr, const u8 *tf)
{
/* get the two higher bits which is ecn */
u8 ecn = tf[0] & 0xc0;
/* ECN takes 0x30 in hdr->flow_lbl[0] */
hdr->flow_lbl[0] |= (ecn >> 2);
}
/* get the dscp values from iphc tf format and set it to ipv6hdr */
static inline void lowpan_iphc_tf_set_dscp(struct ipv6hdr *hdr, const u8 *tf)
{
/* DSCP is at place after ECN */
u8 dscp = tf[0] & 0x3f;
/* The four highest bits need to be set at hdr->priority */
hdr->priority |= ((dscp & 0x3c) >> 2);
/* The two lower bits is part of hdr->flow_lbl[0] */
hdr->flow_lbl[0] |= ((dscp & 0x03) << 6);
}
/* get the flow label values from iphc tf format and set it to ipv6hdr */
static inline void lowpan_iphc_tf_set_lbl(struct ipv6hdr *hdr, const u8 *lbl)
{
/* flow label is always some array started with lower nibble of
* flow_lbl[0] and followed with two bytes afterwards. Inside inline
* data the flow_lbl position can be different, which will be handled
* by lbl pointer. E.g. case "01" vs "00" the traffic class is 8 bit
* shifted, the different lbl pointer will handle that.
*
* The flow label will started at lower nibble of flow_lbl[0], the
* higher nibbles are part of DSCP + ECN.
*/
hdr->flow_lbl[0] |= lbl[0] & 0x0f;
memcpy(&hdr->flow_lbl[1], &lbl[1], 2);
}
/* lowpan_iphc_tf_decompress - decompress the traffic class.
* This function will return zero on success, a value lower than zero if
* failed.
*/
static int lowpan_iphc_tf_decompress(struct sk_buff *skb, struct ipv6hdr *hdr,
u8 val)
{
u8 tf[4];
/* Traffic Class and Flow Label */
switch (val) {
case LOWPAN_IPHC_TF_00:
/* ECN + DSCP + 4-bit Pad + Flow Label (4 bytes) */
if (lowpan_fetch_skb(skb, tf, 4))
return -EINVAL;
/* 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |ECN| DSCP | rsv | Flow Label |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
lowpan_iphc_tf_set_ecn(hdr, tf);
lowpan_iphc_tf_set_dscp(hdr, tf);
lowpan_iphc_tf_set_lbl(hdr, &tf[1]);
break;
case LOWPAN_IPHC_TF_01:
/* ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided. */
if (lowpan_fetch_skb(skb, tf, 3))
return -EINVAL;
/* 1 2
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |ECN|rsv| Flow Label |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
lowpan_iphc_tf_set_ecn(hdr, tf);
lowpan_iphc_tf_set_lbl(hdr, &tf[0]);
break;
case LOWPAN_IPHC_TF_10:
/* ECN + DSCP (1 byte), Flow Label is elided. */
if (lowpan_fetch_skb(skb, tf, 1))
return -EINVAL;
/* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |ECN| DSCP |
* +-+-+-+-+-+-+-+-+
*/
lowpan_iphc_tf_set_ecn(hdr, tf);
lowpan_iphc_tf_set_dscp(hdr, tf);
break;
case LOWPAN_IPHC_TF_11:
/* Traffic Class and Flow Label are elided */
break;
default:
WARN_ON_ONCE(1);
return -EINVAL;
}
return 0;
}
/* TTL uncompression values */
static const u8 lowpan_ttl_values[] = {
[LOWPAN_IPHC_HLIM_01] = 1,
@ -357,7 +459,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
const void *daddr, const void *saddr)
{
struct ipv6hdr hdr = {};
u8 iphc0, iphc1, tmp = 0;
u8 iphc0, iphc1;
int err;
raw_dump_table(__func__, "raw skb data dump uncompressed",
@ -373,49 +475,10 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
hdr.version = 6;
/* Traffic Class and Flow Label */
switch (iphc0 & LOWPAN_IPHC_TF_MASK) {
/* Traffic Class and FLow Label carried in-line
* ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
*/
case LOWPAN_IPHC_TF_00:
if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
return -EINVAL;
memcpy(&hdr.flow_lbl, &skb->data[0], 3);
skb_pull(skb, 3);
hdr.priority = ((tmp >> 2) & 0x0f);
hdr.flow_lbl[0] = ((tmp >> 2) & 0x30) | (tmp << 6) |
(hdr.flow_lbl[0] & 0x0f);
break;
/* Flow Label carried in-line
* ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
*/
case LOWPAN_IPHC_TF_01:
if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
return -EINVAL;
hdr.flow_lbl[0] = (tmp & 0x0F) | ((tmp >> 2) & 0x30);
memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
skb_pull(skb, 2);
break;
/* Traffic class carried in-line
* ECN + DSCP (1 byte), Flow Label is elided
*/
case LOWPAN_IPHC_TF_10:
if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
return -EINVAL;
hdr.priority = ((tmp >> 2) & 0x0f);
hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
break;
/* Traffic Class and Flow Label are elided */
case LOWPAN_IPHC_TF_11:
break;
default:
WARN_ON_ONCE(1);
break;
}
err = lowpan_iphc_tf_decompress(skb, &hdr,
iphc0 & LOWPAN_IPHC_TF_MASK);
if (err < 0)
return err;
/* Next Header */
if (!(iphc0 & LOWPAN_IPHC_NH)) {
@ -550,10 +613,105 @@ static u8 lowpan_compress_addr_64(u8 **hc_ptr, const struct in6_addr *ipaddr,
return dam;
}
/* lowpan_iphc_get_tc - get the ECN + DCSP fields in hc format */
static inline u8 lowpan_iphc_get_tc(const struct ipv6hdr *hdr)
{
u8 dscp, ecn;
/* hdr->priority contains the higher bits of dscp, lower are part of
* flow_lbl[0]. Note ECN, DCSP is swapped in ipv6 hdr.
