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@xxxxxxxxx>
---
net/6lowpan/iphc.c | 290 +++++++++++++++++++++++++++++++++++++----------------
1 file changed, 205 insertions(+), 85 deletions(-)
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index af8af98..e6cdfc9 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -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 */
--
2.6.1
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