*/
dscp = (hdr->priority << 2) | ((hdr->flow_lbl[0] & 0xc0) >> 6);
/* ECN is at the two lower bits from first nibble of flow_lbl[0] */
ecn = (hdr->flow_lbl[0] & 0x30);
/* for pretty debug output, also shift ecn to get the ecn value */
pr_debug("ecn 0x%02x dscp 0x%02x\n", ecn >> 4, dscp);
/* ECN is at 0x30 now, shift it to have ECN + DCSP */
return (ecn << 2) | dscp;
}
/* lowpan_iphc_is_flow_lbl_zero - check if flow label is zero */
static inline bool lowpan_iphc_is_flow_lbl_zero(const struct ipv6hdr *hdr)
{
return ((!(hdr->flow_lbl[0] & 0x0f)) &&
!hdr->flow_lbl[1] && !hdr->flow_lbl[2]);
}
/* lowpan_iphc_tf_compress - compress the traffic class which is set by
* ipv6hdr. Return the corresponding format identifier which is used.
*/
static u8 lowpan_iphc_tf_compress(u8 **hc_ptr, const struct ipv6hdr *hdr)
{
/* get ecn dscp data in a byteformat as: ECN(hi) + DSCP(lo) */
u8 tc = lowpan_iphc_get_tc(hdr), tf[4], val;
/* printout the traffic class in hc format */
pr_debug("tc 0x%02x\n", tc);
if (lowpan_iphc_is_flow_lbl_zero(hdr)) {
if (!tc) {
/* 11: Traffic Class and Flow Label are elided. */
val = LOWPAN_IPHC_TF_11;
} else {
/* 10: ECN + DSCP (1 byte), Flow Label is elided.
*
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |ECN| DSCP |
* +-+-+-+-+-+-+-+-+
*/
lowpan_push_hc_data(hc_ptr, &tc, sizeof(tc));
val = LOWPAN_IPHC_TF_10;
}
} else {
/* check if dscp is zero, it's after the first two bit */
if (!(tc & 0x3f)) {
/* 01: ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
*
* 1 2
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |ECN|rsv| Flow Label |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
memcpy(&tf[0], &hdr->flow_lbl[0], 3);
/* zero the highest 4-bits, contains DCSP + ECN */
tf[0] &= ~0xf0;
/* set ECN */
tf[0] |= (tc & 0xc0);
lowpan_push_hc_data(hc_ptr, tf, 3);
val = LOWPAN_IPHC_TF_01;
} else {
/* 00: ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
*
* 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |ECN| DSCP | rsv | Flow Label |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
memcpy(&tf[0], &tc, sizeof(tc));
/* highest nibble of flow_lbl[0] is part of DSCP + ECN
* which will be the 4-bit pad and will be filled with
* zeros afterwards.
*/
memcpy(&tf[1], &hdr->flow_lbl[0], 3);
/* zero the 4-bit pad, which is reserved */
tf[1] &= ~0xf0;
lowpan_push_hc_data(hc_ptr, tf, 4);
val = LOWPAN_IPHC_TF_00;
}
}
return val;
}
int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
const void *daddr, const void *saddr)
{
u8 tmp, iphc0, iphc1, *hc_ptr;
u8 iphc0, iphc1, *hc_ptr;
struct ipv6hdr *hdr;
u8 head[LOWPAN_IPHC_MAX_HC_BUF_LEN] = {};
int ret, addr_type;
@ -588,46 +746,8 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
raw_dump_table(__func__, "sending raw skb network uncompressed packet",
skb->data, skb->len);
/* Traffic class, flow label
* If flow label is 0, compress it. If traffic class is 0, compress it
* We have to process both in the same time as the offset of traffic
* class depends on the presence of version and flow label
*/
/* hc format of TC is ECN | DSCP , original one is DSCP | ECN */
tmp = (hdr->priority << 4) | (hdr->flow_lbl[0] >> 4);
tmp = ((tmp & 0x03) << 6) | (tmp >> 2);
if (((hdr->flow_lbl[0] & 0x0F) == 0) &&
(hdr->flow_lbl[1] == 0) && (hdr->flow_lbl[2] == 0)) {
/* flow label can be compressed */
iphc0 |= LOWPAN_IPHC_TF_10;
if ((hdr->priority == 0) &&
((hdr->flow_lbl[0] & 0xF0) == 0)) {
/* compress (elide) all */
iphc0 |= LOWPAN_IPHC_TF_11;
} else {
/* compress only the flow label */
*hc_ptr = tmp;
hc_ptr += 1;
}
} else {
/* Flow label cannot be compressed */
if ((hdr->priority == 0) &&
((hdr->flow_lbl[0] & 0xF0) == 0)) {
/* compress only traffic class */
iphc0 |= LOWPAN_IPHC_TF_01;
*hc_ptr = (tmp & 0xc0) | (hdr->flow_lbl[0] & 0x0F);
memcpy(hc_ptr + 1, &hdr->flow_lbl[1], 2);
hc_ptr += 3;
} else {
/* compress nothing */
memcpy(hc_ptr, hdr, 4);
/* replace the top byte with new ECN | DSCP format */
*hc_ptr = tmp;
hc_ptr += 4;
}
}
/* Traffic Class, Flow Label compression */
iphc0 |= lowpan_iphc_tf_compress(&hc_ptr, hdr);
/* NOTE: payload length is always compressed */